I am in the process of researching furnaces to replace a very old one. Currently the furnace is attached to a chimmney stack specifically for the furnace. I have had several companies come out and give estimates. Only one indicated they would eliminate the use of the chimmney and run it directly thru the wall to the outdoors. Is this reasonable. What else should I look for concerning installation procedures. I live in MI (between Detroit and Flint). I have a 1650 sqft two story colonial with a partial finished basement wheer the furnace will be housed. Opinions on Gibson? Thanks.