When you are in the market for new windows, it can be tempting to believe everything you hear from one of the “experts” in the field. However, as a Colorado Springs window contractor, I always explain the U Factor ratings for energy efficiency first. U Factor ratings were developed by the National Fenestration Ratings Council (NFRC) as a way to measure a window’s energy efficiency, using four different criteria. All windows are given a rating between 1 and 3, with the lower numbers being better, so it is easy for consumers to make comparisons between windows. Most Colorado Springs window contractors will sell thermal replacement windows without ever discussing the U Factor ratings, but as a consumer you should always ask for these numbers before deciding what you will buy. The NFRC ratings are done in the following areas: U-Factor – measures the amount of heat loss that occurs through the window Solar Heat Gain Coefficient – measures the level of “heat gain” during the summer months. Air Leakage – measure how much outside are will get through during cold weather months. Condensation resistance – measures the windows ability to resist condensation, which has an impact on energy efficiency. Visible transmittance – measures the amount of light that can pass through a window, and has less to do with energy efficiency than with homeowner preference. As a Colorado Springs window contractor, I encourage my clients to look at all of the relevant NFRC ratings, as each of them play a role in determining which type of window is best for their needs.