The Short Answer
A blower door test measures how leaky your house is. A powerful fan is sealed into an exterior doorway and pulls air out of the house, and gauges measure how much air rushes back in through every gap, crack and penetration. The result is a number, not a guess, and it is the first step of every home energy audit we do.
Want your own home tested? The blower door is part of our free energy audit, along with thermal imaging and a duct inspection.
How a Blower Door Test Works
The test equipment is simple: a frame and an airtight panel that fit into an exterior door, a calibrated fan mounted in the panel and a pressure gauge.
- Close up the house. Exterior doors and windows are closed and interior doors are opened, so the whole house is tested as one space.
- Run the fan. The fan pulls air out of the house and lowers the indoor air pressure.
- Measure the flow. Outside air pushes back in through every leak. The gauge reads how much air the fan has to move to hold the pressure difference steady, which is the house's total air leakage.
What the Number Means
Leakage is usually reported as ACH50: how many times per hour the full volume of air in the house is replaced while the fan holds it at 50 pascals of pressure. The lower the number, the tighter the house. Across the 1990s through 2010s homes we audit most often in North Texas, we typically measure 7 to 12 ACH50. A pressurized envelope test gives you a quantified leakage rate, so a fix can be measured against it.
What a Blower Door Test Finds
The fan tells you how much the house leaks. Finding where it leaks takes a second tool: while the house is under pressure, thermal imaging shows where outside air is moving in, including hidden problems behind drywall. The leaks we find most often in North Texas homes:
- Top plates. Often the single biggest air leak in the whole home, and the easiest to fix.
- Can lights. Older recessed lights that are not IC-rated can leak constantly into the attic.
- Chimney chases. Open chases are massive air bypasses we find on most older homes.
- Plumbing stacks, electrical boxes and attic hatches. Each one leaks a tiny amount. Together they leak a fortune.
How It Fits Into an Energy Audit
The blower door is one of four parts of our audit. Thermal imaging shows where heat moves, a duct inspection looks at HVAC losses, and an envelope walkthrough covers the attic, crawl space, walls, windows and doors. The audit is typically 2 to 3 hours on site, plus another day or two to compile your report.
You walk away with a documented picture of your home's energy losses and a prioritized list of fixes: what to do this year, next year, and what is not worth doing at all. Most of what a blower door finds is solved by air sealing, which we do before any attic insulation goes in.
Duct Leakage Is a Separate Test
A blower door tests the building. Ductwork gets its own test: for duct sealing we pressure-test the duct system first to measure how much it leaks, seal every joint, fitting and boot with mastic, then test again so you see the difference.
Book a Blower Door Test in North Texas
Complete Insulation is a family-owned insulation contractor based in Azle, serving Azle, Fort Worth, Weatherford, Springtown and the rest of North Texas. The audit is free when you are considering having us do follow-up work.
Blower Door Test FAQs
How Long Does a Blower Door Test Take?
The blower door is one part of the energy audit, which is typically 2 to 3 hours on site, plus another day or two to compile your report and recommendations.
Do I Need to Be Home for the Test?
Yes. We walk every room with you and need access to all systems. It is also the easiest way for us to explain what we find as we find it.
Is the Blower Door Test Free?
It is part of our energy audit, which is free when you are considering having Complete Insulation do follow-up work. For a report-only audit, we charge a flat fee. Ask us.