Spent the weekend on my R-49 cellulose upgrade and learned a lot

I went through that same ordeal last November when I realized my 1970s ranch was basially leaking money through the ceiling. I acutally opted for a specialized foam gun like the Great Stuff Pro instead of the individual cans. It made hitting those tiny gaps around the plumbing stacks so much easier without the messy drips or running out of pressure halfway through a bead.

While you went all-in on cellulose, I decided to lay down a base layer of Rockwool Comfortbatt between the joists first, then topped it with about 10 inches of the blown-in stuff. The Rockwool is a bit pricier, but it doesn't settle as much over time and it’s alot quieter when the wind picks up outside. For the attic hatch, I glued a few layers of R-10 Foamular rigid board to the back of the panel and used some heavy-duty weatherstripping. It made a huge difference in that hallway draft. That blower machine from the big box store is definitely a beast to handle. My wife and I were covered in gray dust for days, even with the rental machine’s long hose. We ended up hitting about R-55 just to be safe because of how cold our winters get. It's a grueling weekend, but seeing the furnace cycle less often makes every itchy minute worth it.

I took a slightly diferent path when I redid my crawlspace attic last summer. Instead of the blown-in cellulose, I went with Rockwool Comfortbatt. I’ve always hated the idea of burying my junction boxes and recessed light cans under two feet of loose gray dust. With the stone wool batts, I can just lift a section if I ever need to run a new Ethernet line or check a connection. It’s a bit more of a workout hauling those heavy bundles up a ladder, but the friction fit between the joists is incredibly tight.

For the air sealing, I actualy used a mix of fire-rated caulk and small scraps of rigid XPS foam board for the larger gaps around the chimney chase. I found that the spray foam cans can sometimes pull away if the gap is too wide, whereas the rigid board glued down with sealants stays put. I also spent extra time on an insulated tent cover for the pull-down stairs using some leftover R-10 silverboard. Without that, it felt like all my air sealing was wasted becasue the stairs were basicly a giant thermal hole.

I forgot those old recessed lights when I first started, and let me tell you, those Tenmat covers are a lifesaver. I just popped them over the cans and foamed around the base before blowing in the cellulose. It’s way better than trying to build boxes out of scrap drywall.

I also used some fire-rated caulk and aluminum flashing around the chimney stack. It’s a spot most people miss, but I coud literally feel the heat escaping there before I sealed it up. Also, if you’re doing the blowing yourself, use your phones to talk to the person at the machine—saves alot of yelling and wasted material.

I’m still trying to figure out what a 'top plate' even is, honestly. Do I relly have to suck out all my old insulation just to see them? That sounds like a total mess. I've got some old fiberglass up there now that looks okay, but the house is still freezing. If I use those plastic baffles you mentioned, do they just staple in? I'm worried about accidentally blocking my roof's breathing room. Also, for the blown-in stuff, do you have to wear a special suit or is a normal mask enugh? I'm pretty clueless about the dust.

To the guy asking about top plates: yeah, you absolutely have to pull that old fiberglass back. You can't see the air leaks thru pink batts. I used a 23HP Meyer vacuum rental to suck mine out beacuse doing it by hand is for masochists. For those baffles, go with the ADO Products Durovent—staple them directly to the rafters.

Since you're at R-49, make sure you didn't overlook the bathroom fans. I swapped mine for Panasonic WhisperWarm DC units while the joists were bare. Once you tighten the envelope this much, you need mechanical ventilation or you'll end up with moisture issues. Don't forget to vent them all the way through the roof deck, not just pointed at a soffit.