/Bought goodman furnace and ac. want to install my new system. How do I decide on duct work size and reduction for adequate air flow? Will install units myself and get pro to do hookups. Wonder if gas company will hookup instead. Figure 60k btu and 2 ton a/c for second floor addition (3br, 1 bath added) about 900 sq. ft including hall and stairway. All four rooms on same back side of house, hall on front side as access to them, i.e. straight run 40 feet long.
duct work in hall feeding all 4 rooms. Can fit 8x16 duct to start and reduce as necessary. What to do?