Replace rigid foam sheathing?

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Old 02-07-18, 04:07 PM
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Replace rigid foam sheathing?

Hello,

I have a 300 sq ft "sun", florida room, enclosed porch. I want it to be usable for my kids. It has single pane windows that I am going to replace. In order to do that I need to take off the siding which will expose the rigid foam board used as sheathing. I believe it is foiled on both sides. Can I put osb over it or will that create a moisture issue or should I remove it and put up osb in its place? Any help or thoughts are appreciated.


Steve
 
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Old 02-08-18, 02:18 PM
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You don't state what type of siding or how it is aligned with the walls on the remainder of the house so I will not comment on that. I can't believe the siding on the sun room is only attached to rigid foam. During your upgrade. I would remove the rigid foam and install insulation and OSB before reinstalling the siding.
 
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Old 02-08-18, 03:56 PM
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There is no sheathing other than the foam. There may be nailing strips on the foam, but I doubt it. The 2 corners are plywood I believe because of shear force. This build out is poorly designed including a low sloped roof. The floor was insulated with the paper facing the cold side and there is no roof or soffit venting to boot. It is attached to the back of the house which is brick. I have removed the fiberglass batts under the floor and plan on using roxul and then soffiting it in with something. The interior is gutted because of a roof leak which had mold growing along an entire wall. Room is either boiling hot or freezing cold. I have put down a new tongue and groove subfloor over the old one and want to either slowly gather up some sheathing cheaply to replace rigid foam or want to know about going over the rigid foam with osb, but I am worried about creating a different moisture problem.
 
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Old 02-08-18, 04:38 PM
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I would also vote for removing the foam, replacing it with osb, covering that with Tyvek. I don't think going over the top of the foam would create a moisture problem, but it would create a non-standard wall thickness which would affect your window and door jambs.

Adding roof ventilation and upgrading the windows will be a big improvement. If you want it climate controlled you will need to incorporate the room into your hvac, or maybe get a wall unit ac/heater if that's not possible. Insulation and ventilation alone will not keep the room temperate. It needs a thermostat.
 
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