I would be curious in seeing if you have a good grasp on the numbers I posted originally and the effects they truly have on a home, along with a program you use that actually takes into account some of these things, such as thermal bridging and extremely low infiltration rates...cause ours does. Some of the hvac guys I talked to their programs maxed out at r29 insulation in the walls! Not to mention their "infiltration numbers were, well not numbers at all, but rater "loose, medium, and tight". (tight being 2 ach@50 pac, still way too loose). Its not a fight between who is smarter. Its a matter of new ways of doing things. Tried and true and gut feelings are all fine and dandy on typical code homes, but not here. It gets people out of their comfort zones and actually size things correct, heaven forbid. My HERS rater and ES rater came back with similar numbers now. I guess we are all crazy and the home will really, really suck. (just like the PH homes in VT, IL, MI, and other places that use a single point cooling such as a mini split with great results....)

Thanks for the replies guys. After reading countless threads on this great forum, I think I've determined I've been looking at this the wrong way. My builder gave me the model numbers above and with prices for upgrades. Duel Fuel, increased AFUE, variable speed fan, etc.... I've been trying to crank up the AFUE without looking at what type of system would benefit me in my climate area. So I guess I need help from you all on determining if I should go for a high AFUE furnace like the XV95 or Duel Fuel and utilize the heat pump as much as possible since our winters don't have too many days below 40 here. I know I saw a calculator to determine this with what gas and ac costs are in my area, but I'm a noob and could definitely be pointed in the right direction. Here are some specifics of my house, my builder did not provide me with a J load calculation either. Can they provide that on a NEW house being built? I just don't know these things and what I should be asking for. I just don't want the builder to get over on me and charge me crazy prices for upgrades. I've asked the builder to let me talk to the HVAC guy, IMO they should be telling me what type of system would be the best in my area, no? They're the ones who are the experts and can recommend what type of system based on energy costs would be the best. Am I asking too much? 3412 sq. feet 1 story house, 28 windows(all LowE366), 1/2 inch spray foam on all walls with R13 batting over it. He wants to do dual zone with the 1st zone covering about 1400 sq. feet and the 2nd zone covering the rest(2000). The house is being built in Southeastern Virginia near the coast. Thanks for any help you guys can provide, Dale

I suggest separate systems for the first and second floor. That is the best way to have even temperatures on each floor. It costs more up front, but you potentially have lower operating costs. You could zone the loft off the second floor system. However if you are going to be working 10 hours days with multiple pieces of equipment generating heat then spend the money on a mini split.

Sizing can be less of an issue when you have multiple units. Because each unit is controlled independently, provided of course the unit itself is not over sized for the area in which it serves resulting in excessive short cycling. In your case 3 ton plus 2 ton isn't necessarily equal to 5 tons of cooling... unless you drive those thermostats really low. By having two systems with total capacity of 5 tons (which, most of the time this would be oversized for a 1700 - 1800 sq ft structure) has a few advantages. 1. You have the ability to use one system only during low heat days or set the opposing unit higher. The unit set higher only runs if load conditions warrant.... meaning if it's not hot, the thermostat controlling the unit does not call... the unit can not run without a call... 2. Utility bills can be much less... because you rarely use both systems at the same time. You run the bedroom system when you sleep, the other when you're awake. If you have a home office in one the bedrooms you may need to rethink things a bit. 3. Extra capacity for when it's hot out. When it's hot you have the capacity to cool the home. (even while entertaining guests --- additional people add heat) Remember heat waves come, heat waves go... a so call 'properly sized' AC system is essentially properly sized roughly 10% of the time... especially if that system is a single speed AC system. Alot of people I come across like to sleep cool. So for that reason I doubt I would change the configuration of the space. Once you realize what you have, the choices you make are mostly budget type concerns. Essentially a set up like this runs like a 2 stage system. This kind of subject is above the pay grade of many... choose your contractor wisely. I service the Katy, Texas area.