Understanding Windows Ratings for Replacement Windows
Understanding Windows Ratings for Replacement Windows
There are several ways to rate the energy efficiency of windows. Many people use the Energy Star standards as a guide. While this can be helpful the quality and efficiency of Energy Star rated windows can still vary widely. The main criteria for windows to qualify as Energy Star for the North Central region is a U Factor of .30 or less and an SHGC factor of .40 or less. But what do these factors mean?
U Factor
The U Factor (or U Value) refers to the ability of the window to conduct heat. The lower the U Factor, the better it is at preventing heat to flow between the outside and inside of your home. In the summer time, this will keep the hot air out and the cool air in, and vice versa in the winter months. This rating is tested by the NFRC (National Fenestration Rating Council) which publishes all of the ratings for window brands on their website.
SHGC
SHGC (or Solar Heat Gain Coefficient) measures the ability of the window to block sunlight. The lower the coefficient, the less sunlight is allowed into the home, and the higher the coefficient the more sunlight (and thus more heat) is allowed into the home. A lower SHGC rating will translate into lower energy bills, particularly in the summer months.
In addition to these two important ratings, homeowners will want to consider air leakage (or potential). They should discuss this with the contractor who is helping select their windows. Also, the installation method used will impact the efficiency of the windows over time. Windows should be properly sealed and caulked after installation. The contractor should take into consideration the style of window and framing options to minimize air flow and increase energy efficiency.
Window replacement is a great option when looking at increasing window efficiency. Always research the window ratings before any type of window replacement or installation project. It can save you thousands of dollars over the long-haul.