Pass the blower door test the first time

If you haven’t been through a blower door test yet, chances are you will soon. As Pitkin County, Aspen, Basalt and Carbondale gear up to adopt the latest round of building and energy efficiency codes. The 2015 IECC (International Energy Conservation Code) have houses going for a maximum of 3 ACH50 (Air Changes per Hour at -50 Pascal) and commercial buildings going for a maximum of .40 CFM/square foot of envelope area at -75 Pascal. Most builders I work with could get to 7 ACH50 without doing anything extra. Getting to 3 ACH50 will take some extra care. If you are unfamiliar with the techniques of air sealing, then read up or get an expert on the team. A great place to start reading is the ENERGY STAR Thermal Bypass Checklist . Awesome document- do this stuff and you will pass the blower door test the first time.

Test day

I’m often asked, “what do I need to have done before we test?” Completely done, done, done is ideal; but in reality…  below is my checklist of this that should be done before testing so test results are not significantly degraded:

  1. doors and windows installed
  2. door and window hardware and weatherstripping installed
  3. door thresholds installed
  4. hatches to unconditioned attics and crawlspaces installed and gasketed
  5. dampers in place
  6. fireplace doors installed
  7. plumbing traps filled
  8. conduits leading outside sealed
  9. air handlers and ductwork complete
  10. light fixtures installed
  11. plate covers installed
  12. any other gap, crack or hole between inside and outside that you can find

Setting up the Building

When we test a building for air infiltration the building must be setup in a prescribed fashion. The IECC has it’s section (2009 IECC R402.4.2.1 or 2009 IRC N1102.4.2.1)  that describes how to setup a house. RESNET has their official protocol as well, the document ANSI/RESNET/ICC 380-2016.

  1. Exterior windows and doors, fireplace and stove doors shall be closed, but not sealed with tape;
  2. Dampers shall be closed, but not sealed; including exhaust, intake, makeup air, back draft, and flue dampers;
  3. Interior doors shall be open;
  4. Exterior openings for continuous ventilation systems and heat recovery ventilators shall be closed and sealed;
  5. Heating and cooling system(s) shall be turned off;
  6. HVAC supply and return registers shall not be sealed.

Running the test

I usually takes me 20-30 minutes to set up the blower door equipment and check that the house is prepared. I need an exterior door that is not too small or too big to set up in, power nearby and a space to work in. If the house is more than 5000 square feet or so, I will set up double fan equipment.  Then I will need to shut down the air handler and exhaust fans. At this point, anyone opening a door would void the test. But typically I only need the doors closed for five minutes to get an accurate reading. If it hasn’t been done yet, I will need the drawings to calculate the volume of air inside the house. Then do the math; flow (the results of the test) X 60 divided by the volume of the house = the number of air changes per hour. In the end, I create a certificate, that need to go to the building official.

If you want/need someone else’s eyes on the job, then give us a call. Confluence Architecture has a lot of experience with construction detailing, building testing, improving test results and also does HERS ratings, RESchecks, COMchecks, blower door tests, duct blast tests, IR camera inspections, etc.