Tuesday, February 9, 2010

Energy Star Ratings for High Performance Windows

Why buy hi-performance Denver windows? Created with efficient design and top quality materials, having the most energy efficient windows installed can save large amounts of both energy and cash. According to the US Department of Energy, windows could be accountable for as much as ten to twenty-five % of energy costs. In cooler weather, the issue is the loss of heat energy, in hotter weather, the problem is solar heat entering the home. Energy Star ratings have provided consumers with a guide for purchasing the best Denver replacement windows possible for each climate zone.

Energy Star Standards for high-performance Windows

What makes Energy Star replacement windows different from superseded models? When a product comes with the Energy Star sticker, it is certain to have met specific tenets set by the office of Energy. Energy Star hi-performance windows are tested by the independent agency, the national Fenestration Rating Council to give each new model its explicit ratings.

Generally, these windows are made with at least two panes of glass. Having two, 3, or four panes of glass, either empty, or full of a non-poisonous gas like krypton, provides extra insulation. They must be created with fine quality framing material, such as fiberglass or vinyl. Energy Star windows are usually coated to reflect both infrared and ultraviolet light. This assists in keeping heat within in winter, and outside in the summer. They are also made with warm edge spacers to keep glass panes separated.

Energy Star Ratings

Hi-performance replacement windows are rated according to four different standards. The U-factor, the solar heat gain coefficient ( SHGC ), air leakage, and plain transmittance ( VT ). The first 2 are the first factors ; air leaking and VT are secondary, and don't have to be mentioned on all labels.

-U-factor explains the rate that non-solar heat flows thru the window. This figure reflects the overall performance, due to framing, coatings, and design. The most energy efficient windows have lower figures.
-SHGC represents the solar energy that enters the home through the window. Depending on geographic region, either a higher or lower number may be desirable.
-Air seepage represents the rate that air is able to flow around a product. A low number means a tighter, and more practical window.
-VT is the amount daylight which is visible to the human eye, that's transmitted thru the glass panes and glazing.

The Most Energy Efficient Windows in Cooler Climates

In cooler climates, the most energy efficient replacement windows will be those that keep the cold air outside and have minimum air leaking. The goal is to reduce the requirement for heat energy, by defending the indoors from cold winter air, and sealing in and absorbing warm air. This means that awfully low U-factor and air leaking figures on the Energy Star label are perfect. For example, in the northwards climate zone, the U-factor rating for hi-performance windows should be less than or equivalent to .3 ; in the north-central climate section, it should be less than or equivalent to .32. Similarly, the lowest air leakage figure indicates the greatest quality for cooler climates.

As the SHGC and VT have to do with daylight, both plain rays and heat energy, entering the home, a larger number might be desirable. As an example, in the northerly climate section, the SHGC should be greater than or equivalent to .35. Determine individual climate section by taking a look at the Energy Star informational website.

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