With so many choices in replacement windows it can seem like you are wading through an endless see of similar, if not identical, windows. How can a homeowner be sure he or she is getting a window that will deliver the promised energy performance? Just like in your local supermarket, there are labels for windows that will give you all the information you need to choose the right window for your home.
The label, in this case, is the one attached to every quality replacement window by the National Fenestration Rating Council (NFRC). The NFRC is a non-profit organization that administers “the only uniform, independent rating and labeling system for the energy performance of windows, doors, skylights, and attachment products.” Basically, the NFRC label gives you the “nutrition facts” of the windows, and it is up to you to decide whether to choose the healthy alternative. The goal of the NRFC is to provide fair, accurate, and reliable energy performance ratings in order to help homeowners and builders make informed, environmentally responsible decisions when choosing windows.
So what does the label look like, and what information does it hold? Here is what the NFRC label on every Twin Cities Siding Professionals window looks like, followed by a summary of the test information provided by the NFRC and what it means for window performance.
The most important measure of a window’s performance is its U-Factor. The U-Factor indicates the rate of heat flow through a window. The lower the U-Factor, the more energy efficient the window will be. U-Factor measures the entire window unit — glass, frame, sash, spacers — and is the only measurement accepted by the U.S. Department of Energy’s Energy Star™ program. U-Factor ratings generally fall between 0.20 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 Heat Gain Coefficient (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 in the house.
Visible Transmittance (VT) measures how much light comes through a product. The 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.
Air Leakage (AL) is indicated by an air leakage rating expressed as the equivalent cubic feet of air passing through a square foot of window area (cfm/sq ft). Heat loss and gain occur by infiltration through cracks in the window assembly. The lower the AL, the less air will pass through cracks in the window assembly.
When you shop for new windows, be sure to check for the NFRC label. You deserve windows that will perform up to a certain standard, and no one has loftier standards than the NFRC.
When you’re ready to discuss the installation new, energy efficient windows, call Twin Cities Siding Professionals at (651) 967-0873, or visit our web site at tcsidingprofessionals.com for a FREE in-home evaluation and estimate.