One of the major benefits of replacing your old windows with more advanced windows is energy savings. Quite simply, installing the proper replacement windows has been shown to result in a home’s interior temperature become more easy to regulate, with reduced energy loss through “leaky” frames and glass, and lower monthly heating and cooling bills.
But how can you tell in advance which window is the best for energy savings? Just read the label!
Every replacement window sold and installed by Rescom Exteriors – and by any reputable window company – comes with a label from the National Fenestration Rating Council (NFRC), an independent testing laboratory that measures specific performance characteristics of windows and doors. “Fenestration” is a word that means “opening,” such as a window or door.
The NFRC label is a quick and easy way to see what kind of energy savings you can expect from a new replacement window. According to the U.S. Department of Energy (DEP), the NFRC tests and reports on the following energy performance characteristics:
- U-factor is the rate at which a window, door, or skylight conducts non-solar heat flow. It’s usually expressed in units of Btu/hr-ft2–o 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. The lower the U-factor, the more energy-efficient the window, door, or skylight.
- Solar heat gain coefficient (SHGC) is the fraction of solar radiation admitted through a window, door, or skylight — either transmitted directly and/or absorbed, and subsequently released as heat inside a home. The lower the SHGC, the less solar heat it transmits and the greater its shading ability. A product with a high SHGC rating is more effective at collecting solar heat during the winter. A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gain from the sun. Your home’s climate, orientation, and external shading will determine the optimal SHGC for a particular window, door, or skylight.
- Air leakage is the rate of air movement around a window, door, or skylight in the presence of a specific pressure difference across it. It’s expressed in units of cubic feet per minute per square foot of frame area (cfm/ft2). A product with a low air leakage rating is tighter than one with a high air leakage rating.
- Visible transmittance (VT) is a fraction of the visible spectrum of sunlight (380 to 720 nanometers), weighted by the sensitivity of the human eye, that is transmitted through the glazing of a window, door, or skylight. A product with a higher VT transmits more visible light. VT is expressed as a number between 0 and 1. The VT you need for a window, door, or skylight should be determined by your home’s daylighting requirements and/or whether you need to reduce interior glare in a space.
- Light-to-solar gain (LSG)is the ratio between the SHGC and VT. It provides a gauge of the relative efficiency of different glass or glazing types in transmitting daylight while blocking heat gains. The higher the number, the more light transmitted without adding excessive amounts of heat. (This energy performance rating isn’t always provided on the NFRC label.)
If you are shopping for replacement windows and find one that does not have an NFRC label attached, be very wary. Any manufacturer who does not submit their windows for testing may be hiding poor performance or shoddy manufacturing processes, or low quality materials.
Want to know more about energy ratings? Call the experts at Rescom Exteriors at (866) 410-5884 today to schedule a free in-home window replacement consultation and estimate.