comfortdoc, thanks for the reply. The heatpump I'm looking at would be an add-on to my LP forced-air system. It's a 5yo Trane, single stage 80,000 92%. My 10 SEER 2.5ton A/C would be replaced by the HP. I have one quote for a Bryant HP (same dealer than installed my current setup) and the cost is relatively painless due to a $600 credit from my power company. I'm looking at $2.00/gallon LP vs $.09/kwh electric that has a stable price here in Ohio. If I save 50%, I'd have a payback in about 2 years even if I replace the coil. The installer stated he might be able to replace a piston in my Trane coil and it would work but I've seen posts here that say that's not a good idea. Still researching that one.
As for the house, it's 140 years old, but I've updated a very substantial part of it. Windows & doors are new, many rooms have been gutted and walls insulated. Attics are insulated properly, but I have some venting improvements that could help with cooling. About 50% of the first floor is crawlspace and I do plan to update the floor insulation this fall. The only other real project will be filling the remaining wall cavities (less than 30%) when I install new siding next year hopefully. Most of this has occurred since the last load calc. Duct systems are a little hit-miss due to the age of the house and how some of the lines have to run due to crawlspace. Obviously, this place didn't have forced air when it was built!