Did you maybe mean to put this the other way around? If I do a 2 system house i put the heat pump downstairs(since heat rises and the downstairs system does most of the heating) and the AC upstairs since there is very little need for heat on the second floor in a well insulated home.
Yes, I got it backwards. In some climates you might even be able to get away with heat only downstairs and/or cool only upstairs. In Texas you may not need heat upstairs, in Michigan no A/C may be needed downstairs. IMHO overall temperature balance would probably better with a furnace downstairs and separate A/C upstairs instead of one system trying to do both floors. 2 floor homes is definitely an area that tons/btu per sq ft rule of thumb doesn't apply. Does Manual J account for heat rising up the stairs in a 2 story home?
Does Manual J account for heat rising up the stairs in a 2 story home?
Not that I know of. I use Accuload from Adtek and if you put the floor is over a conditioned space and is a second floor it doesn't "show" any heat gain that I have ever seen. I have not really played with this though. I think it is Manual D that assumes a 6 degree split between floors though. I can't exactly remember where/how I heard that but have seen it a few times.