( o! ?# [" u: k2 W; M2 \option 1: Two seperated furnances and seperated control& D1 f8 ]% T2 M
(for big house > 3000 ft)* u' T9 ~: r) j' H `; M& D( D
option 2: One furnance with Zone Control device " ~; }1 t9 N* m# M
(three zones or fours zone will be good) - total efficiency will be higher6 K: z/ ~- I, v' f
! N2 U- J8 y! p/ v
Total cost is not big difference.