Ever notice a cold draft near the floor along your outside walls in January? Nine times out of ten, the culprit is an uninsulated rim joist โ and most homes in Jonesboro and Trumann have them wide open to the cold.
The rim joist is the band of framing that sits right on top of your foundation wall, where the floor system meets the exterior. It's full of gaps, knot holes, and wood-to-concrete joints that bleed conditioned air 24/7. Building science folks call it one of the top five air-leakage points in a house, and they're not wrong.
The fix is straightforward: cut-and-cobble rigid foam board (R-10 to R-15 with 2โ3 inches of polyiso) or, better yet, spray 2 inches of closed-cell spray foam directly against the rim joist. Two inches of closed-cell gets you roughly R-12 to R-14 and โ critically โ creates an air seal at the same time. That air seal is where most of the comfort gain comes from, not just the R-value alone.
Cost-wise, a typical single-story crawl space rim joist in Northeast Arkansas runs $1.50โ$2.50 per board foot installed for closed-cell spray foam, depending on access and linear footage. Most homes land between $400โ$900 total for the rim joist alone โ one of the best dollars-per-comfort improvements you can make before October temperatures drop.
IRC code section R402.4 requires rim joists to be insulated and air-sealed in Climate Zone 3 (that's us), so if your house was built before 2012 odds are this never got done properly.
Fall is the perfect time to tackle this โ crews are available and it's not yet crawl-space miserable down there. Reply or DM us for a free estimate before the cold sets in.