What blower door test means
A blower door test uses a calibrated fan in a doorway to pressurize or depressurize a house and measure how leaky it is.
Also called air leakage test, ACH50.
Where it matters on a insulation job
New homes in many areas must pass one, and it is the best way to show what air sealing achieved. A before and after result on the invoice is proof the customer can keep.
What the model code says
- The energy code caps air leakage at 5.0 air changes per hour or 0.28 CFM per square foot of enclosure area, tested at a set pressure. (IRC 2021, Chapter 11)
Check which code edition your building department enforces for blower door test before you quote.
What it costs
The attic insulation cost guide has the typical job at $2,500 and the usual range at $1,700 to $3,250. The guide shows its sources and what moves the price. The insulation cost calculator prices a job line by line.
Work it out
- Free calculator: Insulation cost calculator
- Cost guide: Attic insulation cost
- Tools, templates and guides: Free insulation resources
Sources: 2021 International Residential Code, Chapter 11, Energy Efficiency (ICC). Checked October 9, 2026.