" N9 c2 m! V% Z* {; e' H2 ^+ R- U2 Doption 1: Two seperated furnances and seperated control 0 Y Z. H. K4 Y$ P- B3 p (for big house > 3000 ft)1 C+ O) W7 `5 Z
option 2: One furnance with Zone Control device $ L5 i& R9 S4 C0 v4 _
(three zones or fours zone will be good) - total efficiency will be higher - q$ I, s3 e( q- g8 l- @2 s* d; H# {, n, l/ Z. N
Total cost is not big difference.