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Old school single pane fixed windows! Add another pane?

Kev_7 | Posted in Energy Efficiency and Durability on


Quick question:

We’re purchasing an older home that has many (10+) fixed pane windows.

The panes seem to be held by wood blocking and siliconed.

Can we simply add another pane? Will condensation be an issue? Does it need weep holes at the bottom?

We would like to do this 1.) For safety. We have young children and tempered or laminated glass would be safer. 2.) For energy efficiency.

Thank you!!!

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  1. Kev_7 | | #1

    I don't see an edit! Here are pics

  2. NormanWB | | #2

    The easiest solution would be storm windows and doors. In general, trying to add another pane will be a pain. Yes, water vapor will condense and cause the wood to rot if you have no weep holes, so any new glass needs to be on the outside, and storm windows are already set up for that.

    Of course, if the glass in the sidelight that you show is not tempered, then you really need to change it out regardless. In that case, get a sidelight that is made to fit the rough opening.

  3. Expert Member
    Dana Dorsett | | #3

    Adding Hard coat low-E exterior storm windows with adjustable vents to control condensation would bring the performance up closed to that of a code-min window. Larson's low-E storms sold through box stores are pretty decent. In the northeastern US Harvey's low-E storms are top-notch, and they have a hard coat low-E glazing option.

    A non-operating fixed storm window isn't very expensive, even though they would all be custom ordered. The low-E glass may come close to doubling the price, but would "pay back" on energy savings would be quicker than clear glass despite the higher up front cost. Clear glass storms over clear windows are still net energy losers, but the low-E turns them into net energy gainers (even on the north side of the house), despite lowering the solar heat gain coefficient.

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