Two Ways to Test Windows
New devices showcased at the Builders' Show make it easy to measure glass performance, u-factor, SHGC, window thickness, and more.
At the International Builders’ Show, I came across a company called EDTM that makes specialized testing tools for residential and commercial window glass. I was most interested in two tools: an “energy profiler” and a glass “thickness gauge meter,” which can verify things like performance metrics, glass thickness, number of panes, spacing, and low-e coatings.
I have a pretty good handle on testing tools for residential construction, but I had no idea this equipment even existed. During energy audits, this kind of data can explain a window’s performance and help produce more-accurate energy models—especially when window specs are unknown, as is often the case in older homes.
For remodelers, it’s helpful when matching or recommending replacement windows. And for new builds, confirming a window order with actual on-site testing can prevent major headaches. You can find more information on both tools at edtm.com.
Window Energy Profiler WP4501
The Window Energy Profiler WP4501 retails for $800. This U-shaped tool fits on either side of an open window sash and tests four different metrics of the glass: UV, VIS, IR, and SHGC. UV, or ultraviolet radiation transmittance, is the ultraviolet radiation moving through the glass that causes flooring and furniture to fade. Lower UV percentages are more desirable.
VIS is the percentage of visible light that is allowed to pass through, and a lower percentage means darker views of the outdoors. IR, or infrared energy, is a measure of the heat that passes through the glass. And the lower the SHGC, or solar heat-gain coefficient, the less heat from the sun will pass through the glass.
You may want a lower or higher SHGC value depending on the climate where you live and the direction the window faces. Measurements from the WP4501 can differ from those on a manufacturer’s rating decals on the window, which always include the window frame. The WP4501 tests only the glass.
Glass-Chek Elite GC3200
The Glass-Chek Elite GC3200 is a thickness gauge meter that retails for $1700. It measures window characteristics without the need for an operable window sash. Simply place the tool on the surface of the window glass and take a measurement. The GC3200 measures the glass thickness (from 3/32 in. to 1/2 in. for multipaned windows, up to 23/4-in. glass for a single pane) and the air space between the panes.
It detects any coatings (hard coat or single-, double-, or triple-silver soft coats) and confirms on which glass surface the coating is located. The Glass-Chek Elite can test single-, double-, triple-, and quad-pane windows and can even test laminated or safety-glass windows. The tool is supplied with a reference chart that will help estimate expected performance values, including the SHGC, shading coefficient, solar transmittance, visible light transmission, ultraviolet transmission, and U-factor.
— Randy Williams; editor, greenbuildingadvisor.com Photos courtesy of the manufacturers.
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