Rim Joist Insulationfor Minnesota Homes
Trust Works seals and insulates rim joists with closed-cell spray foam, closing off one of the biggest air leaks in your home. Warmer floors, a drier basement, and lower heating bills. Fully insured, with 20+ years of experience.
The rim joist is the leak you never see.
The rim joist, also called the band joist, is the wood frame that sits on top of your foundation wall and runs around the entire perimeter of the house. It is where the framing meets the concrete, and in most Minnesota homes it is one of the largest and most overlooked sources of cold air, drafts, and heat loss.
For decades the standard was to stuff a fiberglass batt into each rim joist cavity and call it done. The problem is that a batt does nothing to stop air. Cold outside air pours in around it, and warm, moist house air pushes out through it and condenses on the cold wood and concrete behind. That is why so many older homes have damp, musty, frost-covered rim joists in the dead of winter.
Closed-cell foam seals and insulates in one pass.
Closed-cell spray foam is the right material for the rim joist. Sprayed directly into each cavity, it expands to fill every gap around the framing, bonds to both the wood and the concrete, and cures into a rigid, air-tight, moisture-resistant layer. It stops the air leak and the insulation gap at the same time, which is exactly what this part of the house needs.
Because closed-cell foam is also a vapor retarder, it keeps warm indoor air from reaching the cold surfaces where it would otherwise condense. That protects your framing and sill plate from the moisture problems that batts leave behind, and it is why closed-cell, not open-cell, is the standard choice for rim joists in our climate.
Warmer floors and a drier basement.
Rim joist insulation is a small job with an outsized payoff. Sealing this band around the house cuts the cold drafts that chill the floors above it, evens out the temperature in the rooms over the basement, and takes a real bite out of the air leakage that drives up winter heating bills.
It is also one of the most affordable spray foam upgrades because the total square footage is small. For many homeowners it is the first place we recommend starting, especially in a basement or crawl space that already feels cold or damp.
Our rim joist process.
Inspect
We look at every rim joist cavity, check for existing batts, moisture, or frost, and note any air leaks or pest damage before we start.
Prep
We remove old fiberglass, clear the cavities, and mask off the surrounding area so the work stays clean and contained.
Spray Closed-Cell Foam
We apply closed-cell foam to the proper thickness in each cavity, sealing the framing, sill plate, and foundation joint in one pass.
Inspect & Clean Up
We confirm full coverage, trim where needed, and leave your basement or crawl space cleaner than we found it.
Insured, experienced, and local.
20+ Years of Experience
Two decades of hands-on insulation and construction work across Minnesota homes and buildings. We have seen how our winters test a building envelope, and we insulate for it.
Fully Insured
Trust Works Company carries insurance on every job. You get the protection and peace of mind that comes with working with a covered contractor.
Statewide Minnesota Service
Based in Savage and serving homeowners and businesses across the state. One local crew, accountable from the first estimate through the final walkthrough.
Frequently asked questions.
Seal the leak around your foundation.
Get a free, no-pressure estimate for rim joist spray foam anywhere in Minnesota.