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Understanding Replacement Window Performance Ratings

Last updated 5 years ago

Your windows help to stop unwanted solar heat and ultraviolet rays from entering your home. Some windows, like Milgard vinyl windows, can even improve the energy performance of your home. Learn about your own home’s energy efficiency by taking a look at this guide to window performance ratings:

• Efficiency Ratings
U-factor and solar heat gain coefficient are the two most common numbers used to measure a window’s efficiency. U-factor reflects the amount of solar heat that is allowed to pass through window materials—a window with a low U-factor is extremely resistant to unwanted heat transfer. The solar heat gain coefficient (SHGC) represents the amount of solar radiation blocked or absorbed by the window. Choose a window with a low SHGC to keep your home interior cool during the summer.

• Visible Performance
The best windows allow in tons of natural light without the heat and radiation. A window’s ability to let in visible light is measured by its visible transmittance (VT). VT measures the amount of visible sunlight that passes through a window. A high VT rating would be great for homes in need of efficient lighting solutions. Alternatively, homes that already have complex lighting or skylights may want to minimize extra sunlight in their homes with low VT windows.

• Performance Information
Great window performance is measured by more than just energy transfer—you should also check out your window’s air leakage (AL) and condensation resistance (CR). Windows with a good AL rating will help you to eliminate wasteful drafts and cooling costs. Similarly, you can use CR to determine if a window will suffer from condensation problems.

The huge selection at California Glass & Window is sure to include replacement windows and doors that fit your needs. Visit us today, and compare your current window’s efficiency ratings against our new models. You can contact us to schedule a visit at (714) 434-8650.


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