Windows, Part 5
windows. If you use a consumer brand of window cleaner it may
have “caustic chemicals” in it. The list of “caustic
chemicals” can include Windex.
The warranty problem with proximity to a moist ocean breeze should tell you something
about the quality of the window seals.
Essentially, many of these window manufacturers fill the hidden
edges of their windows with a special drying agent that absorbs
any moisture leaking into the space between the window panes and
this drying agent simply absorbs any moisture in the space and
that delays the fogging of the window for some period of time,
even for a few years.
The absorbant materials they use include silica gel and Ziolite 3A and Ziolite 13X.
While really spiffy sounding names, think simple cat litter. All of these materials are
liquid absorbers. Of course, just as with a sponge, they can absorb only so much liquid.
So once they have absorbed all that they can, the window will start to fog.
A dual pane window is constructed from two pieces of glass separated
by a spacer. The spacer holds the two pieces of glass apart and
keeps outside air from entering the space between the panes. The
spacer is glued to the glass to keep outside air from entering
the space. Many companies add another outer layer of gooey glop
to protect the spacer. If that gooey glop ever dries out then
it will pop loose and there goes the seal. The glop is depicted
in red in the image.
If the seal at the outer edge of the window between the spacer and the glass fails then
outside air can enter the space. Quite often, outside air is moist - it has a high relative
humidity -- and so once the seal is broken moist air slowly enters the space between
the panes.
Outside air enters the window because the atmospheric pressure changes daily. This
means that the two panes of glass can act like a huge bellows and “breathe” through
the tiny cracks in the seal between the spacer and the glass. The window “breathes” in
moist air as the window panes are pressed together and apart by atmospheric
pressure.
Atmospheric pressure is usually about 14.5 pounds per square inch. Atmospheric
pressure can vary by more than a pound per square inch as weather patterns of storm
fronts and high and low pressure zones move over the earth.
If you have a window that is only one foot on a side you have 144 square inches of
glass surface. The changes in atmospheric pressure can put a strain on that window of
