I have an unfinished basement. It has cement floors with stone walls. The furnace is located in the basement. There is a supply vent blowing conditioned air into my basement. As far as I can tell, there is no return vent in the basement.
It seems a waste to me to be conditioning such a huge space that I don't really live in. But, I don't really understand too much about the reasoning for why certain areas in my home is conditioned. For example, I was told by an energy auditor that the crawl space under my bathroom should be conditioned (which also seems wasteful).
Why is there a supply vent in my unfinished basement?
Should the vent be opened and heating/cooling my basement?