Ducts sized for heating only are almost always too small for A/C systems and should be replaced. The contractor should measure the ducts and see if they meet the cfm requirements of each room for the A/C static conditions, so a complete room by room load calculation should be done to determain this. If the ducts are correct- they can be sealed and wrapped with additional insulation and possibly cleaned if real dirty.

I do not understand why he would oversize the BTUH of the equipment way above what the ductwork sizing will support at reasonable static pressures & FPM velocities. A tech may have to figure out another way to run ducts to those rooms. The linked page will provide some guidelines toward proper duct sizing. It appears you would not need much air conditioning tonnage. I am a retired HVAC/R Contractor since 1993 & do not operate an HVAC/R business or work as a tech anymore. udarrell _ 2007 Here is a link that might be useful: udarrell.com

Thanks, for the replies. I specifically asked about the existing duct work, and all three said it's fine. Actually the noise is probably due to our trying to compensate for the temperature differences between upstairs and down... we have to mostly close the downstairs vents to push enough air upstairs to get the temperature half-way decent. Perhaps with the VS unit running longer, we could open the downstairs vents more and eliminate that problem. It sounds like 2-stage is out simply because it would be too big for our house. Regarding thermostat, he indicated the programmable Edge should provide everything we need and from what I've read, it should include ability to control humidity. But you raise some good points. It sounds like I need to verify a thermidistat is being included... is this a separate sensor, or part of the thermostat itself and I just need to ensure I'm getting the right model (perhaps TP-PRH)? Regarding dryness from outside air infiltration... our house is pretty tight, but this could be coming from the windows... I'm also looking to replace them with more energy efficient vinyl replacements, so that may help that situation as well. I think I'll hold off on the humidifier until the HVAC and windows have been replaced, and then evaluate. Regarding tigerdune's comment about 80% furnace... if I recall the discussion regarding this proposal, the 96 was required to qualify for tax credit. If I were to opt for the hybrid, could this qualify based on the heat pump rating alone? Thanks, Brian

Seems to be a popular size in the UK. Try asking over at HVAC side if you don't get help here. Here is a link that might be useful: http://ths.gardenweb.com/forums/hvac/