Should I replace 1970s fiberglass insulation while my closet walls are open?

If you're in Zone 7a, that old R-11 or R-13 fiberglass from the 70s isn't doing much for you, especally if it's already settled or compressed at the bottom. Since the walls are already open, this is the only time you'll have to address **air sealing**, which is ussually the bigger issue in older homes. Fiberglass is basially a furnace filter; air moves right thru it. If you pull those batts out, you can hit the top and bottom plates with some canned spray foam to stop drafts coming from the attic or crawlspace. Swapping to **Rockwool** is a solid move for a closet. It’s denser than fiberglass so it’s much better at blocking sound and has a higher R-value per inch. Plus, it’s hydrophobic and fire-resistant, which is nice peace of mind in a small enclosed space full of clothes. In a 2x4 wall, you're looking at R-15 with Rockwool versus the likely R-11 or less that's currently sitting in there.

I wouldn’t bother with rigid foam board between the studs unless you’re planning on sealing the edges perfectly with foam. It's a massive pain to cut to fit exactly. Just pull the old batts, foam the gaps where wires or pipes go through the wood, and pop in some new mineral wool. It’ll take you an hour and cost maybe fifty bucks for a small closet space.

You'll defintely regret it if you close it up and still feel a draft through the new shelving or see condensation on the drywall during a polar vortex. Doing it now means you never have to think about it again for the next thirty years. It is one of those small jobs that makes a big difference in the overall comfort of the bedroom.

I'm in a similar spot with my laundry room right now. If I switch to Rockwool like you suggested, do I need to add a plastic sheet over it since it doesn't have that paper backing? I keep hearing mixed things about vapor barriers and I'm terrified of trapping moisture and causing rot. Also, is that canned foam stuff messy for a first-timer? I’m worried about it expanding way too much and getting everywhere.

Careful with the plastic sheets in 7a. If you trap moisture on the wrong side, you're asking for mold. Look into a smart vapor retarder instead of 6-mil poly; it lets the wall dry out if humidity spikes. As for the foam, skip the cheap straw cans. Spend the $30 on a pro-style dispensing gun and a can of Great Stuff Pro. The control is night and day, and you won't end up with a sticky explosion. Just keep a can of acetone cleaner handy for the nozzle. If you're swapping that 70s junk, take five minutes to check for hidden bypasses around the light fixtures or electrical boxes too.

definately yank it out. One thing people forget is that old 70s fiberglass is a magnet for mice. When you pull those batts, look for droppings or nesting material at the bottom of the bays. It’s way better to clean that out and seal the holes now than to smell it later. Also, since the studs are bare, check if you want to add an outlet or a light fixture. It's ten times easier to run a bit of Romex now before the drywall goes back up. For such a small space, it’s a no-brainer to just refresh everthing.

While you've got the bays empty, take a minute to look at the back of the exterior sheathing. If you see any dark staining or tide marks, you might have a flashing issue with the siding or a leak higher up that's tracking down. It’s way cheaper to catch a leak now than after your expensive new closet system is ruined.

Also, keep a shop vac handy. That 70s dust is nasty and will settle into your bedroom carpet if you don't stay on top of the cleanup as you pull the old batts. Wear a mask, those old fibers are brutal on the lungs.