I am in the process of selecting a builder to build an energy efficient home.  After some research I have been leaning towards using ICF construction, Low E windows, Sprayed Expandable polyurethane under the roof, Solar, etc..

Anyway I have spoken to one contractor who state that ICF is "way too expensive" and it is much cheaper to use solid poured concrete instead. He claims there isn't much of an energy difference and is easier to finish.  Can anyone tell me the major differences between the two (as they both are poured concrete) and what are the real energy differences?

By the way the home will be in Central Florida....HOT.

Thanks!

If he's a small residential home builder, there's no telling what his specific agenda is. ICF is not way more expensive than traditional poured concrete. Particularly in Florida, since you have local manufacturers. If you use traditional concrete forming, the contractor will have to handle forms twice, and each time will take longer per sqft than ICF. He will also have to add insulation -- remember, traditional concrete has almost zero R value. Finishing costs are no different unless you plan to just paint the interior of the concrete wall. I suggest you find a contractor accustomed to working with ICF and get his price. Hell, get three or four, there should be no shortage of ICF builders in your area.

If that contractor thinks that there's not much of an energy difference between ICF and poured concrete, you need a different contractor.

Yep, same BS I heard when talking to contractors who didn't know much at all about ICF.

Posted By jdebree on 21 Jan 2013 05:16 PM
If that contractor thinks that there's not much of an energy difference between ICF and poured concrete, you need a different contractor.

Exactly.

I'm sorry but your contractor is a moron. Run, run as far away from him as you can and find someone who knows what they are talking about.

The construction industry is afraid of anything new. I think it really comes down to laziness.

Thank you very much for your help. I have heard some issues with siding or stucco sticking to the Outer foam. Does something specialized have to be done? I imagine folks who use ICF have figured out a way to side it w/o problems.

There are many "stucco-type" finishes for ICF. All of the top manufacturers make products specifically for ICF. You should look at Gigacrete and PermaCrete. Just Google them and you'll find them. Both are highly respected top quality companies.

You have quite a few icf manufacturers molding their blocks in Orlando so shipping should not be a problem

Everyone has a mistake or two that stands out as "the big blunder" in their building experience. You are about to repeat the same big mistake I made. I was going to build a small 8'x10' bathroom using ICF's. I already had the foundations and slab with the vertical rebars sticking out. Along comes the neighbor and his mason buddy. They explained to me how I am stupid and naive and they are smart and expert and know it all. His buddy wanted to earn a buck and make the wall out of concrete blocks instead because he was familiar with that way of doing things and didn't know a thing about ICFs. Dummy me agreed. They told me I could line the insides with styrofoam after the fact. The only problem with this logic is that insulation of any kind does not adhere to concrete easily. I had to have insulation. During the winter the high desert gets freezing cold, often 20F. Water pipes and faucets inside the bathroom freeze and subsequently leak or burst. I could have used 2x4's and fiberglass insulation inside and then the already cramped bathroom walls would be 24 inches less than 8'x10'. The inside of the bathroom would be 6'x8'. I ended up using 2"x2" (actual size 1.5") furring strips and 1.5" styrofoam to line the inside walls. On top of that I used 1/4" durarock drywall. I could have also used styrofoam on the outside of the walls but again I would have to connect and tie it to the walls somehow. Anyway, to make a long story short, it was a long difficult arduous task to fix this mess created by the mason who wanted to earn a buck and build the thing the old fashioned way because it's the only way he knew how. Lesson to be learned here is that when you start talking ICF to people who build things they interpret what you are saying as "I want to make it out of concrete" and that translates to "I can do that just as well out of concrete blocks or concrete pour". But it's not the same thing. Not even close. They're trying to sell you something that they know how to do well. You'll be stuck with something you never wanted in the first place and won't know how to fix easily.

Better tends to cost more, all of the things you listed cost money, as I am sure you already have found. Good windows, Quality and well done spray foam, solar, and yes... ICF cost more than building a cheap trac home. Much like a Mercedes costs more than a Kia, you get what you pay for. Contractors that have no experience with today's energy efficient building methods are the Achilles heel of our industry today, but with the changing codes they may be faced with adaptation vs. early retirement as it will no longer be an option.

Find a builder that has experience building energy efficient homes and has a passion for it, that is the one you want to team up with. The end result you get will be something that you love, and will pay you back the extra money you spent when your AC cycles a tenth as much as your neighbors, or less...

Good luck on your journey, and don't let a lazy builder deter you from what you truly want your home to be!

I agree with all the comments here. Most builders just want your business their way. So shop around and make the right decision.

Posted By BrianBaron on 22 Jan 2013 02:29 PM
  Contractors that have no experience with today's energy efficient building methods are the Achilles heel of our industry today, but with the changing codes they may be faced with adaptation vs. early retirement as it will no longer be an option.

I agree. I talked with one builder not too long ago who is totally against the 2012 IRC and the tight energy requirements. He has been building for 30 years and while a good builder, he refuses to see the reasoning behind making tighter and more energy efficient homes. He comes from the school that houses need to leak air through the walls as houses need to breathe. He doesn't see the value in putting more insulation within the walls, it's R-19 fiberglass batts (Zone 4) and anything over that is overkill in his opinion. I don't even bother bringing up anything energy wise, as it's no use trying to convince him.

When I brought up ICF, he thought it was total overkill and a waste of money. He uses CMU and then frames out the interior walls and stuffs R-19 fiberglass batts between the studs.

Either these builders get with the progress or they need to retire or find something else to do. The 2012 IRC will have a hard time being accepted in many areas and many builders will resist the change.

Posted By Lbear on 22 Jan 2013 07:00 PM

Posted By BrianBaron on 22 Jan 2013 02:29 PM
  Contractors that have no experience with today's energy efficient building methods are the Achilles heel of our industry today, but with the changing codes they may be faced with adaptation vs. early retirement as it will no longer be an option.

I agree. I talked with one builder not too long ago who is totally against the 2012 IRC and the tight energy requirements. He has been building for 30 years and while a good builder, he refuses to see the reasoning behind making tighter and more energy efficient homes. He comes from the school that houses need to leak air through the walls as houses need to breathe. He doesn't see the value in putting more insulation within the walls, it's R-19 fiberglass batts (Zone 4) and anything over that is overkill in his opinion. I don't even bother bringing up anything energy wise, as it's no use trying to convince him.

When I brought up ICF, he thought it was total overkill and a waste of money. He uses CMU and then frames out the interior walls and stuffs R-19 fiberglass batts between the studs.

Either these builders get with the progress or they need to retire or find something else to do. The 2012 IRC will have a hard time being accepted in many areas and many builders will resist the change.

A good builder knows the difference between being vapor-open enough for water vapor to  "breathe"  it's way out compared to being air-permeable.  This guy is FAR from what I'd describe as a "good builder", even if his stuff is all straight, flat, & plumb, with good finish detail quality.

Building air-leaky barely-insulated homes is pretty forgiving from a moisture management point of view, since air-transported moisture leaves almost as quickly as it arrives, especially when the materials are warmer due to lower R values.  But that type of resilience is paid for in much higher energy use than necessary.  It's not that tough to build a resilient structure that is also energy efficient.

Building to IRC 2012 in zone 4 isn't tough, not tough at all- the guy should just get out of the business.  (Seriously- under IRC 2012 a zone-4 stick built wall is only an R20 2x6 cavity fill or R13 + 5c.i. proposition. In a 2x6 wall that can be had with 2.5lb density damp-sprayed cellulose or high-density batts, at only a modest uptick in installed cost from the miserable-performance low density R19.)

My all-concrete house (basement, 2 floors above ground, concrete floors & roof) has poured-in-place concrete walls. Not ICF (which I think are a very good product). I used 4" EPS on the outside of the concrete walls for insulation. The EPS was placed inside the concrete forms before the concrete was poured. The concrete and the EPS bond extremely well and my walls have the insulation on the outside, where it counts the most. I have all the thermal mass on the inside, in spades (8" concrete walls, 4" concrete floors & roof, 6" concrete interior walls).

Why would you use 6" concrete for the 'interior' walls?

Because I like the solid feel.

Posted By galore on 23 Jan 2013 10:30 PM
Because I like the solid feel.

So... 4" was sufficient for the floor and roof, but not a interior wall??

Not ICF ... I used 4" EPS on the outside of the concrete walls for insulation.

A perfectly reasonable design if the price is right. But don't expect the concrete's thermal mass to be of any help when the AC is running 24x7.

I think you can do better than spray polyurethane for a roof.

The 6" interior walls are that thick because I like the look and feel of thick walls.

Also jonr must have misunderstood. The roof insulation is 24" of type II EPS, sloping.
Not 4", that would be silly and not code compliant.
I don't know why my AC would run all the time with R19 walls, R108 roof, triple pane passive house certified windows and lots of thermal mass inside?!

4" was a direct quote.

"On" is what I meant by "running". If you condition the interior to a fixed temperature, interior thermal mass doesn't help you.

'4" EPS on walls' would have been a direct quote. Wall does not equal roof.

Also, thermal mass only makes sense for constant interior temperatures, especially if the outside temperature is fluctuating quickly.

I don't understand why you think that thermal mass doesn't help maintain constant room temperature? That's exactly why you want mass.

Posted By onesojourner on 22 Jan 2013 09:05 AM
The construction industry is afraid of anything new. I think it really comes down to laziness.

Not necessarily. When I was getting ready to build my ICF house I spent I don't know how many hours learning about thermal efficiency, window ratings, various heat systems and how they compare, proper ventilation, good insulation practices, the differences between various foams, and on and on. I had retired not too long before that so I had the time to do all that learning. I got to too thinking that it's no wonder contractors are sometime quite slow to change. It takes time to learn new methods and practices and approaches. When you're busting your rear using your time to produce income, it can be hard to find the time to learn. I don't rack it up to laziness but rather to ignorance of the importance of keeping up with the times.

Obviously, the contractor who doesn't keep up with the times will eventually lose out. But keeping up can be hard. So, instead of being hard on them, let's empathize with them as we watch them fade away from the construction scene.

Posted By galore on 25 Jan 2013 04:25 PM
'4" EPS on walls' would have been a direct quote. Wall does not equal roof.

Also, thermal mass only makes sense for constant interior temperatures, especially if the outside temperature is fluctuating quickly.

I don't understand why you think that thermal mass doesn't help maintain constant room temperature? That's exactly why you want mass.

You are correct, thermal mass DOES HELP maintain constant room temperature. I think he misspoke.

If you use the HVAC system to create and hold a specific temperature, then the interior thermal mass isn't absorbing or releasing any energy. Interior thermal mass only helps when you allow the temperature to vary (albeit less than the outdoor temperature). This is well established basic thermodynamics.

Posted By jonr on 25 Jan 2013 09:30 PM
If you use the HVAC system to create and hold a specific temperature, then the interior thermal mass isn't absorbing or releasing any energy. Interior thermal mass only helps when you allow the temperature to vary (albeit less than the outdoor temperature). This is well established basic thermodynamics.

Not quite the way you have it. The internal thermal mass comes into play, not when you vary the indoor temperature, but rather when you vary the heating or cooling input into the space. If, for whatever reason, you want to be able to allow the indoor temp to swing up and down the interior thermal mass works against you. I found that out fairly soon after moving into my ICF house. The interior mass, coupled with a heat pump for heating, caused the house to take up to four hours to heat up by 5° in the winter. During heating season we keep the temp constant.

This past summer I switched to time of day metering so cut the AC back in the daytime. Because of the mass of the ICF walls and the concrete rat slab in the crawl space the house would rise from 72°F at noon to about, at most, 76° at 9 PM.

A few days ago we had a power outage from 5 AM to 8 AM with the outdoor temp being about -5°F. The house dropped from 72° to 69°.

Wrong (the last jonr post).

The thermal mass is buffering the temperature thus making the HVAC work less to maintain a constant temperature. Because if you would not have mass and the outside temperature changes drastically, any heat transfer through the insulation would go directly to the interior, thus making the HVAC kick in. With thermal mass, this heat transfer goes into/comes from the mass.

For example, if it is cold at night and you have lots of thermal mass, the heat transfer to the outside through the insulation will get its energy from the thermal mass (which if very high will release quite a bit of energy but not lose a lot of temperature because it has all that energy stored in its mass), not the furnace. Likewise, if it's hot outside the following day, the energy that was just lost during the night from the mass, will be replenished, slightly heating up the mass but not the room, so the AC doesn't have to kick in.

If you would not have that mass, the furnace would have to provide the energy flowing out during the night (which costs $$) and the AC would have to sink the heat that comes in during the day (which costs $$), should you want to have a constant interior temperature. So with thermal mass, you save $$$$ in this scenario.

And this is a correct version of basic thermodynamics.

Let's keep our thinking and terminology straight here. The thermal mass of the outside walls absolutely buffers the outdoor temp swings as you say. The thermal mass inside the house has limited value for buffering the temperature unless you are in a heating dominant climate and the interior mass captures solar heating during the day to provide heat during the night. That's why your 6" interior concrete walls, not your outside walls, are being questioned. If you keep your house at a constant temperature then your interior concrete walls have limited thermal value.

I think it is safe to say the generally accepted view here is that the thermal mass of the outside walls has most effect and value in those climate areas where the daily temperature swings are significantly above and below the desired indoor temp, like in the SW. In areas of the north, or in the deep south, where the daily temperature remains below, or above, the desired house temperature for weeks and months on end, thermal mass looses its impact.

Some of you mathematically trying to prove that solid concrete walls will not keep the heat inside. But physically there are some structures that are built with solid concrete walls in somewhere of the planet called earth. Physically I know them well they are not keeping the heat inside or outside. People insulating them with EIFS and stucco. So I am voting on ICF for DIYers.

However I have a point "big constructions companies still are not using ICF".

But next time I will try to use solid concrete slabs instead of engineered slabs (like hambro or comslab).

Posted By dmaceld on 25 Jan 2013 10:49 PM

Not quite the way you have it. The internal thermal mass comes into play, not when you vary the indoor temperature, but rather when you vary the heating or cooling input into the space. If, for whatever reason, you want to be able to allow the indoor temp to swing up and down the interior thermal mass works against you. I found that out fairly soon after moving into my ICF house. The interior mass, coupled with a heat pump for heating, caused the house to take up to four hours to heat up by 5° in the winter. During heating season we keep the temp constant.

