Get instant double glazing

Use an inexpensive kit to stick effective insulation film to the frames of wooden windows. The transparent film creates a layer of still air in front of the glass that acts as insulation – just like double glazing.

  • Can reduce heat loss through glass by almost 60%
  • Reduce condensation
  • Do it yourself with scissors and a hairdryer
  • Great option for renters
  • Available from hardware stores or online shops.

Tips on window insulation kits

The measurement between the inside surface of the window frame and the glass should be at least 5mm. Frames need to be dry, leak-free, and the paint in good condition (inside and out).

Clean and dry the glass, then use the adhesive tape in the kit to stick the film to the frame. Blast with a hairdryer to remove any wrinkles. 

The film is designed to last one season but could last for several years. Just be aware the tape can leave a stain if you leave it more than one season.

Before you buy:

  • The film won’t stick to aluminium windows.
  • Don’t use where people or pets could damage the film.
  • They are transparent – but may make your view less crystal clear.

Install thermal curtains and blinds

When you fit them, create a good seal over windows to stop cold air getting in. The most effective curtains:

  • Are double-layered with a thick lining
  • Touch the floor
  • Have pelmets above them
  • Are wider than the window frame
  • Fit tightly against the wall or window frame.

Find an Eco Design Advisor(external link)

Tips for curtains

  • Close curtains and blinds just before it gets dark to keep the day’s warmth in.
  • Net curtains installed very close to the window, and in contact with the sides of the window frame, can be effective too.
  • Honeycomb blinds have thin tubes that open up when you close the blind, creating air pockets than can provide good insulation.
  • Curtain banks offer free curtains to low-income households.

See if there’s a curtain bank near you(external link)

Double glazing – a big ticket item that makes a big difference

Need to replace or repair your windows? Maybe it’s time for double glazing – it’s a big investment but can reduce heat loss through glass by 70%.

  • Let in as much sunlight as single glazed windows
  • Reduce external noise
  • Reduce condensation
  • Prioritise your main heated areas (such as living room) and large windows.

Tips for double glazing

Double glazed windows have two panes of glass with an insulating layer of inert gas or air between them. Frames made of plastic (uPVC) or wood are less likely than aluminium to attract condensation and will lose less heat.

If you prefer aluminium frames, get ones with a thermal break in the middle – a section inside the frame made of insulating material such as plastic or wood.  

For the best performance, look for:

  • Low-E glass - lets in light and heat and helps to stop the warmth escaping. Double glazing with low-E glass cuts window heat loss by about 30%, compared to double glazing without low-E.
  • Layers of seals – to keep out draughts, moisture and noise.
  • Spacers separating the panes made from plastic or stainless steel, not aluminium
  • Inert gas such as argon between the two panes – it can reduce window heat loss by 3-9% compared to air.

Secondary glazing adds a pane to your existing windows

Instead of replacing your entire window with double glazing, you may be able to upgrade them by forming a sealed, insulating air gap with a second pane of glass. It can be a cost-effective, practical solution – and work almost as well as double glazing.

Options include:

  • Install a second frame inside your window – typically an aluminium frame with sliding panes. Low-e glass can be used with this option.
  • Acrylic sheet magnetically attached to the inside of your window.

Tips for secondary glazing

  • The best option depends on the type and condition of your existing windows – get advice from a professional.
  • Make sure the frames are good enough to last as long as the secondary glazing.
  • Get at least two quotes - compare them with the cost of new double glazing as well.
  • Ask for independently verified performance guarantees and warranties.
  • Make sure there’s at least 1cm between the existing and secondary glass.

Low-E window film reflects heat back into your room

A film with a micro-thin metal coating fitted to the inside of single glazed windows can reduce heat loss by up to 25%. It’s best for houses that rarely experience condensation on windows. That’s because the film reflects heat from the glass, making the glass colder and increasing the likelihood of condensation – and when this condensation happens, the film stops working.

What’s low-e window film like?

  • Virtually transparent and tint-free.
  • Applied directly to single-glazed window glass.
  • Deflected heat and UV light coming in from the sun can reduce overheating and fading of furnishings.
  • Heat deflection can reduce the amount of free heat your house soaks up in winter.

Independent report on low-e film [PDF 742 KB]