What air barrier means
An air barrier is any combination of materials, sealed at the joints, that stops air from leaking through the building envelope.
Where it matters on a insulation job
Insulation does little if air moves through it. Sealing top plates, penetrations and attic hatches before adding insulation is the step that makes the job pay off, and it is what blower door tests measure.
What the model code says
- The energy code defines an air barrier as materials joined in a continuous manner to restrict or prevent air passing through the thermal envelope. (IRC 2021, Chapter 11)
Check which code edition your building department enforces for air barrier before you quote.
What it costs
Koira's attic insulation cost guide puts a typical job at $2,500, with most between $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.