Single paint windows are one of the largest source for heat loss in a home. They have low insulating value, high air leakage and can be responsible for 25 to 50 percent of the energy use to heat or cool a home.
Almost any windows will improve over single pain and new energy efficient glass/window options can even significantly increase the insulating value of dual pain glass.
An easy way to determine window efficiency would be to choose a window with an “Energy Star” label. They do have a National Fenestration Rating Council (NFRC) energy performance label on all windows that will help you compare energy rating on windows. There is five factor used.
* U-factor measures how well a product prevents heat from escaping.
* Solar heat gain coefficient (SHGC) measures how well a product blocks heat caused by sunlight.
* Visible transmittance measures how much light comes through a product.
* Air leakage measures how much air will pass through cracks in the window assembly.
* Condensation resistance measures the ability to resist the formation of condensation on the interior surface.
The optimal combination of U-factor and SHGC depends on the climate zone as well as direction.location of your home. Products with the Energy Star label will include a map to help you determine the right window for your area.
There are a variation of different glass types that can be chosen. Low E Glass is typically the standard in efficiency glass. A Low-E coating is a microscopically thin, virtually invisible, metal or metallic oxide layer deposited directly on the surface of one or more of the panes of glass. There are also argon gas than can be filled in the window to help efficiency as well as Super Spacer® solid silicone foam spacer to help reduce heat transfer. There are also Laminated Glass and Sun coatings that are available dependent on the windows manufacturer.