About 61% of Medicine Hat's housing was built before 1991 - the highest pre-1991 share of any major city in Alberta.
There is also a local reason those houses are often less insulated than their age alone would suggest.
Cheap heat built a habit
Medicine Hat has a long history with natural gas, and for decades heating here was inexpensive relative to much of the country.
When heat is cheap, the financial case for insulating is weak. Nobody was irrational - the payback simply was not there, so houses got built and renovated with the minimum that the standards of the day required, and basements in particular got very little attention because they were storage.
That logic has changed. Energy costs have moved, basements are now living space, and a house built on the assumption of cheap heat is expensive to run once that assumption stops holding.
The practical upshot is that Medicine Hat has an unusually large stock of houses where the easy wins have never been taken. That is a good position to be in - the cheapest improvements are still available.
Start with what has never been done
In a house that has had little attention, do not begin with the expensive items:
- The rim joist. Almost certainly a friction-fit batt, almost certainly never sealed. It is the largest uncontrolled air path in most houses of this era and the best value single job. See rim joist insulation.
- Attic penetrations, sealed before any more depth is added on top.
- The foundation walls, if the basement is lived in or about to be.
Doing them in that order means each stage is cheap relative to what it returns, and you can stop whenever the remaining work stops making sense. An installer who wants to start with the biggest item is not necessarily giving you the best sequence.
Southern Alberta conditions
Hot dry summers and cold winters with real wind mean the envelope is working in both directions. A sealed basement wall is not only a winter benefit - it also slows heat coming in through the summer, which matters in one of the sunniest parts of the country.
The assembly to avoid
If you are finishing the basement, do not build a stud wall with batt insulation pressed against cold concrete and a poly sheet over it. Warm humid interior air finds its way past the poly, reaches the cold concrete, and condenses where nobody can see it.
Closed-cell foam applied directly to the concrete removes the gap and, at adequate depth, keeps the condensing surface inside the foam. If the basement is being developed, do the envelope before the framing goes up - it is the cheapest it will ever be at that moment.
Foam in an occupied basement needs an appropriate thermal barrier over it. See thermal barrier vs ignition barrier.
Water first
Foam is not waterproofing. Any seepage is a drainage problem and gets resolved before anything is sprayed.
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See also basement spray foam insulation province-wide and is spray foam worth it.