Thermal Curtains in Sherbrooke — Keeping the Heat In When It's -25

In Sherbrooke, winter doesn't compromise. When temperatures drop to -25 and the wind comes off Mont-Bellevue, what you have at your windows genuinely matters — not just for visual comfort, but for the heat that stays in the room.

I often hear from clients who tell me they have new windows, double or triple glazed, and that it should be enough. Sometimes it is. But a window, even a high-performing one, is still a cold surface. And cold radiates. What you put in front of that surface makes a real difference.

Why curtains insulate — or don't

A curtain creates an air pocket between the fabric and the glass. If that air pocket is stable — if the curtain falls properly to the floor, if it extends slightly past the frame on each side — it acts as a thermal buffer.

The problem with curtains that are too short, too lightweight, or poorly fitted: the air pocket isn't stable. Cold air slips in at the base, circulates behind the fabric, and creates the drafts people often feel near windows in winter.

The answer isn't always to replace the windows. Often, well-made curtains are enough.

The techniques that make the difference

Thermal lining

This is the most effective element. A thermal lining — a fabric with an acrylic or aluminized backing — is added to the back of the main panel. It blocks cold radiation from the glass and adds weight, which improves how the curtain hangs.

A good thermal lining can reduce heat loss through windows by 25 to 40%. I explain this often, and it always surprises people.

Interlining

One step further: between the main fabric and the thermal lining, an interliner — a layer of flannel or quilted cotton — is inserted. The combined effect is a triple layer. The curtain becomes heavy, opaque, and acoustically absorbent. This is what high-end hotels do. It's also what I recommend for rooms that are hard to keep warm.

Length and width

Curtains that stop 10 cm from the floor let cold air in. Curtains that don't adequately cover the sides of the window frame let light — and cold — in from the edges.

For serious insulation:

• Length to the floor, with 1 to 2 cm of surplus
• Width that extends 15 to 20 cm past the frame on each side

These are details I verify at every measurement. They affect performance by 30 to 40%.

What fabrics to choose in winter

Insulation is invisible — but fabric isn't. The challenge is finding materials that perform and look beautiful.

Cotton velvet is probably my favourite material for living spaces in winter. Dense, warm to the touch, it falls beautifully and absorbs sound. A bedroom with velvet curtains is quieter and better insulated.

Heavy linen (300 g/m² and above) with thermal lining: ideal for those who prefer a natural interior. Linen alone doesn't insulate. With the right lining, it becomes very effective.

Jacquard fabrics: often underestimated, they have a natural density that retains heat better than flat-woven fabrics.

What I avoid for cold rooms: sheers, organzas, lightweight fabrics. They're beautiful, but they have no thermal value.

A concrete example

In November, I dressed the windows of a living room on Plateau Saint-Joseph — two large bay windows, north-west exposure, direct wind. The client had new windows but was still experiencing drafts.

We worked with a 280 g/m² natural linen, thermal lining, and flannel interliner. Pinch pleat, floor-length with a 2 cm puddle, width extending 18 cm past the frame on each side.

The result: the perceived surface temperature near the windows changed noticeably. She wrote to me in early December to say she was no longer cold in her living room.

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If you have windows that "breathe" or rooms you can't seem to keep warm, it's worth talking through before next winter. Get in touch for a home consultation in Sherbrooke and across Estrie.