The blower door’s best buddy is an IR (infrared) camera. That’s because an IR camera sees the cool (or hot, depending on the season) tendrils of air being pulled in by the blower door.
Case in point is this photo. What you see mounted on the ceiling is a combined light and exhaust fan. The fan ought to have a damper installed that would block the bulk of the air back-drafting from outside. But the rays of yellow emanating around this fixture tell us that the damper either was never installed or is stuck open. Hot air from outside is being pulled in by the depressurization of the home and the IR camera is seeing that.
In other words, under normal conditions, that exhaust duct is just an open hole through which your heated or cooled air is escaping. No auditor will find every single source of air leaks but you hope they will find most of them. This is one that, without the help of the IR camera, could easily have been missed.
Did I mention that an energy assessment of your home by the Green Detective will always use this powerful combination of blower door and IR camera?
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