Compact Pi setups - is a Pi 5 ever overkill for a fixed camera unit?

I took a different path with mine. I run an older Pi out under the eave of my garage, wired straight into my network with a long ethernet run, and I deliberately skipped the newest board. It records motion clips to a small drive in the attic rather than trying to keep full resolution video going around the clock. The case barely gets warm even in July, and I stuck a cheap passive block on the chip just because the enclosure is sealed against rain. I get useful footage of the driveway and the side gate, and that is honestly all I need for a homeowner setup.

For me the trade came down to how often I actually watch the recordings. It turns out it is rare, and mostly right after the dog sets off the motion detection at 3am. So the extra sharpness of a bigger sensor was never going to earn its keep in my situation. My brother did go the high resolution route for his front porch and loves the detail on license plates, but his box runs hot enough that he checks on it more than I check the footage itself.

One thing I would suggest before swapping boards is to log your temperatures for a week and see how often you are actually near the ceiling. If it is only during long daytime stretches, a shaded mount location or a simple cutout grid might buy you more than new hardware would.

I landed on the Pi 5 for mine and I'd do it again, but the trick was to stop treating the camera box as the computer box. Mine sits on the garage wall pointing at the driveway, and the Pi itself lives on a shelf inside the house, connected by an extended camera ribbon through a small hole in the wall. The board gets full room air, no sealed cube, no fighting the sun, and the little module outside stays barely warm to the touch. The ribbon swap took an afternoon. I bought a longer cable and a small breakout board for the camera end, and it's been running for most of a year without a single dropout. One thing I learned the hard way: don't cheap out on the extension cable, the first no-name one I tried gave me constant glitches til I swapped it for a proper one. With the board indoors I also stopped worrying about weatherproofing the expensive part, which was always my least favorite part of these builds. Power is just a normal outlet a foot away instead of a run from the eaves. If your camera location is somewhere you can route a cable back inside, I'd keep the Pi 5 and move it out of the enclosure rather than downgrading the whole build to dodge a heat problem. Continuous recording at full resolution has been rock solid for me, and I'd miss it if I went back to clips.

I think your concern about thermal management is valid. I ran a power log on my last setup and found that keeping the CPU utilization under 40% is critical for a Pi 5 in a tight enclosure. My specific camera script is tuned to keep the average draw at 2.4 watts when capturing high-res frames. Don't just focus on the hardware; optimize the framerate so the board isn't idling at peak power all day.

I understand the thermal struggle with a sealed enclosure, expecially when pushing a Pi 5 hard. If you are committed to keeping the full performance but need it confined, you really have to focus on the dissipation pathway. When I was assembling my unit, the difference maker was a specific thermal pad I slid under the CPU heat spreader. It wasn't high-end gear, but it prevented the junction from spiking rapidly, allowing it to handle sustained load without throttling. It might be worth seeing if reducing the output framerate by a single frame can give the passive cooling system enough breathing room to keep the temprature stable.