Rim joist spray foam insulation in Rimbey is the smallest job we do and the one with the best return on a house in the older part of town. The rim joist is the band of lumber that runs around the perimeter of the floor system, sitting on the foundation wall with the floor joists landing into it. It is about an inch and a half of wood with sheathing and siding on the far side, and it is the thinnest part of the entire exterior envelope of the house.
Why this one line matters so much
Go round the perimeter of a basement and you will find a continuous band where the house transitions from concrete below to wood framing above. At that band there is no insulation in the wall cavity, because there is no wall cavity; there is just the rim board, the sill plate sitting on the foundation, and the end of every joist. The sill is set on concrete and in older houses it is set on it directly with nothing in between, so there is a seam running the entire way round the house at exactly the point where the structure changes. That seam is both a conductive weak spot and an air path, and it is at the bottom of the building where cold air wants to be.
The stack effect makes it the entry point
Warm air leaves a house at the top and cold air has to come in somewhere to replace it. It comes in low, and the rim joist is the lowest continuous opening in the envelope. Which means this band is not just losing heat; it is actively supplying the cold air that the furnace then heats, all winter. In a climate where that pressure difference runs for weeks without a break, the rim is doing that continuously rather than occasionally. Insulating it without sealing it achieves very little, because insulation does not stop air movement.
Why batts in the joist bays fail here
The usual treatment is a piece of batt stuffed into each joist bay against the rim board, sometimes with a scrap of poly in front of it. Warm humid basement air gets past that easily, reaches the cold rim board, and condenses on the wood. There is no drying mechanism: the outside face is sheathing and siding, the inside face is now covered, and central Alberta's cold does not let up long enough for the assembly to recover. The result is damp sill plates and dark staining on the rim board, and the batt that was supposed to help is what kept the moisture there.
What closed-cell does in a joist bay
Sprayed into each bay it bonds to the rim board, the sill, the top of the foundation and the sides of the joists, closing the seam completely. At roughly R-6 to R-7 per inch it reaches a respectable value in two or three inches, and at about two inches it is its own vapour barrier, so there is no cold wood surface for interior air to condense on. It is the clearest case in the whole house for this material: a shallow space, an irregular shape, an air seal required, and a surface that must not be allowed to get wet.
Why it is usually the cheapest job in the house
The area is small, the surface is almost always already exposed in an unfinished basement, and there is nothing to dismantle or put back. If a basement is being developed, doing the rim at the same time as the walls costs very little extra and it is the last chance to reach it before the ceiling is closed in.
The crew on your job
We take care of rim joist spray foam insulation Rimbey end to end -- the assessment, the quote, the scheduling and the spraying. Our crews do the work.
Rim Joist Spray Foam Insulation Rimbey: Common Questions
What exactly is the rim joist? The board running around the outside of the floor system, sitting on top of the foundation wall with the floor joists ending into it. It is the thinnest point of the exterior wall.
Why is the sill plate damp or stained? Warm basement air is condensing on cold wood behind a batt that lets air through. The staining is the record of it.
Can this be done at the same time as the basement walls? It should be. The ceiling is open, the surface is exposed, and after development it becomes an expensive thing to reach.
How much does rim joist spray foam insulation cost in Rimbey? It is priced per board foot and the area is small, so this is typically the least expensive item on a quote and often the one with the quickest payback.
How do I choose a rim joist spray foam contractor in Rimbey? Ask whether they will spray onto the sill and the top of the foundation, not just the rim board. The seam is the point of the job.
Size the assembly with the R-value calculator, then get a free Rimbey quote. More on Rim Joist Spray Foam Insulation Alberta province-wide.