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Re: GBlist: Re: windows in FLA

>Beverly A. Weiter WROTE:

>>.....  The main problem seems to be condensation in double paned windows
>>resulting from the extreme heat vs the excessive use of air conditioning
>>and the extreme humidity.  I have a client who needs to change windows and
>I need a fast answer.  Please note that the house is sited N/S but there is an
>>added problem with a child who is severely asthmatic and sensitive to dust.

Hi, Beverly--

One difference between seals in windows is the material and the way its
applies--inexpensive windows may have a layer of polysulfide on either side
of the spacer, better windows may have a double seal--poly plus butyl along
the edge of the glazing unit.

I think that Terry is right about the differential expansion and
contraction. And here along our windy coast we see a lot of foggy windows,
especially big view windows, so I speculate that wind vibrating the outer
pane can cause the seal to fail. That would seem to indicate that smaller
windows would be more resistant to this failure.

One window guy here told me he thinks the seals can be decomposed by UV so
he recommends keeping the window edges shaded, either by the frame itself
or the building structure.

We definitely have seen seals fail where glazing units in site-built
windows were not supported properly along the bottom with butyl blocks, or
they were sloped in sunspace/greenhouse walls and the support was only
holding up the bottom glass.

Best, Mike

O'Brien & Associates
Environmental Building Consultants
Portland General Electric Earth Smart program

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