I own what used to be a ranch house but I converted it to a colonial. It has gas heat and there are 3 cold air returns downstairs. I put electrical baseboard heat upstairs but now I want to extend heat ducts from the furnace up there because of the high cost to use electrical heat. The problem is trying to put air returns in. I have a easy place to put the heat ducts but putting in cold air returns will be a major and expensive problem. Question is, can I forgo the cold air ducts?