The sliding door is about 15 yrs old. It is double pane but leaks between the sliding and fixed part (even with extra weatherstrip).
All my other windows are about 6 yrs old, vinyl, double pane yet they all condense near the bottom when it drops to near freezing.
My theory is because the house is about 60 yrs old and insulation is not up to par, I need to crank the heat to get it comfortable. With the heat cranked the humidifier runs more furnace mounted). When the heat and humidity hit the cold windows it condenses. I'm hoping the plastic sheet will help some. It may not reduce my energy bills, but hopefully it won't condense which can cause mold growth.
That's my theory.
I try to keep the humidity as low as possible and during very cold spells I turn it off completely. Kinda defeats the purpose but better than chunks of ice on my windows.
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