Thermal vs Blackout Curtains: Which Saves You More on UK Energy Bills?

With UK energy prices still high, many households are looking for simple ways to keep the warmth they pay for. Windows are one of the weakest points in a home's insulation, even with double glazing, and curtains are one of the easiest things to change.

So which is better for keeping heat in: thermal curtains or blackout curtains? This guide explains how each works, where the difference really lies, and the fitting tips that make both perform better.

Why Windows Lose So Much Heat

Heat escapes through windows in two main ways. It passes through the cold glass and frame (conduction), and cold air slips in around the frame (draughts). Double glazing reduces both, but the glass is still colder than the wall around it.

A curtain helps by creating a pocket of still air between the room and the glass. Still air is a poor conductor of heat, so the thicker and better sealed that pocket, the more warmth stays in the room.

How Blackout Curtains Help

A blackout curtain has a dense lining on the back designed to stop light. That density also slows the movement of heat and air, so a blackout curtain is noticeably warmer than a thin, unlined one.

• Main job: blocking light for sleep, nurseries and TV rooms.
• Warmth: good, thanks to the extra layer and weight.

How Thermal Curtains Help

A thermal curtain goes a step further. Our thermal lining is an insulated thermal blackout lining, so it blocks light like blackout lining and adds an insulating layer designed to hold back heat.

• Main job: keeping heat in during winter and helping keep sunny rooms cooler in summer.
• Light: it blocks light too, so you do not have to choose between warmth and darkness.

Head to Head

The verdict: if saving heat is your priority, thermal blackout lining wins. If darkness is your main goal and the room is not especially cold, blackout lining is enough. For a fuller comparison including unlined curtains, see our curtain lining guide.

Fitting Matters as Much as Fabric

Even the warmest curtain loses much of its benefit if cold air can flow around it. These steps make the biggest difference:

• Go wider than the window. Let the curtains extend beyond the frame on each side so they overlap the wall when closed. Our measuring guide shows how many panels you need for your pole.
• Mount the pole higher. Fixing the pole or track above the frame reduces the gap where warm air escapes over the top.
• Choose the right length. Floor length curtains that just clear the floor trap more air than sill length ones. If there is a radiator under the window, a sill length curtain stops heat being funnelled behind the curtain and up against the glass.
• Close them at dusk. Drawing curtains as soon as it gets dark keeps in heat that would otherwise be lost through the evening.
• Open them on sunny days. In winter, let the sun warm the room during the day, then close up.
• Seal the draughts too. Self adhesive draught strips around old window frames and a pelmet or a pole fixed close to the ceiling add to the effect.

Is It Worth It?

Curtains will not match the saving of new windows or wall insulation, but they are one of the cheapest and quickest improvements you can make. They also make rooms feel warmer and cosier, which often means the thermostat can stay lower. The Energy Saving Trust recommends closing curtains at dusk as one of the simple habits that reduce heat loss through windows.

For the most warmth, choose thermal blackout lining, a generous width and a well fitted pole, and draw the curtains as soon as the light goes.

Warm, Printed Curtains for Winter

Nordic Pine Tree CurtainsAutumn Forest Leaf CurtainsNavy and Gold Sunflower CurtainsBeige and Brown Plaid Curtains

All our curtains are available with thermal blackout lining, made to order with free worldwide delivery.

Frequently Asked Questions