Hello:

Would appreciate any information on the following:

Will be replacing a very old gas, forced hot air furnace with a new
"high-efficiency" type.

Have just read in the Audel's HVAC manuals that for a "high-efficiency" type
of hot air
furnace, you do not vent thru the chimney (or via a metal vent pipe that
goes thru roof like we now have),
but rather you vent via a PVC pipe thru the side of the house. It wasn't
worded such that you might think that this is an an option, but rather that
this is the (only) way to do it.

Has to do with the fact that the gas is not very hot from these types of
furnaces, and the condensate would flow back and ruin the furnace, etc.

Is it the "only" way ?

Is there a "mid-efficiency" forced gas hot air furnace that would enable
venting in the manner we now are doing it (thru the roof) ?

Sure don't want the expense of trying to configure a new vent thru the back
side of the house !

If so, how would these "mid-efficiency" furnaces be designated: by SEER
Number, or... ?

Any thoughts on this would be most appreciated.

Thanks,
Bob