On average, properties lose 10% of theirheat through windows and doors.Installing energy efficient glazing willreduce this heat loss, keep the homewarmer and reduce heating bills whilealso reducing noise from outside.

Energy efficient glazingKeep the heat in and the noise out

How double glazing worksDouble-glazed windows have two sheets of glass with agap between them which is usually 16mm wide. It is thisgap which creates an insulating barrier to slow down therate at which heat escapes from the home. Triple-glazedwindows are now also available which have three sheets ofglass, and therefore two insulating gaps, to provide evenbetter insulation.

How to choose a double-glazed windowChoosing replacement windows for a property can be acomplicated process; there are many factors to considerincluding the type of glass, the windowframe material andwhether the windows are suitable for the style of property.Here are some tips you can follow when looking forreplacement windows.

The most energy efficient glass for double glazing is lowemissivity (Low-E) glass. This type of glass often has aninvisible coating of metal oxide on one of the internalpanes of glass next to the gap. The advantage of this typeof glass is its ability to let light in but cut down on heatloss. In addition, the gap between the two panes of glassin very efficient double glazing is filled with an inert, non-toxic gas. This gas has a greater density than air, so it moreeffectively reduces the heat loss from the property. Argon is

the gas most commonly used in double-glazed windows,as it is extremely cost-effective, colourless, is non-flammable and does not react to other gases.

When your windows are replaced it is vital to make surethat the building remains well ventilated, as thereplacement windows will be more airtight than theoriginals. Ventilation allows fresh air into your home, andmoisture to escape. If your property does not have muchnatural (passive) ventilation, look for replacement windowswith trickle vents that allow a small amount of controlledventilation.

To help you chose the best windows, theBritish Fenestration Rating Council (BFRC)has developed an energy efficiency ratingscheme using an A-G scale (right) similar tothose used for things like fridges andwashing machines. When calculating theenergy rating the entire window –both frame and glass – is takeninto account. The most efficientwindows (rated A or B) may alsocarry the Energy Saving TrustRecommended logo.

How long does double glazing last?The typical lifetime of double glazing is around 20 years.Over time, the gas within the panes will graduallyevaporate at an estimated rate of 0.5-1% per year. Whenaround 25% of the gas has evaporated, the thermalperformance of the windows will be reduced and replacingthe windows or installing a secondary glazing measureshould be considered (see our factsheet ‘Secondaryglazing: the low cost alternative to double glazing’).

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The gap between the twosheets of glass createsan insulating layer

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Warm, quiet, comfortable and secure

Cumbria Action for Sustainability | home energy advice

Listed properties or in a conservation area If your property is a listed building or in a conservation areathere are likely to be restrictions on what you can do toyour windows, so it is always advisable to contact yourlocal authority before carrying out any work. If you are notable to replace the windows, there are several non-intrusive alternatives which can improve the energyefficiency and warmth of your home. These include puttingup heavy, lined curtains which are closed at dusk, shutters,sealed blinds or secondary glazing - or a combination ofthese measures.

Choosing an installerYou can find a good double glazing installer through oneof these organisations:

Fenestration Self-Assessment Scheme (FENSA) is acompetent person scheme set up by the Glass and GlazingFederation and other industry bodies. FENSA enablescompanies that install replacement windows and doors toself-certify compliance under the Building Regulationswithout the need for an assessment from Building Control:[www.fensa.co.uk | 0207 645 3700]

The Double Glazing & Conservatory OmbudsmanScheme (DGCOS) offers a free service to investigatecomplaints about work carried out by its members. Thisincludes free independent inspections, arbitration and acompensation fund. Accredited installers must offerdeposit protection and a comprehensive guarantee tocustomers: [www.dgcos.org.uk | 0845 053 8975]

Give your clothes a day in the sun andgive your tumble drier a break. Clothesdried in the fresh air feel great, and thereare drying days in winter, too.

Catch ‘em young. Encourage yourchildren to switch off electric toys andlights that they’re not using. They’ll soonget the hang of saving energy.

Be a friend to your freezer. Defrost it regularly tohelp it run more efficiently.

Buying a new washing machine, TVor dishwasher? Look out for theEnergy Saving Trust logo.

Don’t over-fill the kettle (but do make sure youcover the metal element at the base).

Dodge the draught! Fit draught-excluders to your front door, letter boxand key hole, and draw your curtains atdusk to keep the heat in.

Turn your heating down by 1 degree. You’ll hardlynotice the change in temperature, but it’ll make abig difference to your heating bill.

Sleep tight. Make sure all the lights areturned off when you go to bed. If youwant to light a child’s room or a landing,use a low-wattage night light.

Tips for lowerenergy bills

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The glazing on the right willkeep this house much warmer

Eden Rural Foyer, Old London Road Penrith CA11 8ET

01768 210276www.cafs.org.ukoffice@cafs.org.uk

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Charity Number: 1123155Registered Company Number: 06492907

Cumbria Action for Sustainability (CAfS)work to promote low carbon living, energysaving and reduced use of fossil fuelsthroughout Cumbria; we provideinformation, advice and motivation throughevents, site visits and practical projects.

Contact us for more information of ourenergy advice events and workshops andhow we can help you save energy in yourhome.

This leaflet was originally produced by theCentre for Sustainable Energy, a national charity(no. 298740) that helps people change the waythey think and act on energy | www.cse.org.uk

Cumbria Action for Sustainability | home energy advice