Best Thermal Curtains UK 2026: Do They Actually Save Energy?

The Short Answer

Thermal curtains genuinely work — they can cut heat loss through windows by 25–40%, and the difference is noticeable the first night you draw them. If you've got single-glazed or draughty windows and double glazing is too expensive right now, thermal curtains are the best budget fix. Get Deconovo for value or NICETOWN if you want something heavier for a big window. If you already like your curtains, a clip-on thermal lining adds the same insulating layer for less money.

How Thermal Curtains Actually Work

Windows are the thermal weak point of any house. Even double glazing loses heat roughly 5 times faster than an insulated wall. Single glazing is worse still — it loses heat about 10 times faster. In a typical semi, windows account for 15–20% of total heat loss.

Thermal curtains tackle this by creating a trapped air pocket between the curtain and the glass. The heavy, multi-layered fabric acts as a barrier that slows heat transfer. The wider and heavier the curtain, the better it works — and crucially, it needs to cover the window completely from wall to wall and reach the floor (or at least the windowsill) to trap the air properly. A curtain that doesn't touch the sides lets cold air spill out around the edges.

The National Energy Foundation found that heavy, well-fitted curtains can reduce heat loss through single-glazed windows by up to 40%, and through double-glazed windows by 14–17%. That's a meaningful saving for something that also makes your room look better.

What to Look For

• Triple-weave or multi-layer construction — this is what traps the air and provides insulation. A thin, unlined curtain does almost nothing thermally.
• Full coverage — the curtain should extend at least 15cm beyond each side of the window, touch the windowsill or floor, and ideally sit behind a pelmet or return around the wall to seal the edges.
• Blackout lining is a bonus, not a necessity — most thermal curtains are also blackout, which is useful for bedrooms but not essential for thermal performance.

Our Picks

Best Value: Deconovo Blackout Thermal Curtains

The Deconovo range is the best-selling thermal curtain on Amazon UK and it's easy to see why. The triple-weave construction is effective at trapping air, they come in a huge range of sizes and colours (so you'll find something that works for most rooms), and they're priced well under most high street alternatives.

The fabric weight is mid-range — noticeably heavier than a standard unlined curtain, but not as heavy as premium options. For most rooms and most window sizes, they're the right balance of performance and price. If you're doing the whole house, the savings versus buying premium curtains add up fast.

Best for: Most rooms, most budgets. The safe choice that does the job well.

Best for Large / Draughty Windows: NICETOWN Thermal Curtains

If you've got big bay windows, floor-to-ceiling windows, or particularly draughty single-glazed windows, NICETOWN curtains are worth the small premium. They're heavier and denser than Deconovo, which means they trap air more effectively and drape better on larger windows (lighter curtains can billow and break the seal).

The fabric quality is also a step up — they feel more like proper curtains than a budget product. If you're putting them in a living room where appearance matters, these are the ones to go for.

Best for: Living rooms, large windows, and anyone who wants something that looks as good as it insulates.

Best if You Like Your Current Curtains: Thermal Lining

If you've already got curtains you like — or you've spent money on them — you don't need to replace them. A clip-on thermal lining attaches to the back of your existing curtains using curtain hooks, adding a thermal layer without changing the look of the room.

They're cheaper than buying new curtains (£10–£20 per panel vs £20–£45 per pair), and you can remove them in summer when you don't need the insulation. The downside is that they add bulk to the curtain, so if your curtain pole is already loaded, check it can handle the extra weight.

Best for: Anyone who doesn't want to replace existing curtains. Also good for renters — take them with you when you move.

How Much Will You Save?

Window Type	Heat Loss Reduction	Estimated Annual Saving (per window)
Single glazed (no curtains currently)	30–40%	£15–£30
Single glazed (replacing thin curtains)	15–25%	£8–£18
Double glazed (no curtains currently)	14–17%	£5–£12
Double glazed (replacing thin curtains)	5–10%	£3–£7

For a house with 6 single-glazed windows, thermal curtains could save £90–£180 per year. At £20–£35 per pair, the payback is often within the first winter. Even on double-glazed windows, the saving is enough to justify the cost within a year or two.

Tips for Maximum Effect

• Close curtains at dusk, not bedtime. Heat loss through windows accelerates as soon as it gets dark and cold outside. Close them as early as possible.
• Open curtains during the day on sunny south-facing windows. Free solar gain through the glass heats the room — don't block it with curtains.
• Make sure they reach the floor or sill. A gap at the bottom lets cold air fall down the glass, pool at the bottom, and flow into the room. This is the single biggest mistake people make with thermal curtains.
• Use a pelmet or curtain box if you can. A pelmet across the top stops warm room air rising up behind the curtain and hitting the cold glass. It makes a surprising difference.

For more ways to reduce heat loss through windows, see our guide to window insulation film. For the full picture on insulating your home, read our insulation costs guide.