I live in a condo and I'm thinking about a tankless water heater, or a system like Rheem's "integrated heating and water heating system." http://www.rheem.com/products/integrated_systems/ I also am in need of a furnace, so this would make enormous sense.
The existing vent is a combined vent for the furnace and hot water heater. It follows a somewhat convolute path, and the mechanical closet does not allow a simple through-wall direct vent to the outside. What are the venting requirements (generally) for a system like this or a tankless heater? (I'm guessing that my 24 year old vents can't be used for this type of system.) Thank you.