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Closing it up

December 28, 2008

One of the most important elements of a successful super-insulated house is closing up all the air gaps.  Even small holes can transfer heat out of a warm building at such a rate that it can render the official R-Value of the wall assembly irrelevant.  So, for this building, once the wall panels (R-41) and the roof panels (also R-41) are attached, and the windows installed (R-6 to R-8, depending on glazing and operability), the next step is to close up all the gaps between wall panels and the foundation, wall panels and other wall panels in the corners, wall panels and the window assemblies, and between the wall panels and the roof panels.

We knew from early on that the weakness of the insulated steel panel system was going to be the joints, and we have been relying on guidance from a super-insulated  house expert and foam guru, Henri Fennell from Building Envelope Solutions Inc ( who specializes in spray foam solutions to the kinds of problems we anticipate.

The spray foam seals the joint

The spray foam seals the joint

One of the tricks is that for the two chemical foam to work properly, the foam itself needs to be warm, and we have passed the time of year when warmth can be counted on.  But it turns out that if we keep the foam kit warm in the cab of the pickup truck, we can use it even when the house itself isn’t warm.  We did discover,  however, that the expanding closed cell foam can get out of hand when it is windy.

Foam expands and it's hard to clean

Foam expands and it's hard to clean

We needed little cans for the small cracks, like between the window frame and the “buck” into which the windows fit, and big foam for the large gaps.  We buy the kits from Energy Federation Incorporated, which has an office reasonably nearby, in Worcester Mass.  (

Dave foams corner from lift

Dave foams corner from lift

Some of the foam is best applied from the inside, but other spots can only be reached from the articulating forklift platform.  When its done, it looks like big yellow fungus is growing out of the building’s cracks.

Next Tuesday, we will be getting a smoke test to find out where the missing foam needs to go.  Conservation Services Group (, (whose offices are right next door to Energy Federation) will be sending over a team with a blower door fan and a fog machine and we’ll fill the house with smoke, then pressurize the interior, and walk around looking for smoke pouring out of the gaps we missed the first time around.  We’ll have to perform a real blower door test again once the house is more complete, but this time we will focus on the gaps that we won’t easily be able to fill after the building trim is installed.  This should be great fun.

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