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Window rail condensation & freezing

vap0rtranz | Posted in Energy Efficiency and Durability on

What’s a fix for condensation on glass near where the rails meet and frozen bits at the rail between the sashes for double pane, single hung windows?  In other words, the windows freeze up … not that we want to open the windows right now 🙂

I’m following 2 book recommendations:
Taunton’s Insulate & Weatherize
Wing’s Visual Handbook of Energy Conservation

Results that I’ve found:
locked & v-stripped sash – condesation & frozen bits @ rail
unlocked & v-stripped sash – condensation & frozen bits @ rail
unlocked & no v-stripping – condensation but NO frozen bits
locked & no v-stripping – testing this now

Just to be clear: the rest of the top sash glass is not condensing.  Only near the rails.  The bottom sash’s glass is not condensing at all.  And this is happening to all windows.

All these windows are contractor grade vinyl replacement that we inherited with the house, aren’t painted, have no damage that we can tell, and assume are only a few years old. 

Outside temp is 5F + 70% humidity.

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  1. vap0rtranz | | #1

    Attaching picture of Wing's diagram for how I added the v-strip to the rails:

  2. Jon_R | | #2

    > What’s a fix for condensation on glass

    Reduce indoor humidity. Possibly reduce interior pressure (this stops ex-filtration when you can't achieve a good air seal).

    1. vap0rtranz | | #3

      50% indoor humidity is on the high end, if one were to believe the sensor that I'm using for humidity & temp, and getting it down to 30% is on my todo list.

      Ty Jon!


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