Energy performance ratings windows

The lower the number, the better a product is at keeping heat in. Solar Heat Gain Coefficient measures how well a product can resist unwanted heat gain, which is especially important during summer cooling season. Visible Transmittance measures how well a product is designed to effectively light your home with daylight, potentially saving you money on artificial lighting.

The higher the number, the more natural light is let in. Air Leakage measures how much air will enter a room through a product. NFRC also has a condensation rating that is optional for manufacturers to include, so you may or may not see it on the label. The higher the number, the better a product resists condensation. Download the optional label. The circled value shows you the rating a door has received. Solar Heat Gain Coefficient measures how well a product can resist unwanted direct or indirect solar radiation.

The prescriptive criteria require a U-factor of 0. With the equivalent energy performance criteria, products can be considered certified with the following performance: U-factor of 0.

All other zones only have prescriptive criteria. In the North-Central Zone, the U-factor requirement is 0. The South-Central Zone allows U-factors of 0. Windows qualified in the Southern Zone can have U-factors of 0.

The qualification criteria for skylights are prescriptive only and are as follows: In the Northern Zone, skylights must have a U-factor of 0. In the North-Central Zone, skylights must have a U-factor of 0.

In the South-Central Zone, skylights must have a U-factor of 0. In the Southern Zone, skylights must have a U-factor of 0. Glazing level refers to the amount of glass in the door. An opaque door has no glass. A door that is less than or equal to half-lite is comprised of approximately half glass or less. A door that is greater than half-lite is mostly glass; this category includes fully glazed or full-lite doors such as sliding glass doors.

The qualification criteria for doors are as follows: Opaque doors must have a U-factor of 0. Less than or equal to half-lite doors must have a U-factor of 0. Greater than half-lite doors have SHGC criteria that differs by climate zone. These properties can be measured and rated according to the following energy performance characteristics:. The ability of glazing in a window, door, or skylight to transmit sunlight into a home can be measured and rated according to the following energy performance characteristics:.

Review the state fact sheets or use the window selection tool for new construction or existing homes from the Efficient Windows Collaborative to determine the desired performance ratings for your climate.

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Windows, doors, skylights can gain and lose heat through: Direct conduction and convection heat transfer through the glass or multi-layer glazing and framing Thermal radiation into a house and out of a house from room-temperature objects, such as exterior walls and windows, people, equipment, furniture, and interior walls The solar radiation into a house, which is converted to heat when absorbed by building surfaces Air leakage through and around them.

These properties can be measured and rated according to the following energy performance characteristics: U-factor is the rate at which a window, door, or skylight transmits non-solar heat flow. For windows, skylights, and glass doors, a U-factor may refer to just the glass or glazing alone.

NFRC U-factor ratings, however, represent the entire window performance, including frame and spacer material.