The Three Ways Windows Make You Feel Cold
Your windows make you feel cold in three distinct ways — and only one of them is the draft you’re thinking of.
1. Air leakage. This is the obvious one. Cold air physically entering through gaps in the gaskets, seals, or frame. You can feel it with your hand on a windy day. But here’s the thing — in a reasonably modern home, this is often the smallest contributor to your discomfort near windows.
2. Internal convective drafts. Your window can be perfectly airtight to the outside, but air inside the room cools when it contacts the cold glass surface. That cooler air sinks, rolls off the bottom of the window, and kicks off the sill towards you. It feels like a draft, but it’s being generated entirely inside the house. You can’t caulk your way out of this one.
3. The cold wall effect. This is the one most people have never heard of. You’re constantly exchanging infrared heat energy with every surface around you. When you sit near a cold window, you’re radiating heat toward it but receiving very little in return. The net effect is that you’re literally cooling off toward the glass. It feels like the window is radiating cold at you — even though thermodynamically, heat only flows in one direction.
This is why two people can sit in the same room, at the same air temperature, and one person near the window feels cold while the other doesn’t. The air temperature is the same. The operative temperature — the combination of air temperature and radiant temperature from surrounding surfaces — is not.
Understanding these three mechanisms changes how you think about window upgrades. Sometimes the answer isn’t replacing all your windows. Sometimes it’s replacing the one window next to where you actually spend most of your time.
Why Your House Feels Cold Even When the Thermostat Says 21°C
You’re wearing a sweater. Your thermostat says 21°C. And yet, you’re still cold despite it all. What’s going on?
The temperature you feel in a room isn’t the number on your thermostat. In building science, we call it the operative temperature, and it’s the average of two things: the air temperature and the mean radiant temperature of the surfaces around you.
Your thermostat measures air temperature. It doesn’t know what the surfaces around you are doing.
Picture a dining nook — a bump-out with floor-to-ceiling glass on three sides. The thermostat in the hallway reads 21°C. But in that nook, the windows, are dramatically colder than the walls and ceiling. That’s half of the surfaces near you. The radiant temperature drops. The operative temperature drops. You feel cold. Not because the heating system has failed, but because of physics.
This is also why radiant in-floor heating feels so luxurious. Not only is it warming the air, it’s also raising the temperature of the largest surface in the room (the floor). This directly increases the radiant temperature and, therefore, the operative temperature of the space.
When a homeowner tells me their house feels cold, I’m not looking at the thermostat first. I’m looking at the surfaces.
Your Crawl Space Is Inside Your House (Whether You Like It or Not)
Old-school thinking says that the crawl space is outside. Vent it to the exterior, insulate the floor above it, and forget about it.
Modern building science disagrees. The crawl space is inside your house. Seal it, condition it, and insulate the perimeter walls — not the floor above.
Here’s why this matters for your comfort. If your crawl space is treated as a conditioned interior space and your floor above isn’t insulated from it (which is typical in this approach), then the temperature of your crawl space directly affects the temperature of your floor. And the temperature of your floor is a radiant surface that you’re standing, sitting, and living on all day.
A warm crawl space means a warmer floor. A warmer floor means a higher radiant temperature in your living space. A higher radiant temperature means you feel more comfortable — without touching the thermostat.
But here’s the catch I see regularly: the upper portion of the crawl space walls is insulated, but the lower portion — from the bottom of the insulation board to the slab — is bare concrete. Concrete conducts heat extremely well. So heat migrates through that uninsulated lower section and escapes. You’ve insulated the top half and left the bottom half wide open.
Completing that insulation all the way to the slab is one of the best bang-for-your-buck comfort improvements in a modern home. In one recent consultation on Vancouver Island, the energy model showed crawl space insulation saving approximately 5 GJ per year — the same energy savings as a full triple-pane window replacement, at a fraction of the cost.
