I will admit right up front that, despite the fact that our aluminum windows are more than 20 years old, and are obviously inefficient, we never bothered to replace them simply because we didn't want to shell out the bucks. We've lived with these windows (two standard windows plus a patio door) for nearly ten years, and have simply used insulating blinds and curtains, plus the old standby heat-shrink plastic, to keep the winter cold and summer heat at bay. Those methods are certainly budget-friendly, but don't compare to the efficiency of new windows.

One day this past spring, we noticed a large arcing crack across the bottom half of one of the windows. Suddenly we had no choice (HOA laws notwithstanding) but to replace it. And, if we want to make a good impression when we sell the condo someday, we may as well replace all three of them.

Since I work at the National Renewable Energy Laboratory, I'm well aware of how energy-efficient windows can improve my comfort level as well as my utility bill. We live in Colorado, and that means cold winters with hot summers—so the type of window we choose makes a difference in performance. Energy Savers gives great advice for window shopping. For example:

  • Choose a low U-factor for better insulation in colder climates; the U-factor is the rate at which a window, door, or skylight conducts non-solar heat flow.
  • Look for a low solar heat gain coefficient (SHGC)—this is a measure of solar radiation admitted through a window, door, or skylight. Low SHGCs reduce heat gain in warm climates.
  • Select windows with both low U-factors and low SHGCs to maximize energy savings in temperate climates with both cold and hot seasons.
  • And, of course, look for the ENERGY STAR® label.

Information in hand, we got in touch with a local contractor who could give us sound advice on our selection and provide expert installation. He recommended vinyl frames for better efficiency (and economy), double-hung window types which allow us to crack both the top and bottom windows for better airflow (great for summer), and ENERGY STAR qualified. We put down the deposit and waited for the big event.

In Part 2, I'll let you know how they worked out.

Andrea Spikes is a communicator at DOE's National Renewable Energy Laboratory, which assists EERE in providing technical content for many of its websites.