Vertical vents for high efficiency forced air?

JPope

Living in Chicago, in a 3-story 6-flat ~ 120 yrs old.  City ordinances now mandate > 90% AFUE furnaces, but currently each unit has a "mechanical" room in the center of the unit, where both gas water heater and gas forced air furnaces (nom 80% AFUE unites) vent to a common chimney (previously for basement boiler?).  Makeup air to mechanical room is via wall louvers fed from basement area, but it is a *very* loose building.

My question is: Are there any > 90% forced air units that allow vertical vents(w/ makeup)?

Last I checked (~ 10 yrs gao), > 90% units required coaxial (makeup in/flue gas out) horizontal venting, sloped to outside, but Chicago had taken a hard-line against icing/icicle hazards.  Also, there's enough room, but running duct laterally would seem to require ripping out someone's floor or ceiling, not to mention making pretty big holes in a three-leaf brick wall.  Just looking for possible, better solutions.

John Mills_5

PVC vents

You can't common vent with the existing but you can run your PVC intake and exhaust pipes up through the roof if that works. That's always been an acceptable way to do things. The same concentric vent kit that is used on a side wall installation can go through the roof with the right flashing.