I have a 75,000 BTU gas furnace which heats the lower floor of my 1400 sq.ft. house through forced hot air ducts. The upstairs has electric heat which I'm getting rid of. I wanted to run ductwork upstairs but I was told it would be too difficult because of the plaster walls. A friend told me to add another furnace in the attic and run the ductwork from there, it's a pretty common thing. So my house would have 2 zones which is great and could eventually add central air. Is it common to have a gas furnace in the attic? Is it for whatever reason dangerous? What would be the pros and cons? Would I need some sort of ventilation up there? Thanks.