Insulation Cost in Illinois

Home insulation in Illinois averages $2,875 for a typical 1,200 sqft attic project in 2026 — above the national average. Blown-in cellulose for a 1,200 sqft attic runs $1,242; spray foam $3,450 for the same area.

For Illinois: attic insulation — blown-in cellulose or fiberglass ($1.03/sqft) is the best cost-per-R-value choice. Walls — batt insulation ($0.86/sqft) for open cavities during remodel; spray foam for retrofit without opening walls. Crawlspace/basement — closed-cell spray foam ($2.88/sqft) is best for moisture resistance. Rim joists — spray foam is the gold standard for air sealing.

Illinois is in climate zone cold. DOE recommended R-values: attic (uninsulated): R-49 to R-60 in zones 4–8; R-38 in zones 2–3; R-30 in zone 1. Walls (2×4 framing): R-13 minimum, R-15 recommended. Walls (2×6 framing): R-19 minimum, R-21 recommended. Basement/crawlspace walls: R-10 to R-15. The colder your climate zone, the higher the R-value needed. Adding insulation beyond minimum code shows diminishing returns but still improves comfort.

Properly insulating an attic reduces heating and cooling costs 10–20% annually. For a Illinois home spending $2,400/year on energy, that's $240–$480/year in savings. Payback period: 3–7 years for attic insulation; 5–10 years for wall insulation. The 30% federal tax credit (up to $1,200) under the Inflation Reduction Act significantly improves the payback math for insulation projects completed through 2032.