In this edition of LinkedIn Roundup, we look at the value of upgrading windows and the purpose of a blower door test.
The $100K Window Question
A homeowner asked me last month whether replacing every window in her house with triple pane — about $100,000 worth — would solve her comfort problems.
Probably not entirely. And almost certainly not the best use of that budget.
The energy model showed replacing all windows saves about 5 GJ per year in SW BC. Meaningful. But the partially insulated crawl space walls? Also 5 GJ. At maybe a twentieth of the cost.
What actually solved the comfort problem was the heating system. The variable-speed heat pump blower wasn’t running at all during our visit — it was 6°C outside. The Nest thermostat wasn’t communicating properly with the Mitsubishi unit. A service call fixed it. That single thing made more difference to daily comfort than any window upgrade would have.
I’ve seen this pattern enough times that it’s shaped how I approach every consultation. A homeowner in Edmonton was considering $30,000+ in triple pane upgrades. Turned out one window — the one beside his couch where he watched TV every evening — was the culprit. He replaced that window and he was happy.
Windows aren’t irrelevant. But before spending, it’s worth knowing what’s actually making you uncomfortable.
What a Blower Door Test Actually Tells You (And What It Doesn’t)
A blower door test gives you one number: the air leakage rate of your home at 50 pascals. It tells you how leaky the house is overall. It doesn’t tell you where.
That distinction matters a lot in practice. A home at 3.5 ACH50 — air leakage and ventilation combined account for about 12% of total heat loss, roughly 9–10 GJ per year. The energy model treats it as one lump number. But if your home office window is the leaky one and you work from home, you’re sitting next to it for eight hours a day. That single point might be trivial in the model and miserable in real life.
So the blower door test is step one. Step two is keeping the fan running at lower pressure and walking the house with a thermal camera to find where the air is actually moving. That’s where the diagnostic value lives.
For reference: the Canadian average is about 4.65 ACH50. BC Step Code Step 3 requires 2.5. Passive House is 0.6. Below 1.5 is take practice to build without purpose-built construction methods. When a homeowner asks what their number means, I can now give them context — and more usefully, show them where it’s happening and whether those spots are worth fixing.