Interior Greenhouse – wall and ceiling assembly concerns
I’m designing and detailing a greenhouse/garage with bedrooms above. It will be built in two phases; first the garage and greenhouse with a temporary shed truss roof with vented attic space, and a final phase with bedrooms above the garage under a gabled roof. The garage and greenhouse share the same roof and exterior walls (not an add on greenhouse). The greenhouse will have a wall separating it from the garage with a door and a 5′ x 5′ window. Think of it as a 32′ deep by 64′ long garage with a 10′ by 32′ greenhouse on one end. For a variety of reasons, the second level framing and plywd. floor will be built in the first phase. The greenhouse will have lots of windows. The project is in southern North Dakota.
Proposed greenhouse wall assembly:
We’re planning on exterior siding on 3/4″ air space, on 3″ rigid foam sheathing on 6 mil vapor barrier (or peel and stick membrane), on 1/2″ plywood. (not OSB), on 2×6 studs with 2″ high density closed cell spray foam at stud cavities and 5/8″ drywall. There will be mechanical ventilation in the space. I want to prevent mold and rotting problems. Does the spray foam make sense and help the assembly or am I creating a potential problem?
Proposed greenhouse ceiling assembly:
Similar to wall assembly but we have a vented attic space above. We are thinking about 3″ foam or batts at plywd. floor of attic on 16″d floor trusses with 2″ high density closed cell spray foam and drywall. does the spray foam cause issues? Where does the vapor barrier go? Does the insulation at the attic floor make sense?
Our goals are to control moisture in the greenhouse so it doesn’t damage the structure, create mold, or create a problem for the future upper level bedrooms. I know the humidity will not be as great as with a spa or interior swimming pool but I want to avoid any future issues.
Thanks for your feedback.
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