Typical u-factor for windows

You can use the energy performance ratings of windows, doors, and skylights to understand their potential for gaining and losing heat, as well as bringing sunlight into your home. The National Fenestration Rating Council NFRC operates a voluntary program that tests, certifies, and labels windows, doors, and skylights based on their energy performance ratings. The NFRC label provides a reliable way to determine a window's energy properties and to compare products.

These properties can be measured and rated according to the following energy performance characteristics:. The ability of glazing in a window, door, or skylight to transmit sunlight into a home can be measured and rated according to the following energy performance characteristics:.

Review the state fact sheets or use the window selection tool for new construction or existing homes from the Efficient Windows Collaborative to determine the desired performance ratings for your climate.

Subscribe to receive updates from Energy Saver, including new blogs, updated content, and seasonal energy saving tips for consumers and homeowners. Energy Performance Testing, Certification, and Labeling. Heat Gain and Loss. Windows, doors, skylights can gain and lose heat through: Direct conduction and convection heat transfer through the glass or multi-layer glazing and framing Thermal radiation into a house and out of a house from room-temperature objects, such as exterior walls and windows, people, equipment, furniture, and interior walls The solar radiation into a house, which is converted to heat when absorbed by building surfaces Air leakage through and around them.

We recommend using a professional window replacement installer to ensures that you achieve optimal performance from your windows. It seems a bit daunting to a home buyer but we will make this all simple to understand in this article.

The entire window assembly's ability to insulate is called U-Factor. The whole window refers to the frame materials and glazing. Less frequently, the U-Factor may also be referred to as the U-Value. Now we are getting somewhere. The U-Value or U-Factor measures how much heat a window, including the frame, glass, and insulating materials, allows out of the house, which is also known as its thermal transmittance.

Windows are peculiar compared to other home products. You will usually hear about the R-value when discussing insulation values of materials , which is a measure of thermal resistance, or its insulation ability. There are a variety of insulation values that use catchy first-letter naming conventions.

The U. Energy STAR has four zones, designated as:. The divisions assure that homeowners can make solid window buying decisions appropriate for their climate. Let's talk extremes to understand more about U-factor. In states like New York, which are in the Northern climate zone, the sun's light and the sun's heat are welcome guests to a household in the cold and darker months of the long, drawn out winter.

Now compare New York to Southwest Arizona, which is in the Southern climate zone, where it could easily hit degrees Fahrenheit often. If you buy windows made for the Northern climate zone and your house is in Arizona, your energy bills will sky rocket. The sky is so big that the sun blazes indoors, bringing in even more of its heat.

Air conditioning would have a hard time keeping up. For that reason, the two numbers are often paired up and reported on the labels of most windows. As of January 1st , all but the Northern climate zone were required to increase their energy efficiency in order to stay Energy STAR eligible. Windows for the Northern climate zone were required to meet new standards that are much more stringent. Manufacturers had to determine if they could retrofit their Energy-STAR qualified windows to stay on the list of energy efficient products.

Manufacturers could add glazing, coatings to the glass, increase insulation of the framing material, such as adding thermal breaks to stamp out conduction of air across the frame. The manufacturers also had to determine whether it was financially feasible to provide products at a cost that most consumers would be willing to pay. Initially the U. Industry-wide concerns about offering cost-effective windows in the Northern division hampered the time frame. The EPA relaxed its original demands to meet the present-day manufacturing and materials limitations.

The U-Factor determines how well your window keeps warm air inside. SHGC is a measure of how much heat is blocked from the sun. The U-factor generally refers to the energy efficiency of the complete window assembly, which includes the glazing, window frame and spacer. The spacer is the component of a window frame that separates the glazing panels, and often reduces the U-factor at the glazing edges.

The performance rating of the glazing alone, independent of the frame, is known as the center-of-glass U-factor, but use of this rating is less common. For most energy-efficient windows, the U-factor for the entire window assembly is higher than the U-factor at the center of the glass. While beneficial in cooling-dominated climates, a low U-factor is most important for windows in heating-dominated climates.

The following are recommendations for the most effective window U-factors based on the major climate zones in the United States. Get Started. Grow Your Business. Show Menu. When quantifying the energy efficiency of a window assembly, the rate of loss of non-solar heat can be expressed as its U-factor or U-value. Understanding the U-factors of windows is helpful for inspectors performing energy audits, as well as for consumers planning a new build or updating a house with energy-efficient windows.

While windows are rated using both U-factors and R-values, the U-factor is used to express the insulative value specifically of windows, while the R-value is used primarily to rate the energy efficiency of insulation installed in other areas of the building envelope, such as beneath the roof, in the attic, behind the walls, and beneath the floors.

In order to translate a window's U-factor into its R-value, divide 1 by the U-factor. For example, a window with a U-factor of 0.