by A. Smith

Created on: December 24, 2011   Last Updated: December 25, 2011

Up to 30% of all heat loss in your home happens through your windows. Treatments can be applied to window glass to cut heat gain and energy loss. Basic insulating film is a common form of window treatment which can be applied each year to reduce energy loss through windows. Window glass can also be insulated by applying pyrolytic coatings at the factory where the window glass is manufactured.

DIY window films are normally applied on the inside of the window pane. Factory window treatments can be applied on the inside or outside of the window pane, depending on the type of window coating used. Not all films are suitable for all kinds of glass.

A correctly applied coating will keep radiant heat on the same side of the glass as its origin. In the summer, these window treatments will keep heat out. In the winter, these window treatments will keep heat in.

Insulating films

Insulating films which you can apply yourself are the fastest way to insulate house windows. They consist of transparent barriers which fit over the existing window panes. These types of window treatments cut down on heat exchange through the window pane due to radiation by adding a temporary insulating barrier. Read the manufacturer's instructions before applying.

Cut the film to size, working top to bottom. Some types of insulating film should be peeled from their backing and applied to a wet window. Others require heat for a shrink-tight fit on windows. A hairdryer is useful for this purpose.

Factory window treatments

Factory-applied window treatments are metalized, dyed, or ceramic. All of these heat rejection films reduce the amount of infrared and ultraviolet light which passes through a window. Tinted films also reduce the amount of visible light.

Dyed films are subject to discoloration over time. This is not a problem with metalized or ceramic window films. In general, dyed window treatments are the cheapest and ceramic films are the most expensive. All heat rejection films can reduce the amount of radiant heat transfer through your window glass by at least 30%.

Tungsten-doped vanadium dioxide

This intelligent window coating is a relatively new window coating technology which can act as an extremely fast optical shutter. At 86 degrees Fahrenheit and below, it is transparent. Above 86 degrees, it changes to reflective in less than a second. The transition temperature can be changed by altering the amount of tungsten.

A window which has been treated with tungsten-doped vanadium dioxide reduces building interior heat loss during the night and blocks infrared absorption during the day. Both the transparent and reflective forms have a slight yellow-green color, which is not desirable for residential buildings. Cost is also an issue. This coating is still being researched.

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