For our tests, we order 3×5-foot double-hung windows from a variety of manufacturers. Our previous window testing has found that most windows stand up to simulated aging, so we now focus instead on how well a window can withstand the elements.
After installing each window in a wooden frame, test engineers seal one side before using a specially made device that simulates wind. They raise the airflow velocity to 25 mph and then 50 mph, and measure air leakage with a flow meter. They run this test at 0° F and 70° F to evaluate whether a frame holds up even as materials contract and expand at varied temperatures.
To test rain resistance, we simulate windblown rain by pelting the window with 5 gallons of water per square foot per hour. Windows that earn an excellent rating in this test can withstand simulated winds up to 74 mph, or gale-force winds. The worst windows started leaking when winds reached about 35 mph.
