Home About Writers Categories Recent Issues Subscribe Contact File Transfer





Bob Crager
Bob Crager of Lewis Street Glass is a 26 year veteran in the glass business. Lewis Street Glass is a leading Wichita Glass company, serving the entire Wichita/Sedgwick County area since 1919. They do anything and everything having to do with glass, both residential and commercial. They also do Auto glass. They are located at 743 South Market, facing Kellogg on the South, and you can reach them by phone at (316) 263-8259. You can email Bob Crager at bcrager@lewisstreetglass.com
Glass
2006-04-01 12:56:00
Preventing heat from escaping through windows
ANSWER: There's a new breed of glass that outperforms just about every window on the market. A double-pane window of this new "super glass" loses up to 42 percent less heat than a standard double-pane window. It's even better than a triple-pane window because it weighs less, costs about the same, and can save as much or more energy. Most major manufacturers have promoted the super glass in storm windows, as well as patio doors and skylights. It's sold under a lot of different brand names, but it's known generically as low-emissivity glass. A low-emissivity window or patio door looks like an ordinary window or patio door with double pane glass in it, but there is one key difference.  The inside face of the outer pane has a metallic coating that's only a few hundred atoms thick. This microscopically thin coating can barely be seen, but it stops radiant heat loss by not emitting it to the cold outdoors.  Hence the higher R-value of low-emissivity windows.Not only will your heating bills notice this improvement, but you should, too. In winter, your thermostat may be set at a warm 70 F, but you'll feel chilled sitting near an ordinary window. Some of that chill may be due to air leaking through its cracks, but some is also due to the radiant heat loss of your warm body to that cold glass. If your windows are skinny single-panes, the room-side surface of that glass is only 14 F when it's zero degrees outside! If you have ordinary double-pane glass, the room-side glass temperature will be about 41 F. But with low-emissivity glass, the room side surface will be 51 F. For all its benefits, super glass doesn't cost much more than standard windows. Another type of super glass is known as Heat Mirror. It's based on the same principle of reducing radiant heat loss, but in this case the metallic coating is deposited on a clear plastic film, which is then suspended between two panes of glass. You get a window with two benefits: (1) the insulating value of a triple-pane window, and (2) the low-emissivity coating for an R-value of about 4.2. Heat Mirror was developed at the Massachusetts Institute of Technology in the 1970s, partly with federal funds, and has been in production since 1981. It is sold to various window makers, who incorporate it into their lines. When shopping for super glass, look for the longest warranty and the lowest U-value. Window literature generally rates energy performance in terms of U-value. The U-values of super glass vary, depending on the glass manufacturer and the type of coating. The coating can be applied to glass in two ways: by a "pyrolitic" method, while the glass is still molten, and by a "vacuum" method, once the glass is hard. The vacuum method results in a better U-value, but creates handling problems for window manufacturers, and cannot be placed in storm windows. Some information was researched from the World Wide Web. More good stuff next month.
 
The Q & A Times Journal accepts no responsibility for unsolicited manuscripts or photographs.Materials will not be returned unless accompanied by a stamped, self-addressed envelope. Thank you.
 
Wildcard SSL Certificates