Installing foam board insulation over existing plaster walls.
I’m doing a small remodel on a 100 year old home to use as rental property. There is zero insulation in the walls. The walls have the original lath and plaster with 1/2″ drywall over that. I really don’t want to tear all that out and open the walls. I’m not a big fan of blowing in insulation from the outside. For one, it’s too expensive for this project and I know there can be issues with putting insulation in the walls of old houses because there’s no vapor barrier behind the plaster. I know there are many opinions on the subject. I’ve opened the walls of old houses before to find the insulation wet and moldy due to the lack of a moisture barrier on the inside. I thought perhaps I could install 1″ foil faced foam board over the existing walls, fur it out and install 3/8″ drywall over that. I know the R-value would be minimal, but it’s better than zero R-value and should help at least some to slow down the heat transfer. My concern is, will this also create a moisture problem. Will moisture be trapped between the foam board and the new sheetrock? Any and all opinions would be appreciated. Thanks
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