We are putting a second addition on our house, a two-storey faux colonial built in 1961. We have an oil-fired boiler that supplies baseboard radiators and hot water. Currently, we have no AC aside from window units.

I have a HVAC proposal from a contractor suggested by our general contractor (the GC did the first addition and we trust and respect his work) to install a heat pump system to heat and cool the addition and, in a second zone, the first floor of the house. The second floor would be uncooled and heated by the existing boiler.

Specifically, the HVAC guy is proposing a 3 ton Carrier Infinity Green Speed air source Heat pump with a variable air handling unit and 5kW heat unit. The cost quoted is $16K including labor and an additional $2K for "2 Thermostat Zone system and duct". He would have to install ductwork for the addition and first floor. The heat pump approach is a result of space being at a premium in the new addition and our desire to air condition the first floor and get rid of its window AC unit.

Questions I have are:

1) Are we asking for trouble cooling just the first floor?

2) What experiences do people have with Carrier? As with most prominent brands, there's a lot negative on the web re Carrier.

3) Is the proposed price in the ballpark? He has given us a range of units of lower costs/SEERs?

4) Is it appropriate to ask to see his calculations of sizing the system?

I can't put my finger on it, but the proposal, which lacks detail on how the work will be done, does not sit well with me.