Rim joist spray foam insulation in Carstairs is work on the band where the floor structure sits on the foundation, and in a commuter household it has an effect people notice at a specific hour.
The band that decides how the main floor feels in the evening
This strip runs around the whole perimeter of the basement, it is above ground, and it is directly underneath the outside edge of the main floor. When it leaks, the floor near the exterior walls stays cold, and because a Carstairs house has been set back all day that floor is at its coldest exactly when the family comes home. Sealing it changes the surface people stand on at the end of the day, which is a more useful description of the benefit than any figure.
What is usually in there now, and why it fails
In a house of this age there is normally a piece of batt pushed into each bay, and it is doing very little. Batt does not stop air, the bay is irregular because of the joist ends, and the material has frequently slumped or been pushed out of place by wiring. Behind it the joint between the sill and the foundation is open in places. Sprayed foam works here precisely because it seals and insulates in one pass and follows a shape that is awkward to fill any other way.
Why it is the first thing to do in most houses here
It is a small quantity of material in a small area, it is reached from the basement, and it needs no finished surface disturbed. Against that it is one of the largest air leaks in a modern house. Nothing else available offers that ratio, which is why it comes first for most owners in this town and why it suits somebody who wants to spend once, see whether the difference is real, and decide about the rest afterwards.
Doing it alongside the work it naturally pairs with
The rim sits directly above the top of the basement wall, so the two are done together as a matter of course and the setup happens once rather than twice. Where a basement is going to be finished later, doing the rim now does not have to be undone. For a household that is out of the house all day, scheduling is straightforward as well, because this is basement work that does not require anybody to be present in the living space.
Rim Joist Spray Foam Insulation Carstairs: Common Questions
Where is it? The band around the top of the basement wall, directly under the edge of the main floor.
What if there is already batt in there? Batt does not stop air, and this is an air leak more than an insulation gap.
Is it worth doing by itself? It gives more back per dollar than anything else in most houses here, and it pairs naturally with the wall top.
Size the assembly with the R-value calculator, then get a free Carstairs quote. More on Rim Joist Spray Foam Insulation Alberta.