--- title: "Do thermal curtains work? How much heat they save and how to hang them (UK)" description: "Heavy lined curtains cut the heat lost through a window at night, most of all on single glazing. What the tests show, how to hang them so they work, and when a lining is enough." url: https://homecomfortlab.co.uk/heating/do-thermal-curtains-work/ --- # Do thermal curtains work? Heavy lined curtains cut the heat lost through a window at night, most of all on single glazing. What the tests show, how to hang them so they work, and when a lining is enough. By [Pete Harvey](https://homecomfortlab.co.uk/about/), editor. Updated 24 October 2026. This page links to Amazon. As an Amazon Associate I earn from qualifying purchases. [More about how this site is paid for](https://homecomfortlab.co.uk/affiliate-disclosure/). > **The short answer** > > Yes, at night, and most on single-glazed or older windows. Historic Environment Scotland says heavy, lined curtains cut the heat lost through a traditional sash window by 14%. Any curtain that is thick, lined, wider and longer than the window and closed at dusk does most of that job, whether or not it's sold as thermal. Open them in the day so the sun can warm the room and the glass can dry. ## How much they cut heat loss Historic Environment Scotland, which looks after Scotland's historic buildings, gives these figures for how much each change cuts the heat lost through a traditional sash window: | What was added | Cut in heat loss | | --- | --- | | Heavy, lined curtains | 14% | | Timber shutters | 51% | | Secondary glazing | 63% | | Secondary glazing with blinds or shutters | More than 75% | Curtains help, but much less than a second layer of glazing or a shutter that closes tight. They work by trapping a layer of still air between the fabric and the glass. Air that can flow over the top of the curtain or round the sides carries the heat away again, which is why the way you hang them matters as much as the fabric. Modern double glazing loses less heat than single glazing to begin with, so curtains save less on it. On single glazing, especially in a flat you rent where you can't change the windows, good curtains and [window insulation film](https://homecomfortlab.co.uk/heating/draught-excluders-and-window-film/) are the two cheap things you can do. ## What makes a curtain thermal Most ready-made curtains sold as thermal don't state a measured heat-loss figure, so judge them by how they're made: - **A dense lining.** Foam-backed or triple-weave blackout fabric stops air moving through the curtain. - **Weight.** A heavier curtain hangs closer to the wall and moves less in a draught. - **A separate lining** hooked behind a curtain you already have does the same job. It's the cheaper fix if your curtains are already the right size. Thermal and blackout linings are often the same product. That's useful in summer too: closed on a sunny window, they keep the heat out. See [how to keep a bedroom cool in a heatwave](https://homecomfortlab.co.uk/cool/how-to-keep-a-bedroom-cool/). ## How to hang them so they work - **Wider than the window.** Fit the pole or track well past the frame on each side, so the curtains overlap the wall when they're closed and air can't get round the edges. - **Long enough.** To the floor if nothing is in the way. If there's a radiator under the window, stop the curtains at the sill instead. - **Never over a radiator.** A curtain hanging in front of a radiator sends its heat up the gap behind the curtain and onto the coldest glass in the room. - **Closed at the top.** Warm room air can spill over the top of the curtain, cool against the glass and fall out at the bottom. A pelmet, or a track fixed to the ceiling, stops most of that. - **Closed at dusk and open in the morning.** In the day the sun through the glass warms the room for free. ## Curtains and condensation Closed curtains keep the room warmer, but the glass behind them gets colder, because less room heat reaches it. Moist air that gets behind the curtain meets that colder glass, so you may see more water on the window in the morning. Keep closing them at night, and deal with the moisture: 1. Open the curtains when you get up, and wipe the glass and sill dry. 2. Keep trickle vents open, or open the window for a few minutes to let the damp air out. 3. Don't let the curtains rest against wet glass. Damp fabric is where mould starts on linings. More on this in [why your windows are wet every morning](https://homecomfortlab.co.uk/damp/why-are-my-windows-wet-every-morning/). ## Don't forget the front door If your front door opens straight into the living room, a heavy curtain across it at night does the same job as one at a window. A rising door rod lifts the curtain as the door opens, so it doesn't drag. Seal the gaps in the door first: see [how to draught-proof a door](https://homecomfortlab.co.uk/heating/how-to-draught-proof-a-door/). ## Our picks Chosen by how they're made. None of these makers publishes a spec page, so the details come from their listings. We haven't tested them ourselves. Measure your window, including how far past the frame you want the curtains to reach, before you choose a size. ### New curtains for a cold window Enhanced Living Nightfall Supersoft Thermal Eyelet Curtains (natural) - **Type:** Thermal curtains - **Size:** Pair, 66 x 72in (168 x 183cm) A heavy triple-weave fabric, dense enough to slow air through the curtain without a separate lining. In this colour it's sold as room darkening rather than full blackout, and the maker says to hand wash it. [View on Amazon](https://homecomfortlab.co.uk/go/cu-thermal-a/) ### To upgrade curtains you already have Homescapes Blackout Curtain Lining, 3-pass coating (pair) - **Type:** Curtain lining - **Size:** Pair, to fit 66 x 54in curtains A coated blackout lining that hooks onto the heading tape of your own curtains, cut slightly smaller so it doesn't show. Check the size above against your curtains: this pair is a short, sill-length drop, which suits a window with a radiator underneath. Eyelet curtains need lining hooks, so check those are included. Dry clean only. [View on Amazon](https://homecomfortlab.co.uk/go/cu-lining-a/) ### For a front door Enhanced Living Nightfall Thermal Eyelet Door Curtain (natural) - **Type:** Door curtain - **Size:** Single, 66 x 84in (168 x 214cm) The same triple-weave fabric as the window curtains above, in a single panel long enough for most front doors, to hang on a rising rod. [View on Amazon](https://homecomfortlab.co.uk/go/cu-door-a/) ## Sources - [Historic Environment Scotland: how to reduce heat loss from sash windows](https://www.historicenvironment.scot/protect-and-care/owning-managing-and-visiting/looking-after-traditional-buildings/how-to-reduce-heat-loss-from-sash-windows/) Checked 24 October 2026. ## Read next - [Draught excluders and window insulation film](https://homecomfortlab.co.uk/heating/draught-excluders-and-window-film/) (Buying guide) Cheap draught proofing that makes a real difference: door excluders, letterbox brushes and window film. - [Why are my windows wet every morning?](https://homecomfortlab.co.uk/damp/why-are-my-windows-wet-every-morning/) (How to) Morning condensation means warm, moist air is meeting cold glass. What causes it and how to stop it. - [How to draught-proof a front or back door](https://homecomfortlab.co.uk/heating/how-to-draught-proof-a-door/) (How to) The four places an outside door lets cold air in, which seal or excluder suits each gap, and what to leave alone so the house can still breathe. - [Heated airer running costs](https://homecomfortlab.co.uk/heating/heated-airer-running-costs/) (Running costs) What heated clothes airers cost per hour and per load at the current price cap, and how that compares with a tumble dryer. --- As an Amazon Associate I earn from qualifying purchases. Links to shops are marked, and earning from them never decides what we recommend. [How this site is paid for](https://homecomfortlab.co.uk/affiliate-disclosure/). Running costs use 26.32p per kWh for electricity and 7.97p per kWh for gas, the [Ofgem price cap, Direct Debit average for England, Scotland and Wales](https://ofgem.gov.uk/news/changes-energy-price-cap-between-1-october-and-31-december-2026) for 1 October to 31 December 2026.