If anyone has experience with requirements or constraints for horizontally mounting a furnace and on demand / tankless water heater in a crawl space, please let me know as I have some questions that I'd like to ask through PM.

I've read through the building code and I don't see anything that stands out on this topic but hoping to discuss with someone who has HVAC experience prior to hiring an HVAC company as this is still in the very early stages of planning.

Thanks