Rim joist spray foam insulation in Brooks is the smallest item on this site and consistently one of the most worthwhile. The rim joist is the band of framing where the floor structure sits on the foundation wall, running the whole way around the building, and almost nobody has ever sealed it.
In July the same band lets the heat in
Every other page in this group argues the rim joist as a winter item, and in the hottest driest corner of the province that is half the case. A gap works in whichever direction the pressure runs. On a Brooks afternoon in July the air on the outside of that band is well above the air inside, and the basement is the room the household has gone downstairs to use. Warm air arriving at the perimeter is why a basement that should be the coolest room in the house is not, and it brings humidity with it into the coolest surfaces in the building, which is the combination that produces the damp smell people blame on the concrete. Sealing that band is a summer improvement here as much as a winter one.
Batt in the bay is not the same as sealing the bay
The standard treatment is a piece of batt pushed into each opening, which fills the space without closing the joints in the framing behind it. Air keeps moving around and through it. That is true of a house built in the seventies and a house built last year, and it is why the owners of newer Brooks houses are frequently the most surprised to hear the band is untreated.
It leaks in August as well as January
Most explanations of this item stop at winter. In a town where afternoons regularly sit in the thirties, that band is also letting hot outside air into the coolest part of the house, straight into the lower level a family is using to escape the heat. An owner who has never thought of the rim joist as a summer problem is usually the one who notices the difference most after it is done.
What changes in the house afterwards
The floor above the band stops being cold at the edges of the room in winter. The lower level holds its temperature better in summer. The furnace and the air conditioning both cycle less often. Nobody notices an R-value, and on a Brooks house those three together are what people describe when they say the house finally behaves. It is a small item to have that much effect, which is exactly why it is worth naming first rather than last when somebody asks where to start.
Rim Joist Spray Foam Insulation Brooks: Common Questions
If we can only afford one thing, what should it be? If the attic is done, this is it. It is the cheapest item here and the result is felt rather than calculated.
Is spray foam worth it in a nearly new house? It still has the band. Batt fills the bay without sealing the joints behind it, on new houses as much as old.
Does it matter in summer? Here, yes. It is letting hot air into the coolest part of the house, which is the part you are using.
Size the assembly with the R-value calculator, then get a free Brooks quote. More on Rim Joist Spray Foam Insulation Alberta.