About 62% of homes in Bonnyville were built before 1991, and on a house of that age the rim joist is reliably the worst-performing part of the envelope and the cheapest one to put right. Rim joist spray foam insulation in Bonnyville is a small job with an outsized result, and it is the first thing we suggest on most local houses.
What the rim joist is and why it is bad
Go into the basement and look up at the band of wood running around the perimeter where the floor framing meets the foundation. That is the rim, or the band joist. It is where three things meet: the top of the concrete, the bottom of the exterior wall framing, and the end of every floor joist. Each of those junctions is a joint, and in houses built before sealing was a code concern, none of them were sealed. The rim is also a single thickness of lumber with outdoor temperature on the other side and nothing much in front of it, which makes it the coldest surface in the basement.
Why a stuffed batt makes it worse rather than better
The standard treatment was a scrap of fibreglass pushed into each joist bay against the rim. It fails in a way that is worth understanding, because the failure is not merely ineffective, it is harmful. Fibreglass does not stop air, so warm humid basement air passes straight through it to the cold wood. Having passed through, it condenses there, out of sight, with the batt holding the moisture against the lumber. In a district where the cold runs for months without a thaw, that assembly stays wet for the whole season. Rot and mould at the rim on houses of this vintage is a common finding and this is how it happens.
The thing that makes a tight house hard to fix
The rim is awkward. Every joist bay is a separate small pocket with a bay end, a sill plate underneath, often a steel beam pocket or a cantilever to work around, and sometimes a pipe or a wire passing through. Nothing cut to size seals it, because the shapes are not regular and because the gaps that matter are at the back where the wood meets the concrete. Sprayed foam gets into the geometry and seals it as one continuous layer, which is exactly why this is the application where foam has no real competitor.
Why closed-cell and why about two inches
Closed-cell is used here because it stops air and because past roughly two inches it is a vapour barrier in itself, which means the warm moist basement air never reaches the rim lumber at all. At around R-6 to R-7 per inch, two inches also gets to a worthwhile thermal value in a depth that does not interfere with the bay. The sequence matters: the foam has to be against the wood with no batt behind it, so whatever is in there now comes out first.
What people notice afterwards
Three things, in this order. The basement stops feeling draughty at floor level, because the cold air was coming in at the rim and running across the floor. The room above the basement, usually the main-floor living space at the outside walls, stops having a cold band along the perimeter. And the furnace cycles less in deep cold, because a continuous leak around the whole footprint of the house has been closed. It is a short job, often a day, and it is the highest return per dollar available on a pre-1991 house in this town.
Who you are dealing with
You are dealing with the contractor directly on rim joist spray foam insulation Bonnyville. We quote the job, we schedule it, and our own installers do the work.
Rim Joist Spray Foam Insulation Bonnyville: Common Questions
There is already insulation in the joist bays. Is that enough? If it is fibreglass, it is probably making things worse. Air passes through it, condenses on the cold rim behind it, and the batt holds the moisture there all winter.
Why is this the first thing to do? Because it is the coldest accessible surface, the leakiest junction in the house, and the smallest area. Cost and benefit line up better here than anywhere else.
Can it be done if the basement is finished? It depends on whether the rim is reachable. Sometimes a ceiling edge has to come down, and that is worth knowing before anybody quotes.
How much does rim joist spray foam insulation cost in Bonnyville? It follows the linear footage around the house and the thickness, so it is one of the smallest scopes we quote. Whether existing batt has to be removed and whether a finished ceiling is in the way are the two things that move it.
How do I choose a rim joist spray foam contractor in Bonnyville? Ask whether they will remove what is in the bays first, and what thickness they intend to apply. Spraying over old fibreglass leaves the problem exactly where it was.
Size the assembly with the R-value calculator, then get a free Bonnyville quote. More on Rim Joist Spray Foam Insulation Alberta province-wide.