U Value: The Secret To Keeping Heat Where It Should Be
U Value: The Secret To Keeping Heat Where It Should Be
Washington, D.C. – January 22, 2026 – Technically speaking, window films and their performance specifications are complex to a person who is not familiar with what these “numbers” can do. From reflectivity to solar energy rejection, each film has a different objective to achieve once installed on glass. One such specification is “U-Value.” For most people, it may not mean much but for your home or office space, it can mean saving money on heating and cooling costs.
When evaluating window films for homes and commercial buildings, one of the most important performance metrics to consider is the U-value. While often discussed in relation to the window itself, U-values are equally relevant when applied to window films. The U-value itself is a measure of the rate of heat transfer through a material. The lower the U-value, the better that material is at insulating. In the context of window films, a low U-value means less heat moves through the glass, whether that heat is trying to enter the building in the summer or escape it in winter.
During warm months, unwanted solar heat gain is one of the largest contributors to high cooling costs. When sunlight passes though glass with no installed film, it can increase indoor temperatures, forcing air conditioning systems to work harder and longer. Window films with low U-values can help reduce this heat transfer by creating an insulation barrier on the glass surface. By slowing the movement of heat from the hot exterior into the cooler interior, low U-value films can help maintain stable indoor temperatures. This leads to improved occupant comfort, fewer hot spots near windows, and reduced strain on air conditioning systems.
In winter and in more northern climates, the situation changes to a focus on heat retention. Buildings can lose heat through windows far more quickly than through insulated walls. This heat loss forces heating systems to compensate, driving up energy usage. Window films with low U-values help retain interior heat by slowing the transfer of heat from inside to outdoors. This insulation effect keeps indoor spaces more comfortable, reduces drafts near windows, and minimizes temperature fluctuations. Occupants feel warmer without needing to raise thermostat settings, which further contributes to energy savings.
The true advantage of low U-value window films is their year-round performance. Unlike solutions that only address summer heat or winter cold, low U-value films work continuously to stabilize indoor temperatures regardless of the season. This makes them an especially cost-effective upgrade for existing buildings, where replacing windows may be impractical or too expensive. The IWFA recommends talking to a Dealer to assess the needs of your building, and how these types of window films can help you! IWFA dealer members near you can be found by going to https://iwfa.com/dealer-locator.
About The International Window Film Association
The International Window Film Association (IWFA) is a nonprofit industry body of window film dealers, distributors, and manufacturers that facilitates the growth of the window film industry through education, research, advocacy, and public awareness. When you look for window film, look for the IWFA logo. Follow along for news from the IWFA on Facebook, LinkedIn, and Instagram.
