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Your home’s windows and skylights have a large impact on the energy efficiency of your home. The glass type, spacers, and framing all affect the amount of air and heat transfer between the inside and outside of your home. Generally an expensive home improvement project, window and skylight replacements are often eligible for tax credits and rebates to help defray the upfront cost.
Product Types
How It Works
Choosing and replacing windows is a complex process that almost always requires the help of a professional. However, being an informed homeowner can streamline your replacement process and maximize your energy savings. First and foremost, it is important to know your climate zone. ENERGY STAR qualifies windows according to their appropriateness for a particular region of the country.
The National Fenestration Rating Council is a third-party non-profit organization that rates the performance of windows, doors, and skylights. It provides ratings in the following categories:
- U-factor: This number (generally ranging from 0.25 to 1.25) measures the rate of heat transfer and is an indicator of how well the window insulates. The lower the U-factor, the lower the amount of heat being transferred between your home and the outdoors. The window frame is a significant contributor to the U-factor. Generally, vinyl, wood, fiberglass, and some composite frame materials provide greater resistance to heat flow than metal.
- Solar Heat Gain Coefficient (SHGC): This number measures the fraction (from 0 to 1) of solar energy transmitted by the window. A lower number means that the window allows less heat to enter your home. Typical values range from 0.25-0.80.
- Visible Transmittance (VT): The visible transmittance measures the amount of visible light the window transmits. The normal range is from 0.20-0.80; a higher number means more light is visible.
- Air Leakage (AL): There is more to your window than just the glass pane. The AL measures the rate at which air passes through the joints in the window. Most industry and building standards call for a rate no higher than 0.3 cf·m/ft². The lower the number, the better.
- Condensation Resistance: This number measures the window’s resistance to water build-up. While ENERGY STAR qualified windows have a lower chance of developing condensation on the inside of the window, there is always the possibility. The higher this number on a scale from 0 to 100, the better.
Click here to learn more about what makes a window energy efficient
Low Cost Savings Tips
- Plant trees! Deciduous trees planted near South, East, and West-facing windows will keep your home cooler in summer months and then lose their leaves to allow sunlight to warm your home during winter months.
- Seal around your windows, doors, skylights, and other openings as a first step to reducing drafts—it’s a lot less expensive! [Click here to learn about sealing & weatherizing]
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- Choosing ENERGY STAR qualified windows & skylights can shrink energy bills by between 7 and 24 percent.
- The size of your savings depends on the cooling and heating costs in your region and the type of windows you’re replacing.
- Energy efficient windows reduce the amount of heat transferred into your home in the summer, virtually eliminate the drafty feeling caused by old windows during the winter, and safeguard your possessions by acting as a UV-blocking “sunscreen”.
- You can further enhance your energy savings by choosing specific windows for different sides of your house.
- Windows with spectrally selective coatings can reduce the electric space cooling requirements of new homes in hot climates by more than 40%.
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