Windows u value

The thermal losses or U-value for the entire window is critical. This value is affected by the glazing type, frame and spacer see fig. Passive Houses cannot usually be obtained using windows with worse U-values. For determining window U-values, there is a European-wide standard: EN The values determined according to this standard turned out to be realistic - because the standard also considers the thermal bridging effect of the glazing spacer.

This was not the case in old procedures, which is why old procedures often determine much too small specific losses. Do not use these old values, e. To calculate the window U-value U w , EN uses:. In order not to have accurate window characteristics it is crucial to account for all heat losses specified above. This is accomplished using the formula. The linear thermal bridge at the edge of the glazing plays a large role; if one neglects it, the results are much too optimistic.

The illustration on the left shows how large the edge influence is. With the inclusion of the installation thermal bridge, indicated in parentheses, all window losses are accounted for. The individual values used in the formula, are well-known for each passive house window. These windows are Certified by the Passive House Institute.

Strict requirements apply for this certificate - the indicated values must be proven by the manufacturer. Passive house suitable window. At the same time a window allows both direct and indirect sunlight into the building. The Solar Heat Gain Coefficienct "g" indicates what amount of the incident perpendicular solar radiation that passes through the glazing. Passive house windows need to have a positive energy balance in the winter, i. Replacement windows significantly reduce electric and gas bills because they stop unwanted heat exchange through windows and also stop drafts.

Alternatively, if you live in a cold climate, they may allow more of the sun's heat into your home. 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. Generally speaking, the lower the U-value, the better. Ready to shop for new windows? You can also get an estimated quote here.

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