Energy Efficient Windows
Our Guide To Energy efficient windows covers many of the main factors that play into creating efficient windows that will save buyers money and keep homes more comfortable for decades to come. Some of the main energy efficient window factors include well made window frames, strong corner welds, low-e glass, and quality non-metallic spacers. The result is a high quality window with low tolerances and impressive performance data. This data comes through in measurements like U-value, air infiltration and solar heat gain coefficient.
Additionally, we have posted a number of consumer questions and answers toward the bottom of this page that relate to energy efficient windows. If you have questions for either myself or Jim, please contact us using the email link below.
Review By John M. - Site Editor - Publish Date: October 25, 2015
Last Update: October 17, 2025
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Low E Window Glass
Low e glass uses a coating on the exterior of the glass pane that lets in long wavelengths (sunlight) and reflects short wavelengths (heat). Low-e glass coatings are made from metallic particles and should not be confused with a tinted glass that simply changes the color of the glass. The density and consistency of the low-e e coating can change how much sunlight and/or heat is allowed through the pain. Window manufacturers can use one or more coats of low E glass, alter how the layers are stacked or add tinting to affect the amount of light let in, the amount of heat let in, the amount of UV rays and more.
More On Low E Glass
U Factor
U Factor is a measure of the amount of heat loss from a window that ranges anywhere from 0.15 to 1.20. The lower the number, the less heat escapes through the window and therefore the more energy efficient the unit. U factor, often referred to as U-value, is one of the main performance numbers for consumers to look at when shopping for windows for your home.
More On U Factor
SHGC
SHGC stands for solar heat gain coefficient and is a measure of how much heat is allowed through a window. For example, clear glass that has no low E coating will allow much of the solar heat in. This is not necessarily a bad thing, but there are many instances when you need the window to reflect more of the heat than absorb through the glass. The ideal SHGC will depend much on the climate in which you live and the direction that the window faces.
More On SHGC
Air Infiltration
Air infiltration is an important term in determining how energy efficient a window is. The term refers to the amount of air that is able to pass through window unit and will fall somewhere between .30 and 0. Anything over .20 is horrible, anything under .12 is decent and anything under .06 is quite good.
More On Window Air Infiltration Rates
Film In The Middle Of My Windows
My window has film in the middle that is distorted. What are my options?
Donald - Homeowner - March, 2020
Website Editor's Answer
Donald. You can call the window manufacturer. Or you can call a local repair person who can replace the glass. Or you can call the window dealer in your area and see if they cover the issue. Try all three and good luck!
Editor John - March, 2020
Related Topic: Window Capping Cost
* Window Design Pressure