; b' }$ R# R1 [2 X# q8 @option 1: Two seperated furnances and seperated control2 t$ q) N6 Y# s: c1 G
(for big house > 3000 ft) 4 O/ Z: H/ O" F Aoption 2: One furnance with Zone Control device H! N& Q( [9 o4 Q z! Q8 e
(three zones or fours zone will be good) - total efficiency will be higher6 R4 p7 X% o6 h; z
' x7 n# ^+ [3 A! H, a( X9 w* j9 ATotal cost is not big difference.