Window Efficiency Ratings
Choosing windows for your home means facing many numbers – dimensions, price, and even ratings. Considering all this information at once can be confusing. Window ratings are a relatively new part of the window selection process. They exist to help homeowners choose the most energy-efficient windows for their lifestyles. Contact Turner Roofing with questions about ratings, or to get more details.
What Goes Into Window Ratings?
Organizations like Energy Star offer voluntary programs to rate windows for energy efficiency. For those who don’t participate in such programs, window ratings are provided thanks to the National Federation Rating Council (NFRC). A good window rating has many different components including U-factor, solar heat gain coefficient, light-to-solar gain, and visible transmittance.
The U-factor measures the rate at which a window or door conducts non-solar heat flow. For NRFC windows, the entire window is given a U-factor rating. A low U-factor indicates your windows are energy-efficient because less heat is being wasted, and your windows are more dependent on solar heat.
The Solar Heat Gain Coefficient
The solar heat gain coefficient, also known as the SHGC, measures solar radiation admitted through windows and doors. Radiation can be directly transmitted or absorbed. Windows with low SHGC ratings have more shading ability, which can keep you cool in a hot or humid climate. Windows with higher ratings collect more solar heat during winter. The climate in which you live plays a big role in determining what SHGC rating you need.
Visible transmittance, or VT, is the amount of direct sunlight your windows provide. The higher the VT rating, the more natural sunlight your home will receive. This contributes to energy efficiency since natural sunlight often keeps you from relying on an HVAC system to regulate temperature. Thus, your energy bills decrease over time.
Your windows may not be energy-efficient if you notice problems like hot or cold panes, or areas in your home that feel hot or cold because they’re near windows. Contact Turner Roofing for help selecting energy-efficient window options.