When people think about heat loss, they usually think about windows. And yes, windows matter — but they’re not the biggest problem in most homes. Here’s where the heat actually goes.
The attic (biggest offender)
About 25–30% of heat loss in a typical home goes straight up through the ceiling and into the attic. Warm air rises, and if your attic insulation is thin, damaged, or has gaps, that heat is leaving your house constantly.
What to do: Check insulation depth. In Winnipeg, you want R-50 or better. If you can see the ceiling joists from the attic, you’re well below that. Also check around the attic hatch, plumbing stacks, and electrical penetrations — these are common bypass points.
Air leaks (death by a thousand cuts)
Air leaks account for roughly 25–40% of heating loss. They happen everywhere:
- Around doors and windows
- Through electrical outlets on exterior walls
- Around plumbing and wiring penetrations
- At the rim joist (where foundation meets framing)
- Through recessed lights in insulated ceilings
Individually, each one is small. Together, they add up to leaving a window open all winter.
What to do: Weatherstripping on doors, caulking around windows, and foam sealing around penetrations are the easy wins. A blower door test can find the rest.
Basement and foundation
Uninsulated basements can account for 20% or more of total heat loss. The concrete walls radiate cold, and the rim joist area is almost always under-insulated.
What to do: Insulating rim joists is one of the best bang-for-your-buck improvements. Full basement insulation is a bigger project but pays off over time.
Windows (less than you’d think)
Windows get all the attention, but in a reasonably modern home they account for maybe 10–15% of heat loss. If yours are single-pane or have broken seals (foggy between the panes), that’s worth addressing. Otherwise, your money is better spent on air sealing and insulation.
The bottom line
Most homeowners spend money on the wrong things because they guess instead of checking. A quick thermal walkthrough can tell you exactly where your heat is going — and what to fix first.
Book a home check and I’ll show you where the real problems are.