November in Toronto and the temperature drops fast. You're sitting near your window with a blanket and a coffee, and there's that familiar chill — a cold radiating off the glass that makes you want to close the blinds and never open them again.
Most people blame the window. But in the majority of cases, the window itself isn't the problem. The cold you're feeling is a convection current — and your window covering is one of the most effective tools for stopping it.
What's Actually Happening: The Physics of Window Chill
Even a well-sealed, energy-efficient double-pane window is much colder than your interior walls in winter. Cold glass chills the air directly in front of it. That cold air is denser and drops — creating a current that flows down the glass, across your floor, and toward the centre of the room. You feel it as a draft even when no air is actually leaking in.
This convection effect is responsible for a huge percentage of winter discomfort in Canadian homes, and it's almost always blamed on the window being drafty or poorly sealed when the glass and frame are perfectly fine.
How Window Coverings Stop Convection
The goal is to trap a layer of still air between the window and your room. Still air is an excellent insulator. Moving air (the convection current) isn't.
Any window covering that hangs close to the glass and reaches from near the ceiling to the floor will reduce convection significantly. The covering intercepts the cold air before it spills into the room, and the still pocket of air between the covering and the glass stays cold but doesn't circulate.
This is why long curtains that brush or puddle on the floor perform much better thermally than short panels that stop at the sill — they close off the bottom of the air column where the cold air exits into the room.
The Best Window Treatments for Winter Warmth
Cellular (honeycomb) shades are the most effective single product for thermal performance. Their honeycomb cells trap air within the shade itself, adding a second insulating layer in addition to stopping convection. Double-cell honeycomb shades perform noticeably better than single-cell in a cold Canadian climate.
Thermal curtain liners are another strong option — they're a lining you add to existing curtains to dramatically improve their insulating properties. If you already have curtains you like, this is the most cost-effective upgrade.
Roman shades and roller blinds sit closer to the glass and do less to stop convection unless they're made with a thermal or blackout backing. Even then, the coverage at the sides and bottom matters — a blind that doesn't reach the sill or has side gaps lets the convection current escape.
What If There Is an Actual Draft?
If you hold a piece of tissue near your window frame on a windy day and it moves, there's real air infiltration — not just convection. In this case, the fix starts with weatherstripping and caulking around the frame. Window coverings will reduce the discomfort but won't solve an infiltration problem.
The good news: true air leaks in window frames are relatively rare compared to convection discomfort. Most of the cold you feel near Canadian windows in winter is the convection effect, and window treatments address it directly.
Frequently Asked Questions
Will cellular shades make a noticeable difference on my heating bill?
Studies suggest properly installed cellular shades can reduce heat loss through windows by 40% or more. In a Toronto home with many windows, that adds up. The bigger impact is comfort — rooms near windows feel warmer and more liveable.
Should I keep my blinds open or closed in winter?
South-facing windows: open during the day to gain solar heat, close at night to keep it in. North and west-facing windows: keep closed most of the time in winter — they offer little solar gain and lose heat steadily.
What's the minimum a covering needs to do to stop convection?
It needs to reach from close to the ceiling to the floor, and fit relatively closely against the window — ideally with minimal side gaps. A floor-length curtain does this. A 60cm roller blind does not.
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