easyrider470
Basic Member
Posts:112
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| 17 Jul 2014 12:48 PM |
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Alright, the time has come to copmplete my airsealing in the walls and penetrations and decide on final stud cavity insulation. Need some help, I have already used a ton of help from Dana and Bob Irving through this project and am very thankful. Here is the skinny:
located in 47460 right on the line of climate zone 4 and 5 (for my area)
2 story home over walk out basement
9 ft ceilings on all three levels
2x6 exterior walls
1.5" (recycled) Fiberglass Faced Poly Iso foam on the exterior of the sheathing
1x4 furring strips for vinyl siding
OPTION 1....
18-20 INCHES OF CELLULOSE IN ATTIC
ENDS OF ROOF TRUSSES WHERE BAFFLE IS INSTALLED, SEALED WITH OPEN CELL FOAM 20 INCHES HIGH 8 INCHES DEEP
PICTURE FRAME STUD VOIDS AND DOUBLED TOP PLATES AND ALL WOOD TO WOOD CONTACT WITH ECO SEAL SPRAY
INSULATE WITH BLOWN CELLULOSE
OPTION 2....
18-20 INCHES OF CELLULOSE IN ATTIC
ENDS OF ROOF TRUSSES WHERE BAFFLE IS INSTALLED, SEALED WITH OPEN CELL FOAM 20 INCHES HIGH 8 INCHES DEEP
4 INCHES OF OPEN CELL FOAM IN STUD VOIDS
OPTION 3....
18-20 INCHES OF CELLULOSE IN ATTIC
ENDS OF ROOF TRUSSES WHERE BAFFLE IS INSTALLED, SEALED WITH OPEN CELL FOAM 20 INCHES HIGH 8 INCHES DEEP
PICTURE FRAME STUD VOIDS and double wood to wood plates WITH ECO SEAL
R-21 BATTS
Which option with all the calculations for the framing will yeild the best performance? I plan to do the eco seal myself so it's MUCH cheaper than the foam, I am also aware of the affordability of the Batts over the foam. I am concerned about the cost per r-value per inch mostly of the foam. I am also wondering how to insulate the knee walls in the bonus room over my garage
Thanks. |
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arkie6
Veteran Member
Posts:1453
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| 17 Jul 2014 02:20 PM |
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What are you using to support that 18-20 inches of cellulose in your attic?
I don't understand the rational for using open cell foam at the ends of the trusses. What does "20 inches high 8 inches deep" mean? Are you using raised heel or energy trusses to get the full depth of insulation over the wall top plates? If so, why not just extend the rigid exterior foam sheathing up to the bottom of your air battles? You can then seal the rigid foam to the air baffles with a few cans of spray foam if you desire; however, this isn't part of your air boundary - it would just be to keep the loose cellulose attic insulation from spilling out into your soffits and keep any exterior wind from disturbing the cellulose.
Option 1 for the stud cavities would give you the most R value for your $. Whole wall R value would be ~R15, not including the exterior rigid foam. Including this exterior rigid foam @ ~R6/in would increase the whole wall R value to ~R24.
Option 2 not recommended because you aren't filling the stud cavity with insulation which effectively reduces the R value of the studs to only ~R6 (4" deep x R1.25/in). Plus, 4" of open cell foam is only ~R14 @ R3.5/inch. Whole wall R value would only be ~R10 (not including the exterior rigid insulation). |
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easyrider470
Basic Member
Posts:112
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| 20 Jul 2014 12:32 PM |
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The idea in the truss ends is like you said, I have energy heel trusses, but they were not built to the 18" spec I ordered. The enginerr and I discussed my insulation depth and came up with the foam in the ends of the trusses. It will allow me to go 18" deep with the celluloae and not have wind and weather getting into the ends of the trusses and blowing it all away or back away from the top plates
Additionally it seals the top plates which i like.
So the original question was about which is better, I would love to hear some additional opinions....DANA? Bob?
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Eric Anderson
Basic Member
Posts:441
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| 20 Jul 2014 01:49 PM |
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Easyrider 470,
My Take on it
18-20 INCHES OF CELLULOSE IN ATTIC
Great- if you are sure the drywall can handle the weight
ENDS OF ROOF TRUSSES WHERE BAFFLE IS INSTALLED, SEALED WITH OPEN CELL FOAM 20 INCHES HIGH 8 INCHES DEEP
Generally this seems like a waste of spray foam. I would box it off with ½” ply level with the outside edge of the stud wall, then seal the gaps with foam or eco seal. This gives full depth of cellulose over the top plate. All you are really doing is creating a dam to hold in the cellulose and keeping it air tight. I f your really want it to not be a cold corner, run the poly iso you bought on the outside of the plywood dam.
