Insulation for Home With no Wrap or Pape
I would like to insulate the exterior walls of an old home that has redwood siding nailed directly to the studs, with no building paper, wrap or sheathing in between. The inside walls are sheetrock over lathe & plaster. The redwood siding laps over but I doubt is watertight since I can see daylight through some of the seams in the attic. I don’t want to remove the siding if I can avoid it because the house is historic and I think it would never go back on right. The house is balloon framed and as far as I can tell has no firebreaks, so I could pour or blow loosefill down the stud bays and get most of the cavities filled except under the windows, but I am afraid this will soak up moisture and lead to mold problems. As it is we get some mold growth behind furniture on the inside of exterior walls during the wet season. A contractor I spoke to suggested using closed cell pumped-in foam because it would seal the house, and another suggested caulking all the joints from the outside and painting with elastomeric paint. Any suggestions?
Replies
Insulating might make it worse. Right now you have a building with unsealed walls, and nothing in the wall cavities to retain much moisture. It probably gets wet in there and then dries out, because the wind can blow thru. If you fill it with a bunch of blown-in then the moisture will take longer to leave (whether or not the insulating material absorbs it) and increase whatever water damage or mold problems you may already have.
Our current house was built without paper. Parts of it were shingles over 1x6 shiplap sheathing, and parts of it were 1x6 shiplap siding only, all nailed directly to the studs. My approach has been to remove all of the shingles, re-nail all the sheathing and siding, paper over the whole thing, and reshingle. A lot of work... but you gotta ask yourself, do I care if this is still a viable building in 30 or 40 years? Plus, the insulation is only part of what makes you feel warm inside the house. The paper or wrap you put on really helps keep out the wind, which makes a huge improvement. It may not be just insulation you need.
Caulking and painting from the exterior can make a difference if you do a really good job and then maintain it every year.
My parents insulated an old home of similar construction using cellulose, and never had any problems with it. But that was in KY where they don't get long periods of driving rain (though it can be wet for extended periods).
In their case the contractor removed a couple of pieces of siding along each wall in order to blow in the insulation. It was cedar siding and unfortunately split to pieces when removed, but my dad found some used cyprus siding of the same dimension to replace it.