The "heatings" bit was part of the question. I was stunned to see this being listed in some of the DE-EN databases:
https://www.dict.cc/?s=heatingshttps://dict.tu-chemnitz.de/english-german/heatings.htmlYou can find the pluralized form on ENS pages:
https://www.cdc.gov/niosh/mining/works/coversheet1070.htmlhttp://www.eph-ltd.co.uk/category/heatings/But I wouldn't recommend it. It's similar to storage(s), which a certain group of English native speakers (e.g., scientists) will pluralize nowadays. I don't really like that either.
Side note: I know what HVAC is. I suggested "heaters" as an option, as it's not uncommon to use the plural form of a unit to describe some kind of concept, or at least to describe those units collectively.
One example, which includes both "heating" and "heaters":
https://www.electricradiatorsdirect.co.uk/news/electric-heat...Only "heaters":
https://energy.gov/energysaver/home-heating-systems/portable...In short, I wasn't trying to disagree with you at all.
Best