3 Y. J0 B1 f z$ E- g" w0 e2 G% aoption 1: Two seperated furnances and seperated control$ Y4 N; @8 j# s5 D! B* T3 M
(for big house > 3000 ft)9 t* x: |4 e- X
option 2: One furnance with Zone Control device - Z# a! a( \' c! W, L* r f (three zones or fours zone will be good) - total efficiency will be higher ( d- L f9 M; E, K, u5 ]0 V1 ^1 ^# E; U2 _
Total cost is not big difference.