I'd imagine that a 12" SIP made with lower cost materials might have a lower insulating density, especially if it is one of the 'wood on both sides' ones. Since cost is an important factor and if I were building a new home it would be custom, I wouldn't mind a 12" thick wall as long as the interior dimensions are the size I want them to be. I'm not sure if Ecosteel's products are cost effective or not but if they are, that would be my choice.

Having a whole wall performance of R-14 with the air sealing benefits that are built into a solution like this would dramatically improve my R-11 batts in my 2x4 stick frame that I currently have. I'm more and more convinced by the day that if I move from my current house, it will need to be a new one. I'll also have to be sure that they don't install energy star windows on the Southern side of the house, in Minnesota the low-E glass needed to reach the standard raises the heating costs more than what the gain would be from reduced cooling costs, but I'll be sure it has excellent insulating value and would probably use window film during the summer and remove it in the fall to cover the low-E needs.

Another consideration for pre-fab is that the building codes need to be met where you live and sometimes it becomes a challenge when the building inspector comes. I used to work with someone who had a 4-section house built for him and trucked in from the west coast and the building inspector required multiple visits and written documentation from a local architect that the building was sound under our codes for weather conditions such as snow loading, foundation codes, and tornado/wind type stuff. Once his house was built it took about a month to go through the mess. If possible find a company local to where you are building as they will be most familiar with the building inspection requirements. I hear it is hard enough to deal with new construction issues as it is.

No kidding. Especially when you are trying to go so far beyond code. The building inspectors are often out of their element and, like many cops, revert to anger when they feel threatened by their ignorance.

The "2x6 construction" mentioned in the initial post does not necessarily indicate a more efficient house. If you run the numbers on a 2x6 wall with only cavity insulation and then compare it to a 2x4 wall with 1" of extruded foam on the exterior, you'll find that the 2x4 wall is more energy efficient (has a higher average R value).
Now, if you go to 2x6* construction but utilize advanced framing techniques to eliminate all but the structurally necessary framing and then wrap in foam then you have a very good wall. Not passive-house to be sure, but better than the average being built nowadays.
* 2x6s are needed for structure using this technique.

mk1st, good info. With using advanced framing and 2x6's, does that use 24" on center? My roof is supported by 24" on center 2x4's but the framing is 15". It looks a bit odd in the attic to see the top level knee wall at 15" and 24" back to back. R11 on a knee wall facing the attic seems like almost nothing to me. rest of the attic/ceiling is R25 cellulose for now, it'll need some extra insulation, though of tossing a 23" R19 fiberglass batt on top using that framing but then I'd only have the 2x4's holding it in so I'm not sure I'd get above R11 or not. Seems the framing in my attic to support the roof could have been done more efficiently.

Yes, advanced framing would use 24" O/C, but that's just the beginning. What it is is a technique to eliminate the unnecessary framing i.e. that which does not contribute to the strength of the structure. This includes things like lining up all the studs and rafters over one-another, no structural headers in non-load bearing walls and reducing the amount of framing around doors and windows. An engineered framing plan is needed but it's well worth the cost as you can remove up to 30% of the wood from a structure. When production builders get on board with this they can really save a bundle plus the house is more efficient. Obviously, the simpler the structure the easier this would be to implement but we're probably not talking McMansions here:eek:.

As for insulation, the environment it's installed into is as important as the amount. The cavities should be sealed, no air moving through them - especially if you use fiberglass. Cover any exposed knee wall cavities or vaulted ceiling end-walls with rigid foam board (tape & seal seams and edges!) Cellulose is IMO, the best choice for open attics as it "fits" well around obstacles and the joists/trusses themselves, plus it's pretty inexpensive. Round here (southern Wisconsin) we shoot for R50 which is approximately 18" or so.

Western Mass. Near-Zero Energy Homes...
 

I found this interesting video:

YouTube - Business: Home Green Home: Affordable Green Living - NYTimes


-AC_Hacker

Cool.
@1.22 are those bilco doors to the "basements". You don't see those used much on new houses.
I think it's a lack of imagination that prevents people from believing that we can offset a significant amount of our energy usage. Projects like these that include affordable options are a great step forward in helping to visualize the things that can be done.

The SunRise Home - Outsulation with Cellulose
 

You guys might find this build from Alaska quite interesting.

A Passivhaus Design for Alaska
The SunRise Home. | GreenBuildingAdvisor.com

It's a play off the REMOTE/PERSIST method of outboard insulation with foam. This case he built the internal walls as the structural walls, with the exterior sheathing acting as the air barrier, and wrapped the ceiling 2x4 service channel with sheathing as well to complete the airtight box. He then rolled the trusses onto the walkable ceiling plane, and built exterior truss type walls wrapped in WRB which were then filled with cellulose.

There's tons of comments/build specs in the comments... Definately worth a read for anyone interested in passive house / superinsulation, and new building techniques in general.

It seems that anytime a group of people have a “build it better” discussion, we very quickly get to the extremes. Let’s not forget the “Bang for the Buck” principle. Standard house construction is 2x4 studs 16oc some insulation, chip board and vinyl. A 2x6 wall with studs 24oc, insulated board, wrapped & vinyl is better. Two non touching 2x4 walls with studs 24oc is a cut above. Anything above that and I wonder about the “Bang for the Buck” principle.

Silver,

Not sure if you were replying to the post I just put up, but I wouldn't define what the CCHRC folks are working in Alaska as 'extremes'. They live in an extreme climate, and building a 2x4 wall is just ridiculous.

The two techniques I referenced are both configurable to your climate zone, with a house in alaska taking a good 12-16" of cellulose, whereas the same house in toronto could be brought down to say 8".

The important part of the the two techniques is in the method which they create a solid air barrier around the shell of the house. Both methods create a simple to detail complete air barrier, that is protected from the thermal swings, which should mean for a much longer laster building.

Find me a detail for a double stud wall that allows you to draw a line around the entire shell without any zigzagging... It's a difficult problem.

Most of the people building these 'extreme' houses, are doing so based on cost calculations, while also anticipating higher fuel prices in the coming years. To be honest, some people just prefer to spend money on saving energy and comfort, than on something like a granite countertop. Funny how no one ever brings up the ROI on things like that.