Decatur homes and insulation
Decatur has an older housing stock than most of Illinois. Census estimates put the median year built at 1960, against 1971 statewide, and 73.8% of homes are single-family detached houses. Homes from that era often have thin or settled attic insulation and open rim joists in the basement, which is where spray foam is most often used to stop drafts and air leaks.
About 62.9% of occupied homes in Decatur are owner-occupied, so most requests we see from older neighborhoods are owners weighing an attic, rim joist or crawlspace project.
Common spray foam projects around Decatur
- Rim joists and band boards in basements, a frequent source of cold floors
- Attics and knee walls in story-and-a-half and older two-story homes
- Crawlspace walls where moisture and drafts come up through the floor
- Pole barns and shops on properties outside the city, around Mount Zion, Forsyth and the rural edge of Macon County
What to ask any installer
- Open-cell or closed-cell foam, and how many inches in each area
- The R-value that thickness gives you, in writing
- What prep, ventilation and re-occupancy time the job needs
- Whether they are a registered Ameren Illinois Program Ally, if you want that discount
How the referral works
Tell us about the job by form or phone. We pass it to one independent installer who serves Decatur, and they contact you to set up an estimate. We are a referral service, not a contractor, and the referral is free with no obligation.
Sources
Checked October 2026. We link the public source for every figure on this page.
- U.S. Census Bureau ACS 2020–2024 5-year estimates for Decatur, IL (via USAStateStats) — median year built, housing type, owner-occupancy
- Economic Development Corporation of Decatur & Macon County, Utilities — electric and gas provider
- Ameren Illinois, Single-family homeowner upgrades — Program Ally insulation discounts
- IRS, Energy Efficient Home Improvement Credit — 25C status for 2026