A friend posed this question to me: Is forced warm-air heat drier than baseboard heat? There seems to be a concensus that it is but I haven't been able to get a scientific answer as to why. The closest I've come to an answer is this quote:
It's not the furnace that dried out the air. It's the same air that you heat with a baseboard hot water system. The heat source did NOT cause the lack of humidity. Nature and physics did.
Great, but that doesn't answer the question: is indoor air drier if it's heated by a furnace (as opposed to baseboard heaters)and why. Or does it just appear to be drier and if so what is the physiological reason behind the apparent difference.
I understand that when you heat air the relative humidity decreases. Please don't get into an elaboration on that principle. We just want to know if indoor air is really drier with a furnace or just appears so, and why.