This past summer I switched to time of day metering so cut the AC back in the daytime. Because of the mass of the ICF walls and the concrete rat slab in the crawl space the house would rise from 72°F at noon to about, at most, 76° at 9 PM.

A few days ago we had a power outage from 5 AM to 8 AM with the outdoor temp being about -5°F. The house dropped from 72° to 69°.

One thing with thermal mass during winter in climates like the SW. Sometimes during the day due to passive solar and high thermal mass, the home may "heat up" quite a bit, even to the point of seeming too hot. Some might refer to this as "overheating" but that is relative depending on the occupants of the home. A 80F interior temp during a 30F exterior temp might seem cozy and nice to some. Point being is that even at 80F peak interior temps, let's say by 5PM. Your HVAC system SHOULD NOT be programmed to turn on and try and cool down the home during winter, as that is counter productive and a waste of energy. After the sun sets, it will take a while for the home to begin to cool down. By morning the home might be down to 70F but as long as it's sunny again, the process starts all over.

For instance, in a climate like mine where in winter it can get to 55F in the daytime by 4PM and then 25F by 7AM, that is a perfect climate for thermal mass. In the summer in can get to 95F by 7PM and then see 55F by 6AM, thermal mass helps to even out these diurnal swings. During the summer one would want to open some windows at night to cool down the home.


Why do you call it a "rat slab"? Do you get pack rats burrowing underground where you are at?

We currently live in an uninsulated CMU house in FL. There are about 6 months of the year that we don't use heat or A/C. The thermal mass is a big help smoothing out the highs and lows, keeping the house reasonably comfortable unless it is hot or cold for a long spell. We are probably different than the average American, being happy between 60 and 80 degrees. In our case, the thermal mass is a big help. We are currently building an ICF house in upstate SC, and again, much of the year, the weather is what we call comfortable. In the middle of winter, or the middle of summer, the HVAC will be maintaining the interior temperature. But during the shoulder seasons, we should be able to skate by with little conditioning, and once again, I think the mass of the walls will be an effective shock absorber.

I also think that there is a small amount of 'geothermal' help, as the concrete in the walls is thermally connected to the ground through the footing. In SC, the deep soil temperature falls into a pretty comfortable range. I think that's a part of why ICF functions so well in a mild climate, and starts to lose out in a severely cold climate. This is only a guess on my part, though. Time will tell once the house is done.

Posted By dmaceld on 25 Jan 2013 11:09 PM
Let's keep our thinking and terminology straight here. The thermal mass of the outside walls absolutely buffers the outdoor temp swings as you say. The thermal mass inside the house has limited value for buffering the temperature unless you are in a heating dominant climate and the interior mass captures solar heating during the day to provide heat during the night. That's why your 6" interior concrete walls, not your outside walls, are being questioned. If you keep your house at a constant temperature then your interior concrete walls have limited thermal value.

You have it exactly backwards. The thermal mass is most effective if it's on the inside, not the outside because the MASS is what keeps things temperate. For example: You have a beverage that you want to keep cool. If you put it in a styrofoam cup, would you put the ice on the outside (thermal mass on the outside) or the inside (thermal mass on the inside). The ice keeps the beverage cold (like a cold concrete wall keeps the air in the house cold) if it's in the drink, not if it's outside the styrofoam cup. That's also the reason, why insulation on the inside (ICF) works against the mass benefits of the concrete and it's the reason why the international energy code doesn't consider thermal mass, if the insulation in on the inside ("The insulation must be at least 50% on the exterior or integral to the wall to count. Otherwise you're back in the wood frame wall insulation requirements. In other words, brick veneer or log siding don't count."). Some references: http://blog.srmi.biz/energy-saving-tips/insulation-air-sealing/high-thermal-mass-walls/ "The best way to employ thermal mass is to maximize the surface area of the thermal mass facing the interior of a home by making the interior walls massive in addition to the exterior walls." http://www.ornl.gov/sci/buildings/2012/1998%20B7%20papers/070.pdf Kossecka, E. and Kosny, J. - “Effect of Insulation and Mass Distribution in Exterior Walls on the Dynamic Thermal Performance of a Whole Buildings” - DOE, ASHRAE, ORNL Conference - Thermal Envelopes VII, Clearwater, FL - Dec. 1998. "This data shows that the most effective wall assemblies were walls with thermal mass(concrete) being in good contact with the interior of the building (Intmass and CIC). Walls where the insulation material is concentrated on the interior side (Extmass) were the worst performing wall assemblies. Wall configurations with the concrete wall core and insulation placed on both sides of the wall (ICI) performed slightly better than Extmassconfigurations."

Wow.

Jonr assumes that his house has no temperature variation whatsoever when in fact a typical Tstat set point is plus or minus 2 degrees-- potential hours that the AC isn't running in a high mass house. And there is still a diurnal swing in internal temps -- a big one in the case of a large family living in a house with poorly placed windows; small in the case of DINKS who in restaurants and send out their laundry. As DMACELD points out, thermal lag allows set-ahead strategies for summer and setback strategies for winter that narrow the temperature difference between inside and outside and save energy.

Lbear is half right. Thermal mass is a terrific strategy for AZ in summer. But if the winter amplitude is 25 to 55 degrees, heat is traveling in only one direction -- out.

Jdebree is repeating the ICF industry's Holy Grail -- earth coupling that enhances ICF performance. It was put to the test in a joint ICF/ORNLtest house near Knoxville. ORNL's conclusion: No magic chalice in sight.

One caution for the OP: The AC runs right along in the typical leaky, poorly insulated Fla home. Ramp up the insulation and reduce air inflitration to a pittance and AC may not run enough to handle humidity.

In defense of traditionalist tradesmen, without an HRV/ERV, there is a limit on a how tight a home can be and remain healthy.

Posted By galore on 26 Jan 2013 08:18 AM

Posted By dmaceld on 25 Jan 2013 11:09 PM
Let's keep our thinking and terminology straight here. The thermal mass of the outside walls absolutely buffers the outdoor temp swings as you say.

You have it exactly backwards. The thermal mass is most effective if it's on the inside, not the outside because the MASS is what keeps things temperate

Uh, if you read closely you'll see I said "outside wall", not "on the outside of the wall." I'm not saying anything at all about the insulation being on the interior or exterior surface of the outside wall. The impact of its placement is the subject of another discussion, and the comparative value of the inner vs outer thickness is not clear cut when climate is factored in. This has been the subject of many discussions here the past several years.

Posted By toddm on 26 Jan 2013 08:48 AM

In defense of traditionalist tradesmen, without an HRV/ERV, there is a limit on a how tight a home can be and remain healthy.

That's why the mantra now is, "Build it tight and ventilate it right!"

We're talking code here rather than mantra. I have to say I don't know if 2012 IRC requires an HRV or sets MINIMUM infiltration rates. I rather doubt it. Kinda like radon code around here. You need underslab ventilation but don't have to test or add a fan if necessary. (Seven of 10 homes here have radon issues.) An overzealous builder+the wrong homeowner+the wrong building site = ?

Anything inside adds to thermal mass so of course interior concrete walls count as well. If you don't understand this I suggest researching this topic a bit more.

Posted By Lbear on 26 Jan 2013 02:00 AM

Why do you call it a "rat slab"? Do you get pack rats burrowing underground where you are at?

That's the colloquial term that is used to refer to a concrete slab in a crawl space. I think it actually does come from its use in some areas to prevent rats from burrowing into the crawl space. Where, why, when, I do not know!

In my case I placed about a 2" thick concrete slab over 3/4" blue board primarily to help keep the crawl space atmosphere clean and secondarily for thermal mass. I use the crawl space as my supply plenum for heating and cooling.

Posted By galore on 26 Jan 2013 01:17 PM
Anything inside adds to thermal mass so of course interior concrete walls count as well. If you don't understand this I suggest researching this topic a bit more.

I don't say they don't count, just that they don't count enough to justify the expense of installing them for that reason. There's no question mass in the interior moderates temperature swing, but the key word is swing. If your heating/cooling system is set so that the interior temperature does not swing more than a degree or two then there is minimal benefit from the interior mass. I get a benefit from my rat slab but that's mostly because in the summer I let the temp in the house swing +/- 2° to 3° from ideal, and because I use a heat pump that has no excess capacity above the maximum heating and cooling load on the house. But I don't let the temperature swing in the winter. It's uncomfortable waiting for the house to come to temp after letting it cool down. I said earlier, the internal mass both helps and hinders the heating/cooling process.

Keep in mind the purpose of the heating/cooling system is to replace or extract heat that leaves or enters the building envelope. Thermal mass in the building envelope plays a significant part in moderating the flow of heat into and out of the envelope. The only reason it's better to have the insulation on the outside of the thermal mass is solar absorption. If the primary driver for the heat flow through the wall is air temperature, which is pretty much the case on north walls, the heat flow through the wall will be the same regardless of whether the insulation is on the outside or inside of the thermal mass.

Not true, dmaceld. Thermal mass works because of thermal lag -- the combination of high heat capacity and low conductance that slows transfer through massive walls. Ideally, the flux of heat and cold through the 24 hour cycle never reaches the inside surface, and maintains comfort insde as long as the average daily temperature is comfortable. Exterior insulation increases thermal lag obviously but it isn't required (e.g. adobe walls in the SW and rubble filled masonry walls in the Mediterranean.) By contrast, exposing mass to the interior harnesses thermal lag inside the house. Walls that are slow to heat and slow to cool buffer temperature spikes inside the home. The more variation you are willing to tolerate, the more energy you save.And I'm betting even Jonr sweats a bit in spring and shivers a bit in fall before turning the HVAC on. With thermal lag, the honeymoon lasts longer.

You will have thermal lag whether the insulation is on the interior or exterior surface. Which side it's on just determines what the temperature level of the mass is. With insulation on the outside the inner surface of the mass will be near room temp and the outer will fluctuate above and below that. During summer with insulation on the inside, the entire mass will fluctuate with the outer surface fluctuating through a greater range than the inner surface.

Insulation doesn't affect the thermal lag significantly at all because it doesn't store heat. It only affects the temperature difference across its own surfaces.

You can have two walls provide the same interior comfort. In one case, as you say, it can be really thick walls like the adobe houses. In that case the performance is based more on a longer term cycle. Make the wall thick enough, and with the appropriate outdoor temps, you can have a 12 month heat movement cycle. Make the wall something like 2' of foam and you'll be comfortable inside because of very low conductance of heat, not because of heat absorption.

Actually, it would be quite interesting to see the math on these various situations. I'll look to see what ORNL has for models. Or maybe I'll do some in the next few days. It should be fairly easy with a spreadsheet to create several scenarios. Of course, like all things in life, reality doesn't always equal calculation. I will say though, that the heating/cooling calcs for my house couldn't have been much more accurate. My HVAC nephew calculated the heat load at ~30,000 Btuh with an outdoor temp of 9° and indoor temp of 74°. During the cold spell of the last two weeks my Daikin heat pump ran steady. The factory performance chart shows an output of 27,000 at 5° outdoors and 72° indoors. The heat pump kept the house at 70° with the outdoor temp dropping as low as -5°. Extrapolating the factory chart I estimated it was putting out about 24,000 Btuh. I ran my pellet stove for supplemental heat to keep the house at 72°.

There is no longer-term cycle in the dynamic benefit of thermal mass, dmaceld. If you don't get big swings in temperature in a 24-hour period, above and below "comfortable," thermal mass makes little difference in energy use. And thermal lag explains why. If it takes 10 hours for heat to penetrate massive walls, then the peak ambient heat of 5 p.m. turns up inside at 3 in the morning, or would do so anyway, if heat flow hadn't reversed at some point after sundown and began cooling the walls. There is no one temperature in a massive wall; it follows a gradient from, say, 78 inside to some temperature between 55 and 95 to borrow Lbear's summer amplitude in AZ, depending on what time of day we measure it. Insulation isn't necessary; neither is solar radiation.

Insulation on either side is a complication, in fact. Using DOE2 simulation software and the Phoenix climate, for example, ORNL found the greatest energy savings in a R5 ICF wall. But ORNL's work says clearly that exposed mass is better than interior foam. Given the other heat loads on the interior, you want to reach out and touch that 75 degree concrete.

toddm, dmaceld knows what he's talking about. He lives in an ICF home as I do. The problem is probably in assuming that it takes 10 hours for the heat to penetrate. It must take far longer or ICF wouldn't work as well as it does. Now with CMU or other block type non-ICF system I believe you would be correct. Also the gradient you refer to has a slope very close to zero. A gradient without a slope is well not a gradient. Therefore, the concrete being a conductor is largerly at the same temperature throughout with minor differences inside to out. In fact, in a conditioned ICF building the concrete core never varies from the inside temperature more than 10 degrees (extreme cold or hot). Normally it's very close to the set point (about 2-5 degrees). I've run temperature probes now on multiple buildings and this is always the case.

The ORNL report shows an ICF wall that doesn't exist compared with a "mass" system that does not have heat capacity to count as massive!

If you keep your house at a constant temperature then your interior concrete walls have limited thermal value.

I think it is safe to say the generally accepted view here is that the thermal mass of the outside walls has most effect and value in those climate areas where the daily temperature swings are significantly above and below the desired indoor temp,

dmaceld is correct - plus, if the thermal mass is on the inside, you need to let the indoor temp vary.

in a conditioned ICF building the concrete core never varies from the inside temperature more than 10 degrees (extreme cold or hot).

It will be ~1/2 way between the average indoor and outdoor temps with a typical symmetrical ICF.

TexasICF forcing my hand, I am obliged to repeat that Dmaceld has a fuzzy grasp of thermal mass. He was talking about adobe walls here:

"You can have two walls provide the same interior comfort. In one case, as you say, it can be really thick walls like the adobe houses. In that case the performance is based more on a longer term cycle. Make the wall thick enough, and with the appropriate outdoor temps, you can have a 12 month heat movement cycle. Make the wall something like 2' of foam and you'll be comfortable inside because of very low conductance of heat, not because of heat absorption."

And he is dead wrong. Both walls work because of low conductance. In the adobe wall, it's a combination of heat capacity and low conductance that delays transfer long enough for amibient conditions to change. Heat isn't being stored. It's being cancelled out by alternating fluxes of heat and cold within the wall over a 24-hour period. Thermal lag is not storage; it is a measure of time. If the average daily temperature is "comfortable" and mass is adequate, the inside temp of the wall is also comfortable and the AC and/or the furnace stay off. In four-season climates, the benefit is modest and equal parts comfort and savings. (In my part of the world, folks brag about how late they turn their furnaces on. in the fall and their ACs in the spring.) In the desert SW and Greece, mass was once, and often still is, the ONLY means of conditioning.

