If you only do one thing to an older Wainwright house, do this one. The rim joist is the band of framing that sits on top of the foundation wall and carries the floor above it, and it is the one place in the building where you can reach bare outdoor-temperature structure from inside, standing up, with nothing in the way. Rim joist spray foam insulation in Wainwright is the shortest job on our list and usually the one the owner notices most.
What is actually there on a pre-1991 house
A piece of dimensional lumber, a sill plate under it with a gap where the concrete was never flat, and a batt pushed in between each pair of joists with nothing holding it and nothing sealing its edges. Above it is a heated floor; behind it is siding and sheathing and then east-central Alberta. The batt slows heat for the few centimetres it occupies and then air walks around it on five sides.
Wind-washing is the mechanism, not conduction
On a windward wall out here the cavity behind the siding is under positive pressure, so outdoor air is pushed in along the top of the foundation and through the joist bays. That moving air scrubs heat off the framing and off the back of the batt continuously, which is why rim joist losses are so much larger than the thin band of material suggests. It also explains the pattern people report: a floor that is cold along one or two outside walls rather than everywhere, and colder on a windy day than on a still day at the same temperature.
The frost line on the inside of the joist
The other thing we find is frost, not draughts. Warm humid air from the basement reaches the cold sill and the joist ends, and because the cold here is sustained rather than cycling there is no regular thaw to dry it. It accumulates. On a long winter that produces damp sill plates, staining on the joist ends, and sometimes rot in the corners of the house where two exposed walls meet and the airflow is worst.
Why closed-cell is the material for this band
It adheres to the concrete, the sill and the wood, so there is no gap left behind it to ventilate. At roughly two inches it is already a vapour barrier, which means the warm indoor air never reaches the cold wood to condense on it. And it fills the irregular shape at the top of the foundation, where the concrete is never level and no cut piece of anything will ever seal. Open-cell has its uses in a house but this is not one of them.
Do it with the basement, or before it
If you are finishing or re-finishing the basement, the rim joist is done first, before any framing goes up in front of it, because afterwards it is behind a wall for the next thirty years. If you are not touching the basement, it is still worth doing alone. It is accessible, it is quick, and it addresses the coldest surface in the house rather than the largest one.
Who does the work
Rim joist spray foam insulation Wainwright 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 Wainwright: Common Questions
Why is this the first job and not the attic? Because it is the coldest reachable surface and the easiest access in the building. The attic has depth already on most houses here; the rim joist usually has nothing that works.
Our floor is only cold along one wall. Why? That is the wall taking the wind. Positive pressure drives outdoor air into the joist bays on the windward side, which is why one or two walls feel it and the others do not.
There is frost on the wood at the top of the basement wall. That is indoor moisture condensing on cold framing, and in a climate that stays cold it keeps accumulating rather than drying. Sealing the band with closed-cell removes the surface it forms on.
How much does rim joist spray foam insulation cost in Wainwright? It is priced by the linear run of the band and the depth applied, and it is one of the smaller numbers on a spray foam quote because the area is small. Access is the variable, especially where a finished ceiling or ductwork is in the way.
How do I choose a rim joist spray foam contractor in Wainwright? Ask whether they will spray the corners and the joist ends or only the open bays. The corners are where two exposed walls meet and they are where the damage shows up first.
Size the depth with the R-value calculator, then get a free Wainwright quote. More on Rim Joist Spray Foam Insulation Alberta province-wide.