Thanks for the info, Dana! Crawlspace does have heavy plastic covering the bare ground.
If you can lap the edges of the ground vapor barrier plastic three inches or more above grade onto the walls and seal it to the wall with caulk, mastic or construction adhesive, you can then lap the wall foam over the plastic without concern, since the bottom edge of the foam is on the vapor barrier, thus protected from ground moisture.
What I meant by sealing the ceiling before insulating is using fire foam around any cracks and around light cans (have only LEDs in them) from above. I thought about using fiberglass batts, but what you were saying about using cellulose insulation makes more sense, even if I have to install it by hand. I do have one question about that. I installed 2 of those Globe Electric clip-in LED lights and am wondering how to insulate around them.
If the lighting fixture cans are not both air tight & rated for insulation contact (there is usually a label on the fixture for those ratings) you need to establish a 3" clearance on all sides to full meet the letter of the code, even with low wattage LEDs installed. An easy way to do this is to find a cardboard box of sufficient size, tape all the seams with housewrap tape, then seal it to the ceiling gypsum with caulk & mastic, (or can foam if it's easier). Sometimes codes require a non-combustible material (such as half-inch wallboard) to be used rather than cardboard, but for a low wattage LED the risk of using a cardboard box is very low. Where the wiring enters the box you may need to use mesh tape & mastic over the wire to get a good seal. There are commercially made
fireproof buckets for sealing over recessed lighting fixtures out there as well. (Box stores near me keep them in stock for $15-20/each- YMMV. )
^^ "InsulMax" brand can cover made of fire retardent EPS foam^^
One thing I did find out about this house. The entire lower floor has concrete block walls, and someone screwed 2 x 4 framing on inside of exterior walls and covered framing with paneling. I found out by tearing out a couple of panels to see how the wiring was done. Old NM wire comes down pipes that were set into the concrete block and exit through outlet boxes. My point is that no one bothered to insulate these concrete walls. I've tried to learn the best way to do this, and was told to cover the concrete block with 1" rigid foam insulation, build walls over insulation with 2 x 3"s, and then add batt insulation between the studs.
Is this the right way to go about this?
CMU block walls are considered "mass walls" under the IRC. If you look under the MASS WALL column of
TABLE N1102.1 2 in the zone 3 row you'll see two numbers for R value: 8 / 13 . The R values refer to a continuous layer of insulation, the lower number (8, in this case) meets code if half or more of the insulation is on the exterior side of the structural concrete, the bigger number (13) is if more than half the insulation is on the interior side.
If you're going to gut the interior, the easiest way to get there would be 2" of foil faced polyiso foam board (typically labeled R12 or R13) glued to the wall, secured in place with 1x4 strapping through-screwed into the CMU with TapCons, mounting the wallboard on the furring. That takes up 2.75" of depth from the wall, buying back 3/4" of space for the room. If that complicates re-mounting of the electrical boxes there are other ways of getting there.
Cellulose packaged for insulation blowers is sold in tightly compressed bales, and needs to be fluffed up to do it by hand. (Insulation blowers break it up mechanically with the feed from the hopper.) For small areas it's easy enough to break a chunk off the bale, put it in a 5 gallon bucket, and fashion a lid with a hole in it big enough to accommodate the shaft of a paint or mud mixing drill, the
way this guy did: