I'm thinking of finishing my basement. I currently have a main trunk coming off my furnace that measures 20" wide by 6" tall. I'm trying to future proof my home in the event my current furnace can't keep up with my heating needs. I have a number of options:
Add a second furnace. (I don't like this idea because it will eat up a lot of ceiling space running more ducts)
Upgrading my current furnace to meet the needs of the additional SQFT. (My current furnace is only a couple years old. I've been told by a couple contractors that it's just barely under powered for the SQFT in the total house, so I'm leaning away from this to avoid the cost of replacing my current furnace.)
Upgrade my main trunk to accommodate a bigger furnace in the future. This way I don't have to tear my ceiling apart if I decide I need a new furnace. This is where my question lies, do I really need to upgrade my trunk to a 24" by 6" which is what the contractor recommended?
Do nothing and hope for the best? (With my current furnace being "just under powered" for my SQFT, my plan is to put a nice fire place in the basement to hopefully pick up the slack.
I'm looking for advice on any of my options.