Spray foam is a mess, no doubt. I’ve had to toss a pair of gloves or two after a job—once it’s on, it’s not coming off. Dense-pack cellulose has held up better for me than loose-fill, especially in older homes with weird framing. Curious if anyone’s tried mineral wool in tight spots? I’ve found it easier to work with than fiberglass, but it’s not as common around here.
Curious if anyone’s tried mineral wool in tight spots? I’ve found it easier to work with than fiberglass, but it’s not as common around here.
I’ve actually had pretty mixed results with mineral wool, especially in those awkward corners and bays you get in pre-war houses. It’s definitely less itchy than fiberglass, and it cuts cleaner, but I always end up with a bit more waste than I’d like. The rigidity is great for friction fit, but sometimes you’re fighting the framing more than the insulation itself.
From an investment standpoint, I’m always weighing install time against long-term performance. Spray foam is a pain—totally agree there—but it’s hard to beat for air sealing, especially if you’re flipping or renting out and want to minimize callbacks about drafts or cold spots. That said, the mess and cost are real downsides. I’ve had crews lose half a day just cleaning up after a bad spray job.
Dense-pack cellulose is my go-to for retrofits. It fills weird cavities better than anything else I’ve tried, and you can get a solid R-value without tearing out plaster. But it’s slow—especially if you hit old knob-and-tube wiring or find hidden blocking in the walls. I’ve had jobs where what should have been a two-day blow turned into four because of surprises behind the lath.
Has anyone actually tracked how much longer mineral wool takes compared to dense-pack or spray foam in a full house retrofit? I’m curious if the install time really offsets the ease of handling. Also, does anyone have numbers on how mineral wool holds up over time in terms of settling or moisture issues? I keep hearing conflicting things from different contractors.
At the end of the day, speed matters for ROI, but so does not having to redo work five years down the line...
I’ve noticed mineral wool takes me longer than dense-pack, but I like how it stays put—no sagging or settling years later. Moisture-wise, it’s been solid in my old basement walls, but I always use a vapor barrier just in case. Cutting around pipes is still a pain, though...
Mineral wool definitely tests your patience, but I get what you mean about it staying put—worth the hassle, right? I’ve had similar luck with moisture, too. Those pipes, though... ever try using a bread knife for the cuts? Not perfect, but it saves a bit of time. I always wonder if skipping the vapor barrier would really make a difference long-term, but I’m too nervous to risk it.
Bread knife trick is underrated, honestly. I’ve hacked through enough mineral wool to know the “official” insulation knives are just a marketing ploy half the time. It’s not pretty, but it gets the job done, and after a few hours you just want the stuff in the wall, not a perfect edge.
I get being nervous about skipping the vapor barrier. I’ve read so many conflicting things about whether it’s needed, especially in old houses like mine where nothing is square and you’re just trying to keep the drafts at bay. For me, after seeing what moisture can do behind plaster, I just can’t bring myself to skip it, even if it’s a pain. Maybe overkill, but I’d rather not gamble with mold.
You’re right about mineral wool staying put, though. I’ve used fiberglass before and that stuff just sags right out of the joists after a year or two. Mineral wool’s scratchy but at least it doesn’t move. Hang in there—it’s slow going but totally worth it when you feel the difference in winter.