Rim joist insulation is a crucial step in reducing heating bills and improving energy efficiency in homes. The best materials to use for insulate the interior of a rim joist are rigid-foam insulation or spray-foam insulation. Foam board insulation is the best option, as it lowers condensation risk and reduces warm air from contacting cold surfaces. Spray foam is another option, and it can be used in rectangles or as an insulation and air barrier.
In unfinished basements, proper rim joist insulation creates a thermal barrier against heat transfer, sealing the area. A two-component spray-foam kit is the fastest and most efficient way to seal the rim joist. If you have an unfinished basement, you can properly insulate the area by installing foam-based or vinyl-faced fiberglass batt insulation tightly to the cavity and sealing at all edges. Use fire-rated material if the insulation is to be left exposed, ensuring it has no gaps, voids, compression, or misalignment.
A do-it-yourself friendly method for sealing and insulating the rim joist or band joist area is using rigid foam up against the rim joist. Cut EPS pieces to fit between joists and seal them in place with canned foam. Up to 2″ thickness is commonly available in various brands. To prevent problems, only air impermeable insulation, such as rigid foam or spray polyurethane foam, should be used. Any old insulation must be removed before adding fiberglass to the rim joist, and the fiberglass must be cut to perfectly fit the space.
To achieve all of the rim joist insulation steps above, apply closed cell spray foam over the entire area.
📹 Sealing and Insulating Rim Joists – Best Practice
Sealing and Insulating Rim Joists – BEST PRACTICE Rim Joists (also called band joists) and sill plates are often an overlooked …
📹 Rim joist insulation air sealing
Having had this done a little over a year ago upon the recommendation of an air-sealing company, I can say spraying with closed-cell foam has some major drawbacks: It never can be removed if necessary, makes termite inspections impossible from the inside and hides termite damage, makes hunting for leaks impossible, traps water against the wood framing being closed-cell foam if leaks develop which will promote rot. With these observations in my home, I’d caution against it. If anything, I’d suggest using foam to seal cracks and then use bats or foam board. Keywords in the article are quick in and quick out which is exactly what this company I chose did and cut corners which I now regret and will have expensive mitigation in the future.