Joseph Meehan ) said...

Calvin Henry-Cotnam wrote:

HOWEVER, the frame needed to support three panes of glass is a better
thermal bridge than what is needed for double. On many windows, the
gains in R-value for triple is offset, or WORSENED by the frame.


Interesting. I suppose that would be possible. Do you have any source
of figures for it?

Unfortunately, I don't. This was explained to me by a window manufacturer,
who had a monetary incentive to sell me triple over double, so I consider
"facts" coming from him that suggest I go the other way to have a little
more weight to them than most "facts" thrown at me.

Looking at other posts, I see mention about aluminium frames and this jogs
my memory a little more on this issue. The extra support that is needed for
triple tends to come from aluminium components. Even with a thermal break,
I tend to believe that the benefits of triple glazed windows over double
are not realized until the area reaches a certain threshold.

What exactly that threshold is would be interesting and useful to know.

--
Calvin Henry-Cotnam
"I really think Canada should get over to Iraq as quickly as possible"
- Paul Martin - April 30, 2003
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