Thermal Curtains

Three things do the work. The lining: a dense thermal lining or coated backing that slows heat through the fabric. The air gap: a closed curtain close to the window traps still air against the glass, and still air insulates. And coverage: heat escapes around the edges as easily as through the fabric, so the curtain needs to cover the frame, overlap the wall and reach the floor.

A curtain that stops short of the floor lets warm air drop behind it, cool against the glass and spill out at the bottom. That is the draught people feel on a cold night. In summer the same layers reflect radiant heat before it warms the room.

There is a lot of overlap. A blockout curtain uses a coated fabric or lining to stop light, and that coating also slows heat. A thermal curtain is chosen for insulation first and may let a glow through a linen or a light fabric. For a bedroom you want dark and warm, choose a blockout lined curtain. For a living room where you want daytime light, choose a thermal lining behind a fabric you like. Both need width past the frame and floor length.

Blockout curtains

A pelmet is a box or board across the top of the curtain that closes the gap between the track and the wall. Without it, warm air flows over the top, down the cold glass and out the bottom. A ceiling-fixed track does a similar job.

At the bottom, the curtain should touch the floor or sit just above it. Floor length with an overlap onto the wall on each side gives the best seal.

Melbourne has cold, damp winters and hot summer afternoons. In winter thermal curtains keep the heater's warmth in the room, so it warms faster and stays warm longer. In summer, drawn through the afternoon on a north or west window, they keep radiant heat out. They suit single-glazed older homes, weatherboard and brick veneer houses, and apartments with large glass walls.

S-fold on a ceiling-fixed track closes the top gap without a pelmet. Pinch pleat sits well behind one. Tracks should extend past the window, and a double track lets you run a sheer in front for daytime light.

Curtain rods and tracks