Because insulation adds to a mass wall's heat resistance, insulation on etiher side does indeed increase thermal lag. ORNL never really explains why walls with concrete inside-insulation outside outperform insulation-concrete or insulation-concrete-insulation. No matter. I'll take science over TexasICF.

Old hands here no doubt rolled their eyes to hear our favorite carny barker complain again (and again and again) about ORNL simulations of ICF walls that don't exist in the marketplace, in the same way that the Higgs boson obviously doesn't exist because TexasICF can't see it. He is an inveterate maker of claims about ICF mass effect that are not found in evidence. He started this thread a year ago: http://greenbuildingtalk.com/Forums/tabid/53/afv/topic/aff/4/aft/79706/afs/ASC/Default.aspx, the result of which was his fellow ICF sales types urging him to give it up, judging from eye rolls in those quarters.

But, hey, bring it on.

.

Posted By toddm on 27 Jan 2013 04:40 PM

Because insulation adds to a mass wall's heat resistance, insulation on etiher side does indeed increase thermal lag. ORNL never really explains why walls with concrete inside-insulation outside outperform insulation-concrete or insulation-concrete-insulation. No matter. I'll take science over TexasICF.

Old hands here no doubt rolled their eyes to hear our favorite carny barker complain again (and again and again) about ORNL simulations of ICF walls that don't exist in the marketplace, in the same way that the Higgs boson obviously doesn't exist because TexasICF can't see it. He is an inveterate maker of claims about ICF mass effect that are not found in evidence. He started this thread a year ago: http://greenbuildingtalk.com/Forums/tabid/53/afv/topic/aff/4/aft/79706/afs/ASC/Default.aspx, the result of which was his fellow ICF sales types urging him to give it up, judging from eye rolls in those quarters.

But, hey, bring it on.

Here we go again. You point to the former thread in which you made a statement of:

Posted By toddm on 24 Jan 2012 06:18 PM
NO effective R value documentation from forms manufacturers? None?

Then you were proven wrong when you were shown this data:

Energy Efficiency Data & Performance:
* Thickness of the EPS.………………………………………………… 2.625" / wall panel (5.25" total EPS thickness)
* EPS Steady State R-Value (thermal resistance of the material)…. R - 23 (R - 4.55 / inch @ 40 degrees Fahrenheit)
* CTL Group Thermal Resistance R-Value Calculation Report……. R - 23+ calculated in accordance with ASHRAE 90.1
* EPS K-Factor (thermal conductivity of the material)………………. K - 0.22 / inch @ 40 degrees Fahrenheit
* Air Leakage (infiltration rate).….…….……………………………….. 0.05 to 0.10 ACH (average air changes / hour)
* ORNL Thermal Mass Calculator Dynamic R-Value Equivalent…... Greater than R - 32


Why do we have to go round and round with this?

Temp Probe Study

OK, I looked at the ORNL report. toddm, you are right when you say they don't explain why the interior exposure of concrete gives the best performance. It would be nice to see graphs throughout some daily cycles at various times of the year showing the temperatures at each of the surfaces. Also, there is quite a bit of variation in the total number of cooling degree days and heating degree days for the cities used. What is missing in the report is an explanation of how the daily temp cycle affects the flow of heat through the wall.

What I'm thinking is happening with the interior vs. exterior exposure of concrete is this. The outer surface of the concrete in the exterior exposed scenario is in almost direct contact with the sun and air, and because it can swing in temperature much more it absorbs and releases more heat than in the interior exposed scenario. In the exterior scheme the total concrete thickness reaches a higher temp during the day and a lower temp during the night than does the interior exposed concrete. Subsequently, in the exterior exposed scenario the outer surface of the insulation layer fluctuates much more than does the interior surface of the insulation layer in the interior exposed scenario. With a higher and lower temp fluctuation across the insulation layer you naturally have more heat flow going across it.

Another thing I see as quite interesting in their study is that the same thickness of concrete, when installed in two layers with insulation between them has the same performance benefit as the interior exposed concrete scenario. That puzzles me a lot, particularly when there is such a great difference between interior vs. exterior exposed concrete. Another thing they don't discuss is the relative benefit of the 6" concrete + 4" insulation combo (R 17.2) vs the 4" concrete + 3" insulation (R 13.0) combo. The benefit of each vs an equivalent wood frame wall is the same.

You say that in the adobe wall it's a combination of low conductance and heat capacity. You also say heat is not being stored. I disagree. The specific heat of stone, adobe, and concrete is fairly high, meaning it takes a lot of Btus to raise the material temp 1°F. That is the definition of heat storage. It's the capacity to store heat that contributes to the concrete's low conductance and thus to thermal lag. Heat doesn't get from one side to the other very quickly as it's being sucked up by the concrete. In a steady state condition when the concrete has reached its full temp the heat will travel fairly quickly, about 10 to 20 times as fast as through the foam. To be clear I'm talking about heat storage in terms of hours. Like you say, it goes in during the day and out a night.

Given a mass wall thick enough, say maybe 4' to 10', you will have daily thermal lag in the outer several inches, but you can have yearly thermal lag through the entire thickness. Make the mass thick enough and you'll never have temp fluctuations in the inside because the heat and cold never reach the inside. That's the case with caves in the mountain, disregarding what happens at the entrance.

I do take some umbrage at your statement that I have only a fuzzy grasp of thermal mass. I understand it quite well, thank you. I think our issue is mainly a difference of how we explain ourselves, and the fact that I am a bit mystified at the ORNL model results of interior vs. exterior concrete exposure. Their results seem to contradict logic. Just because they are ORNL scientists does not guarantee they didn't make a mistake. I spent 22 years auditing the processes and practices of professionals. Sometimes their mistakes and ignorance were nothing short of astounding.
 

We keep going around because you hope ICF prospects will mistake weasel words like "more than" or "up to" as documentation when it actually says: "We don't have documentation that the FTC will accept so we'll leave the selling to shills like Lbear."

Again, proper documentation begins when the manufacturer builds its wall in an ORNL blessed hotbox. If mass is involved, the point is to determine both R value and thermal lag. (R value is all that matters when ambient temps rise above, or fall below, a "comfortable" daily average and stay there. The difference between Phoenix and Boise is the many more days in a year in the former when mass has an effect.) The manufacturer feeds this data into DOE2 and simulates its performance in the representative climates that DOE2 models. The ICF industry obviously does not like how DOE2 treats ICF walls, which apparently led its sponsorship of the side-by-side test of ICF vs stud wall in Knoxville in 2000. The score: DOE2, 1; ICFA, 0.

Like I say, Dmaceld, insulatiion complicates thermal mass. a ZEH in Tucson, for example, wrapped filled CMU walls in R14 foam and reported, post construction, that thermal mass had no measurable impact on energy use, which was surely news to the residents in the many adobe houses nearby. The immediate failure in this house was inadequate auxiliary heat. As you note, recovery can take a looong time.

We'd understand the process better if ICF manufacturers stepped and gave us some real data. Sad to say, they prefer urban myth.

Sphingers, please ignore this toddm character. He's just an angry troll whose mother weaned him a few weeks too early. He had a bad experience with a disreputable ICF installer and now lays in wait under his metaphorical bridge for unsuspecting normal people innocently asking for advice.

Ray Gladstone, Jan. 24, 2012, on why ICF manufacturers prefer weasel words over proper thermal mass documentation:

"Toddm, it sounded like you were upset with his use of the term, "cave like," and it's not clear why you're concerned with the FTC. "Cave like" is a subjective term, if Tex likes it, he can use it. It would seem that this analysis is not of critical importance. The truth is that 2-1/2" of Type II EPS is what it is. ICF manufacturers spend significant amounts of money for required testing on a regular basis. To spend another $80,000 or $100,000 on a test that will BENEFIT ALL THEIR COMPETITORS does not seem like a prudent way to deploy marketing dollars."

Emphasis added.

Hi Toddy. Nice to see you back putting your words into other people's mouths again. Water getting cold under that bridge?

A March 2012 scientific study released by the National Research Council Canada conducted field testing on ICF walls. So together with NRC/IRC and Natural Resources Canada, they measured the thermal mass of ICF walls in their recent study “Field Monitoring of the Dynamic Heat Transmission Characteristics through ICF Wall Assemblies over a Full Year Cycle of Weather Exposure.”

The findings: (emphasis mine)

NRC Study

The scope of work included the design of the experiments, the installation of test specimens, the commissioning of the instrumentation, the operation of the test facility, the monitoring, data collection & analysis. This research evaluated the dynamic heat transmission characteristics through an ICF wall assembly in FEWF for a one year cycle of exposure to outdoor natural weathering conditions. Correlations between the temperature at the exterior surface of the ICF and the exterior surface of the concrete revealed a buffering effect of approximately 5 days due to the mass of the ICF.

This analysis showed that the ICF moderated heat loss to and from the interior. The interior heat flux through the wall was not following weather changes on the outside instantaneously. This was interpreted as the buffering effect of the mass. The monitored data confirmed that the concrete adds very little to the overall R-value of the wall assembly under steady-state conditions. During the transient conditions, the data showed that the concrete played a significant role in tempering heat loss to the exterior. The thermal mass of the concrete was shown to reduce the peak heat flux through the assembly during cold weather. This research is one of a series of projects that highlight direct and indirect impacts of thermal performance of the building Envelope technologies in houses. This paper provides valuable experimental data to be used for energy simulation models.

Thus, ICF walls have the potential to reduce the peak heating requirement of the furnace, and the peak cooling requirement of the air conditioning system. This may have implications for the sizing and cost of mechanical equipment. This experiment only examined a small section of ICF wall on a west façade. Performance on the whole house level will be affected by other factors including solar gains through windows, and the operating mode of the house (for example: the use of free cooling at night or thermostat setbacks). Whole house modeling would be required to better understand the impact of ICF construction on annual energy consumption.

http://greenbuildingtalk.com/Forums/tabid/53/aff/4/afv/topic/aft/81109/Default.aspx $100 to anyone who can demonstrate that I edited or changed Ray Gladstone's post in any way, except for the emphasis I noted. Honestly, does the ICF industry recruit on used car lots?

Fine, Lbear, now add the the rest of the house, as opposed to a west-facing wall section, test it n another seven or eight representative climates and tell us if it amounts to squat. Oh, wait, ORNL has already done that, and it didn't.

Sphingers, walls are a relatively small contributor to heat loss. And thermal mass effect, except in desert southwest, is an even smaller piece of that, small enough that poor door installs could offset it. Go here for some objective help developed by UCLA: http://www.energy-design-tools.aud.ucla.edu/heed/ Climate Consultant 5 downloads historic weather data from the NWS site nearest you. There is a whole lot of detail there, but also a sort-of recommendations page that lists the number of hours in a year that specific energy strategies will keep you comfortable without hvac. If the answer is insulation, I'd go with ICF. If the answer is thermal mass (doubtful) then the poured wall is still in the running. If you are comfortable with modeling software, UCLA's HEED allows you to build a crude model of your design including windows and doors, orient on it your site and run it through 365 days of typical weather. It has both an ICF and a poured wall option. It's still (sophisticated) guesswork, but at least the software's authors weren't used car salesmen in earlier careers.

Toddy, I was referring to your wise-a$$ed little intro. But then you knew that didn't you? Oh wait, Nurse Ratchet just called to see if anyone knows which bridge you're lurking under today. She says it's time for your anger management group session.

There are two different types of people out there, ones that want to see scientific reports documenting the precise benefits of the thermal mass and insulation. And those that see more worth in talking to people who ACTUALLY live in an ICF home. I prefer to deal with option 2. Pretty easy to venture a guess as to which side of the fence some of the posters above are on.

Can you pour a normal foundation and affix insulation to the concrete, sure. Will it cost less, probably. But then you are left with ZERO attachment points other than anchoring back to the concrete. There is no company to support your efforts, and help you with questions. Setting conventional forms is by far not a task that a DIY can do, and involves more labor with stripping and cleaning. If you are going to argue the fact that EPS does not out perform a stud wall placed next to concrete with some fiberglass stuffed in between the studs, then you just enjoy being difficult and are blinded by being set in your ways.

As an industry, I do not believe you will hear us say very often "change over to ICF, its cheaper". What you get is an easy to build and work with system for forming concrete that leaves you with a finished product ready for waterproofing, finishes, drywall, etc.

Every single manufacturer has a plethora of documented customers utility bills showing a drastic reduction in heating and cooling costs, compare them to whatever you like. Those customers will also tell you about how quiet the house is, the sense of security they get if a storm is coming, and how great the feeling of a dry warm basement is. There is no scientific test for homeowner satisfaction, so I don't have an ASTM report for it. Sorry.

To the OP and anyone else reading these pages of ranting and arguing, don't let the stupid little scientific formulas of thermal mass deter you. Build it once and build it right. I am biased, but feel that ICF can play a strong part in you loving your house for many many years to come. All of my customers sure do, and that is proof enough for me.

Yeah, OP don't let those stupid little formulas sway you. You came to GBT to cheer for your team. Go ICF!

Then again, in the real world, Kia is paying a settlement to owners to compensate them for overstated mileage claims. Publishers Clearing House paid a fine for "Board of Judges" letters that misled consumers. More to the point, the Federal Trade Commission is hot lately on deceptive claims by window companies. http://www.ftc.gov/os/caselist/1123005/120518longfencecmpt.pdf

I'm not saying that anyone here is breaking the law. I am saying that only way for a manufacturer to make a legit thermal mass claim involves an ORNL hotbox and DOE2. I am also saying that the average attentive consumer should look at the official disclosure. If it says R22 than expect to get an R22 wall, cuz if the FTC was cool with "more than R36" that's what the manufacturer would say. Rant? Or common sense?

Posted By toddm on 28 Jan 2013 07:45 PM
Yeah, OP don't let those stupid little formulas sway you. You came to GBT to cheer for your team. Go ICF!

