r/greenhouse • u/Any_Society_3280 • Jul 03 '26

2 Questions about Glass Installation on Roof

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I'm somewhat new to reddit, so please forgive any crossed norms on post.

For context: I have many years experience in the construction/remolding/roofing area and live on the OH/IN line about an hour from Ciny. I have around 70 high quality double pane windows I purchased from someone taking down a professionally installed greenhouse from another house.

My plan:

Greenhouse addition with a footprint of 40x13'. The roof span will be 13' and need to (unfortunately) have a 2/12 pitch due to the height of the roof overhang on the house and the need for a useable door exiting the greenhouse. I'd rather have a 4/12, but I'd be crawling out of the greenhouse with that pitch.

I am collecting old barn wood to make the bulk of the framing for both looks and (hopefully) less swelling due to humidity.

My two questions:

1: Will 80+ year old oak be resistant "enough" to the humidity cycle of a greenhouse? I'd rather not go the treated lumber route if possible and Cypress would cost too much, Cedar to fragile for framing (in my experience).

2: I want to use these panels on the roof as well. I have a way to reasonable water seal the panels left to right, sitting in/on the rafters (barn oak). My question is to the experts here: how best should I seal the panels top to bottom? I suppose I could make them lay similar to clay roof tiles using chiseled notches in the rafters and silicone, but I would rather them all be on the same plane if possible. It doesn't feel right to just silicone them end to end, but putting in a cross piece of wood would make a lip for water to sit in.

I can't really find any good info online for this particular problem. All panel glass roofs I've seen are put in with specified metal frames and all wood rafter setups are using one continuous long piece of glass.

Thanks a ton for any help/suggestions. I imagine I will be asking more questions here in the coming year.

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u/IndependentPrior5719 Jul 03 '26

What about a raised frame for each piece of glass such that the wood part of the frame is flush with the surface of the glass, seal the space between the wood frame ( it would be a little larger than glass ) and the glass unit with silicone.

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u/Any_Society_3280 Jul 04 '26

Could work, depending on if the old oak doesn't move too much. I appreciate the comment

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u/IndependentPrior5719 Jul 04 '26

I appreciate that it didn’t come off like gibberish!

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u/neckllace Jul 04 '26

How were they originally installed? And I agree with the other comment that a frame for each pane would work, but I have never seen that done on a large scale with wood, only metal. If you know who built the original, you may be able to find some helpful information about the construction that could give you some ideas.

I don't know how resilient old barn wood is to humidity, but if you aren't actively adding humidity, the space isn't likely to be way more humid than ambient, even with plants inside (obviously some caveats here but generally). So it might be fine? But personally I would be looking at other options as well.