The husband and I have just purchased a beautiful wooded lot in southeast MI. We will be building a 3000 sq ft 2-story home for our family. We are interested in building as energy efficiently and as green as possible, within the constraints of budget and not sticking out like a sore thumb to more affluent neighbors. We have chosen a floorplan from an online website that requires the least amount of modifications, and don't know where to go from here. We are interested in Passive Solar (we will have a south facing home, on a wooded lot-deciduous trees mainly). We will be using a family member as our builder, and paying for his training as required or assisting finding the proper crew for particular jobs. SIPs or ICF? Radiant heat? Geo? Design? Where do we start? I'd rather not reinvent the wheel here, and just pick up on the shoulders of those of you who've BTDT. Where is the best place to put the money? (the shell) And how do we do that? Thanks!

Yes - the shell is the best place to put your money - by a long shot. You can read through hundreds of multipage threads here for a bunch of different methods and opinions; most are workable if you understand the details that go along with them. Or, better, hire either a Passive House Designer (even if you don't want a Passive House) or PH Consultant, or someone with experience to draw your design with the appropriate details. (for example, www.deapgroup.com). Building an excellent shell is not necessarily expensive and it is do-able by most people, but it is complicated.

My specific advice is to build a double wall house with 10-12" dense pack cellulose insulation, R60 attic using raised heel trusses, triple glazed windows, well insulated foundation and slab, and make it very tight. Thats the least expensive way to get an excellent shell, at least in my opinion, but there are lots off details.

We would agree with Bob I, a good building envelope is likely the best investment. We prefer ICF because concrete can last forever and because we build in areas at high risk of wildfire. If you are interested passive solar and hydronic radiant floor heating, you may find the DIY software and instructions on our website to be worthwhile.

There are many options for an energy-efficient shell, and they can all work well if properly executed. Good, tight homes have been built using conventional methods as long as some added insulation is used, and it is properly detailed. One of the key details is sealing up the envelope. It has been found that air infiltration can be as important as insulation. A well-insulated envelope with lots of air leaks simply will not perform. Some methods, such as ICF or SIP's are inherently more air tight, again, provided they are properly done. There are literally thousands of places for air infiltration in a typical home- Joints in building materials, leaky doors and windows, penetrations from plumbing, wiring, and HVAC, ceiling light cans, even around door hardware.

The next issue is thermal transfer, which is where framed homes struggle. In conventional stick construction, thermal transfer through the studs can reduce insulation performance by 25% or more. External rigid foam does a good job of mitigating the problem.

We built ICF in our mild SC climate, but I'm not convinced that it will perform as well in a really cold climate. There is a concrete core inside the foam, and although I'm told that it doesn't function as thermal mass due to the interior insulation, the mass is still there, buffering heat trying to pass through the wall. In a cold climate, that concrete core could be pretty cold due to thermal transfer from the cold earth, possibly keeping that concrete core cooler than ideal from a heating perspective. I may be all wrong on this; it's just a hunch, and maybe some of the more knowledgeable members here will correct me on that.

There are many, many factors involved. Siting the house, and window exposures can make a big difference. In our southern climate, cooling is a big factor, and we were careful with the house orientation, and the size and exposure of our windows. Our same house would perform differently in an open field than it does in our deep woods, and it would certainly perform differently in Michigan.

Building a good, energy efficient house has rewards beyond low utility bills and the satisfaction that you aren't squandering resources. I'm 61 years old, and I've never lived in a fully insulated house before. The comfort is startling, to say the least. There are no cold spots or hot spots in the house. It's the exact same temperature throughout, and we generally only run one single-source heat pump.

After 24 years in a two storey, double wall R40, attic R60 passive solar stick built home we built a bungalow ICF home in Ottawa Canada, cold winter, hot humid summer climate. This was an infill so not passive solar in any way, heated with gas central heat and electric AC. A completely seperate HRV system.

I am MORE than pleased with the outcome it is the most comfortable home I have ever lived in, the temperature is uniform throughout the house and the walkout basement is not finished or furnished. Due to the open concept the whole house is heated and cooled, 3800 sq. feet. 9 foot ceiling both floors.

The interior of the home is completely isolated, foam under the basement floor which is isolated from the footings and all of the walls are foam covered from the ICF walls. The attic has 2 inches of foam installed before the cellulose was blown in to reach an R60 equivalent.

