Old Windows Vs. Replacement Windows Life Cycle

Life Spans of Old Windows and Replacement Windows

• Wood windows manufactured before 1940 were built from denser, higher quality wood and probably from old-growth timber, which is more resistant to rotting and warping than the softwood used now. Old windows that have reached 50 years without much maintenance could last another 100 years with repair and replacement of the individual parts that characterize their construction. New windows have a life expectancy of 25 years; however, 30 percent of them are replaced in 10 years.

Energy Savings and Payback

• Heat is lost through all windows, old and new. A low-E glass double-pane thermal replacement window instead of a single-pane window/storm window combination will save 60 cents in the first year and $2.03 a year afterward in gas fuel costs. At that rate it takes 222 years for fuel savings to meet the cost of installing a $450 replacement window. Payback for replacing a single-pane window with a double-pane thermal is 41 1/2 years.

Embodied Energy

• Another factor to consider in life cycle comparisons of old and new windows is the embodied energy, which is the energy used to produce and replace building components. About 2,300,000 units of energy (BTUs) are required to produce one window, not including mining the raw materials, shipping and delivery, contractors' energy use and disposal of the old window and the embodied energy it represents. To break even for the total embodied energy for the replacement window takes 40 to 50 years; many don't last that long.

Storm Windows and Other Tips

• Fitting an old window with a storm window results in 15 percent more energy efficiency than a new window produces, and fuel savings will pay for the storm windows in 4 1/4 years. With the addition of weatherstripping, caulking and maintenance, an old wood window can be equal to the energy efficiency of a replacement window. While replacing old windows may sometimes be necessary, but in terms of energy savings or durability, the swap isn't necessarily justified.