Blower Door Test

We are finally done with construction and we’re proud of the fact that we’ve been able to transform an old Model T showroom into a net-zero energy building. Or is it? We haven’t really proven anything yet until the energy usage numbers come in. All of our energy modeling testing shows that our building is so efficient and tight that our estimate to heat it is $300 per year. But the proof is in the numbers that will follow.

One group who will be following the building’s performance closely is the sustainability labs group. They call themselves the “truth window” into the Green Garage. They will be monitoring 3 areas: waste, water and the building comfort systems. Last week the labs group ran their first test: a blower door test. This is a test of a building’s envelope, determining the effectiveness of the seal. The process involves placing a fan in the doorway of a building, and turning it on to achieve a pressure differential between the inside and the outside. It puts a number on the amount of leakage coming from the building.

Last Thursday was the designated day for the test, and Laurie Catey, Chief Labs Scientist, showed up early to prep the building for the test, appropriately dressed for the occasion.


Because we tested the historic and annex sections of our building separately, we first had to tightly seal any openings between the two buildings. This took about an hour.


Once we were sealed up, Ken of Kenco Insulation Company set up the doorway fan in the annex.


While the fan was running, a number of tests took place. Laurie watched the numbers to see how many cfm (cubic feet per minute) of air was being exhausted from the building.


Ken took his thermal imaging tool around to see if he could detect leaks.


Mike McCarty went around with the smoke stick, looking for leaks at doorways and windows.


Much of the data still has to be analyzed, but early indicators are that the building is performing well. The recommended minimal ACH natural infltration is 0.35, according to ASHRAE standards, and we came in at 0.09 ACH natural infiltration, indicating that the building sealing has been very successful at preventing negative heat loss or heat gain on the building. The one area where there was some leakage was our garage door in the annex, and we bought the most well insulated door we could get.

Next month’s experiment involves the trash output of the building. We’ll be getting together on November 4th at 1:30, rubber gloves in hand, to weigh and take apart our trash. We’ll be charting the weight of our trash on a regular basis, and will determine how well we are reducing what is going out of the building. Ah, the glamorous life of the Green Garage Labs Scientists!

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