Keeping Your Home Dry: Insulation Tips for Flood-Prone Areas

I hear you on the “mystery stains” - I’ve seen basements where the only thing growing faster than the mold was the homeowner’s regret. That said, I’ve actually tried the hybrid system in a split-level I flipped last year. Foam board against the block, then mineral wool to fill the stud bays. It did feel a bit like building a lasagna, but it seemed to handle a surprise spring flood better than straight foam ever did.

Sometimes I think the old-school approach - mineral wool, a solid vapor barrier, and just making sure everything can dry out if it needs to - makes more sense.

I get the appeal of letting things breathe, but then I worry about critters nesting in the mineral wool. Anyone ever have issues with that, or is it mostly an old wives’ tale?

Critters in mineral wool - yeah, that’s a thing I’ve heard about, but honestly, I’ve never actually found evidence of it in any of my projects. Maybe it’s more of a concern if you’ve got big gaps or the stuff’s exposed for a while? I always make sure the mineral wool’s snug and the drywall goes up pretty quick after, so there’s not much opportunity for anything to move in. If you’re sealing up the rim joists and keeping things tidy, I wouldn’t lose sleep over it. The bigger headache for me has always been ants finding their way into foam board, weirdly enough.

I’ve run into the same thing - never actually seen critters in mineral wool, but I’ve heard the stories. I think you’re right, it’s probably more of an issue if the insulation’s left exposed or there are gaps. Here’s how I usually handle it, especially in flood-prone areas:

1. I always make sure the mineral wool is cut just a bit wider than the cavity so it fits tight. That way, there aren’t any easy entry points for bugs or mice.
2. Before drywall goes up, I’ll check for any gaps around pipes or wires and seal those with caulk or foam. It’s a little extra work, but it keeps things tidy.
3. If I’m using foam board anywhere, I’ll tape the seams and seal the edges - ants love those little gaps, like you mentioned. Had a client with a whole ant highway behind their foam board once... not fun.

Honestly, keeping everything snug and sealed seems to do the trick. I’d worry more about moisture sneaking in than critters, especially if you’re in a flood zone. Mineral wool holds up better than fiberglass if it gets wet, but you still want to keep things as dry as possible.

Totally relate to this. I’ve heard those critter-in-mineral-wool stories too, but never seen it firsthand either. You nailed it with the “keep it snug and sealed” approach. That makes all the difference.

I always make sure the mineral wool is cut just a bit wider than the cavity so it fits tight. That way, there aren’t any easy entry points for bugs or mice.

That’s the move. I’ve found that if you get lazy on that step, you’re just inviting trouble later. I’d add - if you ever have to leave insulation exposed for a while (like during a longer reno), it’s worth tacking up some kind of temporary barrier. Learned that one the hard way after a squirrel found its way into a wall during a project delay... not a fun cleanup.

You’re right about moisture being the bigger enemy in flood zones. Mineral wool’s forgiving, but it’s still no match for a full-on soak if it sits wet for weeks. Good call on sealing around pipes and wires too. That’s where I always find the weirdest stuff sneaking in.

All in all, sounds like you’re on top of it. Nice work keeping things tight and dry.

Had a similar run-in with critters during a basement reno - left a section of mineral wool open for just a weekend, and came back to find mouse droppings tucked in the corner. Never thought they’d move in that fast. Since then, I’m religious about sealing things up, even if it’s just temporary plastic or cardboard.

I do wonder sometimes if mineral wool is the best call in flood-prone spots, though. It’s definitely better than fiberglass for moisture, but after a big storm last year, I had to pull out a whole section that stayed damp for too long. Mold set in quick. Maybe rigid foam would’ve held up better? Still, mineral wool’s eco-friendly angle keeps me coming back.

And yeah, those pipe and wire gaps are always the weak link. I’ve started using leftover caulk or even bits of scrap insulation to plug them up. Not perfect, but it helps. Funny how it’s always the smallest holes that cause the biggest headaches...