Insulating Plaster-and-Lathe Walls Without Cavities
Hi there. Looking for some feedback and assistance please.
I have an old 1740’s home that has no wall cavities. I am wanting to insulate from the inside by framing out the wall over top of existing plaster/lath with 2×4. Do not want to go 2×6 to avoid shrinking the room size too much. My question is can I insulate directly on top of plaster and would I need a vapor barrier or possibly need to remove plaster altogether ?(which I would prefer not to) I am wanting to use Mineral wool batts to insulate due to its sound damping qualities etc. I just want to know if I should be concerned about the plaster still being present and if moisture etc could be an issue going this route.
I have removed some clapboard from the outside of the house and directly behind it I believe it is a tar paper?? It is flexible and black . Unsure if this is permeable but it was on the house before we came. Behind the paper are 1×6 ish vertical boards that run from the sill to the attic. Then on top of that the lathes and then plaster. House has a full basement, 1st floor and an attic that is vented and fully insulated with blow in cellulose and stays nice and dry. We keep humidity in basement to 50% but other wise it is a dry basement. We run heat pumps/wood stove in winter so humidity is typically low. Plus we vent out the bathroom and vent while cooking etc to control moisture. We are in zone 6, Connecticut shoreline.
Would really appreciate any feed back on this.
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