How to stop heat loss through windows in winter

Windows play a big role in retaining heat in your home. A single pane of glass can lose almost 10 times as much heat as the same area of insulated wall. 

Heat loss from windows

Reduce heat loss through windows and save money on your winter heating bills. Appropriate window protection creates an insulating layer of still air on the inside of the glass. This can be achieved by the addition of thick curtains and a pelmet. 

The diagram below shows the difference between a poorly fitted and a well-fitted curtain and the effect this has on heat loss. The poorly-fitted curtain allows heat loss to occur, while the well fitted curtain combined with a pelmet significantly reduces heat loss. 

Window coverings and heat loss


  • Use closely woven, close-fitting curtains or blind
  • Ensure there’s a snug fit on both sides of the window and at the top of the curtain to stop warm air from moving down behind the curtain and cooling
  • Install pelmets or solid barriers above the curtain rail, or position the curtain within the window space (pelmets can be as plain or as decorative as you like – for some great ideas, visit Pinterest and search for 'pelmets'
  • Use curtain tracks that provide a return of curtain to the wall to create a seal
  • Close curtains or blinds when you have the heating on, especially at night – by leaving curtains or blinds open, you're wasting money and energy 

More information