We are replacing our windows and are considering a triple pane window over a double pane. Is there a major difference?
According to a study conducted by Purdue University, the R-value (the R is the resistance to thermal transfer) for a double pane window with 1/4-inch air space between the two panes of glass is less than that of a single pane window with a storm window, which together is rated at R-1.69.
If the spacing between the two panes were to be increased to 3/4 of an inch, then the double pane window’s R-value would increase to an R-2.38, far better than either a single pane with a storm or a standard 1/4-inch-spaced double pane window.
If you add a low E coating to the glass with a 3/4-inch spacing, then the R-value is increased to an R-3.13.
A triple pane window with the glass set 1/2 inch apart without a low E coating has an R-value of R-3.23 for a difference of R-0.10. That’s not a lot of R-difference, but you will find the cost difference to be significant. While it may take many years for new windows to pay off in energy savings, the added comfort will more than likely offset the costs.
If you are still shopping for windows, look for Energy Star-rated windows with a low E coating on both panes of glass. Check with your utility company to see if it is offering rebates on certain upgrades such as replacement windows or other energy-saving products. Once you have selected a window, make sure the installers are trained professionals approved by the window’s manufacturer to maintain the window’s warranty.
According to the EPA, there are other things you can do with exiting or replacement windows and doors to conserve energy, which will help to lower your utility bills.
In the summer use white shades, drapes or blinds on the sunny side of the home to reflect heat away from the house.
During the daytime, close curtains on windows facing the sun. Install awnings to shade the south- and west-facing windows or apply reflective films on the windows to reduce solar heat gain.
C. Dwight Barnett is a certified master inspector with the American Society of Home Inspectors.