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Attaching greenhouse to externally insulated wall

Manny_G | Posted in Green Building Techniques on

I’m looking for suggestions on how to attach an uninsulated space such as a greenhouse to a wall of a house so as to minimize thermal bridging. Ideally, I would like to maintain a continuous layer of external wall insulation on the house and fasten the greenhouse roof and wall edges to the house sheathing/studs without compromising the external insulation, but I don’t know if this is a structurally sound idea. 

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  1. Expert Member
    BILL WICHERS | | #1

    Before you worry about the structural issues, consider the moisture isses. Having had a house before with a wall-attached greenhouse, I would recommned a free standing greenhouse every time. It is very difficult to keep the high mositure in the greenhouse from being a problem with the house. I had soffit issues especially.

    That said, I would add a layer of rigid foam as your exterior insulation, then use either furring strips (1x4s) or a layer of 3/4" plywood over the rigid foam to provide a secure mounting surface for the greenhouse components. Screw the outer structure (furring strips or plywood) through the rigid foam to each stud with structural screws. I'd use the plywood if the greenhouse structure doesn't line up dimensionally with the studs since the plywood will make it easy to attach things wherever you need to without worry.

    If you're going to keep that shared wall insulated, then the heat from the house doesn't help to keep the greenhouse warm. This, to me at least, means there are more potential downsides than upsides to a lean-to style greenhouse. A free standing greenhouse doesn't pose any risks to the main house so it's a safer option.


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