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Short answer
The curtains that keep the most sun heat out are coated blackouts, or any curtain with a blackout or thermal lining, with a pale back facing the window. Hang them on a ceiling track, wider than the window and down to the floor, and close them before the sun reaches the glass, especially on west-facing windows in the afternoon. A sheer alone does little for heat. For the hottest rooms, combine curtains with window film or an external shade.
How curtains keep heat out
Sunlight passes through the glass and warms whatever it hits. A curtain that blocks and reflects that light before it reaches the room stops much of the heat from building up inside. Three things decide how well it works:
- Opacity. The less light passes through the fabric, the less heat. Coated blackouts block the most.
- The back facing the window. A pale or white back reflects sunlight back out; a dark back absorbs it and warms up.
- Gaps. Warm air and light escape round the top, sides and bottom of a curtain, so fit matters as much as fabric.
Which curtains reduce heat best
| Curtain | Heat reduction | Notes |
|---|---|---|
| Coated blackout | The most | The coating blocks light and usually has a pale back; TEKUSU MIDORI is silicon-backed, about 400 gsm |
| Any curtain with a blackout or thermal lining | High | Keeps the face fabric you want; see Curtain Lining |
| Woven blackout | High | Opaque without a coating; drapes like normal fabric |
| Heavy dimout or velvet | Moderate | Dense fabric absorbs some heat; better with a lining |
| Light dimout | Some | Cuts glare more than heat |
| Sheer | Little | Softens light but lets most heat through |
See Blackout Curtains for the types of blackout.
Fit matters as much as fabric
- Ceiling track or curtain box, so heat does not escape over the top.
- Wider than the window, about 15 to 30 cm each side, with returns to the wall where possible.
- Overlap in the centre so the pair closes fully.
- Floor length, about 1 cm above the floor.
Tip
Close the curtains on west-facing windows before the afternoon sun reaches the glass, not after the room has heated up. A room that never gets hot is far easier to cool.
Colour and heat
The side facing the window matters most. A dark curtain with no lining absorbs sunlight and becomes warm itself, radiating some heat into the room. A pale lining or coated back reflects more of it. Inside, choose any colour you like; just give a dark face fabric a pale lining on a sunny window. See How to Choose Curtain Colours.
Double layers
Most Malaysian homes hang a sheer and a main curtain on a double track. By day, the sheer alone lets light in but does little for heat; on hot afternoons, draw the main curtain too. A blackout or lined dimout as the main curtain gives the best of both. See Blackout vs Dimout vs Sheer.
When curtains are not enough
Curtains stop heat after it has passed through the glass, so some still enters the space between curtain and window. For very hot west-facing rooms, add a solar window film, or an external blind or awning that shades the glass before the sun reaches it. Inside, a roller blind behind the curtain adds another layer. See Curtains vs Blinds.
Good to know
Keep a small gap between curtain and glass in air-conditioned rooms, so condensation does not soak the fabric. See Mouldy Curtains.
Blackout fabrics
The JOTEX blackouts, updated from the catalogue. See the blackout fabric page.
Browse blackout fabric →
Frequently asked questions
Do blackout curtains reduce heat?
Yes. They block most sunlight, and coated blackouts usually have a pale back that reflects it, so less heat builds up in the room, especially on west-facing windows.
Which colour curtain keeps a room coolest?
What matters most is the side facing the window: a pale back or lining reflects sunlight. The room-side colour can be anything.
Do sheer curtains reduce heat?
Very little. They soften the light but let most heat through. Draw a blackout or lined curtain on hot afternoons.
What are thermal curtains?
Curtains with a lining or backing designed to insulate, such as a thermal or blackout lining, which reduces heat coming through the window.
Are curtains or blinds better for heat?
Both help; external shades work best because they stop the sun before the glass. Inside, a coated blackout curtain that fits well is very effective, and a blind plus a curtain is better still.
Will a blackout curtain lower my electricity bill?
It can reduce how hard the air-conditioner works in a sunny room, but how much depends on the window, its direction and how the room is used. Close the curtains before the room heats up.
Curtain maker, upholsterer or designer?
Specifications are public on every collection page. JOTEX dealers can log in for live stock and pricing, and our team can send samples or open a dealer account.