There is a simple test for whether your rim joist is the problem: does the house feel worse on windy days than on merely cold ones? If it does, rim joist spray foam insulation in Lethbridge is usually the answer.
If it does, you are not losing heat through the insulation. You are losing it through gaps, and wind is doing the pushing.
Why wind targets this particular spot
Insulation is rated in still air. It slows heat conducting through a material and does nothing about air moving around it.
Wind creates a pressure difference across a building - higher on the windward face, lower on the leeward. That difference drives air straight through any unsealed path in the envelope. The rim joist is usually the largest such path in a house, because it is a junction, it is penetrated repeatedly, and it is typically stuffed with a batt that air passes through freely.
In one of the windiest cities in Canada, that adds up to something you can feel. It is also why the discomfort is intermittent rather than constant: on a calm cold day the house behaves reasonably, and on a windy one it does not. Insulation depth cannot explain that pattern. Air movement can.
The measurable consequence
A leak driven by wind pressure moves far more air than the same gap under still conditions. So the cost of an unsealed rim joist in Lethbridge is higher than the identical defect in a sheltered part of the province, and the payback on fixing it is correspondingly shorter.
If the house sits near a coulee edge or on open ground with no shelter belt, that effect is larger again.
What sealing it changes
- The draught at floor level on the main storey, because you have closed the intake.
- Cold floors, for the same reason. See cold floors.
- How the basement feels on a windy day, which in a finished basement is the difference between a usable room and a storage space.
Closed-cell foam is used here because it adheres to the surfaces, leaving no gap for air to travel in, and at adequate depth keeps the dew point inside the foam rather than on cold wood.
Do the top as well
Warm air escaping the attic is what creates the pressure pulling air in at the rim joist. Sealing only the bottom leaves the driver in place. The attic penetrations and the rim joist are two ends of one system, and the usual order is attic first, then rim joist.
See how to fix a draughty house.
Rim Joist Spray Foam Insulation Lethbridge: Why Work With Us
Alberta's spray foam specialists. We see the building before we price it.
Rim Joist Spray Foam Insulation Lethbridge: Common Questions
How do I test whether it is leaking? On a windy day with the furnace off, hold the back of a wet hand along the top of the basement wall. Moving air over damp skin is obvious in a way it is not to a dry hand.
Why is it worse in a wind corridor? Because wind pressurises the assembly. A gap that leaks slowly in still air moves a great deal more when it is being pushed.
Is it worth doing on its own? It is the single cheapest job with a result you notice, so yes - though bundling it with anything else in the basement saves the mobilisation.
How much does rim joist spray foam insulation cost in Lethbridge? The rim joist is a small area with a large consequence, so it is priced as a detail rather than by square footage, and it is one of the few jobs that can stand entirely on its own. Doing the top of the wall at the same time is what makes the sealing continuous rather than partial.
Best rim joist spray foam insulation contractor in Lethbridge? Ask whether the top of the wall is included as well as the rim joist. Sealing one end of a cavity and leaving the other open is half a job that measures like no job.
No price without a site visit. Get a quote, and tell us whether the draughts track the wind.
See also rim joist insulation province-wide and Lethbridge basements.