"Understanding Your Home" by Building Inspector Mark Visser
Home Page
About Us
Fireplace/Wood Stove
Heating and Cooling
Windows and Doors
Window Purchasing Considerations. Net Heat gain. Net Heat Loss

Window location
Net heat gain
Net heat loss

Net heat losers

All single glazed windows are net heat losers.

All windows facing north are net heat losers.
Net heat gain
Double glazed windows are net heat gainers for SW, S and SE locations.
Triple glazed windows are net heat gainers for SE, S, SW and W locations

Net Heat gain
Net Heat Loss

Window Purchasing Considerations
Net Heat gain. Net Heat Loss
Need more information? Use our search box

Window Purchasing Considerations. Net Heat gain. Net Heat Loss
When old windows are beyond repairs or need replacing, you can reduce the heat loss by decreasing window size. Alternatively, larger windows might enhanced views or greater solar gain. Windows can also be relocated to enhance natural lighting and ventilation.
Infiltration accounts for the largest part of window heat loss. Consider installing fixed-pane windows if ventilation or emergency exit is not required. Where ventilation is required, consider some combination of fixed and operable window, especially for large windows.
When purchasing double or triple glazed windows, keep in mind that it is the thickness of the air space between panes that determines the insulating value. Buy windows with at least 1/2" (12.7 mm) air space. Anything less is money down the drain. A 3/4" (19mm) air space offers even better insulating values.
A double glazed window with a low emissive coating (E coated) has the same insulating value of a regular triple glazed window. It may not always be practical to install triple glazed units due its weight.
In addition to E-coated windows you also have another option to increase the insulation value by purchasing windows where the air between window panes has been replaced with Argon gas. Argon gas is a motionless gas that manufacturers use to fill the space between panes of glass to reduce the heat loss. Argon gas is often used because it is a better insulator than air.

Back to Top