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Blower Door Test Update #2

A second blower door test was recently conducted on our current new home construction project. This test was done after completing the insulation installation to ensure that we had sealed the shell adequately. Our initial test result was 1.89 ACH/50 before air sealing and insulation completion. The second test result was 1.62ACH/50.

My first reaction was a disappointment, having utilized hundreds of dollars of spray foam and a bit of my time sealing every inside sheathing seam, panel edge, and penetration. This was in addition to the insulation contractor’s efforts which were substantial.

During the test, a smoke generator showed that the weak links in the airtightness of this structure are the double-hung windows, doors, and zero clearance fireplace flue and combustion air supply. Nothing can be done about the windows other than utilizing much more expensive euro windows and avoiding double-hung windows.

We have utilized Marvin windows which are very good. The doors should get better with the permanent hardware and corner pads installed, which will be done after we paint. There is nothing that can be done to seal the fireplace further.

A final blower test will be done after drywall installation, and the permanent door hardware and corner pads have been installed. My expectations are for some additional but modest improvement on the final test result.

As I think about things, I have made the following conclusions:

  • The ZIP sheathing with ZIP taped seams do a pretty good job at sealing the shell and probably do not require further air sealing on the interior side
  • The 1″ DOW foam that is applied to the exterior with seams taped helps airtightness as well
  • The Protecto Triple Guard sill seal is more effective than traditional sill seal products to seal the foundation wall/sill plate joint
  • The cost to upgrade windows and decided to forgo the fireplace in an attempt to achieve a test result of less than 1.0ACH/50 is probably something that many homeowners are not willing to do given the high added cost of the windows and lifestyle choice of having a fireplace
  • Our test result of 1.62ACH/50 (and maybe a bit better after our upcoming final test) represents a very well-air sealed home that will be very efficient to heat for its occupants.