Short answer: It’s a window with a wood frame on the inside and aluminum-clad wood on the outside. And it’s the most expensive window you can afford.
Even if you have to skimp on other energy-saving items like attic insulation, don’t buy cheap windows. And don’t buy vinyl windows! Vinyl windows conduct heat and deteriorate under the punishing Arizona sun. Vinyl windows wind up “smiling” at you as the metal sags and deforms.
Rosie loves wood windows because they do not conduct heat, they’re beautiful and you can paint them any color you like. Still, wood also deteriorates under constant exposure to the sun’s ultraviolet rays.
Aluminum-clad wood windows work better for two reasons. First, because the window frame is a combination of wood and aluminum rather than solid metal, the heat transfer from the sun to the window frame is reduced considerably. Second, because the wood is wrapped in aluminum, it does not deteriorate or become sun scorched.
A bonus: The aluminum is maintenance-free and never needs painting.
What about the glass? Go for windows with two panes of glass rather than a single one. These so-called “double glazed” windows have a thin space of air or Argon gas in between the two panes. Two panes are better than one because glass is a poor insulator and can let a lot of heat into your home. It can also let your cool, air-conditioned air leak out.
Doubling up prevents leaks. It also increases something called the R-value, which is a measure of how much heat can get through the window in an hour. Windows with a high R-value allow less heat to get in on hot days—and less to leak out when you’re running your furnace on chilly evenings.
Choose a window with a space of at least 5/8 of an inch between the two panes. And choose one that comes with a “low-E” coating on the glass. Low-emissivity coatings—thin, see-through coatings of silver or tin oxide—let the light come through the glass, but don’t let heated air in your home escape. Ask for the new “southern low-E” glass, which reflects the sun’s radiant heat back outdoors so it doesn’t get into your home when it’s hot outside.
A bonus: Double glazed windows let less noise into the house than single panes.
Does that mean three panes are better than two? Not necessarily. Triple-glazed window glass is the most energy-efficient choice, but it’s expensive. The payback in energy savings can take more than 10 years.
If you want to bolster your energy savings, try adding a storm window or energy-efficient plastic film to your double glazed windows.