How a Blower Door Test Works — and Why It Matters
- Chase Boyer
- 5 days ago
- 1 min read
A blower door test is one of the most valuable diagnostic tools in home energy performance.
How It Works
A large fan is mounted in a doorway and depressurizes the home.
Air from outside is pulled in through leaks and gaps.
A calibrated gauge measures how much air enters — giving an ACH50 reading (air changes per hour at 50 Pascals).
What It Reveals
Hidden air leaks
Poor insulation areas
Attic bypasses
Duct leakage problems
Moisture and airflow patterns
Why It’s Important
Helps pinpoint comfort issues
Shows exactly where your home is losing energy
Confirms whether improvements are working
Allows you to compare before-and-after results
Removes guesswork from the process
Most insulation companies skip this step — but it’s the foundation of all building-science-based improvements.
