Windows account for just 10% of home heat loss so there isn’t the potential for large savings as with loft insulation. That doesn’t mean you should do nothing, there are low cost options that will save money and improve your comfort.
Existing Windows – Improving Energy Efficiency
Double Glazed Windows – Image from FENSA who certify glazing installers
Draught Proofing
If you have single or double glazed windows in good condition then it will not be cost effective to replace them. New windows are not cheap. Do check for any draughts. A good way is to light an incense stick and watch the smoke on a windy day.
With single glazed wooden windows, thin draught stripping on the opening lights is cheap and easy to install. Available from most DIY outlets. Draughts around the frame can be sealed with appropriate silicon sealants applied from a tube with a gun.
If the seals are faulty on double glazed windows allowing draughts through the opening lights, they can be replaced. Check for a double glazing repair specialist or contact the installers if known.
Thermal Barrier Blinds
Adding a roller blind or vertical blinds just in front of the window will reduce heat loss at night. The enclosed air between the window and the blind acts as a sort of insulation preventing convection from the warm room. You can get ‘thermal’ blinds but I doubt they’re worth the extra cost.
Curtains as Insulation
Next add heavy, lined curtains in front of the window and blind. These can look and work well in front of external doors. For extra efficiency enclose the tops of the curtains in a pelmet. Very 1950s but they work! You can also fix velcro to the side of the curtains and the wall to hold them still and stop warm air escaping to the outside.
Radiator Shelves
Often radiators are sited under a window. Really not clever from an energy efficiency standpoint but it heats the cold spot so the installer doesn’t get any complaints! The heat rises up, often behind the curtains, and your money is spent warming the world.
Placing a shelf above the radiator will divert the heat out into the room and you will be more comfortable whilst using less energy. It’s simple to do, inexpensive and looks well. Cats love them as heated beds!
Secondary Glazing
We’ve had a house with secondary glazing inside from single glazed windows and we have tried the film secondary glazing that is attached to the existing window. They may have saved some energy but they caused a lot of condensation on the inside and fogging of the windows. Not recommended.
New Windows
In Scandinavia many houses actually have double, double glazing or triple glazing at least. If replacing windows make energy efficiency your first priority. The size of the air gap between panes makes a difference, larger is better. 20mm gap on double glazed, 12mm on triple should be looked for. Argon gas filled gaps improve efficiency as well.
The type of glass is important – low-emissivity glass (or low-e glass as it is commonly referred to) is a type of energy-efficient glass designed to prevent heat escaping through your windows to the cold outdoors. Low-e glass such as Pilkington K Glass™ has an invisible coating which reduces heat transfer and reflects interior heat back into your room.
You will pay more for these energy efficiency features but it is well worth paying the extra for something that should last 25 years.
Ensure your contractor is reputable and can offer an insurance backed guarantee so you are covered even if they go out of business.
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