What's a rim joist, and why should you care about it in July? It's the band of framing that sits right on top of your foundation wall โ and in most Northeast Arkansas homes built before 2010, it's either completely uninsulated or stuffed with old fiberglass batts that have long since sagged away from the wood.
Here's the problem. A typical 1,500 sq ft home has roughly 150โ200 linear feet of rim joist. Each bay is a direct thermal bridge between your conditioned living space and the hot, humid air outside. In a Jonesboro summer with heat indexes pushing 105ยฐF, that's a serious load on your HVAC system โ and it shows up on your electric bill every single month.
The fix is surprisingly affordable. Two inches of closed-cell spray foam applied directly to the rim joist delivers about R-13, air-seals every gap in one shot, and resists the moisture that's almost always present near grade level. Material and labor typically run $1.50โ$2.50 per board foot in this market. A full rim joist job on an average crawl-space home usually wraps up in two to four hours.
Fiberglass batts alone won't cut it here. IRC Section R402.4 requires continuous air barriers, and a loose batt is not an air barrier โ it's just a filter for the drafts coming through. Closed-cell foam is both insulation and air barrier in one pass, which is why building inspectors in Craighead County are increasingly flagging uninsulated rim joists on energy-code inspections.
If your central air has been running nonstop this week, the rim joist is one of the first places we'd look. Reply or DM us for a free estimate โ we serve Jonesboro, Trumann, Paragould, and the surrounding area.