Thanks for the quick responses! The existing furnace is an oil-fired York, 125 KBTU, which is at least 30 years old. I have been told it's horribly inefficient, but I don't know the number. The AC condenser is 3 tons and 25 years old (also not efficient). The house should probably have 2 zones (especially to deal with better cooling the second floor in the heat of summer), but I have been told that's not possible (at least not for a reasonable price). Otherwise, there are no noticeable issues with the current system, other than those endemic to scorched air heat. Each room has at least one supply vent and one return. The basement is below grade and is used as living area. There are two supply vents and one return in the basement area. There is no insulation between floors, but the basement walls are insulated (R-7.5). Beefing up the attic insulation is on the near-term to do list. The house currently does not have a humidifier, and while no one is suffering nose bleeds, the air is dry. So, I thought a humidifier would be helpful. I would definitely like to tighten the house (and new windows may be on the radar in the near future), but given that it is an older home, I think there is only so much that can be done. The Carrier dealer said the furnace would be no more than 100 KBTU, with the final determination after the house is measured and a load calculation performed. Both companies will also do a whole house energy audit prior to commencing work. So I would assume (and hope) the Lennox dealer will modify his numbers accordingly after the load calculation and energy audit. Our natural gas marginal price/therm is $0.83 Our electricity marginal price/kWh is $0.22 for on peak, and $0.07 for off peak. With regard to the Carrier condenser, what makes the 24ANB6 superior to the 24ACC6? I know a lot of people on this forum prefer Carrier over Lennox. All else equal, I have no problem going with Carrier (I know the Infinity controls are fantastic), but there is a $1,500 price difference... Thanks again for your help.

You need to sit down with the contractor and go thru all of that in detail with them. There is just too much detail and unknowns in this for me to give advise here. It never hurts to get more opinions. The dampers will work if installed correctly and will help the upstairs a lot. I like that contractors proposal.

Hi, Thanks very much for your responses. - Everyone I've spoken with, and you've confirmed, that one zone per floor makes sense. If I'm missing anything else about "zones", please let me know! - How much should it cost to go from 2 zones to 4? - We are definitely going to put in all new ductwork. Is there anything here that I should be aware about or ask for? Any sites (besides GW) to get more knowledge on this area so I can ensure we get the ducts sized properly? - Good comments on getting more info on the geo wells, piping, etc. Will do. - Can I get a Manual J done even if the house is under construction? Framing is almost done, but the exterior work is not complete, and so it's open to the elements right now. - Yes, we have a natural gas furnace and electric AC in the house. It appears that a NG furnace was installed in 2007. The unit is a Lennox Signature Collection, model CX34-62D-6F. We also have an electric hot water heater, AO Smith ProMax Plus, model FCG 75 300. Does it make sense to re-use these or upgrade? Obviously, the furnace will be out if we go with geo. - Here's a summary of our NG and electricity rates. I hope I'm doing this correctly -- taking the bill amount and dividing by the energy used. Some months may need to be taken out because the numbers are too high/low. Please note that we have not lived in the house, so this is what we were paying for several months before construction commenced. So I would expect actual usage, and thus our bills, to be higher, but I guess that the cost per unit would be somewhat proportional. Natural Gas Monthly Charge / Therms Used / All-In Cost Per Therm $18.06 / 5.1 / $3.54 $16.76 / 5.1 / $3.29 $51.90 / 32.5 / $1.60 $78.53 / 57.7 / $1.36 $339.62 / 314.7 / $1.08 $362.71 / 321.1 / $1.13 $184.41 / 154.8 / $1.19 $81.98 / 60.4 / $1.36 $66.62 / 47.4 / $1.41 $18.45 / 7.1 / $2.60 $16.18 / 5.1 / $3.17 $1.97 average Electricity Monthly Charge / KWH Used / All-In Cost Per KWH $285.18 / 1757 / $0.16 $137.36 / 786 / $0.17 $77.44 / 416 / $0.19 $57.91 / 316 / $0.18 $66.29 / 382 / $0.17 $86.87 / 524 / $0.17 $61.02 / 341 / $0.18 $24.50 / 76 / $0.32 $25.22 / 80 / $0.32 $38.34 / 73 / $0.53 $21.23 / 53 / $0.40 $32.62 / 140 / $0.23 $0.25 average - It must not be code on my state (MD) to have each floor zoned. Our bids have been for two zones (on per system, one system covering basement and first floor, second system covering second and third floors), or for four zones (running off two systems). - Thanks for the heads up on the tax credits. My husband is tracking these, so I'll make sure he knows this. - The addition is on a loggia, not crawl space. So the basement is a walk-out basement, and the loggia will in effect extend the basement, and then the kitchen/family room addition will be above this, and our master bedroom addition above that. It's at the back of the house. Here's an early photo so you get the idea. The house is brick, and the addition will be part brick, part clapboard. - I am trying to learn what an HRV is, so am looking into this. - If it's not a good idea to go with spray foam insulation, let me know! Thanks for the info on what type would be good. - More thoughts on what system to go with, pricing, etc.?? THANKS AGAIN!!

In dealing with multi zone set ups the enemy is always over capacity. The more speeds the system has the better it will handle a multi zone setup because if you have 1 or 2 zones calling the system is better able to match the capacity needed to the call being received. Even better if you go to a variable speed (compressor) model. These kinds of systems aren't meant to 'only' save you money on the light bill, the are meant to give you the best in comfort. They will save you money too, but that isn't the only reason to buy one. You have to think: what is comfort worth to you. If you pair a full variable speed system (compressor of the condenser is full variable speed not just the furnace blower or furnace blower and condenser fan motor) They make a slew of different model units to confuse you. So getting back to the point if you have a full variable speed system including the compressor the best way to control this kind of system is via communicating thermostat. Communicating is different in that the system actually talks with the thermostat(s). Communicating is like having a network run via your thermostat wires. This is only one option, in some cases you could hook these systems up the old fashioned way of power signals. Problem is the power signal way may cut the functionality somewhat. These systems were designed to 'communicate'. Proprietary zone boards have their place because they were designed for the system you are attempting to design. Me personally I know there are better options available else where. This comes from over 20 years of experience and heavy control knowledge. Most zone boards operate via the way of sending a 'voltage signal' the communication application is in it's infancy. These things only started trickling out over the past few years. The non-propriety zone boards that have communication capabilities come at a hefty cost and in many cases will require more than one board, not to mention the cost of multiple communicating thermostats. There are ways to cut costs and maintain a good communication balance. But that requires astute control knowledge. Something you may have to look for in many different service providers. Your service provider will play an integral role. Because this is who you will ultimately call on if the system needs servicing.