News
LPEA experiments with heated windows
January 19, 2006
By Dale Rodebaugh | Herald Staff Writer
Heated glass, common in supermarket freezer doors and jet plane windshields to prevent fogging, is making its architectural debut in North America at La Plata Electric Association headquarters in Durango.
For the next year, 10 electrically heated Thermique Hot Glass Technology window panes in the LPEA boardroom will be evaluated for energy savings. The $93,000 project is a partnership with the national rural electric cooperative and Chicago-based Engineered Glass Products.
"The technology has been used in architectural construction in Europe for almost 20 years," LPEA spokesman David Waller said. "But it's never found a market in the United States, although a river of heat is lost through widows."
Physics students at Fort Lewis College, under the guidance of professor Laurie Williams, will monitor readings by a remote on-campus computer.
"About 4 percent of total energy used in the United States is lost through windows," Waller said. "Heated windows almost completely stop the loss. It costs to heat window panes, but an overall energy bill could be reduced because you're able to lower the thermostat."
As Fort Lewis College seniors Crystal Delgai and Jake Gruber installed wiring in the boardroom last week, Waller measured with an infrared thermometer the inside surface temperature of a heated pane and one not yet functioning. Temperature varied from spot to spot on each pane, but the heated pane registered an average temperature of 85 degrees, the unheated pane 64 degrees.
The FLC student monitoring team includes Jacob Nester in addition to Gruber and Delgai.
Taking panes to Durango
Heated-glass windows for buildings came to the United States via George Usinowicz, a builder of solariums for trophy homes and a Durango resident for 20 years, Waller said.
"George was in Europe about three winters ago," Waller said. "On an occasion when he was seated next to a large glass window in a restaurant in Brussels, he anticipated a miserable dining experience. But the window was warm."
Impressed by what he learned about heated-glass technology, Usinowicz became determined to introduce it to the United States, Waller said. He persuaded Engineered Glass Products to build a prototype, which he took to LPEA.
LPEA hooked up Usinowicz with its energy provider, Tri-State Generation and Transmission Association, and with the Cooperative Research Network, the research arm of the National Rural Electric Cooperative Association, Waller said. The research network invested $52,000 to cover the installation of the windows and the cost of monitoring, and Engineered Glass donated the windows and control equipment, a value of $41,000. LPEA contributed money for metering equipment and staff time.
How it works
The Thermique double-pane windows, installed in early January, are coated with invisible tin oxide. Electrical wires concealed in the window frames are attached to the glass. The electrical resistance of the tin oxide produces radiant heat, reducing condensation and providing comfort for people near the window.
The lower bank of 10 LPEA boardroom windows measuring 42 inches high have been replaced with Thermique panes. The panes in the upper bank of widows will not be altered. Computers will monitor air temperature at a dozen locations in the boardroom, the temperature of the Thermique panes inside and out and the humidity and dew point of each window pane. A small weather station outside the conference room will monitor outdoor conditions.
Each pane being tested can be controlled individually. Controllers can provide zero to 30 watts of electricity per square foot - in five-watt increments - to each pane. If no current is applied, the panes are comparable to any other double-pane Low-E window. Ten watts of electricity will raise the temperature of the pane to 75 degrees and 30 watts will heat the glass to about 105 degrees.
Computers also will monitor the thermostat setting of the 1,200-square-foot boardroom, the individual heat setting of each window pane and the occupancy level of the board room. An anonometer will measure air current near the bank of windows.
Comparing panes
The performance of two Thermique panes installed in the office of staff engineer Jake Wills will be compared with that of ordinary glass windows in a similar office. The electricity for the two panes will supplied by photovoltaic panels on the roof of the LPEA building when the sun shines. At night or early in the morning, power will come from the grid.
The cost of heated glass is at a premium - $120 a square foot, compared to $35 per square foot for Low-E glass currently used in construction.
"Heated glass has some history - in supermarket freezer doors and airplane windows," Williams said. "That's why they don't fog up."
But despite the precedent, heated-glass windows are probably too pricey except for high-end homes, Williams said. Right now, they're a niche market.
"But as the technology becomes established and if energy costs go up, production costs could come down with wider production. But I'm going to let the data tell the story."
daler@durangoherald.com
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