PICTURE FRAME STUD VOIDS AND DOUBLED TOP PLATES AND ALL WOOD TO WOOD CONTACT WITH ECO SEAL SPRAY
perfect
INSULATE WITH BLOWN CELLULOSE
Works for me- I would be just as happy with wet spray cellulose , or dense pack behind a membrane in the walls. No reason to pay the price differential for open cell foam in the walls if you are willing to airseal it anyway. Caution, if you wet spray the cellulose, use a couple of large dehumidifiers and run the hell out of them afterwards. Ideally you would use a moisture meter with long probes to make sure it has dried out before the drywall is installed.
If you are going to sprayfoam anything, it should be the floor rim joist area. This is a weak area in many homes.
Cheers,
Eric
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| Think Energy CT, LLC Comprehensive Home Performance Energy Auditing |
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easyrider470
Basic Member
Posts:112
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| 21 Jul 2014 06:50 AM |
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Thanks Eric. I was pretty discouraged when I got the first bid from a local spray foam contractor. The foam is expensive, but they charge a TON of money for the airselaing as well. Plus they are using caulk in the wood to wood contact areas instead of a spray like eco seal.
I like the idea of using the wet sprayed cellulose, especially during this time of year when there resally isn't a major concern with the drying.
I am spray foaming the entire rim board in the basement, as well as the rim board of the upper level, I am also considering doing the outside corners to avoid any areas where the cellulose could fall or not fill up as well as the foam will.
" I would box it off with ½” ply level with the outside edge of the stud wall"
I am considering using the baffles that fold down and create this dam so the foam guy can spray and seal those to the top plate. The ONLY reason I am considering this is because the engineer that did the trusses laid it out and the company I purchased my lumber from is paying for it to be sprayed in foam. I guess I could do it with the baffle and save that money? |
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Bob I
Veteran Member
Posts:1435
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| 21 Jul 2014 07:54 PM |
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In general, foam is not worth the cost over cellulose. I would avoid fiberglass batts for everything except interior sound walls (between bedrooms, for exampl e). If you really want to do batts for DIY reasons, use Roxul. So my advice would be cellulose. Sounds like a good assembly. |
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| Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant |
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easyrider470
Basic Member
Posts:112
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| 21 Jul 2014 08:45 PM |
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Ok, so the eco seal in the wall plus the cellulose is the better insulation product.
I got a quote today from an insulator for the whole home with 4" thick foam in exterior walls, 2 inches at bottom of trusses in the attic, roof deck in bonus room over garage from top of knee wall to ridge vent, also the back side of knee walls in bonus room and the rim board al around the basement and the second floor, also the stick built walk out wall in the basement. In addition there is 12" of cellulose in the attic and in the bottom of the bonus room trusses....TOTAL 13,000 That price includes caulking all the doubled studs anywhere in the house and air sealing around windows and doors
The cost to do the cellulose in the walls with just the outside corners and rim boards with foam was 10,600. Trouble is, I would still have to do the eco seal to get those stud voids air tight.
Is it worth the extra 2400 to have the stud cavities air tight and done. He is saying the R-value is only 15.6 with the 4" foam but it's 20.6 with the cellulose.....that extra R-5 plus my R-9 rigid exterior foam is a big jump.....what are your thoughts??????
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Bob I
Veteran Member
Posts:1435
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| 22 Jul 2014 09:29 AM |
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this is open cell foam, not closed cell, so the R value is similar to cellulose and it is permeable so moisture passes through it, as it does with cellulose and fiberglass. There have been moisture issues - condensation - observed in roofs insulated with open cell foam, so it is definitely NOT recommended for roof application. It can can shrink, so there may be gaps that develop between the foam and framing members. It does not bond as well as open cell, so when your studs dry and shrink, as they will, they will shrink away from the foam and leave gaps. Cellulose, and blown fiberglass, are "loose" so they will conform to irregularities unlike either foam. |
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| Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant |
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arkie6
Veteran Member
Posts:1453
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| 22 Jul 2014 04:48 PM |
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Posted By easyrider470 on 21 Jul 2014 08:45 PM
....The cost to do the cellulose in the walls with just the outside corners and rim boards with foam was 10,600....
That seems pretty high to me unless you have a lot of area that will be foamed. Did they break out the cost for the foam separate from the cellulose? I've gotten quotes for wet sprayed cellulose in the walls @ ~R20 (5.5") for $0.75/sq ft of wall area. |
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Eric Anderson
Basic Member
Posts:441
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| 22 Jul 2014 05:48 PM |
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On the ceiling I see no need for foam if you are going to air seal. I think your first idea to do the airsealing yourself is the way to go. If I did commit to foam, it would be closed cell foam, not open cell. Same applies to the rim joist area.
Wet spray cellulose in walls should be quite a bit cheaper than foam- just due to cost of materials.
YMMV
Last time I bid out foam vs cellulose + airsealing, foam was around 60% higher
Cheers,
Eric |
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| Think Energy CT, LLC Comprehensive Home Performance Energy Auditing |
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easyrider470
Basic Member
Posts:112
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| 22 Jul 2014 08:19 PM |
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Not sure what area you are in Arkie but .75 is very affordable per sq ft pricing.
