> Windows and saving on heating and cooling costs

Windows, doors and other openings account for up to 40% of a buildings energy consumption in heating and cooling. This is can end up being one of the most significant day to day running costs in a home; this article will explain a few simple and sensible tips to save money and be green in the process too.

Windows, where do you place them?

One of the most important decisions is where to place your windows to both take advantage of the natural solar cycle and minimize heat loss. In Australia this usually means the majority of the window area is on the North side of the building, in this way the heat of the Winter Sun can enter into the building and asset in keeping it warm in Winter. Although you need to make sure that a sufficient 'overhang' is above the window to keep out the higher Summer Sun. The side that has the least window area is the South side, as this never gets any natural direct sunlight; so you just want to get a basic level of light, otherwise you run the risk of the glass area literally 'sucking' the heat of your rooms...  Note: In the Northern hemisphere the references to North and South are reversed.

Convection through the glass

A plain glass window will act as a very good medium for equalizing the temperatures on either side. In effect the colder temperature side 'cools' the glass and this is transfered through to the inside which in turn cools the air next to it and you get a down draught as a result - this down draught then pulls more air in contact with the cold glass and the cycle continues until the whole room is cooled down...

Drapes and Curtains

Any form of covering over such glass, like a drape or curtain will create a separate area of air distinct to the air in the room. This on its own will drastically reduce the heat loss by preventing the cold air interacting with the air in the room.

The glass used

The particular type of glass you use in your windows will have a dramatic effect on the amount of heat 'lost' through the window. For instance a 7mm thick pane of glass will loose heat at approximately 30 times the speed of double glazing. Even putting a simple plastic film over the single pane of glass will reduce the heat loss to a quarter of its previous rate.

The frame used

Given the information above it should come as no surprise that the particular frame used can also have a dramatic effect on the rate of heat transfer. There are a few options available for the frames as follows:

• Simple aluminum frames - simple extruded aluminum formed to make a frame; usually quite bad at creating 'thermal bridging' with the outside environment - i.e. heat is lost via the frame itself.