32 heat, but the thinking can be applied to 16 heat. When I was hitting a wall, picking boons for specific gods to make a targeted build really helped. For 16 heat, a pretty easy pact configuration would be:
Damage control (2 heat): for some weapons, this barely matters. I was using bow (aspect of chiron), so I was doing a million hits anyway.
Extreme measures rank 2 (3 heat): extreme measures versions of the furies and bone hydra are pretty easy to deal with in the grand scheme of things.
Jury summons (3 heat): having to deal with more enemies isn't so bad.
Routine inspection rank 2 (4 heat): the highest level mirror buffs aren't that crazy. You can live without the slightly higher chance for epic boons or whatever.
Middle management (2 heat): adding an elite to mini-bosses isn't too bad. Obviously this doesn't affect most rooms either, which is nice.
Calisthenics program (2 heat): takes longer to kill enemies, but they're not being made more threatening.
This will depend on weapon though, of course.