What is U Value in Windows?

U-factor and U-value measures how well a window insulates, indicating heat transfer rate. Lower values mean better insulation.

U value is the window's overall ability to resist heat flow, the lower the value the better the window resists heat flow. During the summer months, an energy-efficient window should resist heat flow into a building and during winter a window should keep the heat inside the building. When it comes to a building windows are responsible for 25%-30% of heating and cooling energy use according to the U.S. Department of Energy. There has been a goal by the Department of Energy to get to a net-zero energy goal by 2050. Net-zero means that we produce as much energy as we use. In order for buildings to get to that level, buildings need windows that have the lowest u value possible. 

Net-Zero Energy Contribution

Peerless is contributing to the Net-Zero Energy Goal in Buildings by providing windows with the best overall design, frame, glass package, and spacer systems. The G541 window can get a low .14 u-factor, which is one of the lowest in the industry. The G541 is certified by the Passive House Institute of the United States, a "non-profit 501(c)(3) organization committed to decarbonizing the built environment by making high-performance passive building the mainstream market standard."

Energy Efficient Window Demonstration

The photo below shows window frames on heaters to demonstrate how thermal breaks affect window performance. You can see the frame that has no thermal break on the far right, and the chocolate is fully melted. The thermal breaks get larger as you move to the left; the chocolate is still hard to the touch. The melted chocolate shows how the heat could come in through your window frame during the summer or out through the winter.

Thermal Image Mockup

During a replacement project mockup, we captured why it is so important to replace windows in older buildings. The mockup was installed on a 30°F day. The old window on the right is a much lower temperature than the new window on the left. Replacing older windows with new thermally broken windows will save money on heat and air conditioning and provide the end-user with a better environment.

U value plays an important role when choosing the windows for your next project. Choosing a window with a poor u value can lead to a poor-performing building that needs windows replaced sooner. After years of testing and experimenting, we have the experience to help meet u value goals on your next project. 

For help on your next project, contact your area Representative. 

Please visit our Design Studio for product downloads and project submittals!