The closed cell in the rim joist and airsealing myself is an option, a much more affordable option over the foam. And the cellulose yields a higher r-value for less money so I am pretty much certain that is the way to go. |
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easyrider470
Basic Member
Posts:112
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| 22 Jul 2014 08:24 PM |
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I got a quote this evening for just the airsealing in the outside walls with caulk on all doubled studs and fire caulk in the outside walls, installing foam baffles in the attic and spray foam in the rim joist areas..quote was 1776.00 pretty cheap. I might have those guys do the top plates and just do the picture framing of the stud voids myself. |
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kogashuko
Basic Member
Posts:169
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| 23 Jul 2014 10:38 PM |
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The prices of foam are pretty frustrating. I got quotes that ranged from $1.25 or so a board foot up to two or three times that amount. There are cheaper DIY alternatives that are not for the faint of heart. If you ever want to know what I did and what I learned not to do let me know. I had a whole thread that I wrote about how I was doing mine and it disappeared. I have contacted a mod by PM and have not gotten a reply. So just hit me up by PM and I will tell you what I learned. |
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easyrider470
Basic Member
Posts:112
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| 24 Jul 2014 12:45 PM |
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I've been doing some thinking.....I have a TON of left over 3" XPS BLUE BOARD that I used to insulate the exterior of my basement foundation. If I used that in the rim board and sealied the edges with closed cell foam from a spray can I could save some money AND have a better air tight seal since the closed cell foam they want to use can crack over time with the shrinkage of the lumber. Any thoughts on this being a better method? Not faster obviously but it would be WAY WAY cheaper seeing as how I go the 3" foam for FREE. |
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arkie6
Veteran Member
Posts:1453
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| 24 Jul 2014 01:17 PM |
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Posted By easyrider470 on 24 Jul 2014 12:45 PM
I've been doing some thinking.....I have a TON of left over 3" XPS BLUE BOARD that I used to insulate the exterior of my basement foundation. If I used that in the rim board and sealied the edges with closed cell foam from a spray can I could save some money AND have a better air tight seal since the closed cell foam they want to use can crack over time with the shrinkage of the lumber. Any thoughts on this being a better method? Not faster obviously but it would be WAY WAY cheaper seeing as how I go the 3" foam for FREE.
Definitely the way to go if you want to save some $ and have the time to cut and install the foam. Get a good foam dispensing gun (~$45), some cleaner (~$6), and a case of the pro spray foam (~$107) and you will only be out ~$160 (see the "Frequently Bought Together" in link below) assuming 1 case of foam will do all you need to do. Cut the rigid foam so you have ~3/8"-1/2" gap around all sides to allow injection of the spray foam and give it room to expand and fill the void. http://www.amazon.com/Dow-Great-Stu...E1XGJKSN2E |
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easyrider470
Basic Member
Posts:112
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| 24 Jul 2014 02:35 PM |
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That's what I was thinking arkie6. The R-Value of the XPS in that area would not be as HIGH as the foam if I used closed cell spray foam. But I have also thought about doubling the XPS. I have 10" poured walls so I could easily double, possibly triple stack it in there and be better than the spray foam. If I get the cavity sealed well I'm at R-15 with one piece and R-30 with 2....if I could get three in there were talking R-45. |
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easyrider470
Basic Member
Posts:112
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| 24 Jul 2014 02:37 PM |
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trouble is....I am working with I-Joists.....so it will be tough to get them SUPER tight...I can just cut to fit inbetween the top and bottom cord of the I-=joist and spray foam the voids....doesn't the quality spray foam have the same R-valu per inch? |
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Eric Anderson
Basic Member
Posts:441
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| 24 Jul 2014 07:20 PM |
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Easyrider,
What you are talking about is what is called cut and coble insulation and is a fine, but time consuming way to go. Cut the foam so there is about 3/8” gap all around. Glue it in place with construction adhesive. When you are done, go back around with 1 part foam and foam them in completely. If the gap is too tight, you can't get a foam bead in there. You can fill in the rest of the space with roxul stonewool. At the same time run a bead along the sill- plate connection as this is often a leakage spot unless you used an epdm gasket under the sillplate.
Cheers,
eric |
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| Think Energy CT, LLC Comprehensive Home Performance Energy Auditing |
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Bob I
Veteran Member
Posts:1435
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| 25 Jul 2014 09:51 AM |
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Modular companies use foam blocks too, but they're mostly 2x stock. You could cut the foam into blocks & add 1" fillers of foam in the middle, or buy a small froth pak & zap each side pretty fast. |
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| Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant |
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easyrider470
Basic Member
Posts:112
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| 29 Jul 2014 06:36 AM |
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Ok, so correct me if I am wrong....closed cell is ideal for the rim board pockets simply because it is BETTER against moisture correct? I am concerned about the shrinkage issues people talk about. Is that something I really need to take into consideration? Will the foam actually crack and allow moisture and air to penetrate the area it was supposed to be keeping ait tight? |
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