Then again, in the real world, Kia is paying a settlement to owners to compensate them for overstated mileage claims. Publishers Clearing House paid a fine for "Board of Judges" letters that misled consumers. More to the point, the Federal Trade Commission is hot lately on deceptive claims by window companies. http://www.ftc.gov/os/caselist/1123005/120518longfencecmpt.pdf

I'm not saying that anyone here is breaking the law. I am saying that only way for a manufacturer to make a legit thermal mass claim involves an ORNL hotbox and DOE2. I am also saying that the average attentive consumer should look at the official disclosure. If it says R22 than expect to get an R22 wall, cuz if the FTC was cool with "more than R36" that's what the manufacturer would say. Rant? Or common sense?

You just insinuated that ICF makes false claims and then you try and go back and claim that you didn't say that.

Once again, I post this for your review:

Energy Efficiency Data & Performance:
* Thickness of the EPS.………………………………………………… 2.625" / wall panel (5.25" total EPS thickness)
* EPS Steady State R-Value (thermal resistance of the material)…. R - 23 (R - 4.55 / inch @ 40 degrees Fahrenheit)
* CTL Group Thermal Resistance R-Value Calculation Report……. R - 23+ calculated in accordance with ASHRAE 90.1
* EPS K-Factor (thermal conductivity of the material)………………. K - 0.22 / inch @ 40 degrees Fahrenheit
* Air Leakage (infiltration rate).….…….……………………………….. 0.05 to 0.10 ACH (average air changes / hour)
* ORNL Thermal Mass Calculator Dynamic R-Value Equivalent…... Greater than R - 32

If the above "Thermal Mass Calculator Dynamic R-Value Equivalent of Greater than R-32" is a false claim like you insinuated, then report them to the FTC. Your above paragraph claims that if it states "more than R36" then the manufacturer would make that claim. The reality is that they do make that claim but you choose to ignore it and act like it's not there.

The reality of it is that the dynamic R-Value equivalent claim of "Greater than R-32" is a valid claim and ORNL and DOE2 and FTC cannot say otherwise because it is validated by scientific studies.

Here's a graph I put together of the ORNL model. What they are showing by their Dynamic Benefit of Mass Systems (DBMS) index is how much better a frame wall would have to be to equal the annual energy cost of the ICF wall. Glazing is 10% of the total wall area. This is for a wall of R-17.2, 6" concrete, 4" foam.

What bothers me most about their results, as I said earlier, is the dramatic difference between concrete on the interior vs. exterior. The first two points in the graph represent the 6" concrete installed in two separate slabs with the insulation between. Both of those, plus the third point, have concrete on the interior surface. The DBMS is almost flat regardless of the thickness of the concrete on the interior except for Miami, which is cooling predominant. The last three points represent 1", 2", and 4" of foam on the interior side. In 4 & 5 the concrete is sandwiched between the two foam layers. There is a steady drop in DBMS with increased foam thickness on the interior.

According to the model, any insulation on the interior side dramatically lowers the benefit of the mass, except for Minneapolis, but they don't explain why.

The upshot, as I see it, is that even in a heating predominant climate like Minneapolis, or a cooling predominant one like Miami, there is a measurable benefit derived from the mass in the wall. In fact, according to the model 6" of concrete on the interior side provides as much benefit in Miami as it does in Phoenix! Now why is that? That certainly goes against the argument that in a south climate where the heat flow is constantly to the inside, mass provides no benefit.

CORRECTION EDIT: 3/18/13 For data point 3, the exterior foam value should be 4", not 0".



Here's the corrected version, with the data included.

Here is the FTC's R value rule for consumers: http://www.consumer.ftc.gov/articles/0107-home-insulation-its-all-about-r-value. The manufacturer's claims must be based on standard tests. To my mind, a calculator is not a test, but my opinion and a dollar will get you a cup of coffee, In the normal course of events, Fox Block's competitors would be screaming bloody murder at the FTC. It is instructive that the industry apparently is not. Clearly, ICF makers could claim higher r values everywhere, albeit far lower ones than the R45 my contractor claimed based on a 90s industry-funded test that can be best described as scurrilous. (BTW I knew he was woofing me; my criticism here of ICF mass claims predates my building permit by a year. Proof cheerfully furnished on request. And I'd choose ICF again. For perimeter walls in a cold climate slab on grade, ICF is far superior to standard practice CMU and cheaper besides.)
Why ICF manufacturers don't claim mass effect is probably a regional thing, a bloc of distributors (north? southwest?) that would suffer the kind of competitiive disadvantage that Ray Gladstone suggests. Note that Fox' use of mass effect is climate-free.

Now, I will confess that I am not the easiest sale in the world. But the last thing I want in products is a mystery. I repeat, if it says R22 then treat it as R22.

One thing about the ORNL model to keep in mind is that it is based on a set of assumptions that may or may not be accurate for a specific case. How willing you are to let interior temperate vary (and/or various other things) has a huge effect.

At least a partial explanation of interior mass sometimes being better is that it will heat/cool infiltrated air.

You're right Todd, we should go out and spend tens of thousands of dollars to have a thermal mass test done that less than 1% will understand or care about. Great idea.

We have testing data that shows the exact R-Value calculations of our variety of R-Values. It looks very similar to the one posted above. If you are still referring to old statement that was made about the "Effective R-Value of 50+" from the R-22 form... I agree that was a bit of BS, but had some valid points to in pertaining to the air tightness etc. Thankfully the ICFA put somewhat of an end to it. I was looking at one of my competitors website the other day and they still have that on their site. Don't fault salesman for being salesman, the majority of the country is a salesman in one form or another. An engineer sells his engineering services, a builder sells his building services, I could go on all day. Comparing us to car salesmen is a stretch, but sometimes I also say things to make a point that may be an exaggeration, we all do.

What exactly do you do for a living, and what experience you had in the past caused you to have such a hair across your you know what about ICF? If you refer to someone above as "your contractor" I thinks its safe to assume you are not a builder, so what career is it that makes you son enthralled with ORNL and DOE2 reports? Just curious, that's all...

Posted By Lbear on 28 Jan 2013 09:08 PM

* EPS Steady State R-Value (thermal resistance of the material)…. R - 23 (R - 4.55 / inch @ 40 degrees Fahrenheit)

Again you throw out a performance number a temperature that is completely irrelevant to most of residents of the US.

The ~R4.5/inch number is the performance when 40F is the AVERAGE TEMPERATURE THROUGH THE MATERIAL, not when the exterior is 40F.  So, yeah, when it's +10F outside, +70F inside, that's about how well it performs in an ICF.  If +10F your wintertime outdoor average, not daily low, but wintertime AVERAGE, great, use that number!   But that only applies to the tiniest fraction of the US population (not even a majority of the population in Alaska!)
 
If you live in the cooler parts of US climate zone 7 (International Falls MN, say) that will be a reasonable estimate of it's wintertime performance, but even on the warmer edge of zone 7, (such as Fargo ND, or Anchorage AK) the 10-coldest weeks binned hourly temp is warmer than that.  For Zone 5 the wintertime average performance of your example ICF would already be under R22, and in warmer zones it would be lower still. 

Calling it R23 steady-state just because there happens to be a 40F rating on the spec sheet is pure BS, since that's not the average temperature through the EPS most readers of this forum are going to experience.  Calling EPS R4.5/inch in an ICF for most of the US is as bogus as calling polyiso R6/inch in a cold-climate sheathing application. (In International Falls iso should be derated to ~R5.5/inch if it's only the exterior third of the insulation, if you want to estimate the real performance in the application.) 

Using R4.5/inch for EPS is reasonable in exterior sheathing applications when it is less than half the total R in climate zones 5 or 6, but not in ICFs.

Since you don't really HAVE to make stuff up or exaggerate to demonstrate the relatively good performance of ICFs, it's better to stop using irrelevant datapoints when trying to make the case.

Looking back at the original post for this thread sphingers writes,

"By the way the home will be in Central Florida....HOT."

Better derate that R23 to ~R20-R20.5 for him, since the average temp through the ICF will be north of 85F during the cooling season, not the R4.15- R4.2/inch it would be rated for an 70F or 75F average temp through the material.

An ICF that fat has no economic or comfort advantage in his location- shopping around for a cheap R16 (yes, they still make 'em) would be about right as an ICF solution, or going poured concrete with 2-3" of rigid exterior EPS if the quotes are cheaper and the contractor has proven methods using that approach. (Furring through-screwed to the concrete works fine for securing the foam, whether interior or exterior, it's easy to hang just about any kind of siding or wallboard on the furring. For FL hurricane resistance exterior furring may need to more substantial than 1x pine though.)

ICFs are great and all, but not always the best investment. Insulate the walls sure, but if other methods are cheaper spending the difference on a higher-R attic and/or better windows may be a better place to put his money. But when labor costs are high and with "time is money" factored in, the case for a minimalist ICF might still be made here.

Posted By Dana1 on 29 Jan 2013 02:13 PM

Calling it R23 steady-state just because there happens to be a 40F rating on the spec sheet is pure BS, since that's not the average temperature through the EPS most readers of this forum are going to experience.  Calling EPS R4.5/inch in an ICF for most of the US is as bogus as calling polyiso R6/inch in a cold-climate sheathing application. (In International Falls iso should be derated to ~R5.5/inch if it's only the exterior third of the insulation, if you want to estimate the real performance in the application.) 

Using R4.5/inch for EPS is reasonable in exterior sheathing applications when it is less than half the total R in climate zones 5 or 6, but not in ICFs.

Since you don't really HAVE to make stuff up or exaggerate to demonstrate the relatively good performance of ICFs, it's better to stop using irrelevant datapoints when trying to make the case.

When you correct the R-Values of wood frame and cellulose or fiberglass do you use such language as you do for the above? I am just at a loss why you call the manufacturers data specs "BS" but I don't see you using that same language/emotion when it comes to data specs from wood frame building systems? My observation is echoed by others.

I didn't make up anything or exaggerate anything. I simply copied the manufacturers energy specs and posted them on the forum. I didn't do the calcs, I didn't make them up.

I have YET to personally find a stick frame builder that will detail a wood frame home to the point where it is significantly air tight. You know that leaking wall structures derate the R-Value of the insulation. Reading the posts here shows that I am not alone in this issue. When forum users were building their homes, many of those forum users had to go back and fix the detail work of their contractors. This is a luxury that many don't have, as they have families and jobs that would not allow them the time to fix those details while their home is being built. The point of this is that with ICF, it is by nature air tight. Of course windows and doors have to be done correctly but that also applies to wood frame. When it comes to a wall assembly, stacking ICF and pouring 6" of concrete within the core produces a very tight wall assembly. Doing the same with wood is not as easy because it requires greater detail that most contractors will not go to the extent of. In addition, wood frame builds involve many different trades and all it takes is one of those trades to drop the ball and you have a poor wall assembly. Are there wood framed homes that are tight? Yes, of course but they are either owner/builder or they paid a hefty price tag to find a contractor that does tight stick frame builds.

So if you are going to be that critical of ICF then you should not be disingenuous and do the same for wood frame. If someone posts an R-Value of R-20 or whatever on a stick frame wall with cellulose or fiberglass, respond in the same fashion. Call it "pure BS" and factor in the thermal bridging of the studs, the lack of details of the framers, the insulation tech who didn't pack the wall as tight as he should with cellulose, the guy nailing the OSB who left a larger gap between sheets, the company that did the exterior house wrap, the fiberglass batt that was not put in correctly, etc. Then factor in the air leaking through the wall assembly and de-valuating the R-Value of the entire wall assembly.

How many ICF projects have you done? Do you recommend ICF of are you mainly stick frame?

Actually, I DO point out the performance differences of other insulation types & construction methods relative to as-installed or temperature variations quite regularly, including pointing out the difference between center-cavity vs. whole-wall R on stick frame (on nearly a daily basis on this website!)

If the manufacturer's spec has a pinky on the scale squeaking out a 5-10% difference between true performance in most real world installations it's worth pointing out rather than parroting it like as if it were gospel. The 40F spec for EPS is not a valid spec in an ICF for most people for the reasons stated, whereas it IS a reasonable spec in an exterior sheathing app in a cold climate, but definitely NOT in a hot climate.

ICF vendors who apply the 40F number to the whole assembly really ARE being disingenuous because over the ASTM C518 test range the wall would fall well short of that, and it doesn't take a building scientist to spot the error in reasoning. (If the average heating season temp of the concrete is 40F it's legit, but that will never be the case in US climate zones 1-6 or even for most of the population of Canada.)

I call it BS here because it's intentionally being disingenuous- the manufacturers DO KNOW BETTER, and some have a history of even more egregious performance claims (worthy of FTC intervention.)

I have similarly called the ASTM C518 ratings of low-density R23 and R19 batts BS (both here, and on other forums) because when installed in the very 2x6 cavities they are designed for, they are at a different thickness than their tested loft, and BY THE MANUFACTURERS OWN PUBLISHED DATA perform 5-10% lower than the ASTM rated value even at center-cavity. As with the EPS in an ICF, it's utter BS, because the labeled-marketed value is KNOWN not to be the as-installed performance for the majority of cases. They're only allowed to label an R23 batt as such because they're allowed to test at the manufactured (arbitrary) 6.25" loft, not the as-installed 5.5" nominal compressed thickness where it performs at about R20(!), according their own data.

But even though it's BS for center-cavity R, a change from R23 to R20 doesn't move the whole-wall number very much. A true R23 at center cavity in a 25% framing fraction results in an R13.8 wall, assuming wood siding and gypsum interior. A true R20 center cavity studwall comes in at R13.1. It's only about a 5% difference, (just like calling an ICF that really performs at R21-R22 in most installations an R23 wall :-) ), but it's BS just the same, and should be labeled more appropriately.

I've often point out that fiberglass batts above a certain density and cellulose both increase performance slightly as temperatures drop, particularly in wall assemblies, but only if they're installed nearly perfectly. I also regularly point out that low density fiberglass in horizontal assemblies without topside air barriers fall woefully short of their ASTM C518 rated performance when at the temperature extremes, whereas cellulose and high-density (1.8lbs/cubic-foot or better) fiberglass DOES hold up.

The tightness of cellulose has very little effect on it's center-cavity R value- in fact over 2.8lbs density it's R-performance begins to fall a bit. With the thermal bridging of the framing it takes a rather LARGE change in the center cavity R to move the whole-wall R up or down by even 5%. (As I point out to folks thinking about filling the cavity with closed cell foam, my motto is "I it's the thermal bridging, stupid- save the foam budget for the exterior!")

