Windows and Doors

Introduction

If you are thinking about changing your windows or doors you will need to think about U-values. A U-value measures of the rate at which heat escapes through a fabric, so the lower the figure, the better.  A U-value of zero means that no heat is escaping.  It is expressed as Watts per square metre (W/m²) but it is really only the number that matters. 

Double and triple glazing

Double or triple glazed windows are another form of insulation. However, as you can see from the figures below, it is not generally so efficient as wall and roof insulation. Replacing a single-glazed window with a reasonable quality double-glazed unit will more than halve the heat loss.

The Energy Saving Trust estimate that you will save £165 a year by replacing single glazed windows with B-rated double glazing. You will also reduce noise from outside, and experience less condensation.

However, only about 10 per cent of the total heat loss from the house is through the windows, so there is really no point in putting expensive double-glazed windows in un-insulated walls. Similarly, it's only worth investing in the best triple glazed windows if you have super-insulated the property first.

Glazing

Standard windows will have air in the gaps between the panes of glass. Higher performing ones tend to have argon or other gases between. They will also have a low-E (low emissivity) coating. This allows the heat from the sun into a room, but reduces the amount that escapes again.

Frames

UPVC are a low maintenance option. However, the Centre for Alternative Technology recommend that they should be avoided as their production is energy intensive, and they are polluting at manufacture and disposal.

Alternatives include wood (which needs more maintenance), aluminium and composites which have wood on the inside and aluminium on the outside.

New double glazing is required to have trickle ventilation in the frame (even if the ones you are replacing do not). This is because modern windows are more air tight than older ones.

Efficiency

Some manufacturers label their windows with the standard A-E measures of energy efficiency

C & L Windows and Conservatories Ltd

65, Seymour Road

Gloucester

Gloucestershire

GL1 5PT

01452 526028

www.candlwindows.co.uk