If you look at how much heat is lost
out through a skylight (as we did two
months ago in this column) and how
much is gained, you discover that for
most orientations with low-e, argonfilled
units there is little or no energy
penalty. In fact, even plain old double
glass skylights aren't all that bad. I
think there are a couple of reasons
skylights got a bad energy reputation.
First, in the old days, they were built
on site and weren't insulated or sealed
very well against air leakage. Second,
many of them were built with or later
developed water leaks.
Well, weatherstripping and flashing
have been taken care of by the
manufacturers of modern skylights.