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.
How a blower door test works
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.
What the number actually means
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.
Why leakage drives your comfort and your bills
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:
- Rooms that never get comfortable. Leak-driven drafts and pressure imbalances leave some rooms hot, others cold, no matter where you set the thermostat.
- Higher power bills. The system runs longer to make up for air that's constantly escaping.
- Humidity that won't quit. Leaky homes pull in humid outside air all summer, so the house stays sticky even when it's cool.
- Premature wear. Equipment that runs more hours wears out sooner.
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.
Where the test fits in a whole-home energy audit
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.
Why Anderson owns six blower doors
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.
