A blower door turns "your house feels drafty" into a real, measured number. Here's what that number means for your comfort and your power bill — and why we'd rather measure your home than guess at it.
Updated June 2026 • Written by the team at Anderson Heating, Air & Insulation, serving Calhoun since 1978 🐾
A blower door test measures exactly how leaky your home is — as a number, not a hunch. A calibrated fan seals into an exterior door and pulls air out of the house; the fan then reports how much air it takes to hold that pressure, which equals the total air leaking through every gap and crack in the building. The result (CFM50 or ACH50) tells you how hard your HVAC system has to fight outside air. The higher the number, the leakier the house — and the more you stand to gain from air sealing. It's the central measurement in a real energy audit, and Anderson owns six of them.
A blower door is a calibrated fan mounted in an adjustable panel that seals into one of your exterior doorways. We close the windows and exterior doors, open the interior doors, and run the fan to pull air out of the house — lowering the indoor air pressure relative to outside. To hold that lower pressure, outside air has to rush back in through every leak in the building shell. The fan measures precisely how much air it's moving to maintain the pressure, and that flow rate is your home's total leakage. No drilling, no damage — just an honest measurement that takes a routine visit.
The result usually comes back two ways. CFM50 is the cubic feet of air per minute leaking when the house is depressurized to 50 pascals — a raw leakage figure. ACH50 (air changes per hour at 50 pascals) takes that leakage and compares it to the volume of your home, so you can compare a small house to a large one fairly. A tight, well-built home has a low ACH50; an older, leaky home has a high one. The point isn't the jargon — it's that we now have a real baseline. We can re-test after sealing and prove the leakage dropped, instead of asking you to take our word for it.
Air leakage is invisible, so it's easy to underrate. But every cubic foot of conditioned air that leaks out is replaced by hot, humid summer air or cold winter air that your system then has to recondition from scratch. In a leaky home that's a big share of your HVAC's workload — which is why the symptoms are so familiar:
This is why we treat air sealing as a load-reduction step that comes before talking about bigger equipment. Sealing the leaks the blower door finds often does more for comfort than upsizing a system ever would.
The blower door is the heart of a real whole-home energy audit, but it doesn't work alone. We pair it with a duct blaster that measures how much air is leaking out of your duct system specifically, and we check insulation levels and how the HVAC equipment is sized. The blower door answers "how leaky is the shell?"; the duct test answers "how leaky are the ducts?"; together they tell us which fixes — air sealing and insulation, duct sealing, or equipment changes — will actually move the needle in your home.
Most HVAC companies in North GA don't own a blower door at all, and the ones that do usually share a single unit across the whole company. Anderson keeps six blower doors and six duct blasters so our crews can measure homes as a matter of routine — not as a rare special event. As a BPI-certified building-science company serving Gordon County since 1978, measuring before we prescribe is simply how we work. We'd rather show you the number than ask you to trust a guess.
We'll measure it with a blower door, show you the number, and tell you which fixes actually pay off.
Call (706) 629-0749It tells you exactly how leaky your home is, as a measured number. A calibrated fan in an exterior doorway pulls air out of the house, and reports how much air it takes to hold that pressure — which equals the air leaking through every gap and crack. The result (CFM50 or ACH50) shows how hard your HVAC has to fight outside air. The higher the number, the leakier the house.
Every bit of conditioned air that leaks out is replaced by outside air your system has to heat or cool all over again. In a leaky home that's a big share of the work your HVAC does — higher bills, rooms that never get comfortable, equipment that runs too long. Sealing the leaks a blower door finds is often the most cost-effective way to lower bills, because it cuts the load before you spend on bigger equipment.
The blower door is the central measurement in an energy audit, but a full audit adds more — a duct blaster test for duct leakage, an insulation inspection, and a check of the HVAC equipment and sizing. The blower door answers how much air is leaking through the building shell; the audit answers what to do about it.
Most North GA shops don't own one at all, and many that do share a single unit company-wide. Anderson keeps six blower doors and six duct blasters so our crews can measure homes routinely instead of guessing. As a BPI-certified building-science company serving Gordon County since 1978, measuring before we prescribe is how we work.