Windows provide light, warmth, and ventilation, but they can also negatively impact a building's energy efficiency. You can reduce energy costs by installing energy-efficient windows or improving your existing windows.

What can you do?

Caulk and weather strip.

Caulking and weather stripping can reduce the leakage of windows thereby increasing comfort and decreasing the load on your heating and cooling system.

Add window film.

Window film allows the sun's visible light to enter while reducing the heat gain.  It is also helpful for reducing the sun's glare and can help prevent fading.  Window film is relatively inexpensive and comes in a variety of designs.

Use light to your advantage.

Being mindful of when to open and close windows and use curtains to provide weather-appropriate heating and cooling.  During hot summer weather, keeping windows and curtains closed will help keep the heat out. In the colder winter months, keep curtains open to provide to allow the sun to enter, by providing natural warmth.​

Upgrade to energy efficient windows.

If your building has very old and or inefficient windows, it might be more cost-effective to replace them than to try to improve their energy efficiency. New energy-efficient windows eventually pay for themselves through lower heating and cooling costs, and sometimes even lighting costs.

Choosing Energy Efficient Windows

It is important to first understand the energy efficiency performance ratings of windows.  There are three main factors that describe the efficiency of a window.


In addition to energy performance ratings, an ENERGY STAR approval will indicate high energy efficiency.


It is also important to remember that even the most energy efficient windows will not be effective if they are not installed properly.  Hiring a trusted contractor and obtaining a permit from your local municipality will ensure proper installation.   Be sure to check with your city prior to installation to be sure that you're meeting all of the cities codes  

Funded by the Local Government Strategic Plan Strategies Program

under the auspices of the California Public Utilities Commission.

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