National Fenestration Rating Council (NFRC) provides accurate information to measure and compare energy performance of windows, doors and skylights. The two most important values to look for are U-Value (also commonly called U-Factor) and Solar Heat Gain Coefficient (SHGC). The lower the U-value, the greater a window’s resistance to heat flow and the better its insulating value. SHGC is a number between 0 and 1 that indicates the fraction of heat from the sun entering through your window. The lower this rating is, the less amount of heat is allowed to pass through you windows. This rating is important in the warmer months. A low rating results in a cooler him during the summer. At Power Windows and Siding, we are proactive in making sure our products rate well below state requirements for both U-Value and SHGC.

Our windows are able to achieve some of the best performance ratings in the industry thanks to our advanced technology:

NFRC and ENERGY STAR

The energy performance of all ENERGY STAR qualified windows, doors, and skylights must be independently tested and certified. This is done in accordance with testing procedures established by the National Fenestration Rating Council (NFRC).

The NFRC is a third- party, non-profit organization that provides certified rating and labeling programs that enable consumers to compare the energy and performance features of windows, doors, and skylights so they can make an educated decision before purchasing new windows or doors. Each window and door is rated on air leakage (AL), which is its ability to keep warm air out in the summer, cold air out in the winter and how well it resists wind. Windows and doors are also rated on condensation resistance (CR), which is how well it resists condensation. This rating system ultimately determines the energy efficiency of a product.

NFRC, however, does not distinguish between “good” and “bad” windows, set minimum performance standards, or mandate performance levels. This is where ENERGY STAR comes in. ENERGY STAR helps consumers to easily identify NFRC-certified products with superior energy performance.

This is a sample of the NFRC label that shows why a given window earns the ENERGY STAR in all Climate Zones.

Performance Ratings

The NFRC label, which can be found on all ENERGY STAR qualified windows, provides performance ratings in various categories:

• U-Factor measures how well a product prevents heat from escaping a home or building. U-Factor values generally range from 0.25 to 1.25. The lower the U-Factor, the better a product is at keeping heat inside the building.
• Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat from the sun. The lower the SHGC, the better a product is at blocking unwanted heat gain. SHGC is measured on a scale of 0 to 1; values typically range from 0.25 to 0.80
• Visible Transmittance (VT) measures how much light comes through a product. The higher the VT, the higher the potential for daytime lighting. VT is expressed as a number between 0 and 1.
• Air Leakage (AL) measures how much outside air comes into a home or building through a product. AL rates typically fall in a range between 0.1 and 0.3. The lower the AL, the better a product is at keeping air out. Note: AL is an optional rating, and manufacturers can choose not to include it on their labels.
• Condensation Resistance (CR) measures how well a product resists the formation of condensation. CR is expressed as a number between 1 and 100. The higher the number, the better a product is able to resist condensation.

Note: ENERGY STAR qualification is based on U-Factor and SHGC ratings only.