Energy Star


The U.S. Department of Energy and the U.S. Environmental Protection Agency have developed and instituted an Energy Star designation for products which meet specific energy performance requirements. This program, developed for the energy efficiency of windows, doors, and skylights is separated by product recommendations for the four climate zones: a mostly heating zone (Northern), two heating and two cooling zones (North/Central and South/Central), and a mostly cooling zone (Southern). According to the U.S. Department of Energy, inefficient and poorly insulated windows and doors account for up to 25 percent of the average household's energy bills. Other sources have estimated these numbers to be as much as 40 percent. The way you lose energy really depends on which of the four regions you live in.

  • Cold climates lose energy primarily in the form of heat
  • Hot climates lost energy primarily in the form of cooling

The more drastically hot or cold the climate you live in is, the greater you can benefit from replacing your windows. For more information on the Energy Star program click here

NFRC Rating

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The National Fenestration Rating Council (NFRC) is a nonprofit, public/private organization created by the window, door, and skylight industry. It is comprised of manufacturers, suppliers, builders, architects and designers, specifies, code officials, utilities, and government agencies. The NFRC label appears on all window, door, and skylight products which qualify for the Energy Star program. The NFRC's labels provide product-specific performance ratings for U-factor, solar heat gain coefficient (SHGC), visible transmittance (VT), and condensation resistance (CR).



u-factorU-factor is the measurement of how well a product prevents heat from escaping. Depending on a specific window style and manufacturer, a U-factor is given based on the window's assembly. U-factor rating generally fall between .20 and 1.20. The lower the U-Value, the greater a window's resistance to heat flow and the better its insulating value.




Solar Heat Gain Coefficient

solar_heatSolar Heat Gain Coefficient, also known as SHGC, measures how well a product blocks heat caused by sunlight. The SHGC is the fraction of incident solar radiation admitted through a window (both directly transmitted and absorbed) and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits into the house. In hot climates, where air-conditioning bills are a major concern like in the greater Los Angeles area, choosing windows with lower SHGC will reduce the amount of heat that comes in through your windows from the outside thus reducing your energy bills.


Visible Transmittance

Visible Transmittance (VT) measures how much light comes through a product. Visible transmittance is an optical property that indicates the amount of visible light transmitted. VT is expressed as a number between 0 and 1. The higher the VT, the more light is transmitted.

Condensation Resistance

Condensation Resistance (CR) measures the ability of a product to resist the formation of condensation on the interior surface of that product. The higher the CR rating, the better that product is at resisting condensation formation. While this rating cannot predict condensation, it can provide a credible method of comparing the potential of various products for condensation formation. CR is expressed as a number between 0 and 100.