Von Löwen Designs

The National Fenestration Rating Council (NFRC) is a nonprofit organization created by the window, door, and skylight industry. Membership includes manufacturers, suppliers, builders, architects, designers, specifiers, code officials, utilities and government agencies. The NFRC label provides the only accurate and concise method to ascertain fenestration energy performance features that will help establish how well a product will aid with cooling your home in the summer, warming it through the winter, keeping out wind, and resisting condensation. By utilizing the information included on the label, designers, homeowners and builders alike can reliably compare one product with another, and make informed decisions about the windows, doors, and skylights they buy.

The NFRC label appears on all products certified to the NFRC standards and on all window, door, and skylight products, which are part of the ENERGY STAR program. At this time, NFRC labels on fenestration units give ratings for U-factor, solar heat gain coefficient (SHGC), visible transmittance (VT), and condensation resistance (CR).

All energy performance values on the NFRC label represent the rating of windows and doors as a whole system, including glazing and frame.

U-Factor.

U-factor measures how well a product prevents heat from escaping a home or building. U-factor ratings generally fall between 0.20 and 1.20. The lower the U-factor, the better a product is at keeping heat in. U-factor is particularly important during the winter heating season. This label displays U-factor in U.S. units. Labels on products sold in markets outside the United States may display U-factor in metric units.

Northern Climate: Select windows with a U-factor of 0.35 or less. If air conditioning loads are minimal, windows with U-factors as high as 0.40 are also energy-efficient if the Solar Heat Gain Coefficient is 0.50 or higher. Some double-glazed low-e products have U-factors below 0.30. Some three-layer products have U-factors as low as 0.15.

North/Central Climate: Select windows with a U-factor of 0.40 or less. The larger your heating bill, the more important a low U-factor becomes.

South/Central Climate: Select windows with a U-factor of 0.40 or less. The larger your heating bill, the more important a low U-factor becomes.

Southern Climate: A low U-factor is useful during cold days when heating is needed. A low U-factor is also helpful during hot days when it is important to keep the heat out, but it is less important than SHGC in warm climates. Select windows with a U-factor lower than 0.75 and preferably lower than 0.60.

Solar Heat Gain Coefficient (SHGC).

The SHGC is the fraction of incident solar radiation admitted through a window, both directly transmitted, and absorbed and subsequently released inward. In other words - SHGC measures how well a product blocks heat from the sun. SHGC is expressed as a number between 0 and 1. The lower the SHGC, the better a product is at blocking unwanted heat gain. Blocking solar heat gain is particularly important during the summer cooling season.

Northern Climate: To reduce heating, select the highest SHGC you can find (usually 0.30-0.60 for the U-factor ranges required in colder climates) so that winter solar gains can offset a portion of the heating energy need. If cooling is a significant concern, select windows with a SHGC less than 0.55. Use a computer program such as RESFEN to understand heating and cooling trade-offs.

North/Central Climate: If you have significant air conditioning costs or summer overheating problems, look for SHGC values of 0.40 or less. If you have moderate air conditioning requirements, select windows with a SHGC of 0.55 or less. While windows with lower SHGC values reduce summer cooling and overheating, they also reduce free winter solar heat gain. Use RESFEN to understand heating and cooling trade-offs.

South/Central Climate: A low SHGC is the most important window property in warm climates. Select windows with a SHGC less than 0.40.

Southern Climate: A low SHGC is the most important window property in warm climates. Select windows with a SHGC less than 0.40.

Visible Transmittance (VT).

The visible transmittance (VT) is an optical property that indicates the amount of visible light transmitted. The NFRC’s VT is a whole window rating and includes the impact of the frame, which does not transmit any visible light. While VT theoretically varies between 0 and 1, most values are between 0.3 and 0.8. The higher the VT, the more light is transmitted. A high VT is desirable to maximize daylight. Select windows with a higher VT to maximize daylight and view.

Air Leakage (AL).

Heat loss and gain occur by infiltration through cracks in the window assembly. 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. AL is an optional rating, and manufacturers can choose not to include it on their labels. This label displays AL in U.S. units. Labels on products sold in markets outside the United States may display AL in metric units. Select windows with an AL of 0.30 or less (units are cfm/sq ft).

Condensation Resistance (CR).

Condensation resistance (CR) measures the ability of a product to resist the formation of condensation on the interior surface of that product. CR is expressed as a number between 1 and 100. The higher the number, the better a product is able to resist condensation. CR is an optional rating, and manufacturers can choose not to include it on their NFRC labels. While this rating cannot predict condensation, it can provide a credible method of comparing the potential of various products for condensation resistance and formation.

They say a picture is worth 1,000 words, so before you leave be sure to visit Von Löwen Designs to view an assortment of refreshing examples in kitchen and bath design concepts, refined palette and interior finishes, and sustainable yet chic, green remodeling ideas that may encourage and inspire your next remodel or home improvement project.