a question...
I am presently in the midst of getting quotes for windows. One company is offering, at no extra charge, a double low-e coating on a double-paned window as opposed to the usual, one. (i assume one coating on each pane)
does another low-e coating make any real difference, or are we just splitting hairs here?
unfortunately, this company has no test results for a Canadian ER rating so it is hard for me to do an apples-to-apples comparison.
double low-e
double low-e
Double low-e is slightly better than than singular. Example:
the u-value at Center-of-Glass (COG) for a regular double-paned window with an aluminum spacer is about 0.5.
the u-value at COG for standard low-e glass with argon and an aluminum spacer is about 0.33
the u-value at COG for double low-e glass with argon and an aluminum spacer is about 0.25
Remember, the lower the u-value the better the insulating value
Also, you can approximate a window's r-value by dividing 1 by the u-value
thus, the last example above would have an r-value of 4, as oppossed to 3 or 2, respectively.
This data is based on the vinyl windows I deal with on a daily basis at work.
the u-value at Center-of-Glass (COG) for a regular double-paned window with an aluminum spacer is about 0.5.
the u-value at COG for standard low-e glass with argon and an aluminum spacer is about 0.33
the u-value at COG for double low-e glass with argon and an aluminum spacer is about 0.25
Remember, the lower the u-value the better the insulating value
Also, you can approximate a window's r-value by dividing 1 by the u-value
thus, the last example above would have an r-value of 4, as oppossed to 3 or 2, respectively.
This data is based on the vinyl windows I deal with on a daily basis at work.
Depends on what they mean by a "double LowE coating". If they mean a LowE2 (squared) versus a standard LowE, then yes, there is a significant improvement.
If they mean placing the lowE coating on both lites and not just one, then that is something of a gimmick and it isn't worth the trouble.
I have seen a good many cases where the salesfolks simply don't understand the mechanics of the LowE coating and they think that a "dual" LowE means placing the coating on two lites of glass when in reality they are looking at a LowE2 coating on one lite. Or, they think that a LowE2 means coating one pane twice - also not correct.
Canadian ER rating also includes solar heat gain in the calculations. A standard LowE coating has a good bit of direct solar gain. A LowE2 has virtually no solar gain. This difference can get technical, but for the moment I would (if I were you) clarify exactly what the window company means by their "double LowE" before going further with them.
If they mean placing the lowE coating on both lites and not just one, then that is something of a gimmick and it isn't worth the trouble.
I have seen a good many cases where the salesfolks simply don't understand the mechanics of the LowE coating and they think that a "dual" LowE means placing the coating on two lites of glass when in reality they are looking at a LowE2 coating on one lite. Or, they think that a LowE2 means coating one pane twice - also not correct.
Canadian ER rating also includes solar heat gain in the calculations. A standard LowE coating has a good bit of direct solar gain. A LowE2 has virtually no solar gain. This difference can get technical, but for the moment I would (if I were you) clarify exactly what the window company means by their "double LowE" before going further with them.
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