I think this would add to the mod, and provide more ways to heat up/cool down. It would also help you to feel more immersed, while not being overly apparent as long as values are made well and balanced. You'd need multiple blocks of the type in order to have a noticeable effect.

Right now the Body Heat mechanic is nice and the hot blocks that it checks for is also a neat system. It had me thinking of if heat values could be added to common blocks like stone, cobblestone, glass, wool block to start with maybe. This way you could use some blocks as insulation to keep your house warm, like wool blocks, while a cobblestone floor might radiate a cooler value and the glass too, or if you're down in a cave and jump out of some water but you're standing on stone, surrounded by stone, you might be cold and need some hot blocks to warm up or some hot item that gives you heat.

Alternatively to the heat values being added to blocks if that wouldn't work, there's also the possibility of adding heat levels to areas depending on how deep you are, if that makes sense? So going deeper underground leads to it getting hotter and hotter, absent of hot blocks around. Even hotter if you are next to a hot block. Likewise, the higher you go, the colder it gets. If there was some sort of breath mechanic that could factor into both as well. This would be nice, but I understand right now that you're focused on trying to revamp the heat mechanics and make it more balanced to survive in general so that's why I think it's a nice alternative but my first suggestion would be better for players to be able to build themselves a hotter/cooler place of living with specific blocks types.

I tried this one out with the formatting, hopefully it's a little easier to read and get the necessary info than my last request. Thanks for the response on that one by the way, the JSON work looks really promising and I'm excited to see where it ends up!

Hi, sorry for the long delay. I have also thought about this, but unfortunately, such system would be really resource intensive to implement, since it would involve a lot of raytracing each second.

But the second approach you highlighted might actually work. Currently, the only thing similar to that is that the caves have constant temperature (which is set in the config). I will try to see what I can do, but so far it seems to be fairly easy to implement. But from the realism and balance point of view, I am not really sure which values to put to make it scale realistically.

EDIT: About your first proposed feature... You can already add new blocks to emit heat, but they're just that... passive heat emitters. They can't function as isloation (unless heavy raytracing was involved, as mentioned above).