Is it normal for my new attic insulation to look so uneven?

Uneven fiberglass batts are more than just an eyesore; they represent a significant loss in thermal performance. Insulation works by trapping still air, and whenever you have 'valleys' or gaps in that R49 layer, you're creating thermal bridges where heat can bypass the insulation entirely. In a hundred-year-old house, those gaps are often where the most heat escape happens. If it looks like they just tossed the batts in without trimming them to fit snugly against the joists, you aren't getting the full R-value you paid for.

The most critical thing to find out is if they performed any **air sealing** before laying those batts down. If they didn't use spray foam or caulk on the top plates, light fixtures, and plumbing stacks, then that new insulation is just acting as a giant air filter. Those discolored spots you noticed near the rafters and wires are a huge red flag. That usually indicates 'ghosting,' which happens when air is moving through the fiberglass and leaving dirt behind. It means your conditioned air is leaking straight into the attic. As for the cardboard baffles, they are technically a valid material, but they're the budget option. They tend to sag or get crushed easily compared to the rigid foam ones. Their only job is to keep the insulation from blocking the soffit vents so your attic can breathe. If they're installed sloppily and allowing the insulation to spill over into the eaves, you're going to end up with moisture issues and potential mold on the underside of your roof deck.

You should definitely call them back. A professional install should be level, tight-fitting, and shouldn't have gaps around the electrical wiring. Tell them you're concerned about the compression and the visible airflow marks. If they're a reputable crew, they'll come back out and tuck those batts in properly. It’s a lot easier to fix this now before you have a season of high utility bills to prove the job was subpar.

I had a similar mess in my old place. Those crews ussually just jam the batts in, but I found that 'stuffing' them around the wiring actualy creates big air pockets underneath. I ended up going back up there myself with a utility knife to notch out the fiberglass so it sat flat against the drywall and hugged the wires instead of arching over them. Also, make sure you can actually see where you're stepping. If you don't have a catwalk or some 2x4s laid down now, you're going to trample that R49 into nothing the first time you have a roof leak or need to pull a new wire.

If they didn't air seal before the install, you're just heating the outdoors. I'd grab a couple cans of Great Stuff Gaps & Cracks insulating foam sealant and hit every wire penetration and top plate myself while they're back out there fixing those batts. Those cardboard baffles are trash for a century home; I always swap them for the AccuVent plastic baffles beacuse they actually hold their shape and don't rot if you get a little condensation. If you see dirt on the fiberglass already, that's air movement, and spray foam is the only real fix.

Back in the day, we didn't have these fancy R49 batts; we were lucky if the homeowner had a few inches of rockwool or just old cedar shavings. But the basics haven't changed. If you're seeing discoloration alredy, that's 'filter effect.' Those batts are acting like a furnace filter for your house air. Did they even bother to check the chimney masonry? In a house that old, there’s ussually a massive gap where the brick meets the framing. If they didn't wrap that with some metal flashing and high-temp caulk before tossing the fiberglass down, you're just throwing money out the roof. Don't let 'em leave until they've cleared the debris from your soffits too.

Oh wow, I'm so stoked to finally be looking into this for my own place! This thread is a goldmine. It's crazy how much science goes into just stuffing fluff in a ceiling, right? I'm totally new here, but seeing everyone talk about these air leaks has me wondering—does the type of lightbulb you use in those old recessed cans make a difference for the heat buildup under the batts? I'm worried if I upgrade my insulation I'll accidentally melt my vintage fixtures or somethig!