If you have been shopping for replacement windows, you may have noticed those white labels with window ratings. These are metrics established by the National Fenestration Rating Council (NFRC) to measure window performance. In today’s post, the local window contractors at Renewal by Andersen® of Seattle share a quick guide to these metrics, and how you can use them to get the right windows for your home.
U-Factor measures the amount of heat that can escape through a window after installation. Ratings can range from 0.20 to 1.20; the lower the value, the better insulation the window has. A well-insulated window can help you save on heating and cooling costs thanks to its low thermal transfer rate. Some windows may have an R-value instead of a U-factor. While they both measure insulation, R-value measures resistance to thermal transfer. This means a window with a low U-factor will have a correspondingly high R-value.
Solar Heat Gain Coefficient
Solar heat gain coefficient (SHGC) measures how well a window can resist heat gain from sunlight, with values that range from 0.00 to 1.00. The lower the value, the more savings you can get from your cooling bills. Homes in colder climates may benefit from windows with high SHGC, as it can help the homeowners save on their heating bills.
Visible transmittance (VT) measures the amount of sunlight that can enter a building through a window, with values that also range from 0.00 to 1.00. The higher the VT value, the more natural light you’ll get through the windows. For windows facing harsh light sources, as is the case with south-facing windows, choose those with middle-to-low VT values. Certain types of glass coatings make it possible for replacement windows to have low SHGC with high VT values — that is, less solar heat but with more natural light.
All of the above are mandatory ratings for replacement windows. Additional ratings include air leakage, which measures how airtight a window is, and condensation resistance, which measures a window’s ability to resist condensation from forming on the inside surface. Combined, all of these ratings can help you find the right replacement windows for your home.
Renewal by Andersen® of Seattle is your leading provider of replacement patio doors and windows. Give us a call at (206) 777-0954. You can also fill out our contact form to schedule an appointment. We serve customers in Seattle, WA, and the surrounding communities.