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The situation is this….200 yr old timber frame house, plaster interior walls (mostly still good) but the walls are only 3″ thick with blown in fiberglass. The exterior has been opened up for some sill beam repair and the siding needs replacement anyway so that is coming off. The sheathing is big, wide oak planking. It was suggested that I add some rigid foam insulation directly to the outside of the existing sheathing and then reside with cedar shingle. Is this a good idea? I can cope with a thicker wall but don’t want condensation problems. Do I need Tyvek or something in there? And should there be an air gap under the shingles? What if anything can be done for a little more R value? (I’m in CT) Appreciate any suggestions.
Ron
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Replies
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if it were me and i need the extra insalation i would go over it with an air space and weep holes at bottem just in case there is condensation , and i would use some kind of mosture barrier
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The situation is this....200 yr old timber frame house, plaster interior walls (mostly still good) but the walls are only 3" thick with blown in fiberglass. The exterior has been opened up for some sill beam repair and the siding needs replacement anyway so that is coming off. The sheathing is big, wide oak planking. It was suggested that I add some rigid foam insulation directly to the outside of the existing sheathing and then reside with cedar shingle. Is this a good idea? I can cope with a thicker wall but don't want condensation problems. Do I need Tyvek or something in there? And should there be an air gap under the shingles? What if anything can be done for a little more R value? (I'm in CT) Appreciate any suggestions.
Ron
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Gotta be careful Ron. If you put a vapor barrier on the outside with none against the inside, you will trap the moisture that is trying to leave your house within the wall cavity. Even if it's Tyvek, I'd be hesitant (supposedly Tyvek allows vapor to pass through it, but there's some doubt passed around among us) unless you knew the interior wall surface or underneath it has a form of vapor barrier, if you live in a heating climate.
Otherwise, I would agree with George, an air space under the cedar would be good, although I've seen guys on this board recommend putting cedar directly on felt too. Backprime the cedar though, just in case.
Do you have a plan for your windows and doors? You'll have to make extensions...
Good luck,
MD