The rim joist is the band of lumber that closes off the floor framing where it sits on the foundation wall. It runs the whole way round the house, it is only a few inches tall, and it is the single most leaky accessible surface in nearly every pre-1991 building. With about 46% of Crossfield homes in that bracket, rim joist spray foam insulation here is the item we recommend first more often than any other.
Why this strip leaks more than anything else
Look at what meets there. The top of the concrete or block foundation, a wooden sill plate laid on it, the rim board standing on the sill, the ends of the floor joists landing against the rim, and the subfloor and bottom plate of the wall above. That is five or six separate pieces of material from three different trades, all terminating in a band a few inches wide, with shrinkage gaps between them and no single layer running past. In an older house there is no gasket under the sill and no sealant anywhere in the stack. It is a continuous seam round the perimeter of the building.
It is at the bottom of the stack, which is why it is cold
Warm air rises and leaves a house high up, which pulls replacement air in low down, and the rim joist is the lowest leak available. Cold air arrives there and runs along the floor, which is why basements in these houses are cold at ankle height even when the furnace is keeping up, and why the floor above the rim feels cold near the outside walls. It is also the coldest surface in the basement, so when humid household air reaches it the water condenses on the wood and on the joist ends. In a shallow older basement the whole band is within arm's reach of anybody standing on the floor, which is unusually convenient for a defect this significant.
Batt in a rim joist bay does not work
The standard fix in these houses was a piece of batt pushed into each bay, sometimes with a scrap of poly in front of it. It cannot seal, because it is cut material against irregular framing and air goes round it. Worse, it holds the cold surface in place behind itself and gives any moisture a cool damp spot to sit in, out of sight. The bays we open frequently have stained wood behind the insulation and nobody in the house knew. Closed-cell foam sprayed into the bay adheres to the rim, the sill, the joist ends and the top of the foundation at once, filling the shrinkage gaps and cutting the air path, and at roughly R-6 to R-7 per inch it reaches a worthwhile R-value in the few inches available.
The newer houses in town are not exempt
On the subdivision edge the rim joist is usually a rim board against engineered floor joists, and builders here commonly put a bead or a thin pass of foam at the joist ends. Commonly, not always, and not always well. We find bays skipped behind ductwork, behind the furnace, in the corners and anywhere the sprayer could not get a clear line. It is a short inspection and when it is the only item on the list it is a short visit, which makes it the most sensible first job on a newer Crossfield house too.
Who you are dealing with
Rim joist spray foam insulation Crossfield is work we take care of ourselves. We scope it, we quote it, we schedule it, and our own installers are the ones holding the gun.
Rim Joist Spray Foam Insulation Crossfield: Common Questions
Why start with the rim joist? Small area, large effect, easy access. In a pre-1991 Crossfield basement it is the coldest reachable surface and the biggest low-level air leak in the building.
Can we just push insulation into the bays ourselves? Cut material cannot seal against irregular framing, and it tends to trap a cold damp surface behind itself. The value here is the adhesion and the air seal, which a batt cannot provide.
Our house is newer. Is the rim joist already done? Partly, usually. The skipped bays are behind the ducting, around the furnace and in the corners, and finding them is a quick look.
How much does rim joist spray foam insulation cost in Crossfield? It prices on the length of the band and the depth sprayed, so it is one of the smaller pieces of work available on a house. Clearing access along the basement perimeter beforehand keeps it that way.
How do I choose a rim joist spray foam contractor in Crossfield? Ask whether every bay is included, the ones behind the ductwork and the furnace as well. Those are the bays that get left, and they leak like the rest.
Size the job with the R-value calculator, then get a free Crossfield quote. More on Rim Joist Spray Foam Insulation Alberta province-wide.