Rigid foam boards definitely have their quirks—been there with the caulk and tape battle myself, felt like I was prepping for a submarine voyage rather than insulating a basement. Hemp insulation is interesting though; I've heard mixed things. Your buddy's experience makes sense—natural fibers tend to hold moisture longer, which could be a real headache after flooding. But I wonder if pairing hemp insulation with a solid vapor barrier or drainage system might help offset that drying issue? I've seen some promising setups where people combine natural insulation with smart drainage solutions, and it seems to work pretty well. Still, I'd be cautious about using it in areas prone to serious flooding...maybe better for general humidity control rather than full-on flood protection. Curious if anyone else has tried combining hemp insulation with other waterproofing methods and how that turned out.
I tried hemp insulation once on a client's basement reno—thought I was being all eco-friendly and progressive. Then came the big storm, and let's just say it turned into a soggy granola bar situation real quick. Ended up ripping it out and going back to foam boards with a proper drainage mat behind them. If you're set on hemp, definitely pair it with a robust vapor barrier and drainage system...otherwise, you might as well toss your cash straight into the sump pump.
"Then came the big storm, and let's just say it turned into a soggy granola bar situation real quick."
Haha, soggy granola bar...that's a visual I won't forget anytime soon. But I'm curious—did you have any kind of vapor barrier in place initially, or was it just straight hemp insulation? I've heard mixed things about hemp's moisture resistance. Wondering if pairing it with something like a dimple mat or a drainage plane from the start might've made a difference. Anyone else tried this combo successfully?
I've run into this exact scenario a few times, and yeah... soggy granola bar is spot-on, haha. Hemp insulation can be great stuff, but moisture management is definitely its Achilles' heel. A few quick thoughts from experience:
- Hemp alone doesn't really cut it in flood-prone or high-moisture areas. It breathes well under normal conditions, but once it gets soaked, it holds onto water longer than you'd like. Learned that the hard way on a basement remodel a couple years back—client insisted on hemp for sustainability reasons (which I totally get), but after one heavy rainstorm... well, let's just say the granola bar analogy would've been perfect there too.
- Vapor barriers can help, but they're not a silver bullet. If moisture gets trapped behind them (which can happen if installation isn't perfect), you might end up with mold growth behind the barrier itself. Seen that happen too—it's not pretty.
- Your idea of pairing hemp insulation with a drainage plane or dimple mat is actually pretty smart. I've done similar setups using mineral wool insulation combined with a drainage plane and had good results. The key is making sure there's an easy path for water to escape if it does get in. Think of it like giving water an obvious exit route rather than letting it hang around and cause trouble.
- One other thing to consider is elevating your framing slightly off the slab or foundation wall (if possible). Even just an inch or two can make a huge difference in keeping insulation dry during minor flooding or heavy rains.
Honestly though, if you're regularly dealing with flooding or high moisture levels, I'd probably steer clear of hemp altogether and go with something more naturally hydrophobic like closed-cell spray foam or rigid foam boards. I know they're not as eco-friendly as hemp, but sometimes practicality has to win out—at least until hemp tech improves a bit more.
Just my two cents from the trenches... hope it helps!
Good points overall, but I wouldn't completely dismiss hemp insulation yet. I've seen it work surprisingly well in a couple of challenging projects—though it definitely needs careful planning. A few things I'd add from my own experience:
- Moisture issues often aren't just about the insulation itself. If your drainage and foundation waterproofing are dialed in, hemp can still be viable. It's more about the entire assembly rather than just the insulation material alone.
- Agree that vapor barriers can be tricky, but instead of traditional barriers, I've had good luck using smart membranes like Intello or similar products. They adapt permeability based on humidity levels, helping avoid that dreaded trapped moisture scenario.
- Also, pairing hemp insulation with a breathable lime plaster finish on interior walls can significantly help moisture regulation. Lime plaster naturally resists mold growth and lets your walls breathe better than drywall or typical finishes.
Definitely requires more upfront planning, but if sustainability is a key goal, hemp insulation isn't necessarily a no-go—even in damp areas. Just gotta get all those details right.
