Energy Efficient Windows

Attractive young woman using silicone sealant on the window and repairing the windows of her house
Q:  My windows are old and drafty, and I’m thinking about replacing them. What should I consider?
A: Drafty windows will affect your home’s energy efficiency. Replacing or performing thorough and regular maintenance can help. Start by identifying the type of windows you have — are they single pane or double pane? Looking closely at the window’s edge, you can see the number of windowpanes. Are the frames metal, wood, or vinyl? Any windows with metal frames are the least energy efficient. 

Window Efficiency

Window efficiency is rated in U-factor and Solar Heat Gain Coefficient. U-factor measures heat transfer through the window, which relates to how well it insulates. The lower the U-factor, the more efficient the window. The SHGC measures how effectively the window blocks heat from the sun.  Several components can make windows more efficient. High-quality frame materials insulate and reduce heat transfer. Two or more panes of glass with space in between (filled with air or gas) improve the window’s insulation capability. Warm edge spacers separate the panes of glass to the proper distance apart and help insulate the edges of the panes. 

Replacement and Maintenance

If you want to replace your existing windows, I recommend shopping for Energy Star®-certified windows. Energy Star sets specific U-factor and SHGC requirements based on your geography so you get the best fit for your location. As with many industries, the window industry has been impacted by price increases over the past few years, so keep in mind this may be an expensive upgrade. Be sure to get multiple quotes to compare pricing and scope of work. You may find additional savings with federal tax credits for window upgrades. Visit to find products, tax credit information, and purchasing tips.  If new windows are not in your budget, dedicate some time to maintain your existing windows. Keep the paint and caulking on the exterior in good condition. Caulk around the inside trim, and ensure that sash locks are installed properly and seal tightly when locked.  Whether you replace or repair what you have, making efficiency improvements to your windows will add year-round comfort to your home.

Miranda Boutelle is the chief operating officer at Efficiency Services Group in Oregon, a cooperatively owned energy efficiency company. She writes on energy efficiency topics for NRECA, the national trade association representing more than 900 local electric cooperatives. Click here to get more energy efficiency tips to help you save money on your energy bill.