I've never done a whole house as ICF. I've recommended ICFs for whole houses, but more often for foundations, particularly in high labor-cost locations, or on time-critical projects.

I was personally involved in a deep energy retrofit on a 3 story balloon framed house with a full basement that came in at 464cfm/50 in the past year, a tightness <1ACH/50, and a tightness hit far more easily in new construction with 4x8 sheet sheathing than this plank-sheathed antique beast of a house. And there are performance builders who can hit that every time. Canadian R2000 builders hit it (nearly) every day, even thought the spec allows 1.5ACH/50.

Under IRC 2012 all homes would have to be under 3ACH/50, but that's been proven remarkably easy to hit, even with stick built.

It's pretty easy to make ICF homes that tight, but most aren't unless they're actually trying (or required to by local code.) It's not rocket science- it's goop science, and even ICF builders would need to get with a more rigorous air tightness program to hit under 1ACH/50 every time. Just because it's comparatively easier to make an ICF or SIP air tight doesn't mean they are inherently air-tight. Any time you think something is foolproof a more creative fool will prove you're wrong.

But even code-min 3ACH/50 tightness is a pretty reasonable number for an R20 whole-wall house from an energy use perspective, and spending a lot of money making it half-that or a third that may not always be the best investment.

Of course you can point out that tract housing production builders still build crap (and they do) but anybody spending the kind of money it takes to build an ICF house isn't in that market. And anybody looking for price/performance can usually find stick-framed builders that "get it", as well as ICF & SIP builders who regrettably, don't.

Posted By Dana1 on 30 Jan 2013 06:43 PM

It's pretty easy to make ICF homes that tight, but most aren't unless they're actually trying (or required to by local code.) It's not rocket science- it's goop science, and even ICF builders would need to get with a more rigorous air tightness program to hit under 1ACH/50 every time. Just because it's comparatively easier to make an ICF or SIP air tight doesn't mean they are inherently air-tight. Any time you think something is foolproof a more creative fool will prove you're wrong.

But even code-min 3ACH/50 tightness is a pretty reasonable number for an R20 whole-wall house from an energy use perspective, and spending a lot of money making it half-that or a third that may not always be the best investment.

Of course you can point out that tract housing production builders still build crap (and they do) but anybody spending the kind of money it takes to build an ICF house isn't in that market. And anybody looking for price/performance can usually find stick-framed builders that "get it", as well as ICF & SIP builders who regrettably, don't.

You are stating that "most" ICF homes "aren't" tight. Can you provide some data to show that?

When building stick frame homes, most contractors do not build tight homes. Finding a builder that will build a tight stick frame home is not easy and comes at a premium price. The other option is to pay a consultant to work on the project with the contractor and the consultant oversees the build and the different trades involved in order to get the home built correctly. So when it comes to price/performance, the numbers are not always clearly represented with stick frame builds. They don't include all the fees and surcharges for getting that home up to snuff.

Posted By Dana1 on 30 Jan 2013 06:43 PM

I've never done a whole house as ICF. I've recommended ICFs for whole houses, but more often for foundations, particularly in high labor-cost locations, or on time-critical projects.

Thank you for your honesty. I assume you have at least been INSIDE of an ICF home, am I correct?

Posted By Dana1 on 30 Jan 2013 06:43 PM
Actually, I DO point out the performance differences of other insulation types & construction methods relative to as-installed or temperature variations quite regularly, including pointing out the difference between center-cavity vs. whole-wall R on stick frame (on nearly a daily basis on this website!)

Can you find me a post where you come out and state, "pure BS" against stick frame R-Value claims? I don't remember you using that terminology except for ICF.

Posted By Dana1 on 30 Jan 2013 06:43 PM
But even though it's BS for center-cavity R, a change from R23 to R20 doesn't move the whole-wall number very much. A true R23 at center cavity in a 25% framing fraction results in an R13.8 wall, assuming wood siding and gypsum interior. A true R20 center cavity studwall comes in at R13.1. It's only about a 5% difference, (just like calling an ICF that really performs at R21-R22 in most installations an R23 wall :-) ), but it's BS just the same, and should be labeled more appropriately.

Let me understand this correctly. You stated above that because ICF claims R-23 when it's really R21-R22, it's on the same category as when wood frame claims of R20 is really R13.

My brother was in the manufactured home business for several years, leaving it about 8 years ago. Even back 10 to 15 years ago manufactured houses were being built good and tight. Walls are usually 6" packed w/ cellulose insulation. Every joint is caulked so air leakage into the house is extremely low. We were talking about house construction methods and he commented that the one thing the buyers of the newer and better built manufactured homes never complained about were their heating bills!

"You are stating that "most" ICF homes "aren't" tight. Can you provide some data to show that?"

I've previously posted an air tightness studies comparing homes in TX where in the ICFs sampled the ACH/50 average was in the 5-ish range:

http://eec.ucdavis.edu/ACEEE/2002/pdfs/panel01/04_289.pdf

Avoiding stupid-attacks like recess lights on the top floor probably would have made the difference, but that's pure speculation on my part, since the locations of the leakage wasn't detailed. The data are out there, but it's in drips & drabs. If you're in show-me mode, I invite you to show me an industry report that gives a different air tightness number over a reasonable sample indicating that the homes in the TX study were outliers.

BTW: A vendor of sheet EPS was selling it labeled at the 40F test numbers rather than the 75F ASTM C518 number it would be in violation of FTC regs. Because ICFs are not purely insulation they get away with using the 40F test numbers by putting in a spec rather than a label, but it's clearly intended to deceive. I'd hazard that nine out of ten BUILDERS & ARCHiTECTS who read that spec assume that it refers to a 40F outdoor temp rather than the average temp through the the material, and a much higher fraction of home buyers would too. Most people designing and simulating for specific performance goals in a particular climate/site would not make that assumption.

" I assume you have at least been INSIDE of an ICF home, am I correct?"

Yes, I have been inside an all-ICF home (more than one), and a portion of my own home is built with ICF. While the local ICF homes I've been in are better than code-min, they're NOTHING like the true high-performance deep energy retrofit I helped my friend with on his 3 story balloon framed house a few miles away. (~R40ish wholewall, ~R60-ish roof, U0.18-0.20 windows throughout, <1ACH/50.) But to assume that I'm down on ICF would be a mistake, even as I criticize the marketing sleight of hand. As stated previously in this thread there is no NEED to make these types of exaggerations, given the pretty good true performance of ICF.

"Can you find me a post where you come out and state, "pure BS" against stick frame R-Value claims?"

Search functions aren't very good on this site. I may have used the more legal term "fraud" rather than BS most recently, but I assure you I've used similar terms regarding ASTM C518 lableling on batt insulation. See response 17 & 28 on this thread (another forum). I've made similar comments on this website, some less polite than stated on that thread.

http://www.greenbuildingadvisor.com/community/forum/general-questions/25395/why-there-such-bias-against-fiberglass

Curiously and R21 high density batts perform at R21 in a 2x6 cavity, whereas an R22s & R23s only hit R19-R20. The low density R22s & R23s are cheaper than the R21s, but the labeled R is still higher, making them APPEAR like the better deal. Compare the R22s vs R21 performance in a 2x6 cavity in the Owens Corning compression chart:

http://www.owenscorning.com/literature/pdfs/10017857%20Building%20Insul%20Compressed%20R-Value%20Chart%20Tech%20Bulletin.pdf

Other manufacturers have similar charts, but not all are online.

How is that not utter BS or even fraud? It's in the minutae of the wording of the labeling regulations.

"Let me understand this correctly. You stated above that because ICF claims R-23 when it's really R21-R22, it's on the same category as when wood frame claims of R20 is really R13. "

Nobody in the code or building science biz has ever considered the center cavity R of a stick-framed house as equivalent to continuous insulation methods, and it's not fraud or BS to use the enter-cavity R at the installed loft to represent the R value of the insulation fraction of the wall. But the whole-wall performance requirement enshrined in code-minimums are pretty equivalent between cavity-insulated and continuous-insulated assemblies. (Eg: R20 cavity 2x6 is pretty equivalent to R13 2x4 + 5 continuous insulation, etc.)

Only ignorant or unsophisticated builders & architects would be confused by that, but it's probably a common misconception/lack of understanding amongst home-buyers of typical low-to-middlin' performance homes, less so for those looking for high performance.

An R20-ish wall is a pretty good wall- better than code even in climate zones 6-8. But it's not a particularly high performance wall in zones 5+. It's nearly impossible to get to Net Zero with anything under R30 even in zone 5, or under R40 in zone 6, with corresponding upgrades to other assemblies. The greenbuildingadvisor "pretty good house" concept for zone 6 is U0.20 /R5 windows, R10 sub-slab, R20 foundation wall, R40-whole-wall for above grade, and R60 roof/attic, and most of those COULD become net-zero with photovoltaic panel arrays that actually fit on the roof.

Wall-R is just part of the equation, but it's an important part, and it's pretty expensive and makes for a fairly thick wall to hit a true R40 with ICF. My friend's DER hit pretty close to R40 with cellulose cavity fill on a full-dimension low framing fraction 2x4 wall and 4.5" exterior polyiso at about 11" from paint to paint. An R40+ ICF would be well over a foot even without siding & interior gypsum, which is but one reason I shy away from them for high-performance homes in my climate zone. But in climate zones 3 & 4 ICF can be a pretty good option even for Net Zero designs. In climate zone 1 & 2 maybe, but there may be more cost-effective ways to get there.

The original poster wasn't looking for anything like Net Zero, but an R20-R22 ICF could get you there in a central FL climate, provided the rest of the design was up to snuff. The prescriptive code min under IRC 2012 for mass walls with at least half the R on the exterior for zone 2/central FL is a measly R4, and even the worlds cheapest R16 ICF is 400% of code. I wasn't kidding when I recommended seeing if 2-3" of exterior EPS was cheaper and spending the money elsewhere, since 3" of exterior EPS would already be 3x code min, and the bulk of the heat gain is from other factors like roofs & windows, with walls being a distant third. While ICF construction would be really nice there, it wouldn't be a performance driver, and if it's more expensive than poured concrete with R8-R12 exterior rigid EPS, upgrading to ICF is not necessarily going to be a value proposition for him.

Posted By Dana1 on 31 Jan 2013 11:57 AM
Yes, I have been inside an all-ICF home (more than one), and a portion of my own home is built with ICF. While the local ICF homes I've been in are better than code-min, they're NOTHING like the true high-performance deep energy retrofit I helped my friend with on his 3 story balloon framed house a few miles away. (~R40ish wholewall, ~R60-ish roof, U0.18-0.20 windows throughout, <1ACH/50.) But to assume that I'm down on ICF would be a mistake, even as I criticize the marketing sleight of hand. As stated previously in this thread there is no NEED to make these types of exaggerations, given the pretty good true performance of ICF.

As you said yourself, the law of diminishing returns. What are the true market costs to do such a retrofit and what is the ROI? It's a lot different when someone has to pay consultation fees, labor and construction costs vs. having a buddy do it for them.

You are also aware that ICF manufacturers have forms that have thicker exterior facing foam or they allow one to add foam panels to increase the R-Value up to R-40 for use in Zones 6 or higher.  We are comparing wall structures so roof values and window values are inconsequential.

Posted By Dana1 on 31 Jan 2013 11:57 AM
"You are stating that "most" ICF homes "aren't" tight. Can you provide some data to show that?"

I've previously posted an air tightness studies comparing homes in TX where in the ICFs sampled the ACH/50 average was in the 5-ish range:

http://eec.ucdavis.edu/ACEEE/2002/pdfs/panel01/04_289.pdf

Avoiding stupid-attacks like recess lights on the top floor probably would have made the difference, but that's pure speculation on my part, since the locations of the leakage wasn't detailed. The data are out there, but it's in drips & drabs. If you're in show-me mode, I invite you to show me an industry report that gives a different air tightness number over a reasonable sample indicating that the homes in the TX study were outliers.

According to the study you referenced, they did state the location of the air leakage:

"in one case the ICF home was tighter than the frame home while in the other the trend was reversed. This may be attributed to the fact that only the walls of the ICF homes were constructed differently from the frame structures, while the slab-on-grade foundation and wood-framed roof designs were similar. Construction details at the attic and at the junction of the first and second floors are critical to the airtightness of these homes, as is the amount of duct leakage."

So basically the roofs leaked like crazy and the details in the stick frame attic were atrocious as were the details in the floor junctions. This was noted in how the stick frame homes leaked air just as bad, as they were 5.0 & 5.1. They might as well should have left a window open or just left a gaping hole in the wall when they did the blower  door test. You picked out a very poorly done study and even so it showed that stick frame homes leak air just as bad when the roof details were poorly done. One did not need a study to tell us that. Even so, the ICF walls still performed better.

Your example study proved nothing other then a leaky roof will give you a leaky home and whether you build the walls out of wood or concrete, a leaky roof gives you a leaky home.

Posted By Dana1 on 31 Jan 2013 11:57 AM
  If you're in show-me mode, I invite you to show me an industry report that gives a different air tightness number over a reasonable sample indicating that the homes in the TX study were outliers.

ICF Blower Door Study

Study

There are plenty of studies that prove that ICF walls are much more air tight than stick frame walls. If you compare wall structure to wall structure, the answer is clear. If you take your example study which clearly admitted that the roof was very leaky, you get an unclear answer.

Posted By Dana1 on 31 Jan 2013 11:57 AM
Nobody in the code or building science biz has ever considered the center cavity R of a stick-framed house as equivalent to continuous insulation methods, and it's not fraud or BS to use the enter-cavity R at the installed loft to represent the R value of the insulation fraction of the wall.

That sounds contradicting to me. As Bill O'Reilly states, "I am a simple man" and what you stated above is a contradiction. In one instance nobody considers center cavity insulation R-Value of a stick frame home to be equivalent or representative of the true R wall value but then it's OK to use the center cavity R value to represent the insulation value of the wall, yet it's not a true number. So it's OK to give a false representation of a stick framed wall R value because everyone knows it's false.

Give it a rest Lbear or whoever you are. The MIT study was bought and paid for by the concrete industry. If memory serves, TexasICF averred in a post that he had nominated some of his finest work as candidates for the study.

For Texasicf, Brian and the other sales types here, people come here to OVERCOME sales pitches, to get a handle on the answer before they ask the question. If your goal is to turn them off on ICF you are doing a bang-up job.

