Glazing can save energy and money
Have my neighbours done this?
What is it?
Fitting more efficient windows that waste less heat
What will it save me?
Could save around £150 per year
How do I get it?
Usually installed by a specialist contractor
What does it cost?
Quite expensive, typically over £5,000 (2013) secondary glazing may be cheaper
What are the technical details?
Replacement double glazing is the most popular home improvement, even where the existing windows are still serviceable, but it‘s not necessarily for energy saving reasons. Pound for pound, it’s still a very expensive way to reduce fuel bills. However, it certainly does save energy and it's best to have the most efficient ones but there are a few different ways to achieve effective energy savings.
- Double glazed units rely on 2 sheets of glass separated by a sealed cavity where the cavity provides the additional insulation value and the optimum width for the cavity is around 20mm. This can be improved by filling the cavity with an inert gas such as argon and coating the glass with a material that reflects radiant heat back into the room.
Double glazed windows will have a raised inside surface temperature and be less likely to cause condensation to form, although if the seal is defective, condensation is very likely in the cavity.
- Triple glazed units are widely used in other European countries and follow the same principle as double glazed units but with another sheet of glass and another cavity and the cavity increases the resistance to heat loss significantly.
- Replacement frames are normally fitted with double or triple glazing and the material and construction of the frame has a large influence of the overall heat loss from the window. The most efficient frames will contain a thermal break so that there is a separation between the outside face of the frame and the inside face to reduce heat flow. This can be achieved with most windows although PVC is the most commonly used. One of the key features of replacement frames is that they will have integral draught proofing which is usually very effective and less conspicuous than retrofitted draught proofing.
Where this is not desirable or permissible, as in listed buildings or some conservation areas, traditional timber windows can be manufactured to original designs and still incorporate energy saving features.
- Secondary glazing is perhaps the least destructive way of improving the energy performance of existing windows. This consists of an additional window fitted on the inside of the original one and usually in the existing window reveal or attached to the existing frame. The additional window will include draught proofing and openable glazing to allow for cleaning and opening the existing window.
Whilst it is possible to install secondary glazing and replace individual window units as a DIY job, replacing window frames may be too difficult for even a skilled DIY task.