How Past Experience Can Get In The Way


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The systems inside of homes can be interesting, difficult, and often frustrating. When it comes to figuring out what’s really going on among these systems, we often head down blind alleys or make wrong turns because of preconceived notions, established thoughts, and past experiences.

Six years ago, when we first started conducting ratings on new homes constructed for enlisted personnel at Ft. Drum in northern New York state, we experienced the frustration that comes from preconceived ideas.

At the time, multiple phases of housing construction were active, and one phase in particular proved to be quite challenging. Different companies (framing, insulation, and air sealing) were performing the work on these homes, and we hadn’t really had an opportunity to train them on what they would need to do in order to ensure these homes would pass EPA Energy Star v2.0 testing. Specifically we were concerned with infiltration testing, which ensures the home meets or exceeds Energy Star’s requirements. We had had challenges in several of the other phases, but had made significant progress in getting the necessary subcontractors trained and performing their work in such a manner that homes would consistently pass testing without requiring any remediation.

We conducted our usual series of thermal bypass inspections, checking for proper installation of insulation, air sealing materials, and thermal/air barrier alignment. We encouraged, cajoled, and once and awhile chastened the various subcontractors as this new phase moved forward. We thought we had things under control. And then …

We started testing the homes, and first one, and then another, and another, wouldn’t pass the blower door testing. Our field staff spent hours, days, and eventually weeks diagnosing and testing, trying to figure out what was causing the test failures.

We sealed exterior outlet boxes (because they were drafty). We caulked walls to sill plates (concerned perhaps that the sill seal had failed). We hunted and searched, and yet after each improvement effort, nothing would change.

Then finally one day we tried something outside of the box. These homes were constructed slab-on-grade with an eighteen inch interstitial space between the first and second floors. We went to the second floor and removed one of the floor registers and dropped a floor boot into the space. Air rushed at us like a small hurricane. We certainly weren’t expecting that to happen. So we started our search anew.

We placed flashlights into the interstitial space and then using hand held mirrors started looking around for obvious holes. We didn’t see anything, so we decided to pull back some carpeting and cut some more holes into the floor so we could get a better look. This is when we found it.

The second floor of these homes was connected to a roof line for a breakfast/dining area that extended out from the side of the house. What we found was a six-inch high, 12-foot long opening where the gable end of the roof was connected to the band joist of the house…viola, a six-square-foot hole in our home.

Once we sealed this hole with 1” rigid insulation and spray foam, the home passed the blower door test with flying colors.

It was a valuable lesson for us. By the time we did our thermal bypass inspections, this particular opening was invisible to us. It was covered with insulation installed on the band joist (once again proving fiberglass insulation makes a great filter but doesn’t stop airflow). After discovering this opening, we inspected the homes pre-insulation installation, looking for any openings or bypasses that we felt would require solid blocking material and foam to prevent air movement.

The most valuable lesson we learned was not to get trapped by our own ideas. We spent weeks assuming the problem was caused by the typical exterior penetration issues we had seen in other buildings.  We would have saved significant time and energy if we had performed zonal diagnostics to guide us in our efforts to determine where the big hole(s) were located.

When in doubt, do the testing and let it guide you in your efforts to find the problems and develop solutions.

Ellis Guiles

Posted In: Building Performance, Residential Buildings

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