Just because the Concrete Industry Sponsors the testing, does not mean they paid for positive results. I highly doubt MIT would risk their reputation for a couple bucks. It would make more sense to me that the Concrete Industry's faith in the product gave them the confindence to spend the money prior to the testing. In other words - they knew it would reflect well on them before the researchers even began the study.

It seems that anytime a study/test shows anything positive for ICF it is automatically viewed as "marketing hype" or "salesman BS." Has anyone considered the possibility that this is simply a way to build an energy efficient home that is inherently air tight and easy to heat/cool? I have seen some over-the-top claims from some manufacturers' websites, but that does not automatically mean everytime a claim about the efficiency of ICF is made that it is "bought and paid for" by the Concrete Industry/ICF manufacturer.

Lbear: Yes, I undestand that it's possible to hit R40+ with some ICF systems. But it's not usually the most cost effective way to achieve the thermal performance, and it's a pretty fat wall.

The financial aspects of high-R buildings is partly in reduced (or eliminated) mechanical equipment costs, and it's not 25 years to NPV+ if natural gas is the heating fuel, but it can be if heating oil is the only option. The Building Science folks took a stab at where the easier-to-analyze R-value limits are, broken down by climate zone, but with the caveat that local material/labor costs and local energy cost can skew their middle-of-road recommendations by quite a bit. IRC 2012 code min is still a 25 year payback in some locations, but sub-10 in others. The BSC middle-of-road takes a longer lifecycle view, and the recommendations can be found in Table 2, p10 of this document:

http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones

Note that in their table R40 wall R doesn't show up until zone 7, but in high-energy cost markets in zones 5 & 6 there can still be a rationale, especially when using a lowest-cost (="not ICF") approach.

The link labeled "ICF Blower Door Study" doesn't mention blower doors or offer any air tightness data. It does offer a big "ICFs are more efficent than current code min stick built" kind of shocker conclusions (as if anyone would be surprised by that?!)

The link labeled "Study" didn't give data on the sample of 15, the one example given hit 2.23ACH/50 (Congratulations, it even meets code!), and is about 3x as leaky by all measures including ACH/50 as by friend's DER on a balloon framed plank sheathed antique.

The text cited in the referenced TX study didn't really speak to the specifics, only hinted at it. It basically says that the builders didn't even try to make them air tight. (The duct leakage issue makes them perform even worse than a tight-ducted house.) So what if the stick built sub code crap in the same study performed no better or even slightly worse than the ICFs? I was never asserting that stick built was inherently tighter, only that the presumed air-tightness of ICF can't be presumed, and damned few were as tight as my friend's <1ACH/50 retrofit. In that particular small study NONE of them would meet IRC 2012 code for air tightness, yet 10s of thousands of stick built units out there do.

And the vast majority of the tens of thousands of R2000 homes built since 1980 are stick built, and tested <1.5ACH/50 as part of commissioning. (I'm not sure what fraction tested <1ACH/50, but it's not rare.)

But I'd bet that as a retrofit it would be easier to pull the ICF houses in that TX study into compliance. But that doesn't mean stick-builders with even hint of goop-science can't make an OSB or plywood sheathed building as air tight as any ICF without much expense- it's only a matter of training the crews to get them into the habit- the extra labor is negligible. Under 1.5ACH/50 is tougher, but in a building with mere R20 whole-walls it's a "who cares" kind of difference between 3ACH and 1.5ACH. (Air leakage issues become a bigger fraction of the total heat loss/gain at higher R values.)

Since you're still in show-me mode, show me the "plenty of studies" that demonstrate how much tighter ICF is than stick built, ones with real numbers, eh? (Really- I'd like to see something other than onsie-twosie studies or "representative examples" of a larger study!) So far you've shown me exactly one study with the numbers for exactly one house. (I at least dug up four, two crappy stick-built and two crappy ICFs. :-) ) C'mon, if they're plentiful, they should be easy to find!

While I firmly believe it's easier to make an ICF tight, experience shows that it's also not hard to make a stick built house air tight when code or builders/buyers demand it. Now that there's a 3ACH/50 hurdle to clear the former crummy tract building crews are having to come up to speed on that, and some ICF builders will need to step up too.

If you're using Bill O'Reilly as your authoritative source on ANYTHING I'm going to have to admit defeat and slink away!

It's not false to state what the center cavity R is, (even if the batt vendors play games with that for labeling purposes- use the compressed-batt data in lieu of label), nor is it false to use center-cavity R to characterize the thermal performance of a stick framed wall, which falls within a reasonably tight range over the typical range of framing fractions. A 2x6 fiber or open cell cavity filled wall is nearly always going to run between R13 and R15 for whole-wall R, (concentrated toward the R13 end in the real world) independent of stud spacing and other typical framing differences. It takes quite a large framing fraction to bump it to R12.

But it IS false to say that continuous insulation R is the same as center-cavity R, and I doubt anybody who has thought about it for more than 7 minutes wouldn't understand it. Running the U-factors on framing fraction for a 2-D model does NOT take hard math. Code drafting bodies and designers/architects have long understood the difference, even if it's still a bit fuzzy to simple guys like Bill. The cavity insulation can only insulate the fraction of the wall that it actually covers, it's not a hard concept. But it does reasonably represent performance at typical framing fractions. When the majority of the housing stock is being built that way, using center-cavity R is a reasonable shorthand for comparative purposes between other stick-built structures. I didn't invent it, and I'm not crazy about it (I'd prefer more precise whole-wall Rs), but I understand how it got to be that way. Hint: It wasn't a fraud or a finger on the scale perpetrated by fiber insulation manufacturers (even though they're far from immune to exaggerated claims.)

OK, invoking his holy highness O'Reilly was the last straw- I'm done here! :-)

But if you're able dig up the statsitical studies of ICF air tightness with real blower door test ranges & averages, DO start a new thread on that subject, eh?

TexasICF on June 12, 2011: (snip): I do appreciate your opinion and the link to the report from a few posts back.

I contributed 15 Texas houses to the recent MIT study. MIT reported ICF buildings to be 20% more efficient than conventional. I believe this 20% better number is low (at least for Texas). (anip)

http://greenbuildingtalk.com/Forums/tabid/53/aff/4/aft/78798/afv/topic/afpg/3/Default.aspx

BTW, the 20 percent figure compares ICF to code min stud walls (less R value) not clear if IRC06 or 09.

Why do these discussions devolve to personal attacks and conspiracy theories? Of which ToddM is at the forefront of these attacks. The term "internet bully" comes to mind.

By the way, my referencing Bill Oreilly had to do with his statement of , "I am a simple man" and it had nothing to do with him as an authoritative source. It's basically the premise that people complicate matters that are not that complicated, just to cause a diversion to avoid addressing the issue. I assume by your statement that you dislike the man but the fact is that he is one of the last hard hitting journalists out there and he doesn't drink the KoolAid of the right or the left. I now know what side you lean towards but that is another topic altogether.

Posted By BrianBaron on 29 Jan 2013 01:50 PM
...If you are still referring to old statement that was made about the "Effective R-Value of 50+" from the R-22 form... I agree that was a bit of BS, ...

It is not really BS if you look at how the information is used.  When looking at wood framed construction, almost everyone, at least until the last few years, referred to the wall's insulating value as whatever the R value was of the material stuffed in the cavity between the studs and plates.  If you had a 2x4 wall with R13 fiberglass batts between the studs, that was an "R13 wall".  In reality, when you factor in the higher thermal conductivity of the wood framing, the actually wall R value was approximately 9-10.  Similarly with a 2x6 wall @16" OC with R19 batts was an "R19 wall" when in reality it only comes in at around R14-15 accounting for the wood framing.  And most if not all of the heat load calculating programs of a few years ago just used the cavity insulation value as the input for the wall R value, i.e. "R13" was the value input for a 2x4 framed wall with R13 fiberglass batts.

Now lets assume we try to make a wood framed wall with comparable insulation value to an ICF wall rated R22 which is pretty close to actual due to virtual elimination of the thermal short circuits.  How much R value would you have to stuff in the wood framing cavities to equal R22 whole wall?  A lot more than you think.  Somewhere around R45.

As an example, say we build an imaginary 7" thick wood framed wall with studs @ 16" OC and fill it with closed cell spray foam at R6.5/inch.  The cavity R value would be 7" x R6.5/in = ~R45.  The whole wall R value for this assembly is ~R22 assuming R1.25 per inch for wood framing and a 25% framing fraction.  When calculating your heat losses, your HVAC contractor would input R45 for your heat loss calculation when in fact, the total wall R value is actually closer to the R22 of the ICF wall.

Arkie, I am the last person that is going to argue against the effectiveness of ICF vs Stick Built, or any other method for that matter. I was implying that in the sales process, most did not explain the details of that comparison to a customer. If explained correctly, it can be a good analogy... If you just tell someone that a R-22 ICF wall is the same as a R-50 stick built wall, then its a bit untrue.

Posted By BrianBaron on 01 Feb 2013 01:16 PM
Arkie, I am the last person that is going to argue against the effectiveness of ICF vs Stick Built, or any other method for that matter. I was implying that in the sales process, most did not explain the details of that comparison to a customer. If explained correctly, it can be a good analogy... If you just tell someone that a R-22 ICF wall is the same as a R-50 stick built wall, then its a bit untrue.

From purely an energy use point of view the better analogy would be to compare it to standard 2x6 stick built with 2" of exterior foam- bump that to 2.5" if EPS rather than iso or XPS.

To get to a rationale for calling it R50 would have so many caveats about where/when/how/what conditions that even my lawyer couldn't read it.

From a quietness in the wind and structural capacity point of view there's no comparison- ICF wins by several furlongs.

I was pushing the merits of ICF to my in-laws several years back when they built on the top of windswept hill with nice New England foliage views, but after the initial sticker shock on competing ICF quotes they opted for 2x6 + R7.5, spending the difference on radiant floors and nicer interior finish. I'm not sure if they regret it, but I often notice the sound of the wind when visiting their (VERY nice and quite comfortable) house- it's not a screamer, but I'm confident ICF would have been quieter. They've since had to adjust the venting on the wood-burning stoves  to avoid backdrafts from wind currents too.  It's better than code, but not what I'd call a high performance building for their cool edge of climate zone 5 location. (At current heating oil prices the financial rationale for going much higher performance is clearly there, but in 2005 who knew?)

There are two problems with this comparison. The first, which continues to this day, is its assumption that home buyers can't get the foam without the concrete. In fact, no one would spend a minute thinking about how to pack R-45 between the studs. They'd switch to foam sheathing even if they knew nothing about whole-wall R values vs stud bay r values, and in doing so, the ICF advantage would begin to disappear. This misdirection is particularly egregious here. No one who wants a code min stud wall winds up reading GBT.

The second problem is the comparison's use of a commercial buildiing code compliance model to develop thermal mass numbers which the authoring engineering firm itself acknowledged was not appropriate for this use, (although probably good enough to compare A with B.) Once again, we're back to the mystery of why DOE2, which was develoiped specifically for this purpose, is being studiously avoided by ICF industry. No, Brian, I'm not asking you to pony up ~$80k or so necessary to make a legitimate thermal mass claim. I am saying that if you are not willing to meet the FTC's requirements for a standard test, then shut up about thermal mass. And kudos to Dana1 for pointing out that the FTC polices labels as opposed to specification sheets.

ICFs don't NEED no steekin' ASTM C518 tested label, since it's not being marketed as strictly insulation product, but as a wall system.

SIPs don't either, and the under-rating of the thermal bridging of SIPs is also sometimes a marketing sleight of hand, but I've yet to see a SIP vendor use the 40F test value for EPS rather than the 75F number as seems all to common with ICF vendors. I've seen some pretty aggressive statements about the R-values of polyurethane core SIPs though, which appear to be using initial R rather than aged R, and ignoring all of the thermal bridging at the plates, window framing, etc. (Yeah, right this SIP performs at R7/inch, straight across... and all the knobs on my guitar amp go to 11 too , not the usual 10, see, 11, 11, 11, 11...)

EPS rigid sheet product and products like batts DO need that label, since it's being sold as insulation to be incorporated into assemblies, not a system, the theory being that it's then possible to do apples-to-apples performance comparisons. That theory kinda-works, but then kinda-doesn't sometimes, as in the tested vs installed loft of low density batts. But the performance of the assembly into which it gets installed is entirely up to the designer/installer. It doesn't take an idiot of Bill O'Reilly's creativity to figure out how cut the legs out from under the labeled performance in a real world assembly.

There are plenty of instances of people asking about spraying 5" of closed cell foam into 2x6 studwall cavites on this website, as foolish as that may sound. That 5" x R6= R30 really sounds great, but spending $5 per square foot just for the insulation portion on something that performs around R14-R15, not so much, when an inch of iso on the exterior of a cellulose or batt filled studwall delivers R19 or better.

"It's the thermal bridging, stupid!" has yet to sink into the public consciousness, but it's the mantra of performance builders modeling real designs everywhere.

The mass effect of ICF is real and models well with DOE2, but concrete is a fairly expensive thermal mass in $/MMBTU of buffering capacity, just as all-EPS insulation isn't exactly a $/performance leader for insulation. The real value proposition is in the structural capacity of building with concrete, but that's no always a choice-driver. Cheapskate high-mass low-energy home builders like Brian Carsten manage do do a lot with dumpster-dived-EPS scrap, stress-skins, and tons & tons of dirt- not exactly an approach that appeals to everyone ( including me), but you CAN get there from here at well under ICF cost. The mass effects of ICF is an overhyped value, value way behind structural aspects of building with concrete in my mind. (YMMV)

As a system it's a quick & reliable way to insulate a concrete wall (or foundation assembly) to a decent value. But if you don't need/want/value the structural aspects, it's an expensive way to build from strictly a price/thermal-performance point of view, and that's why I don't expect it to displace timber framed wall assembles in US homes any time soon. While can still be cost-competitive for insulating foundations in high-labor cost markets (including mine), even there many performance builders still use sheet goods or spray foam, even at R15-R20ish values. I personally prefer ICF to other foundation insulation methods, for the simplicity of aligning foam sheathing of a timber-frame with the exterior EPS of the ICF to get a continuous thermal break that's comparatively easy to air seal- following the "It's the thermal bridging, stupid" line of thinking. It's pretty easy to park an ~R25-R30 whole-wall 2x4 foam sheathed assembly cleanly on top of a minimal R16-R20 ICF with excellent thermal breaks and good air tightness, which comes in at about 2x code min in my area, and it doesn't break the budget. Again YMMV.

