Basement & Rim Joist Insulation in Davenport, IA

Basement and rim joist insulation is often the best value in an older Quad Cities house. The rim joist is the band of framing that sits on the foundation wall all the way around the house. In most basements it is bare wood with gaps where it meets the sill and the subfloor, and cold air pours through every one of them. That chills the basement, the floors above it and the pipes that run nearby.

Why closed-cell foam

Rim joists are awkward: short bays between joists, wiring and pipes running through, and a cold surface where warm basement air can condense. Fiberglass batts pushed into those bays do not stop air, and moisture can collect behind them. Two to three inches of closed-cell foam, at R-5 to R-7 per inch according to HomeGuide, seals the gaps and insulates in one step, and it does not absorb water. HomeGuide puts a typical rim joist foam job at $2,000 to $2,500.

Basement walls

Concrete and block walls lose heat to the soil, especially the upper part above the frost line. If you plan to finish the basement, insulating the walls before framing is far easier than tearing out drywall later. Closed-cell foam on the wall, or foam board with sealed seams, keeps warm, damp indoor air off the cold concrete. We avoid fiberglass directly against below-grade walls, because it traps moisture against the concrete.

Flood history matters

Davenport is the largest city on the Mississippi without a permanent flood wall, according to Wikipedia, and Duck Creek has flooded parts of Davenport and Bettendorf too, including in 1990 and 2008. Even far from the river, many Quad Cities basements have taken on water at some point. Before we insulate, we look for staining, efflorescence, damp sill plates and signs of past water. If the wall is wet now, we tell you to address the water first. Insulation is not waterproofing.

Crawl spaces

Some older houses and additions sit over a crawl space instead of a full basement. Those usually do better as a sealed, conditioned space: a vapor barrier on the ground, closed-cell foam on the walls and rim, and the vents closed off. HomeGuide lists crawl space encapsulation at $3 to $10 per square foot.

Code targets

Iowa's code table, adopted from the 2012 IECC with state amendments, sets R-values by climate zone, and Scott County is in Zone 5A. For an existing basement, the code is a guide rather than a rule, since Iowa's rule leaves remodels of one- and two-family homes out of scope. We list the R-value we plan for each wall and the rim joist on the quote. Get a free estimate