I am in the process of converting my 3-season porch to become a 4-season porch. I am located in Wisconsin and I need both both the heater and air conditioner to run on the same day. Just kidding about that but I do need both heat and cooling. Right now we cannot use the 3-season porch in the heat of summer because it is much to hot. In the winter it is not heated and we cannot use it because it is much to cold.

The sun porch was built on a deck. Therefore I would like to tap into a takeoff from my basement and cut a hole through a beam to allow the ductwork to the underside of the deck. The room is 16x14 with cathedral ceilings. How big should my ductwork be and how many run do you think I should have? I am planning on insulating all the ductwork that is outside.