large storm window

    A friend has a large, non-opening window (about 4' by 5') that he wants to put a piece of plexiglass over so as to minimize heat loss.
    The problem is that we're in a very humid climate. Come winter, the windows will fog up from the water vapor trapped between the window and the storm window. What's the best way to solve this?
        TIA
                    Peter
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Seal it well. I have a Pella sliding glass door. It has the normal glass on the outside, a removable panel on the inside. It is just gasketed and gives a good seal. No condensation between them at all. I'd put a gasket material around the window frame and the put the plexi against it. The put a clip every 10 inches or so to hold it snug.
Ed
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On the inside. I'd say "seal it poorly" on the outside.
As in "put the vapor barrier on the warm side."
Nick
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The window manufacturers use a dessicant between the panels of glass, by filling the seperator portion ( the frame around the glaas, but between the pieces) then seal it against further moisture with a *spread-on* type of hardening sealer. since no moisture gets in after that, there's no reason to change the dessicant at all.
I am betting you could likely just put some of the dessicant in a cloth bag or something similar, and lay it in the bottome between the plexi and the existing window and eliminate the mosture issue. This would likely need to be changed each "wet season" due to the fact that many dessicants are not feasibly re-useable without a long dry out session in the oven, costing more than replacing the actual product.
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Plexiglass is not a good idea for that size of window, due to expansion and contraction. For a window that size, the plexiglass would probably need an inch or more of expansion space.
You could use plexiglass if you build it into a frame. The frame will need to accomodate the expansion, while not allowing air to pass through. (Not easy to design, or build.)

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Good point. Acrylic does expand and contract from temperature and humidity changes - Just not that much!
From 0 to 100 Def F. It would expand about 1/4" along the 60" side. Considering deflection foreshortening from winds or someone pushing on it, there needs to be some additional tolerance in the framing system.
As mentioned, plexi is better suited for a [channel] framing system considering the previously mentioned issues. John

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