Pre-Drywall Blower Door Test
With the Railhead rough-ins complete and the house fully insulated, we decided to proceed with a pre-drywall Blower Door Test. We’ve been eagerly anticipating the results for months. In fact, we started to speculate what results we’d see from the test when we first modeled the home earlier in the year. The results, measured in ACH (Air Change per Hour) did not disappoint – we achieved our minimum target of an EnerGuide 86 rated home, setting the Railhead apart as a high performance energy-efficient home.
Hot2000 software was used to model the Railhead, establishing the initial EnerGuide benchmark rating of 82. Through the optimization process, we adjusted several variables on the project to improve building performance and establish a target rating of EnerGuide 86. To lower our ACH, we had to optimize the building envelope as the Hot2000 software defaulted to an average ACH of 3.57. Based on our informal research, the average home in Alberta ranges between 3 – 3.5 ACH, while older homes can vary from 4 – 9 ACH. High efficiency homes are usually below 1.5 ACH. As required by our EnerGuide 86 target, the Railhead needed to be below 1.0 ACH.
So how does one determine ACH? By hiring a Certified Energy Advisor to perform a Blower Door Test. In conjunction with Eco-Synergy, Rob Gawreletz from Alberta Eco-Visors was hired for our test. A Blower Door Test consists of a calibrated fan used to de-pressurize the house so that it creates a 50 pascal pressure change between the inside and outside of the house. A device is also used to monitor the pressure created by the fan. The combination of the fan and device determine the building’s airtightness. The values established during the test were plugged back into the Hot2000 modeling file developed for the Railhead. Hot2000 then provided an accurate ACH for the Railhead.
Other than the end data it produced, one of the most beneficial pieces of the test was that it allowed us to go around the entire house and feel for air leakage at all connections; wall to wall, wall to roof, wall to window / door, wall to joist…were all surveyed for air leakage. With cans of foam in hand, suspect areas were quickly sealed. The data at the end of the test showed a marked improvement in airtightness, resulting in a final pre-drywall ACH of 0.74.
mike eliason
December 21, 2010 at 11:36 pm //
did you guys use any tapes or gaskets for airtightness as well? e.g. siga or 3M? and would you in the future? 0.74 is ridiculously tight for a non-passivhaus project. congrats.
admin
December 22, 2010 at 12:11 am //
Thanks Mike. We were pleasantly surprised with 0.74 ACH, pre-drywall…using fairly standard connections. No tape was used, however we took a few extra precautions. We ran a bead of PL over all seams at all interior & exterior joints and (interior) corners. During our BDT, we used a rudimentary method of running our fingers along every connection in the house checking for drafts, and then plugged any leaks with foam. The few tedious hours that it took will represent huge savings over time. The results at the beginning of the test and then after the foaming were dramatic. We’re looking forward to our final BDT in a few months. Very interesting blog BTW…looking forward to learning more about what you’re up to.