Posted By toddm on 01 Feb 2013 03:49 PM
Once again, we're back to the mystery of why DOE2, which was develoiped specifically for this purpose, is being studiously avoided by ICF industry.

Maybe because it doesn't work that well for ICF? I've never used DOE2, or even looked closely at it, so I'm really not sure how to interpret what the ORNL authors wrote in their mass study report. Here's a quote from the Introduction.

"Application of the newly developed equivalent wall theory enabled whole building dynamic energy analysis for complex three-dimensional wall material configurations. Normally, complex building envelope components cannot be accurately analyzed using one-dimensional computer models like DOE-2. Typically, thermal modelers have to use simplified one-dimensional descriptions of complex walls. This significantly reduces the computer modeling accuracy because of the complicated 2 and 3-dimensional heat transfer which can be observed in most wall assemblies.

In this work, response factors, heat capacity, and R-value were computed for complex walls using finite difference computer modeling. They enabled a calculation of the wall thermal structure factors and estimation of the simplified one-dimensional equivalent wall configuration. Thermal structure factors reflect the thermal mass heat storage characteristics of the wall assembly. The equivalent wall has a simple multilayer structure and the same thermal properties as the complex wall. The equivalent wall and complex wall dynamic thermal behaviors are identical. The thermal and physical properties describing the equivalent wall can be used, very simply, in whole building energy simulation programs with hourly time steps. These whole building simulation programs require simple one-dimensional descriptions of the building envelope components. In this work, DOE-2.1E was used to calculate heating and cooling loads for six U.S. climates."

What that says to me is the heat transfer characteristics of an ICF wall is more complicated than what DOE2 is designed to handle. They had to use a much more sophisticated program to develop an equivalent simple wall that would work in DOE2.

The report is here: http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/dyn_perf/

So now it's SIPs turn to get attacked by Dana.   I wish these forums would be moderated so that this type of nonsense wouldn't have to take place. People come here to learn and use different building methods but people like Dana and ToddM are just here to promote their egos, attack others and attack other building methods.

No wonder so many people leave this forum and never come back. Internet bullies abound...

In this forum you need to support your contentions with actual data based on a firm foundation of physical science. It's not enough to just Google and Noodle electron bites off the web. That's what I like about it.

dmaceld,

You are wasting your time. I've spent some time trying to explain this report and how some wishfully interpret it.  I doubt if some of these guys have even read it once.   At least one of em thinks that the Hot Box and DOE2 are are the same thing.  They use data like a drunk uses a lampost for support rather than illumination.  Regards to those that see the light.  

No wishful thinking on my side. As we have been over before (and over and over) the ICFA sponsored a side-by-side test in Knoxville in 2000 of ICFvs studwal housesl. Judging by ORNL's specific demurrer that the comparison found no evidence of a magic earth coupler in ICF walls, the test, in fact, represented wishful thinking by some parties. At any rate, the ICF house performed 7 percent better than the less well insulated stickbuilt in unoccupied tests. DOE2 had predicted 6.8 percent. http://www.greenbuildingtalk.com/Forums/tabid/53/aff/4/aft/79706/afv/topic/afpg/2/Default.aspx

Follow the link to read the apologiists' arguments that the test was the worst conceived and executed such comparison in the history of the planet. By extension, I guess, the ICFA in those years was run by the dumbest collection of trade group execs ever assembled on the planet.

I'm with Dana on this one, all systems have their warts including the new-old idea of offset stud walls with 12" of dense packed cellulose which I've written about before , but that is for a different thread. I started my business career in insulation and gravitated toward icf's. There are systems on the market now that allow for much greater wall insulation values and I think this will increase in the future.

According to the New York State Energy Research and Development Authority (NYSERDA), the cost to do a deep energy retrofit on an older single family home is about $110,000. The conducted a study on 4 wood framed buildings in Utica, NY. The homes were around 1,000 - 1,500 square feet. Even with that amount of cash outlay, they did not meet their goals. The buildings still leaked air at 2.0 - 5.0 ACH50, and even though overall energy use dropped by 60% - 65%, the actual electricity use went up. The payback on these $110,000 deep energy retrofits was shown to be around 140-150 years. Even then, that is a slight of hand number because it did NOT include the cost of GC/Consultation & engineer work which would easily have added 20%+ to the cost, so add at least another $20,000 to the cost. This then bumps the ROI to 175 years or more. Is that stick frame house even going to be standing 50-100 years from now?

Go read the September 2012 issue of Journal of Light Construction about how it cost $300,000 to do a deep-energy retrofit on a stick frame duplex in Massachusetts.

When prices are quoted for new stick frame builds that are high R, tight, and done by a professional energy wise contractor, they throw out numbers like $130 per sqft for construction costs. As they say, the devil is in the details. That price was for "construction costs" and does NOT include the GC charge & the consultation work. The real number is more in the realm of $160+ per square foot but of course that is a detail that is left out.

OK. So after all of this very intelligent spirited debate on many an Items that I am too pea brained to read, would you recommend ICF as a construction tool here in Central, FL? Any other "Big" items that you would use to make your home energy efficient?

Thanks

Posted By sphingers on 03 Feb 2013 10:43 PM
OK. So after all of this very intelligent spirited debate on many an Items that I am too pea brained to read, would you recommend ICF as a construction tool here in Central, FL? Any other "Big" items that you would use to make your home energy efficient?

Thanks

There are many ways to skin a cat. Since you are in a Zone 2 area, you don't need Zone 6 + R60 in your walls. In your area the biggest problems are going to be termites, hurricanes, tornadoes and rain/moisture. To which ICF addresses all those issues. When the hurricanes and severe thunderstorms roll through, your ICF home will be like a fortress. Of course your windows are always a weak link but you can install exterior storm shutters.

As far as what other items to address. What do you plan on doing for a roof? You might want to consider a Steel SIP roof or if you have the $$, an ICF/concrete roof. The latter option depends on design and budget but you can build a 100% concrete wall and roof home. The SIP option is also a very good option and less costly. I would go with a Steel SIP roof but OSB is doable as long as you detail it correctly.

Of course, you get the exact same qualities with a poured wall.... My advice is to go with the flow in your area. Your first contractor was telling you he doesn't you to be his ICF practice house. The next guy may be perfectly happy to make you his practice house, after which you will look back wistfully on the first guy's grasp of reality. The problem with most of the technologies on this site is something called the learning curve. There isn't enough call for them in many specific local markets for contractors to develop proficiency, and more importantly, to gin up the competition necessary to get an ICF house built as reliably and inexpensively as whatever mode of construction IS common and competitive. Florida may well be the exception. Visit your local building inspector. Ask him how much ICF he sees. Ask him for names of engineers who specialize in ICF. (Many are barred from making recommendations, so you may need an oblique approach. "If I looked at the plans of the best ICF buildings, what nameplates would I find?") Most of the engineers I've met have low tolerance for BS.

That said, focusing on walls is majoring in your minors. I'm guessing the most important factors in central florida are cool roofing, overhangs and/or orientation that keep the sun off the windows in summer, attic insulation and efficient hvac.

Yes, it's more complicated to model an ICF wall structure to high accuracy, but high-accuracy isn't really required to get within a few percent of measured performance for the whole house.

DOE2 modeling of mass effects good enough for characterizing ICFs at the macroscopic level, even if it's not very satisfying to the science nerds. The magnitude of the error is less than the inherent error of window & door U-factors in a particular house, and lower in magnitude than the inherent errors in site factors such as the thermal conductivity the soil when simulating the energy use of any real house & real site. Don't lose sight of the forest by the complexity of the patterns in the bark of the nearest tree- from a macroscopic point of view it really doesn't matter- the mass effect errors of a DOE2 simulation of ICF will NEVER be as far off as the errors in marketing-hype numbers even on simple things like steady-state R-values.

Accuracy implied by ever more sophisticated modeling is usually an illusion when looking at the bigger picture, but the bigger picture elements are still the same- the amount of mass in an ICF wall can't make R22 EPS perform like R40-lower-mass systems over any relevant time period, even if it might from a peak-load contribution from walls point of view under some narrow sets of circumstances.

Posted By Lbear on 02 Feb 2013 05:22 AM
So now it's SIPs turn to get attacked by Dana.   I wish these forums would be moderated so that this type of nonsense wouldn't have to take place. People come here to learn and use different building methods but people like Dana and ToddM are just here to promote their egos, attack others and attack other building methods.

No wonder so many people leave this forum and never come back. Internet bullies abound...

It's not SIPs that I take issue with- only marketing exaggerations used by some SIP manufacturers to imply higher performance than gets realized in the real world.

SIP vendors have rarely taken the flights of fancy of radiant barrier folks or some (and clearly not all) ICF vendors.

I've both recommended and used ICF- have yet to build with SIPs but I have no problem with using them and have recommended them. (Speed of assembly is a HUGE advantage with SIPs!)

If there's nonsense taking place it's using the 40F average temp R value for EPS for characterizing ICF rather than the 75F average temp number allowed for insulation vendors- sufficient nonsense that it needs to be called out, even if the effect on total house performance is pretty small.  I guess my BS-alarm is set to about 5%- call it a hair-trigger, but I can't find any legitimate reason for making that exaggeration in the case of ICF.  If they used that to characterize the exterior half of the EPS for the average winter-time only performance it would have some legitimacy, but that wouldn't be enough to get them to round up an R22 ICF to R23.

Fair enough- I'm here to promote toddm's ego, but can't tell if it's being reciprocated.

Dana and I have had disagreements but I have never doubted his knowledge or his good intentions. Dana's advice is a major plus for this site. I've benefited myself.
Speaking of which, I haven't seen Wes for a while but here is a shout out for counseling me to enlarge my downstairs bath and give it a second, public entry. Here is the result:




The pony wall covers plumbing stubbed up through the floor into what was supposed to be a wall between bath (small) and closet (tiny). The long suffering Mrs. M came up with idea of doing it in tile, plus the notion that what 5x12 room really really needed was a granite racing stripe.

Posted By toddm on 04 Feb 2013 02:00 PM
Dana and I have had disagreements but I have never doubted his knowledge or his good intentions. Dana's advice is a major plus for this site. I've benefited myself.
Speaking of which, I haven't seen Wes for a while but here is a shout out for counseling me to enlarge my downstairs bath and give it a second, public entry. Here is the result:




The pony wall covers plumbing stubbed up through the floor into what was supposed to be a wall between bath (small) and closet (tiny). The long suffering Mrs. M came up with idea of doing it in tile, plus the notion that what 5x12 room really really needed was a granite racing stripe.

Picture worth a thousand word. Explains why we don't use the Knoxville Report. Just like the fancy tissue dispenser it was not well researched so we tend to use the more practical approach of leaving the tissue on the counter ;-))

I have been examining many options for a small 2-storey, motel style project we're designing to build.

After countless hours of reading posts, gathering opinions from some very intelligent contributers, weighing the pro's and con's from stick built with ample PU spray foam insulation, to osb sips, mgo sips, etc... it seems to me that the overall performance levels achieved (big picture) by using ICF's is the way to go.

I agree there is no one perfect fit for all wall systems, but from all I have learned online, ICF's have me converted. Now for the fun part...pricing!

One of the unique advantages to using ICFs for Hotel/Motel projects is the acoustic properties. A 6" ICF wall willl have an STC rating of 57 or better and that makes for a very quiet building.

6" ICF with STC of 57? Most spec's I have seen list 6" ICF of 50-52. Feel free to correct me on that.

The local Fairfield Inn & Suites here in Russellville, AR was built using LiteForm ICF a few years ago.

https://plus.google.com/111261312952616603770/photos?hl=en

6" ICF with STC of 57?

You may be thinking about the naked wall. 6" ARXX walls were lab-tested at 55 STC. That is with sheetrock both sides. If you add some space on one side or another it can go up to the 70's.

Posted By ICFHybrid on 19 Mar 2013 11:10 AM

6" ICF with STC of 57?

You may be thinking about the naked wall. 6" ARXX walls were lab-tested at 55 STC. That is with sheetrock both sides. If you add some space on one side or another it can go up to the 70's.

Is that with standard 1/2" sheetrock?

Is that with standard 1/2" sheetrock?

The 55 STC is specifically with 5/8" on the source side, but only 1/2" on the receiver side.
Getting up to 71 STC required the addition of a " 2-1/2" non load bearing steel stud cavity".

Posted By ICFHybrid on 19 Mar 2013 03:04 PM

Is that with standard 1/2" sheetrock?

The 55 STC is specifically with 5/8" on the source side, but only 1/2" on the receiver side.
Getting up to 71 STC required the addition of a " 2-1/2" non load bearing steel stud cavity".

…which interestingly enough is TF System’s new TransForm vertical ICF product that is being used for the 72,000 SF Pensmore build.  Unfortunately, this new TransForm product is currently about twice the cost of their original ThermoForm vertical ICF product.

Well, I joined this forum today in hopes of narrowing down my decision on ICF or poured concrete walls (and if ICF, who recommends I/C/I vs C/I/C) for a basement. I didn't realize I would have to read through 3,394 posts that amount to a Richard measuring contest, but I can appreciate each person's passion on the topic.

Here is my situation: I live along the I-64 corridor between Richmond and Williamsburg. I have been inside homes with block basements as well as homes with poured concrete basements, both finished and unfinished. I was totally impressed with the poured concrete basements over blocked basements and always said if I built a new home, I would have a poured basement. That was before I stumbled on ICF during my research. Now, I am torn and undecided.

I wish to build a log home over a full 9'tall walk out basement. Initially, this will be unfinished to save cost (more later on that issue). My rationale is this: My wife and I want a smaller square foot home we can easily keep up as we get older, but we need extra space when our five kids (and future grand kids) visit. So the idea is to build a 2000-2500 sq ft log home over a full basement and the full basement would be the overflow area for sleeping rooms and large parties/dinners.

