Part 2: Energy Efficiency in Windows

Energy Efficiency in Windows

We continue with our 2 part blog series, this week with “Improving the Energy Efficiency of Existing Windows”. Last week we discussed “Selecting New Energy-Efficient Windows” and energy performance ratings.

Light. Warmth. Ventilation. These things and more are what windows provide to a home. Windows are a critical part of the home that impacts a home’s energy efficiency. But, how do you decide whether to keep maintaining or to replace old windows? Below are some tips on improving the energy efficiency of existing windows, maintaining existing windows, and when it’s time to replace old windows.

Improving the Energy Efficiency of Existing Windows

You can improve the energy efficiency of existing windows by adding storm windows, caulking and weatherstripping, and using window treatments or coverings.

Adding storm windows can reduce air leakage and improve comfort. Caulking and weatherstripping can reduce air leakage around windows. Use caulk for stationary cracks, gaps, or joints less than one-quarter-inch wide, and weatherstripping for building components that move, such as doors and operable windows. Window treatments or coverings can reduce heat loss in the winter and heat gain in the summer. Most window treatments, however, aren’t effective at reducing air leakage or infiltration.


Cold Weather Window Tips

  • Use a heavy-duty, clear plastic sheet on a frame or tape clear plastic film to the inside of your window frames to reduce drafts.
  • Install tight-fitting, insulating window shades on windows that feel drafty after weatherizing.
  • Close your curtains and shades at night to protect against cold drafts; open them during the day to let in warming sunlight.
  • Install exterior or interior storm windows, which can reduce heat loss through the windows by approximately 10%-20%, depending on the type of window already installed in the home. They should have weatherstripping at all movable joints; be made of strong, durable materials; and have interlocking or overlapping joints.
  • Repair and weatherize your current storm windows, if necessary.

Warm Weather Window Tips

  • Install white window shades, drapes, or blinds to reflect heat away from the house.
  • Close curtains on south- and west-facing windows during the day.
  • Install awnings on south- and west-facing windows.
  • Apply sun-control or other reflective films on south-facing windows to reduce solar heat gain.


General Maintenance Tips

Make Maintenance Mandatory

One of the simplest methods to ensure continued performance for your building’s windows is to perform regular maintenance as suggested by the manufacturer. If a window’s hardware, glass, gaskets, or finish is compromised, its efficiency will likely suffer as well! If your windows’ distributor does not offer maintenance programs, try reaching out to local, reputable window contractors to perform periodic maintenance.

Use the Right Attachments

From shades to shutters and awnings, there are a multitude of window attachments available to help reduce heat gain, eliminate glare, and improve daylighting capabilities. If you’re considering installing one or more of these options, you don’t want to make a mistake by choosing the wrong attachment. Use a free tool such as Efficient Window Coverings that uses building-specific information about your facility and goals to suggest the proper attachment choice.

Cover Up!

One quick solution to make windows more efficient and improve performance is to add films. Window films, typically made from Polyethylene Teraphthalate (PET), can be applied to most windows and are designed to cut costs by mitigating the effects of solar heat gain while also letting in natural light, which reducies the demand from artificial light. Additionally, window films can help to retain the heat from inside the building when it’s cold outside, decreasing the need to run your HVAC system in the winter.


Handle Small Repairs

Whether it’s a broken lock or degraded weather stripping, small repairs on your facility’s windows can maintain security and performance while ensuring that little problems don’t become big ones. In addition to obvious issues, be aware of more subtle problems that can crop up such as foggy glass or windows that let in drafts.

It’s Time To Replace Your Windows

1. They’re damaged, warped, or broken

It’s sometimes possible to repair a window instead of replacing it. If your window’s problem is minor, such as needing new weatherstripping or hardware, a repair might be the best option. But replacing a damaged, warped, or broken window sash or frame is almost always preferred to attempting a repair. “Even if the windows are still operable, they can develop problems,” says Kris Hanson, Senior Group Manager in Product Management at Marvin Windows and Doors. Do your windows fog up? Are they drafty? Do they stick when you try to open or close them? Do they refuse to stay open? If your windows are communicating in those ways, they’re telling you to replace them.

2. You want to reduce your energy bill

Windows provide some heat in the winter by letting in sunlight. But drafty windows can cause your energy bills to be about 10% to 25% higher, according to Replacing your windows with energy-efficient ones can reduce your heating and cooling bills. Bonus: If you’re considering listing your home for sale, those new windows — and the resulting energy cost savings — can be a big selling point.


Windows are a big investment and energy saver in your home. Take your time to learn about energy efficiency and windows to make the right decision that best fits your needs.



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