I see a lot of "Radiant Floor Heating" with a rubbery tubing stapled under the floor. SInce I tend to be in horror of any kind of leaks, I wonder why they don't use some compresses gas instead?
Mind you, I have even had experience with central venting "leaking": I haven't used a/c since my folks died but my uncle's a/c duct sweats onto my ceiling. That's the price for freeloading (hot air rises) off his a/c.