james wrote:
....

I know turning up the heat or using a dehumidifier could solve the
problem, but I'm looking for a cheaper (long term) solution. Replacing
the windows with vinyl frame is too expensive, however.

Storm windows or if really cheap, the stretchy film route.

Condensate is undoubtedly penetrating under the poly on the side more
than actually penetrating thru as ransley points out.

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