Ever wonder why your floors feel cold in January even after you've insulated the attic? The rim joist is probably the culprit โ and most homeowners have never heard of it.
The rim joist is the band of framing lumber that sits on top of your foundation wall, right where the floor system begins. In a typical older home in Jonesboro or Trumann, those cavities are either completely empty or stuffed with deteriorating fiberglass batts that have zero air-sealing value. Cold air pours in, warm air leaks out, and your HVAC runs longer than it should.
Closing off those cavities with 2 inches of closed-cell spray foam hits roughly R-13 and โ more importantly โ creates a genuine air barrier. IRC Section R402.4 requires air sealing in these junctions in new construction, but retrofit jobs in existing Northeast Arkansas homes are just as critical. A typical single-story ranch might have 100โ150 linear feet of rim joist; at roughly 1.5โ2 SF of cavity per linear foot, you're looking at 150โ300 board feet of foam. At $1.00โ$1.50 per board foot installed, the whole job often runs $150โ$450 โ one of the highest ROI insulation upgrades you can make.
We've seen homeowners in Craighead County report $30โ$60 per month in heating savings after a rim joist seal โ payback in under a year. Fall is the perfect time to schedule this before the first cold snap hits, usually late October here.
Reply to this post or DM us for a free estimate on rim joist insulation. Takes our crew a couple of hours; savings last for decades.