I hear you on the paranoia—after managing a bunch of rentals over the years, I’ve learned to be suspicious of anything that makes it impossible to see what’s going on behind the walls. Had a unit where the previous owner went nuts with spray foam in the bathroom, thinking it’d solve all his draft and noise issues. Fast forward a couple years, and I’m tearing out half a wall because there was a slow leak at a supply line elbow. The foam hid everything until the drywall started to get soft and stink. By then, it was a mess.
I get why people like spray foam for energy efficiency, but in bathrooms? That’s where I draw the line. Too many pipes, too much potential for leaks or condensation. I’d rather deal with a little draft than hidden rot or mold that costs thousands to fix. Mineral wool’s been my go-to for a while now—at least you can pull it out and see what’s happening if you need to. Maybe I’m old school, but I’ll take repairability over “set it and forget it” any day.
Totally get where you’re coming from. I’ve seen way too many headaches hidden behind walls because of stuff like this. You nailed it here:
The foam hid everything until the drywall started to get soft and stink. By then, it was a mess.
- Spray foam is great for certain spots, but in bathrooms? I’m with you—too risky around plumbing.
- If there’s ever a pinhole leak or a bad joint, that foam just traps moisture. Mold and rot love that kind of environment.
- Mineral wool or even just batt insulation makes it so much easier to inspect or repair stuff later.
- I’ve also had jobs where someone used closed-cell foam and it actually made tracing a leak almost impossible. Ended up costing the homeowner more in demo than the original repair.
I get why folks want to seal everything up tight, but sometimes “old school” just works better. At least if there’s an issue down the line, you can actually get to it without tearing apart half the house.
Yep, I’ve seen spray foam turn a small drip into a full-blown nightmare. Once had to rip out half a wall just to find a leaky elbow behind a thick layer of foam—what a mess. I lean toward mineral wool too. It breathes better, and if you ever need to get at the pipes, it’s not a total demolition job. Plus, it’s got some soundproofing benefits, which is nice for bathrooms. Not perfect, but way less hassle long-term.
I get where you’re coming from with mineral wool. It’s definitely easier to deal with if you ever need to open things up again, and I agree the soundproofing is a nice bonus—especially if you’ve got teenagers blasting music at all hours. But I’ve always wondered about moisture. Some folks swear mineral wool can still hold onto a bit of dampness if there’s a slow leak, even though it’s not supposed to support mold growth. Have you ever run into that? I had one spot behind a tub where the insulation felt just a little clammy after a few years, but maybe that was more about poor ventilation than the material itself.
Curious if you did anything special for vapor barriers or just stuck with standard practice. Bathrooms are tricky with all that steam floating around... sometimes I feel like no matter what you do, water finds a way.
Yeah, bathrooms are just a pain for moisture no matter what you use. I’ve seen mineral wool get a bit damp too, but honestly, I think you nailed it—it’s usually more about airflow and how well things are sealed up than the insulation itself. I helped my uncle redo his bathroom last year and we found a patch behind the shower that felt a little cool and clammy, but there was a tiny gap in the caulking above. Once we sorted that and made sure the vent fan was actually doing its job, it dried out fine.
For vapor barriers, we just stuck with the standard poly sheeting behind the drywall. Some folks go nuts with extra layers or fancy products, but as long as you’re careful with your seams and tape, it seems to work out. Water really does find a way, though... I’m convinced it’s got a mind of its own sometimes. Sounds like you’re thinking it through, which is half the battle.