I understand the long range cost savings of the ICFs, however, the reality is that the basement will only be used periodically for entertaining and sleepovers, so if you ask me if I would rather put my construction cost towards more sq ft upstairs or better insulation in the basement, I'm going to say I want more sq ft in the log home. My understanding is that I have to fireproof (drywall) ICF for fire codes. What I don't know if drywall alone in a basement equates to taxed sq ft (I will find that out this week). I know there are a lot of factors to consider in order to give me a reasonable answer, so I will add that I plan to install a radiant floor heating in the basement slab and I will also have a fireplace/wood stove in the basement to heat the basement when we are using it for visits/events.

So my question is this: Throw out the future cost savings argument for now: For materials and labor in my area, how much more (%) will ICF plus drywall for 200 linear feet of basement cost me versus just going with a poured basement (that I really do not care if it is insulated and walled at this point). If the price difference is small, then yes, obviously I will pay a little more for ICF so long as it does not qualify my basement for taxed square footage and it doesn't decrease my sq ft I can build topside.

Also, is there a simple answer to this question (without going into logarithms, NASA statics calculations and 9 pages of Richard measuring): How thick of a poured concrete basement wall would I need to pour to get the equivalent energy savings (thermal mass) of ICF (thickness recommended in my area). In other words, would it be less expensive to simply pour a thicker poured wall than going ICF?

Lastly, what are the pros/cons of I/C/I vs C/I/C ICFs and are pests/rodents eating away the insulation really a problem?

Thanks for everyone's time.

In other words, would it be less expensive to simply pour a thicker poured wall than going ICF?

Not if you mean thicker concrete. But a poured wall with EPS foam either in the forms or attached to the outside of the wall may be.

Is there any truth to posts on the Internet that rodents eat the insulation (wherever the insulation is placed) and would that cause structural weakness at all if for instance the insulation between inner/outer concrete is gone and now has a void? It's on the Internet, so it must be true, :-)

We build ICF houses in Virginia and you are under the 2009 IECC so you have to have a certain amount of interior insulation on your basement wall to begin with, it would usually be R11 if you are building to "just" meet code compliance, so the point here is you will need some kind of insulation on your interior wall regardless of the composition of the basement wall. Another criteria is whether you will be "finishing" the basement area, if so then the ICF has an added benefit of being ready to receive drywall, along with complying with the code requirements.There are numerous other reasons to use ICF, none that i am going to go into, i assume you have already googled most of them. the point i would make is this, if you are trying to compare a strip form concrete basement wall or cmu wall to an ICF wall, then you have missed the whole point of using ICF and i would suggest you need more research on ICF, if however you are completely money driven then ICF is obviously not an option at all, it is without a doubt 2x the cost of a strip form wall and 1.5 cost of a CMU wall. I see this problem alot with clients in that they are trying to compare costs of ICF straight up with the cost of strip form walls in just the basement! it is analogous to comparing a formica countertop to a granite countertop and then standing back looking at the whole kitchen and trying to figure out whats wrong with this picture, in other words you can't do the comparison that way and if you do then you better be finishing the basement! otherwise it makes no sense and you should just build your wood house to "meet code". ICF construction by its nature is "Code+" construction and in my opinion the only way to capture the true benefits of ICF construction is to take it to the roof plates and spray foam the attic, its all about air-tight envelope, that makes the numbers work much better and usually we can get the pay back in 5 years or less, it is after all an investment decision as well.if you have plans we can do the cost analysis so you can see the comparisons between a traditional house and an ICF house.
Virginia also offers a property tax credit if the house exceeds 30% increase in energy performance from their baseline house, every ICF house we have built so far as exceeded that requirement, there are other incentives to build energy efficient as well, if youi go to the dsire website it explains those as well.
finally i have lived in 2 different ICf houses, i would never go back to a stripform or cmu foundation again, i am actually between ICF houses, sold my last one a bit sooner than i anticipate and i am living in a "traditional" stickframe concrete basement(albeit finished basement), the temperature difference is outrageous between the upstairs and downstairs, just incredible, i had forgotten the intangibles!

the bug thing not an issue if you cover the icf, the only time i have seen animals in the ICF is where it has been laying around(usually waiting to start a project), and yes rodents do understand the value of insulation! but in a finished house there is no weather exposed components or there isn't suppose to be, the rest is just normal termite and insect remediation you would normally do on any house.
hope that helps, let me know if you want the wood vs icf comparison done.
good luck and Happy New Year.

Well said, Bill. MGFarmVA, I sent you a private message with more info.

Bill - which ICF product do you use and what is the price of your ICF concrete mix, if I may ask?

MG -
When doing the comparison add the cost of the stud wall and insulation to the cost of the cast in place basement if you need it to meet code.

Find a few ICF installers in your neighbourhood and let them price the plans. ICF pricing can vary greatly from area to area.

No additional thickness of concrete will make up for insulated mass. If the mass is not within the insulated building envelope, it will be an energy loss. So if you want to go for mass and c.i.p. concrete, at the least you would have to put a number of inches of foam on the outside of the wall.

You will find lots of ici product to choose from but very few cic products. They are normally limited to precast panels or shotcrete. Both have a lot of thermal bypass due to the reinforcing.

While it is true that under some circumstances, rodents will tunnel through the foam. They do not "eat" it as it has no food value to them. The foam in an ICF has no structural value so the rodents cannot hurt the structure of the building.

Thoughts everyone - building central florida home, on a central florida sandy-soil hill. We are looking to do a steel bar reinforced basement under the home. We are interested in hurricane and tornado protection (did anyone see what the F3 did to Lady Lake and the Villages a few years back?....)

ICF or Poured Concrete???

Thanks in advance to anyone who has some thoughts they are willing to share on this topic!!

In terms of strength, ICF is poured concrete, it's just a matter of how you form it and insulate it. With non-ICF, you can attach rigid foam afterwards or you can drop rigid foam into the forms. Cost will be highly dependent on local quotes.

Engineers view ICF as a "poured in place" concrete wall. It's basically a solid poured concrete wall where the "forms" (EPS foam) stay in place and are not removed.

The R-value of concrete is about 0.1 per inch. The R-value of EPS is about 5 per inch. A typical ICF has about a total EPS thickness of about 5 inches or a total R-value of about 25. 25 divided by 0.1 is 250 inches (or about 21 feet) and is about the concrete thickness that you would need in order to have a similarly insulated wall. Somehow I think that thick a wall will cost more than the ICF wall…

So if the end goal is an insulated concrete wall, ICF makes good sense. If you just want an uninsulated concrete wall, a standard poured wall makes good sense. Either wall can be made as strong as you need. Like Lbear indicated, the only difference is that the forms remain in place (i.e., don't need to be subsequently removed) with the ICF wall and become the insulation, and the forms typically must be subsequently removed for the standard concrete wall (i.e., with perhaps some associated increased labor cost).

Posted By blacksunshine6973 on 31 Oct 2014 09:43 AM
Thoughts everyone - building central florida home, on a central florida sandy-soil hill. We are looking to do a steel bar reinforced basement under the home. We are interested in hurricane and tornado protection (did anyone see what the F3 did to Lady Lake and the Villages a few years back?....)

ICF or Poured Concrete???

Thanks in advance to anyone who has some thoughts they are willing to share on this topic!!

Given the deep soil temperature in central Florida is approximately 72F to 75F, you don't really need any insulation on your basement walls if the top of the walls are at or below grade level.  If you have a portion of your basement walls exposed above grade level, you could insulate just that portion with a couple inches thickness of borate treated EPS foam.  A poured concrete wall would likely save you some money since with the ICF wall you would be paying for a lot of insulation that you don't really need.

Thanks for all the replies on the insulation values. Any thoughts on settling with icf vs poured concrete? From what I understand, because the ground is heavy sandy clay soil and not rocky soil, homes tend to undergo a lot of settling, and you do see many homes up there with cracks, etc. I am wondering if one or the other is stronger against settling.

Blacksunshine, ICF is poured concrete. The only difference is that with ICFs, you don't remove the forms. Your concern should be with the footing design and reinforcement regardless of whether you use traditional removable forming system or a stay in place system like ICF.

Brucepolycrete, are there any seams in the concrete with icf or is it poured as one structure within the forms? Any thoughts on footing/foundation design and reinforcement?

Cracks occur because of differential settling (and other things), not settling. So besides making it stronger (rebar, thicker concrete, wider footings), you should also look at water management such that the footings stay evenly dry. For example, a sheet of sloped plastic just below the perimeter surface can divert water away from the foundation. Avoid irrigation and plants near the foundation. Think about water coming off the roof or running down the walls (wind driven rain)

If you are really concerned about it, you can use a frost protected shallow ribbed mat/raft slab that is post tensioned (no basement).

Posted By arkie6 on 31 Oct 2014 11:50 PM

Posted By blacksunshine6973 on 31 Oct 2014 09:43 AM

Given the deep soil temperature in central Florida is approximately 72F to 75F, you don't really need any insulation on your basement walls if the top of the walls are at or below grade level.  If you have a portion of your basement walls exposed above grade level, you could insulate just that portion with a couple inches thickness of borate treated EPS foam.  A poured concrete wall would likely save you some money since with the ICF wall you would be paying for a lot of insulation that you don't really need.

Arkie - I wonder if there would be some significant advantage in using ICF as it might prevent condensation during times when the basement walls would be the coolest surface in the house?

Having the minimum footing width given the soil properties and the type of building (i.e., the effective building weight/loading) is what mitigates settling. Your local building regulator will likely tell you what this minimum footing width and other associated design parameters must be. I would certainly expect that condensation would be an issue to consider and address in Florida.

The PM gives you the required footing size based on soil and what's being placed on top of it. Pour the footing and walls in one step and your saving time and money.

It is going to be much cheaper and conducive to having an unfinished basement to go with poured wall and attach Thermax foamboard insulation to the inside.

You will save the cost and inconvenience of finishing the basement when you may not be ready to finish the basement with respect to electrical and a drywall fire barrier.

Having the forms stripped will allow you to verify the pour and make sure the walls were properly vibrated.

Also keeps the cost of finishing the outer exposed ICF section out of the equation including the transition from exterior siding to a thicker surface underneath the siding. (you can undersize the foundation to accommodate some of the difference, most poured wall companies will probably give you the finger with that plan, and inspectors can differ on allowable overhang of a mudsill onto non structural foam). For example, say you are building a 10'x10' house with 2" foam on the outside foundation wall. 10' wide is framing, plus 1/2" sheathing plus siding of typically 3/4" means with a 10' wide foundation there will be 3/4" of foam sticking out past the bottom of your siding (2"-1/2"-3/4"=3/4") You could ask for a 9'8"x9'8" foundation to put the outside of the foam in the same plane as typical construction, however my inspector for example, will only allow the mudsill, which you need to be 10' for your 10' floor framing, to overhang off structural bearing (concrete) by half the thickness of the mudsill. So for a 9'8" foundation wall, I would need 3 plies of mudsill to get an ok on the 2" overhang. You could also ask for a 9'10 1/2" foundation wall to take advantage of your allowable overhang of 3/4" per side and at least have the foam flush with the bottom of the siding. Poured wall contractors can and will do this, but they are not exactly finish carpenters and you start to take 3/4" off every dimension in a typical not simple square house and it becomes ridiculous. So we simplified things and go with interior basement foam, and everything is reasonable.

Thermax is fire rated to be left exposed, put up whatever thickness of EPS foam board you want against the interior wall and clad over it with 1/2" of Thermax, you will want to do this because of the cost of Thermax.

Posted By FBBP on 01 Nov 2014 10:56 AM

Posted By arkie6 on 31 Oct 2014 11:50 PM

Posted By blacksunshine6973 on 31 Oct 2014 09:43 AM

Given the deep soil temperature in central Florida is approximately 72F to 75F, you don't really need any insulation on your basement walls if the top of the walls are at or below grade level.  If you have a portion of your basement walls exposed above grade level, you could insulate just that portion with a couple inches thickness of borate treated EPS foam.  A poured concrete wall would likely save you some money since with the ICF wall you would be paying for a lot of insulation that you don't really need.

Arkie - I wonder if there would be some significant advantage in using ICF as it might prevent condensation during times when the basement walls would be the coolest surface in the house?

Condensation occurs when the surface temperature is lower than the dew point of the air.  A wall temperature of 72F-75F is approximately the same temperature as the conditioned air temperature in most homes in the south, so no condensation will occur at that temperature unless the humidity level is approaching 100%.  Even if the indoor air temperature was allowed to rise to 80F, it would take a humidity level of over 77% to equal a dew point of 72F, which would be unlikely and infrequent in my opinion.

Posted By greentree on 02 Nov 2014 07:13 PM
It is going to be much cheaper and conducive to having an unfinished basement to go with poured wall and attach Thermax foamboard insulation to the inside.

If he was going to insulate the walls, it would cost much less to put the insulation on the outside of the poured wall.  Borate treated EPS could be used at ~1/4 the cost of Thermax.  Plus, foam insulation on the outside of the concrete wall would provide some protection for the waterproofing during backfill.

Arkie6, I disagree. Its true if your buying full 2" sheets of Thermax, not true if you're cladding over eps with 1/2" Thermax.
You have to pay to clad that exterior foam, and it becomes an ongoing maintenance item.

Posted By greentree on 03 Nov 2014 08:03 AM
Arkie6, I disagree. Its true if your buying full 2" sheets of Thermax, not true if you're cladding over eps with 1/2" Thermax.
You have to pay to clad that exterior foam, and it becomes an ongoing maintenance item.

My response was to address the basement proposed by blacksunshine6973.  Assuming this is a below grade basement, there would be no need to provide a clad on the exterior foam other than maybe the top foot or two above grade - for the below grade exterior foam just backfill and be done with it.  For any exposed exterior EPS foam above grade, just parge it with a low or no maintenance cementitious coating.

Cause this looks good..

Thanks all for the knowledge here! These are starting to get very technical and I am about to force my husband to start reading them! Another question we had was with the ICF - there must be gaps or seams between the foam blocks. Has anyone had issues with rodents, bugs or snakes getting into them?

There shouldn't be any sizable gaps in the ICF. If there are, concrete will ooze into the gap and fill it pretty much. On our build, there might be some gaps big enough for a few bugs, but they have nowhere to go; there's solid concrete in there. Also, the foam must be covered in some way, inside and out. On the inside, drywall is attached directly to the foam, so no gaps there. Outside, I put the siding over a drainage plane, with insect screening top and bottom. Below grade, the foam is protected by peel and stick membrane. Very, very few places for a bug to get in, and nothing big enough for a rodent or snake.