Curtains and blinds

Well-installed curtains and blinds can help to reduce heat loss through your windows. “Sealing” the curtain or blind, stopping air movement between the window and the room, is much more important than the material it is made from.

Open curtains and blinds during the day and close them just before it gets dark to allow your house to gain heat from the sun during the day, and better retain it overnight. In summer, close curtains and blinds on the side facing the sun and open windows to help keep your home cool.

How curtains and blinds reduce heat loss

The aim is to create a good seal between the curtain or blind and the window, preventing cold air from the window from getting into the room, and keeping warm air in. In cold weather, the air close to the window cools down and gets heavier. Without a good seal, it will simply fall out at the bottom of the curtain or blind, and warm room air will continuously replace it at the top.

Curtains that are installed to create a good seal can reduce heat loss through single glazed windows by up to 60%, and up to 40% to 50% through double glazing. However, as they only work when drawn, curtains are not a substitute for double glazing.

Tips for curtains

To provide good insulation your curtains should:

  • be floor-length and touch the floor, or have pelmets above them with only a minimal air-gap between the top of the curtain and the pelmet (sill-length curtains are ineffective)
  • fit tightly against the wall or window frame
  • be wider than the window frame
  • preferably be double layered with a thick lining.

Net-curtains installed very close to the window, and in contact with the window frame, can be effective too.

Tips for blinds

  • To provide good insulation, your blinds should have a snug fit with the window frame, creating a good seal to trap the air in the gap between them and the window (if there are gaps around the blinds, their thermal effect will be minimal).
  • Specifically designed thermal blinds (sometimes described as ‘honeycomb’ or ‘cellular’ blinds) may provide additional insulation, but only if they can be installed without any gaps around them – which is hard to achieve in practice.