Just finished the attic overhaul: R-0 to R-69 and feeling good

I did the same thing in our 1920s bungalow last November, though I went with blown-in cellulose over a base layer of Rockwool Comfortbatt. You aren't kidding about the air sealing—I used about two dozen cans of Great Stuff and a few tubes of fire-rated caulk around the plumbing stacks. I found that even with the insulation, those little gaps around the light fixtures were dumping heat like crazy until I got them capped off.

One thing I did differently was build some raised walkways with 2x10s before I started. Having a stable place to move around made the wiring updates way easier to manage without accidentally stepping through the plaster ceiling. My energy bills dropped about 30% in the first full winter month, and the street noise from the bus stop outside almost completly disappeared. It’s a grueling weekend or two, but the silence and the lack of a drafty living room make it the best investment I've made since moving in.

I ran into a massive headache trying to use batts in my 1910 Victorian becuase the joist spacing was all over the place. Some spots were 14 inches and others were nearly 19, so I was wasting half my time cutting Rockwool into wierd slivers just to avoid gaps. I eventually gave up on the manual labor and rented an Atticat machine to blow in loose-fill fiberglass. It filled every nook around the chimney and wiring much tighter than I coud have done by hand.

One thing I had to be careful about was the airflow at the eaves. I spent a long Saturday stapling in those plastic Durovent baffles before the insulation went down. If the insulation blocks the soffit vents, you're just trading a cold house for a mold problem in a few years.

I only went up to R-49 since my attic is so low-slung, but even that made a huge difference. Getting those baffles right was honestly more stressful than the air sealing, but seeing the snow on the roof stay frozen all winter instead of melting into ice dams tells me it is working.

You defintely need to address the attic hatch now that you're at R-69. It’s ussually a massive thermal bridge that people overlook. I put in an Owens Corning Attic Stairway Insulator and the difference in the hallway temprature was immediate. It’s way more effective than trying to DIY a foam board cover that never sits right. Also, if you find any more wire penetrations, grab a roll of 3M 8067 All Weather Flashing Tape. It’s a lifesaver for sealing those tricky gaps where the foam won't reach or just makes a mess. It sticks to old lumber better than anything else I've tried.

This all sounds so complicated but amazing. I'm just starting to look at my own attic and I honestly don't know much about this yet. When you guys talk about 'air sealing' before the insulation, does that mean I have to move all the old dusty stuff out first to see the gaps? Also, for the rockwool you mentioned, is that somthing a total newbie can cut with regular scissors, or do I need special tools to get it to fit right?