How Does an Energy Star Window Work?

Energy Star Window Benefits

Energy Star rated windows provide many benefits for the homeowner. Installing efficient Energy Star windows saves money because less energy used will reduce greenhouse gas emissions from power plants. This helps the homeowner save energy and lower the monthly heating bill. A home’s indoor temperature is maintained at a comfortable level because Energy Star qualified windows regulate indoor air temperatures to retain heat in winter and the cooler air inside in the summer months. Windows with the Energy Star rating symbol are manufactured with a special glass coating that acts as a sunscreen for the home to prevent valuables from being destroyed from the strong rays of the sun that can fade or discolor furniture or other items. Energy Star rated windows work by the way in which heat enters or leaves the home.

Heat Transfer Process

Heating leaves the home through windows by conduction, convection, radiation and air leakage. Conduction happens when heat moves from inside the home to the outdoors through a solid material such as a window. Convection happens when the cold glass is exposed to warm air and the warm air in the house collects on the floor to cool down the air temperature in the area above the floor and below the ceiling. Glass from the window pulls this warmer air away from inside the home creating drafts. When heat moves as a long-wave source of heat energy from a warmer place to a colder place it is identified as radiant transfer. A glass window that does not have an Energy Star rating will absorb heated air and send it outside the glass window away from a home’s interior. Half of a home’s heating and cooling energy escapes outside whenever there is an air leakage emanating from standard windows in the home.

Heat Transfer Solutions

Using multiple-glazed Energy Star rated windows to capture low-conductance gases such as argon and retain these gases in between the glass panes will resolve the problem of conduction. The problem of convection is addressed when windows with multiple panes of glass filled with low-conductance gases and warm edge spacers work with thermally resistant frames. Low-E coatings are inserted in glass to send back energy wavelengths that will prevent hot summertime air from entering the house to reduce radiant-heat loss. Energy Star rated windows include durable weather stripping and high-quality closing devices to prevent warm air from escaping through the windows. The heat transfer problems associated with conduction, convection, radiation and air leakage are quantified using U-values or U-factors to measure the amount of insulation. A lower U-value is an accurate measurement of the higher insulation value contained in an Energy Star rated window.

Peter Wendt is a writer and researcher working out of the great state of Texas. He has been writing about this subject for several years, and he finds that a great resource is the website at http://www.windowestore.com/.