Blower door test and airtightness

Measuring the air leakage rate instead of guessing it.

A blower door is a calibrated fan that pressurises or depressurises the house and measures how much air it takes to hold a given pressure difference. The result is an air change rate at 50 pascals — ACH50 — and it is the single most useful number in the building.

It matters because air leakage is frequently the largest heat loss in an older Canadian house and it is invisible. Two houses with identical insulation can differ by a factor of three in what they cost to heat, entirely on airtightness. Without a measurement, any energy model is guessing at the biggest variable in it.

A blower door test is part of every EnerGuide evaluation we do, so if you are having an evaluation you are having one of these. As a standalone service it is used for new construction compliance — the BC Energy Step Code performance path and several provincial codes require a tested result — and for diagnosis, where we run the fan and go looking for where the air is actually moving.

The diagnostic version is worth the money on an old house. With the house under pressure and a thermal camera in hand, leaks that no one would have found in a year of looking turn up in twenty minutes.

For homeowners — the rest of it