About 61% of Medicine Hat's housing was built before 1991 - the highest pre-1991 share of any major city in Alberta. In almost every one of those houses the rim joist was filled with a friction-fit batt and never sealed.
That makes this the cheapest meaningful improvement available in the oldest housing stock in the province.
Why it was never done here
Medicine Hat's long history of inexpensive natural gas is the honest explanation.
When heat is cheap, sealing work does not pay back quickly, so it does not get done. Nobody was being careless - the arithmetic genuinely did not support it. Builders met the standard of the day, homeowners had no financial reason to go further, and the rim joist was left as it came.
Energy costs have moved since. What has not changed is the buildings. So there is an unusually large stock of houses here where the single highest-return job has simply never been touched.
That is a good position to be in. The easy win is still on the table.
What the rim joist is, and why it matters
It is the band of framing sitting on top of the foundation wall, carrying the floor above and running the entire perimeter of the house.
It leaks for three structural reasons: it is a junction between two different materials and two different trades, it is penetrated repeatedly by floor joists and by services leaving the building, and a batt pushed into that cavity filters air rather than stopping it.
Then the stack effect does the rest. Warm air escapes at the top of the house, which pulls replacement air in at the bottom - and the bottom is the rim joist. That cold air spills across the basement and comes up through the floor system.
The draught you feel at ankle height in the living room usually entered here.
Why it is good value specifically
Small area, disproportionate effect, and usually reachable without demolition. If your basement ceiling is open, an installer can get at the whole perimeter directly.
Act on that. Once it is boxed in behind drywall the same work means opening things up first.
The southern Alberta angle
Wind is a constant here, and wind does not just make you feel colder - it pressurises the building and drives air through any unsealed path. The rim joist is the largest such path in most houses. Sealing it delivers more in a windy location than the same work would somewhere sheltered.
Practicalities
Pricing follows access more than area. A clear perimeter is quick work; one crowded with ducting, wiring and stored boxes is not. Clearing what you reasonably can before the crew arrives genuinely helps.
What we do
We are a referral service. We do not install. We connect you with vetted installers - certification, insurance and WCB standing checked - and they quote directly.
No price without a site visit. Get a quote, and say whether the basement ceiling is open.
See also rim joist insulation province-wide and Medicine Hat basements.