What R-value means
R-value is how well a material resists heat flowing through it. The higher the R-value, the better it insulates.
Also called thermal resistance.
Where it matters on a insulation job
Code minimums for attics, walls and floors are written as R-values by climate zone. Quote insulation by the R-value you will reach, not just the depth, and leave the bag label or a certificate as proof.
What the model code says
- The energy code defines R-value as the inverse of the rate of heat flow through a body per unit area and temperature difference. (IRC 2021, Chapter 11)
Check which code edition your building department enforces for R-value before you quote.
What it costs
For R-value, the closest koira.ai price is the attic insulation cost guide, near $2,500 for a typical job and $1,700 to $3,250 for most. 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.