: Y8 ?: l( y: @) b5 k4 R n* zoption 1: Two seperated furnances and seperated control6 M. Q3 V @/ ]- I1 W
(for big house > 3000 ft)' y; _8 q. j0 k0 W2 k2 y! u
option 2: One furnance with Zone Control device " }4 j0 Z1 f, o' p p) v (three zones or fours zone will be good) - total efficiency will be higher 5 a9 Z! d3 {8 R o6 \" D: [" M! ^5 m0 Z9 B* g
Total cost is not big difference.