Was it a furnace or a boiler?
Your biggest issue with a gas-furnace (if not a boiler) would be finding something right-sized for your actual loads. Getting a good grasp on your heating and cooling load numbers will be essential for maxing out both comfort and efficiency. A 5x oversized furnace or air conditioner will heat & cool the place, but it's the opposite of comfort.
Do you have enough of a heating history on it to
run a fuel-use based load calculation on wintertime-only gas bills? Since that is the "before upgrades" picture would establish a firm upper bound on the furnace sizing.
Start with a room by room, zone by zone Manual-J type load calculation. If using an freebie online version such as
loadcalc to calculate the loads be aggressive on R-value, infiltration & duct leakage assumptions or it will oversize by quite a bit.
Most tightened-up 1100' 1.5 story houses would have a design heat load at +12F (Cincinnati's
99% outside design temp) would be less that 17,000 BTU/hr, and could be less than 14,000 BTU/hr if the basement is insulated to the current IRC code minimum. The only gas hot air furnace I know of that fires that low is Detton's modulating
Chinook series, which is a bit special. The smallest 2-stage condensing Goodman
GMEC96 0303ANA is still over 20,000 BTU/hr at low fire (and I think it's been discontinued) but would be about as good as it gets in more standard 'merican style equipment. A hydro-air handler running off a condensing water heater can be appropriately sized for smaller houses, but that requires a bit more design smarts by the installers.
You may be better off with a 1.5- 2 ton heat pump solution, even though that's almost certainly oversized for your cooling loads. A modulating 1.5 ton Fujitsu -
18RLFCD or -
18RGLXD wouldn't be too bad though, since either could modulate down to less than half your likely load, yet still deliver ~18,000 BTU/hr @ +5F (over 20K for the 18RLFCD). The -18RGLXD is an easier retrofit onto existing ducts due to it's higher static pressure capacity, but the ducts are probably sufficiently oversized to do OK with the cheaper, higher capacity and more efficient (but less beefy blower) 18RLFCD.
It's likely that you'll want to zone the upstairs and down stairs separately. The heating and cooling loads of a couple of upstairs bedrooms is pretty tiny, probably less than 8000 BTU/hr in the "after upgrades" picture, which is within range of Fujitsu's 7RLFC mini-duct cassette, which would have to be used with a multi-zone compressor. A 2 ton
AOU24RFXFZH can run up to 3 zones, but setting it up with a 12RLFC or 18RLFC for the main floor and a 7RLFC for the upstairs would work reasonably efficiently. At max speed that 2 ton compressor will deliver 25,500 BTU/hr @ +5F, (which is overkill for your house), but it has a decent modulation range, and can throttle down to 6100 BTU/hr @ +47F.
At 2 ton
Carrier Infinity Greenspeed doesn't have the same modulation range or low-temp capacity of a Fujitsu (and would probably be more expensive), but it could surely handle your loads.
BTW: Since that house was almost certainly sheathed with ship-lap or t & g planking it isn't very air tight. Even though it's quite a bit more expensive than Tyvek/Typar etc, a fully adhered vapor permeable membrane housewrap like
Blueskin VP100 would be a cheap efficiency upgrade in the end, vastly reducing air infiltration issues. (Think of it as 4' wide strips of housewrap tape.) Fully adhered membrane housewraps are really the only way to do plank sheathed houses right without resorting to foam insulation cavity fill and lots of detailing with caulk & can-foam.
