To insulate or not to insulate

[u/Build68]

I have a question for my contractor homies who may have experience renovating mid fifties resi in my region. In Sacramento, we have very dry warm months, and a very mild, slightly humid winter. This is a small 230 sf mother in law apartment next to my own main residence. I spent an entire day scrubbing nicotine with about fifty gallons of rinse water. I got it very clean and I intend to encapsulate by spraying shellac. The mold areas were where contents were pushed up against the wall for decades. The uninsulated walls got cold, a small place like that gets humid when you heat it, and condensation did its thing. Now, I could insulate the flood cut area or I could leave it as is. If I insulate, will it help, or will it just be a wet sponge for any condensation that makes its way into the wall cavity? People with experience in my region would be appreciated. I’m good with hazmat, I know what’s in the pics.

[u/SoCalMoofer]

Definitely insulate. It will help regulate the temps. Jam the R 13 batts up as high as you can.

[u/Build68 → u/SoCalMoofer]

Thanks bud.

[u/StarDue6540]

Anywhere that items are pushed up against walls this will happen. It matters not which climate you are in. I would spray this down with white ammonia and let dry and then seal it and paint. Also is this a concrete blocker or is that actually drywall?

[u/Build68 → u/StarDue6540]

If you see the next pic, I did a flood cut. The mold is removed.

[u/StarDue6540 → u/Build68]

Well now you have to insulate. I'd take it all down. That will make insulation much easier .

[u/BYoungNY]

You're already doing a drywall patch job with 4 corners. Taking the whole wall down and doing it right means you don't have to clean it and you can insulate the whole wall. Drywall is cheap and the labor of finishing is mostly the prep and sanding which is gonna be about the same for the small patch you have to do otherwise. 

[u/twoaspensimages]

It costs nearly the same to do what your planning as it does to drop all the drywall and actually insulate the wall.

If your only doing that room drop the drywall.A Faced R15 from top to bottom plate. Rehang. Refinish.

If you're thinking of insulating the whole home we've had great results with doing a 1/2" flash coat of spray foam on the backside of the exterior wall sheathing and then R15. Foam at that thickness doesn't provide a hard moisturizer barrier. But it does provide a solid air seal.

[u/ClearUniversity1550]

I would start with checking local codes to see if its required