There are three main reasons for fitting double (glazing) to your windows: to reduce the amount of heat getting out, to reduce the amount of noise getting in and to increase comfort for people in the room or house - mainly by cutting down draughts.
Reducing heat loss - Around 10 to 20 per cent of the heat loss from a house is through the windows.
Double glazing can reduce this by up to a half because of the layer of still air between the two panes, which acts as an insulator.
The optimum thickness for this air gap is about 20mm.
Double (glazing) is not normally cost effective unless you do it yourself.
Cutting down noise - Double glazing may not, on its own, solve a noise problem but where the noise is getting in through the windows - traffic noise is an obvious example double glazing can be very effective.
The thickness of air gap needed is quite large.
The normal recommendation is for an air gap of between l00mm and 200mm - practical considerations rule out gaps any larger than this.
This size of air gap still provides effective heat insulation.
Increasing comfort - One of the effects of a single-glazed window is to create a pool of cold near the window.
In addition, the cold inside surface of the window will create draughts.
Because the inside pane of a double-glazed window is warmer, both these effects are reduced and more of the room becomes comfortable to sit in.
Central heating radiators no longer have to be put under windows.
Another important effect of double (glazing) is to reduce condensation.
Because condensation is caused by warm moist air meeting a colder surface, the warmer inside pane of double glazing will reduce it or eliminate it altogether.
However, condensation can occur on the inside of the outer pane if the air gap is not properly sealed from the room.
This can be reduced by venting the air gap to the outside with holes drilled through the window frame.
Because some types of double glazing (especially replacement windows) improve draught proofing, they can actually increase condensation elsewhere in the room.
Extra ventilation may then be needed.
Reducing heat loss - Around 10 to 20 per cent of the heat loss from a house is through the windows.
Double glazing can reduce this by up to a half because of the layer of still air between the two panes, which acts as an insulator.
The optimum thickness for this air gap is about 20mm.
Double (glazing) is not normally cost effective unless you do it yourself.
Cutting down noise - Double glazing may not, on its own, solve a noise problem but where the noise is getting in through the windows - traffic noise is an obvious example double glazing can be very effective.
The thickness of air gap needed is quite large.
The normal recommendation is for an air gap of between l00mm and 200mm - practical considerations rule out gaps any larger than this.
This size of air gap still provides effective heat insulation.
Increasing comfort - One of the effects of a single-glazed window is to create a pool of cold near the window.
In addition, the cold inside surface of the window will create draughts.
Because the inside pane of a double-glazed window is warmer, both these effects are reduced and more of the room becomes comfortable to sit in.
Central heating radiators no longer have to be put under windows.
Another important effect of double (glazing) is to reduce condensation.
Because condensation is caused by warm moist air meeting a colder surface, the warmer inside pane of double glazing will reduce it or eliminate it altogether.
However, condensation can occur on the inside of the outer pane if the air gap is not properly sealed from the room.
This can be reduced by venting the air gap to the outside with holes drilled through the window frame.
Because some types of double glazing (especially replacement windows) improve draught proofing, they can actually increase condensation elsewhere in the room.
Extra ventilation may then be needed.
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