Three dogs that like to pose for photos.
If your home has a layer of sill-seal between the foundation wall and the mudsill -- most newer homes do -- then the information you read does not apply. It's false.
If you have an older home without any sill-seal, the information is partially true. Insulating a rim joist on the interior will reduce the ability of the rim joist to dry to the interior. In most older homes, the benefit of the insulation outweighs the risk.
The riskiest insulation jobs are on homes where the rim joist is close to the exterior grade, and the rim joist is shaded by bushes. Less risky jobs are those where the rim joists is at least 8 inches above the exterior grade, and the exterior is exposed to sunlight and air.
There are several ways that you could insulate the walls of your old barn. The approach you choose will depend on your performance goals and your budget.
If you like the existing metal siding, and you plan to keep the existing siding for many years, then you don't need to create an air gap between the wall insulation and the oldest layer of siding.
Since your wall lacks an exterior air barrier, the best insulation to choose in your case would be spray polyurethane foam.
There are other options, of course. If you are going to remove the existing siding, you might want to strip the exterior down to the studs and install new plywood or OSB sheathing, followed by plastic housewrap and new siding.
If you don't want to install spray foam insulation, you can use a different product -- perhaps dense-packed cellulose -- but you'll have to settle for more air leakage (and slightly higher energy bills).
Finally, if you are worried about thermal bridging through the studs, you would need to install a continuous layer of rigid foam, either on the exterior or the interior side of your studs. Of course, a layer of rigid foam will increase the cost of the job.
Thanks very much for this important blog. My son Moses is now in Ecuador -- he is in the Peace Corps, teaching English at a high school in Azogues. During the earthquake, he was far away from the epicenter, and there weren't any deaths in Azogues. (A later earthquake broke some windows at the school where he is teaching, though.) Our thoughts and prayers are with the people of Ecuador at this difficult time.
I worked for more than a year in Armenia helping with earthquake reconstruction after that country's 1988 earthquake, and the recent earthquake in Ecuador brought back a lot of memories.
So, I agree with you: let's all remember to tighten those nuts, and remember why we need building codes.
Senior editor, Green Building Advisor
Thanks for posting this description of the Jung Haus. I'm glad to hear that two minisplit units are keeping the occupants comfortable.
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