How do I get insulation into a narrow slanted ceiling without blocking the vents?

You'll want to use rigid foam baffles, often called rafter vents or 'accuvents,' to preserve that air channel before you even think about adding insulation. Since you can't reach the far end by hand due to the roofing nails and tight clearance, the trick is to staple a baffle to the end of a long 1x2 furring strip. You slide the baffle down the cavity until it hits the top plate of the wall, then use a long-reach stapler or even just a few carefully placed screws to tack it to the rafters. If the gap is too narrow for standard foam baffles, some guys use pieces of 1-inch rigid EPS board ripped to width, though that’s much more labor-intensive.

Once those baffles are securely in place, they create a physical barrier between the roof deck and your new insulation. For the actual material, **blown-in cellulose** is usually the way to go beacuse it fills the irregular gaps around those electrical lines much better than fiberglass batts. You can rent a blower from a big box store, but you’ll need to extend the hose with a smaller diameter PVC pipe—maybe 2 or 2.5 inches—to snake it down into that narrow cavity without snagging on the nails.

Start at the furthest point and slowly pull the pipe back as the cavity fills up. The baffle will keep the airflow moving from the soffit up to the ridge, while the cellulose packs tight against the ceiling. If you try to just shove R-13 fiberglass batts down there with a broom handle, they almost always bunch up, leave huge air gaps, and eventually slide down and block the soffit anyway.

Another approach if the heat is truly unbearable is to go with **closed-cell spray foam**, but that’s a professional job and it turns the roof into a 'hot roof' design, meaning you’d actually block the vents entirely and seal the space. In Florida, that’s often more effective for radiant heat, but it’s expensive and you have to commit to sealing the whole attic section for it to work right. For a DIY fix, stick with the baffles and a modified blower hose.

Totally agree on the PVC pipe trick, it's the only way to reach those deep corners. One thing that helped me when I did my sunroom was using a bright flashlight from the outside once the baffles were in. If you have someone stand on a ladder at the soffit and shine a light up, you can see exactly where the baffle landed from the attic side. It's way better than guessing if you acutally hit the top plate or if the baffle caught on a shingle nail and buckled halfway down. Saved me from a major headache later when I realized one had slipped.

Back in the day, we didn't have those fancy plastic baffles. We’d rip down some old 1/8-inch luan or even heavy cardboard and staple them to the rafters to keep the channel open. It was a pain but it worked. If you're going the cellulose route, make sure you don't skimp on the density. If you blow it in too loose, that Florida humidity makes it settle like a lead weight over a few summers, and you'll be right back where you started. I've crawled trough enugh tight eaves to know those roofing nails will scalp you if you aren't wearing a hard hat or a thick beanie.

I’m totally new to this, so bear with me, but how do you acutally know if you've filled the cavity enough with the PVC pipe method? Since you can't see down into that narrow gap, I’m worried I’ll either leave a huge empty pocket or pack it so tight it breaks the baffle. Is there a trick to feeling the resistance through the hose, or do you just measure the volume of material you've used? Also, is cellulose okay with the humidity here, or does it get moldy if the soffit vent isn't perfect?

Quick update—I tried that PVC pipe trick to slide the baffles in, and it really helped get past those nasty roofing nails. The flashlight idea from the soffit was a game changer too. I can finally see the gap! One thing though, do you think the plastic baffles might crack if I pack the cellulose in too tight like that last person mentioned?