This ICF shell was built at a premium price to the regular build in the area, but well worth it! I am very, very satisfied!

The only thing I did not consider with the first custom build in 1987 was with the resale of the home. You will never recover the actual cost of rebuilding the home. I sold it to someone that had some knowledge of home building, he knew he was getting a good deal and I wasn't making any great financial benefit through my efforts in building the house or upkeep of it! It would cost more to build a home like it then what I sold it for.

Again I built a home that is what I wanted, not for any financal gain! I will not be able to sell it for what it cost to build in today's market maybe in ten years I will regain the cost but for now I will have a house that I wanted to live in!

John

SIPs and ICF are fairly expensive from a price/thermal-performance point of view. ICFs have a durability advantage over most other construction methods however.

A starting point on the long term cost-effectiveness of R-values/U-factors measured against energy cost savings can be found in Table 2 p.10 of this document:

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

Mind you, those are "whole assembly" R values with all thermal bridging factored in, not center-cavity stick-built R. (eg A 2x6 wall 16" on center with wood siding and R20 insulation is actually about R14 after factoring in the thermal bridging, but can be brought up to R20 performance by adding 1.5" of continuous rigid rock wool or EPS foam over the exterior of the sheathing, between the sheathing & siding.)

And of course, the methods & type of insulation have a huge impact on the cost, and thus cost-effectiveness. The recommended R30-ish whole-wall is more cost effective if done as say, 2x6 construction 24" o.c. with open cell foam or cellulose cavity fill (~R15 after thermal bridging), with 4" of EPS on the exterior is quite a bit cheaper than a ~9-10" thick EPS core SIP. The marketing fluff from SIP manufacturers will tell you it's R40 or something, but it isn't, since the thermal bridging of the internal structural elements are not factored into their numbers, and they often use unrealistic performance numbers for EPS, often based on an average temp through the foam of 40F or 25F (which would be fine if you lived in Fairbanks AK, but not SE MI, where the average temp through the foam averaged over a heating season is north of 45F.) Closed cell polyurethane construction or ICFs that meet that performance point is even more expensive, so the crossover point on financial reality occurs at a lower R-value.

For truly high performance homes such as Net Zero Energy or PassiveHouse double studwalls filled with cellulose are often the best bang/buck. Dense packed cellulose costs about 5-7 cents per R per square foot, which is cheaper than EPS, which is about 10 cents/R-ft or open cell polyurethane at ~13 cents/R-ft, or closed cell foam at 17-18 cents/R-ft. Dense packed fiberglass is more expensive but higher R/inch than cellulose, so you can get away with a ~15-20% thinner double studwall.

Energy costs will also be a large factor in the overall cost-effectiveness, and that varies quite a bit with energy source and HVAC efficiency. In SE MI type climates it's sometimes cheaper to go a bit better than the Table-2 recommendations on R/U-factors to be able to use highly efficient but cheap ductless air source heat pumps for heating & cooling. Plenty of issues to think about before embarking on that road, but it's do-able.

ANY new home construction should consider the roof line orientations and site shading factors for rooftop photovoltaic power. The price of rooftop PV has been crashing, but still has plenty more to go. By 2025 it will be the cheapest energy source of any type, but if you've locked yourself out of that by your roof shape, orientation, or site shading you won't be able to take advantage.

Modeling the energy use while tweaking the design and orientation can be done in a relatively straightforward manner using BeOpt (a freebie download, courtesy of the US taxpayers). It's accuracy is plenty good for planning & comparative-performance purposes, and what it may lack in absolute precision is more than made up in simplicity of use. (Occupant behavior is a bigger error factor in the actual energy use than the inherent error in the tool.)

https://beopt.nrel.gov/download

Whatever the construction type, get religion about air-sealing during the building process. While SIP & ICF construction is easier to air-seal, they are by no means guaranteed, despite inherent advantages. The more idiot-proof the system, the more creative the idiots become. There are plenty of SIP & ICF houses that do not meet even the fairly easy air tightness standards in the IRC 2012 building code (3 air exchanges per hour at 50 pascals pressure or "3ACH/50".) Hitting under 2ACH/50 is fairly easy even in stick-built construction if you're paying any attention at all to air sealing as it comes together. PassiveHouse specifies a somewhat tougher 0.6ACH/50, but even 1.5ACH/50 that isn't an energy disaster- the additional heat load of that much leakage is small relative to the rest of it, if building at ~R30 whole-wall type levels.