It looks like you could possibly do the 2 furnace circuits on the one side and the 2 GFCI outlet circuit on the other to open a duplex spot.

All the other 120 circuits appear to be afci.

Otherwise maybe you could get a 15-60-60-15 quad breaker and only do the one side.(I know square D has them that style)

But if you have the physical space nearby to add a sub panel that may be a better option long term.

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It also seems that the more lights I add to the circuit the louder the buzzing gets.

Here is a photo of one of the knee well attic spaces with a vent at the top: https://imgur.com/a/U5GcyLP

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Ahh you're right, I didn't realize AFCI breakers are required these days. That's whack lol.

No insulation in the attic floor, except for a couple inches of 80yr old insulation where they added a second floor on top of the first floor and didn't put in the effort to remove it. Newer parts of the house you'll just see the ceiling drywall from the room below.

There is roughly 2-3" of spray foam under the roof decking/between the joists. Colorado front range for climate reference.

It probably won't be to code if you slap in those mini breakers, because they put in the AFCI or combo AF/GF. Your homeowners won't cover you if something happened.

Your real problem is I don't think you have enough overhead to slap another 60A in there. You might be close to limit if 200A service. You might want to check, but I'm the summer of you have 50A to car charger and two 30A A/C units running, and you have say electronics lighting, fridge. Then you turn on stove, it might exceed your service.

The better option might be to put in a sub panel of a 100A double, and move the A/C breakers to it and add car charger there in a sub panel with 8 slots.

At max load, the house is pulling 41A, peak summer based on provider data. Installing the Tesla wall charger that will continuously draw 48a on a 60amp breaker.

On max load, I’m drawing 41A based on data from my provider. That’s mainly peak summer here in TX

Top or front loader? Front loaders typically have a little "gate" inside the detergent compartment that determines how fast the water flows through it/trickles down into the drum.

Top

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But, if it's a new enough house to have an AFCI circuit, now you're below code unless you're installing an AFCI outlet on each circuit, and those aren't cheap either.

This sounds like a scam.
How much insulation is in the attic floor?
A cold loft has floor insulation and lots of ventilation to keep the moisture rising from the house below moving outside. There should be a gap along the top of cavity walls and a draught blowing through the loft.
A warm loft is insulated under the rafters with air moving around the timbers above the insulation.
Insulation under the tiles with air blowing around the open loft space defeats the object.
One advantage though, would be to reduce heat transfer through the roof in summer.

Ok I checked all the lights and they are dimmable, they are led canned lights, so the slim kind that you can’t really change out a bulb without replacing the whole light itself

If you get non-afci tandems then it's definitely not easier and cheaper to do that but the sub panel is the smarter move.

So what do you pull at full load as is.

Reminder tandom breakers are only going to be one leg of power.

Is your charger a 115 or 208/230?

You might be going too fast. If you’re pushing the saw faster than the blade can nibble the wood it will bend. Go slow and keep your eyes on the spot where blade cuts the pencil line. It that wood is very hard this will take a long time.

Maybe double check that all your bulbs are dimmable. The only time I've run into that buzzing is when I have a bulb that isn't dimmable. Alternately, you might have a bulb that's going bad and not dimming correctly.

Breakers should work but I'd recommend just installing a sub panel. It's going to save you down the road for new circuits.

It seems the buzzing starts after I add the second light, although it is much quieter than when all are connected

If they're AF/GF breakers, that's "probably" for a reason. You'd have to check local codes and see if it's required for a given circuit (if you're subject to modern codes, they're required in lots of places). If it is required, you'd have to put GFCI outlets in, and you'd maybe have to switch your main breaker out for an AF one? (Not cheap!)

I'd look long and hard at the actual charging rate you need. 60A is big and could push the load calculation for your panel over it's limit, especially if you've got a big AC or anything like that. Have you done a load calculation (you better, if you're adding a 60A load)?

Most people charge their cars overnight, and even 20-30A (at 240V) is more than plenty for that, even doing large amounts of driving per day.

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