One of the most important pieces of advice Glass-Rite can offer to consumers is to compare windows by checking the NFRC labels. The National Fenestration Registration Council (NFRC) has adopted a label for energy performance that lists the manufacturer, describes the product, provides a source for additional information, and includes ratings for one or more energy performance characteristics. Energy codes in most states, including New Mexico, require NFRC certification of windows. These labels will help you determine how well a product will help to cool your home in the summer, warm the building in the winter, keep out the wind, and resist condensation. By using this information builders, as well as consumers, can reliably compare one product to another and make informed decisions.
Sales people might try to muddy the waters by using “R” values instead of “U” values (remember, windows are not measured by “R” values), and give comparisons of values for insulated glass units, which are better than the values for the overall window. By instead using the NFRC labels as a comparison you’ll eliminate the confusion.
For starters, make sure that the label is for the company you are buying the windows from and that it has the features listed that you want. If a window is not NFRC certified, you have no idea what the real values are. So, lets now talk about the values that are critical to energy performance.
U-Factor measures how well a product prevents heat from escaping. Simple. The rate of heat loss is indicated in terms of the U-Factor or U-Value of an assembled window. U-Factor ratings usually 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, or SHGC, measures how well a product blocks heat directly caused by sunlight. SHGC is expressed as a number between 1 and 0. It is the fraction of solar radiation that is admitted through a window and then released inward. The lower a window’s solar heat gain coefficient, the less solar heat it allows and transmits.
Visible Transmittance, or VT, measures how much visible light comes through a product. VT is expressed as a number between 1 and 0. The higher the VT, the more light is being transmitted.
By checking and comparing the values listed on the NFRC labels, you will be better prepared to compare apples to apples when shopping for windows. You may like the look of a product, but if it is not certified, or has poor ratings, you may want to keep looking! At Glass-Rite, all of our window selections, including vinyl windows, aluminum windows and wood windows, are NFRC certified and always list U-Factor, SHGC, and VT numbers. Contact us today for a free estimate or come by our showroom and we will assist you in making an informed decision on your window project.