Rim Joist & Basement Insulation in Green Bay, WI

Rim joist and basement insulation starts at the band of framing that sits on top of the foundation. In most Green Bay houses built before the last couple of decades, that rim is bare wood or has a loose batt stuffed against it. Cold air leaks in through the sill plate, the joist ends and around every pipe and wire that passes through, and that is why the floor above feels cold and the basement stays chilly all winter.

Why closed-cell foam fits here

A fiberglass batt against a cold rim lets warm, humid basement air reach the wood, where it condenses and can lead to mold. Closed-cell foam sticks to the wood, seals the gaps and keeps moist air off the cold surface. HomeGuide rates it at R-5 to R-7 per inch, so 2 to 3 inches does a lot of work in a small space.

Foundation walls

If you plan to finish the basement, the time to insulate the walls is before the framing goes up. The Wisconsin code summary lists R-19 cavity or R-15 continuous insulation for basement walls in Zone 6. Closed-cell foam or rigid board on the concrete keeps warm air off the cold wall, and the framing goes in front. We look at the walls first for cracks, efflorescence or seepage that needs attention before anything covers them.

Crawl spaces under additions

Some houses have a crawl space under an addition or porch. We insulate and seal those walls the same way and lay a vapor barrier over the dirt, so the cold and damp under that part of the floor stops reaching the rooms above.