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Community and Q&A

Repairing Windows and Energy Efficiency

artisanfarms | Posted in General Questions on

I’m salvaging an older Four Seasons tinted curved glass sunroom for use on my “Pretty Good House” renovation project.  I will be using the glass for a partial South Wall to enclose a back porch behind the garage. The porch will house a 7×7 hot tub. The glass will sit on an insulated knee wall. The glass coverage in the room will be less than 20% of the total wall area.

I am in Zone 5, Central NY, and plan to keep the room relatively cool thru the winter, using the hot tub as the primary heat source and warming up the air with an electric heater as needed when I use the tub.

My question regards my used glass.  Some of the seals on the curved glass have failed and I have condensation in those panes.  I’ve read about cosmetically repairing the windows by drilling a small interior hole in the glass and allowing them to vent to the interior of the room.  Given how I plan to use the room, will this type of repair cost me enough in lost efficiency to justify replacing the failed panes with new glass, or will it be cheaper over the life cycle to pay extra to heat the space?

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  1. jordglokyt | | #1


  2. oberon | | #2

    I seem to recall that the curved lites in the 4 season sunroom are tempered. If they are tempered, as I believe is almost certain, and you drill into them, you will find out one way or the other pretty much immediately. If you do decide to drill into them, I would strongly recommend that you wear eye and face protection.
    In any case you are suggesting drilling a hole to expose the interior airspace of the IGU into a room that is likely going to have a high level of relative humidity due to an active hot tub in an enclosed space. Even if you can do it, why do you think that it's likely that the interior airspace of the IGU will dry out in those conditions?
    From an energy performance perspective there will be no appreciable difference between the dual pane units as they are now versus what you will have even if you can dry out the insides. Seal failure does affect energy performance as it lets argon escape or as it corrodes LowE coatings, but drying the space isn't going to improve the performance of the unit once the argon or LowE coating is no longer a consideration.

  3. walta100 | | #3

    Note it is not possible to drill a hole in tempered glass. If the glass was within so many inches of the floor code requires the glass to be tempered. Seems like the number was 36. Almost all temper glass will have the word “tempered” etched in one corner so look before you drill.

    I seems to me that when the seals fail at first you notice moisture between the pains in the morning but by afternoon it would evaporate. Before long minerals begin to building up on the glass and it was never clear again.

    I have to ask will this addition add value to the home?

    Purposely installing failed window seems unlikely to add value in the long run.

    Hot tubs generally have a negative value in real estate transaction.


  4. Expert Member
    NICK KEENAN | | #4

    When the seal fails the big hit is if the window is argon-filled, argon-filled is typically 15-20% better insulation than air-filled. I don't believe there is a meaningful decrease in an air-filled window when a small hole is made to clear condensation.

    If the window is tempered you can put the hole in the spacer and frame rather than in the glass.

  5. Expert Member
    Akos | | #5

    I'm curious. Does drilling a hole actually work? Wouldn't a failed seal be the same as a small hole?

    In cold climate, I could see a hole on the top and bottom on the outer pane would allow some air exchange with outside air which should be dry enough on most days. You would sill get a fair bit condensation in the mornings when the glass is cooled by night time radiative cooling.

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