Tips for updating 1960s attic insulation that nobody talks about

I did almost this exact job on our 1964 split-level two summers ago, and sealing the penetrations made a night-and-day difference in our upstairs bedrooms. I bought a dispensing gun with a few cans of Great Stuff Pro and spent an entire Saturday just hitting every wire hole, the plumbing stack, and the framing gaps. Finding two completly unsealed bathroom fan rough-ins buried under the old yellow fiberglass was eye-opening. The only thing I would add is not to rush the prep before bringing in the cellulose blower. I rented the machine from Home Depot and blew about 16 inches of Greenfiber to hit around R-50, but I almost forgot the soffit baffles. If you don't staple up those plastic Durovent baffles at every single rafter bay first, the blown-in stuff will choke your intake ventilation imediately. Also, build a sturdy plywood dam around your attic hatch before you start blowing. I made mine out of flimsy scrap cardboard that was too short, and the first time I pushed the hatch cover up a few months later to check on things, half a bag of gray cellulose rained straight down onto the hallway carpet.

I'm completly new to all this and trying to plan out our attic. What do you do if you have recessed can lights up there? Our 1968 house has a few in the hallway, and I honestly don't know if you're allowed to spray foam right against them or bury them under that much cellulose, or if that's a fire hazard with older fixtures.

Also, dumb question, but how did you actualy haul the old fiberglass out? Are you just stuffing it into contractor bags up in the crawlspace and dragging them down thru the house, or is there a way to do it without making an absolute mess?

For those 1968 can lights, you almost certainly have non-IC (Insulation Contact) rated housings, which require a strict three-inch clearance from all combustible materials and thermal insulation to prevent thermal cutout tripping or potential ignition. If you intend to preserve the existing rough-in cans instead of simply retrofitting modern airtight IC-rated LED wafer units, you will need to construct rigid enclosures—typically fabricated from 5/8-inch Type X drywall or foil-faced polyisocyanurate board held togather with high-temprature foil tape and sealed at the drywall plane with fire-rated caulk—maintaining that required interior airspace before blowing any loose-fill cellulose across your joists.

Have you ruled out ceiling sag before dumping 16+ inches of heavy cellulose up there? alot of 1960s builds used 1/2-inch or even 3/8-inch drywall fastened with smooth nails. Adding hundreds of pounds of loose fill across the whole lid can definitely pop nails or cause bowing, expecially on 24-inch joist spacing.

Also, did you verify what's going on with the wiring first? If there's old cloth-jacketed Romex running thru those bays, burying it under R-60 can cause it to run significantly hotter than it was ever rated for.

Quick update — grabbing a pro foam dispensing gun made air sealing the top plates way cleaner, huge shoutout for that tip. But that comment about ceiling sag definitly got in my head. I checked and our drywall is thin and nailed on 24-inch centers. For folks with older framing, did you re-screw the ceilings from below first, or switch to blown fiberglass to keep the weight down?