Double Pane Windows

If you need to replace the existing windows in your property you really should consider installing double pane windows. Double pane windows can be made to measure and bought in all the styles that ordinary single pane widows come in, yet a double pane window will have far superior energy efficiency.

More efficient windows mean that you will lose less heat through the windows which in turn means you’ll need less energy to heat your home. These two things combine to save you money on fuel and increase the green credentials of your property, making both it and you more environmentally friendly.

Heat Insulation

The principle behind double pane windows is quite simple. Glass is quite a good conductor of heat, whilst air is a relatively poor conductor of heat. A double pane window has two sheets of glass with a small air filled gap between them, usually between 3/8 and 1/2 inch; the two sheets of glass are separated by silicone and butyl seals.

By having a gap between the inner and outer panes of glass any heat arriving at the inner pane is not directly conducted outside by the glass; and the layer of air between the panes impedes the transfer of heat to the outer pane, even by convection. The net result of these two things is less heat loss through the windows. In the window trade double pane windows are referred to as Insulated Glazing Units (IGUs).

A single pane glass window has an R value of around 0.88. A second pane of glass with air space of ½ inch increases the R value to around 2.00, which means the glass has more resistance to heat passage.

Sound Insulation

The double panes of glass with an air gap between them also make excellent insulators of sound. Subsequently double pane windows can also be used to great effect in reducing the level of noise entering a building from a busy road, airport or industrial estate etc.

Special Coatings

Coatings can be applied to the window panes to give them a tint or even a reflective appearance. The panes can also be given a Low-E (low emission) coating. This can be applied to either retain heat or inhibit solar radiation entering the room. If applied to the side of the glass inside the air space it will help reduce heat loss and yet encourage the suns natural energy to heat the room.

However, if applied on the outside of the outer window pane it will reflect solar radiation, thus helping to keep the room cool. So, a double pane window can work the same as a greenhouse; absorbing long wave radiation and reflecting short wave radiation.

If you live in a hot climate you could, therefore, end up using your ‘air con’ less and make the same savings as someone in a cold climate wanting to retain heat in their property.

Double Pane Window Materials

You can have a double pane window made out UPVC, wood or metal. UPVC has been a popular choice of material for several years as it is durable and does not need regularly treating or painting. Some concerns are made about the production of the UPVC and the ultimate ‘green’ credentials of UPVC double pane windows; so you might prefer to go for a traditional wooden frame.

Metal, especially steel frames, are an excellent option if it’s important to get the maximum amount of light possible in to a room through the window. The engineering strength of steel means; that the frame can have a very low profile with a maximum expanse of glass.

If you are not replacing all the windows in the property you’re advised to use the same material for the new window frames as the other older windows. If you eventually want to sell the property you may well find that ‘odd’ window frames detract from its over-all value.

Window Terminology

Some terms to be familiar with if you go shopping for double pane windows follow:

Awning window: top mounted hinge lets the window swing out and up to open, common un bathrooms

Casement window: side mounted window that swings open on a hinge

Double-hung window: has two sashes sliding vertically on tracks to open, more common in older homes

Framing: the structural support of the window in the wall.

Sill: the bottom board of the window frame

Stool: the part of the sill on the interior that slopes downward