If choosing between all the eco-friendly options seems like a difficult algebra problem, you’re not alone. We’re here to help you sort through what the ratings and jargon mean for energy efficient replacement windows.
By the Numbers: Ratings and Coefficients
The EPA’s Energy Star label can be your first guide toward energy efficient replacement windows. Many windows meet the Energy Star requirements, however.
These numbers provide a lot of information:
- U-factor: This is an indicator of insulation power. Lower U-factors provide greater insulation. For the Bay Area, look for ratings of 0.4 or less for the best results. The full range is 0.2 to 1.20, and you definitely want a rating under 0.6 for energy efficiency.
- Solar Heat Gain Coefficient: This measures how much a window blocks out the sun’s heat. Again, lower numbers are better. Look for an SHGC of 0.40 or less in rooms that get a lot of sun or otherwise need plenty of air conditioning. You can go up to 0.55 in more shaded areas where air conditioning is less of an issue.
- Visible Transmittance: The VT rating tells you how much light the window lets in. On a scale of 0 to 1, a higher number means more natural light. A strong SHGC rating combined with a high VT means that your energy efficient replacement windows will let in maximum light. This is measured by Light-to-Solar Gain, which is simply the ratio of VT to SHGC. A high LSG ratio indicates energy efficiency with lots of light.
Types of Energy Efficient Replacement Windows
You can find energy efficient replacement windows of any style and window type you like. If you’re unsure, we can recommend the best window type for each location of your home.
Ultimately, the energy savings of any window will depend on the precision and quality of the installation — especially windows with movable parts. Professional installation prevents air leakage and delivers the efficiency you expect.
Choosing the right energy efficient windows can be particularly tricky in the Bay Area climate. Talk to us about the renovations you want and we’ll help you choose the perfect new windows.