Confirmation of the value of ICF construction, which most of us already know.

www.builderonline.com/energy-effici...R110105002

Some comments to above regarding the report.   I provided 10-15 homes here in Texas for the MIT test.

Renangle said:

“Hasn't most that have experience in ICF builds found that once complete they are substantial more than 20% more energy efficient? Also, they would require a much smaller HVAC than a code compliant wood-framed building.”

 - yes, typical savings substantially exceed 20%.  It is my unproven hypothesis that the reason the result of the report is low is because they did not differentiate between homes with conventional attic (e.g. BAT) and a more modern sealed attic (e.g. semi-conditioned using foam).  When the detailed report comes out I may be proven wrong but I don’t think so since I’ve seen many of  the blower door tests (including many for ICF homes with conventional attics).   I did not provide a single home that did not have a modern attic.  In fact if someone wants ICF and they don’t want to do the attic properly I usually walk away.  Why?  They are almost guaranteed to be unhappy or at least less happy.  I call ICF with conventional roof / attic “a screen door on a submarine”.   The fact that these screen doors were also included in many homes knocked the data down substantially.

ICFHybrid said:

I think the interim report can be summarized as;

1. Concrete buildings are tight and save energy.
2. Saving energy over the lifespan of the building tends to offset the higher upfront carbon cost.
3. Particularly when you use 75 years as a lifespan.

Basically, I agree with you.   I would like to add however,  that even with (what to me is unrealistically low 20% savings), the carbon cost accounting is vastly in favor of the ICF in only the first few years. 

From the report:
“More than 90% of the life-cycle carbon emissions are due to the building’s operation phase, with construction and end-of-life disposal accounting for less than 10% of the total emissions.”

Thus it will only take a very few years for the ICF home to beat conventional.   I didn't bother to do the math but if you go out 75 years if the wood home is still standing it will have created a huge Carbon footprint a least a magnitude higher than the ICF home.   I may have to do that math but at 20% better every year it's a lot better.  

In summary from the report:

In an interview with BUILDER, Ochsendorf conceded that the higher construction costs which builders typically ascribe with energy efficiency continue to be “an honest-to-God barrier” to better building, especially when builders are hardly ever the operators of what they build, so their concerns about long-term post-construction energy efficiency often end at the closing.

Imagine that!

Regards,

Posted By ronmar on 05 Aug 2015 11:45 AM
Since you dredged this thread up TexasICF, can you elaborate on the makeup of your "more modern" sealed attic spaces? IE: A conventional attic space would be, from bottom to top: Drywall, vapor barrier, bottom chord, batt or blown-in, ventilated space, top chord and roof system. We are about to start construction and are planning a conventional attic. Just trying to get my brain around the makeup of a possibly better way

Thanks

Posted By FBBP on 05 Aug 2015 10:59 PM

You are absolutely correct that the thermal envelope is critical but why would you enlarge it? Even a low 4/12 pitch adds a few points to the envelope. Also you have that many more cubic feet of airspace to condition.
If foam is the answer, why not just spray the top of the drywall? Wiring, can lighting and all?

Posted By ronmar on 05 Aug 2015 07:18 PM
Risk from condensation of high humidity on the upper side over an air conditioned space? I could see that back east or south especially if there wasn't much insulation I am in the Pacific Northwest, no air conditioning here, only ventilation and heat in the winter months. My consideration of an air barrier was purely to aid in air leakage control to try and get a low leakage air infiltration number, and to keep inside moisture away from the winter cooler attic space. I don't think there is too much of a chance to get condensation on the top side here.

The OSB layer sounds interesting though, as there will be a buttload of insulation up there. how do you seal the seams? Being in a seismic zone, there is a large re-enforcement bracing requirement for the walls thru the roof structure(ratruns every 48") which will bear some of the insulation weight.

Perhaps I didn't express myself clearly initially. Can someone describe the makeup of a non habitable, non storage sealed attic constructed with conventional wood trusses? Or is there no such thing using conventional trusses?

Thanks