We built in MN and moved in about 1 1/2 years ago. Two story plus full basement walkout. We have 2 Econar geothermal units, one hydronic and one forced air with 8 - 1,000 ft horizonal loops. The hydronic pumps water for the radiant floors in the garage slab, basement slab, upstairs bath, master bath, 1/2 bath and mudroom. The forced air unit is for all other areas and provides A/C in summer. Our insulation is closed cell spray foam and it's awesome. I wanted to wait to see how the humidity was in winter and it was around 25%, which is too low. So I'm looking at adding a Honeywell Truesteam humidifier that will add water directly into the ducts and is controlled automatically by the thermostat with an outdoor sensor. I did all the underside-of-the-floor mounted radiant pex tubing (and accompanying insulation) myself as well as the floor insulation under the slabs. It's critical that you have a thermal break between the concrete and the ground. I used 2" XPS (rigid pink foam board insulation) on the ground and taped all joints. I also used a reflective bubble-wrap type insulation around the perimeter walls and interior footings. No concrete touches the ground at all. You mentioned carpet in the basement. As long as your installer knows what flooring you're installing, he can change how close together he puts the pex tubing loops. For carpet the loops will be closer together to create more heat. Geothermal is very quiet. The fan is on all the time so it doesn't come on like a jet engine and shut off all the time like propane or natural gas. Quiet, steady heat. In the summer there is no condenser outside and thus it's silent. Love it.

nc I just finished building a home in N. VA, Blueridge Mtn area - similar climate to yours. We live on the main level of the house - second level is just for guests like you plan. We have heat pumps (it's geothermal but still a heat pump) with electric auxilliary heat (what I call toaster mode). Here are some things we did and learned - hope they help: The new heat pump system works great but only because we were nuts about making sure the house was well insulated and sealed properly. We used 2x6 framing, blown cellulose insulation in attic & walls, added extra insulation in attic (R40), used high quality windows & doors. Pick an exterior door type that is designed to provide a tight seal all the way around the door - with 3 point latching. Caulk every nook and cranny on the inside of the house including at the floor and ceiling along the stud top and bottom plates and between butted wall studs where large air gaps are common. Use foam in areas where cellulose won't stick too well. Personally inspect every inch of the house after the insulatimg company says they are "done" - you will find holes that need to be plugged. I had an old lenox heat pump in the first home i bought and the emergency heat always came on - and the bills were out of sight AND the house was never comfortable. After I replaced the lenox with a high efficiency Amana heat pump, it was a huge improvement in both comfort and reduction of toaster mode. Heat pumps have come a long way and you are in a great climate to consider them. In my new home the toaster mode only comes on when a) it is below zero outside, or b) the heat breaks - both cases are rare. It is nice if you go with a second stage gas burner, but probably not needed if you do the insulation right. The main reason I wish I had seond stage gas heat is that you can run it off a backup power generator. Both my main and Aux Heat is electric and would need a massive generator to run it. So my backup heat is wood burning and gas firpelaces. If I could do it all over again, I would go with the second stage gas heater. If you go with that make sure that the second stage and the blower fan can be operated off a backup generator if the main power goes out and stage 1 heat is out and wire it that way, even if you don't do a generator right away. It takes a lot of power to start a compressor used in stage 1 but almost nothing to run the HVAC contols and start the second stage gas burners. We have separate heat pumps for the main level and the second story and I do recommend that. But I also zoned the second floor system because in my past homes, the second floor bedroom temps varried quite a bit depending on sun angle and season. Plus - when my parents come to town my dad likes to create his own tropical environment - and so I really put the zones in so he could do whatever he wanted in that 1 room and not mess up the rest of my house:) I have been doing a lot of experimenting with the tstats ans found that when I set the upstairs tstats to 62 and the downstairs to 65 - the upstairs HVAC system almost never turns on. In summer I set the second floor to 81, downstairs to 78, and again second floor HVAC almost never on. So that saves us money and we like that feature. Soon after we moved in, I added humidifiers to my heat pumps in the basement (but not on second floor unit). I had thought that with a heat pump I would not need these, but I was wrong. Bypass humidifiers are not expensive and well worth the money and effort to put them on. When you are planning out your plumbing, have them add a hot water pipe and valve near each of your your units. It won't cost much to do this and using hot water in the humidifier is better than cold, especially with a heat pump. With humidification, the house will feel warmer at a given temp than a dry house will. A few months after we moved in to our newly built, energy efficient humidified home - we started to sense a musty smell around the June time frame. Turns out that since our house was so tight, we had mositure building up in our basement on humid days and it had no place to go. Learned that I needed a whole house de-humidifier to fix that problem and so far that has worked great. You live in a humid area so you may want to have one of these incorporated into your system, or at least plan for one. We found that when we contolled the humifity level to within 45 to 55%, the house feels cooler and it allowed us to keep the tstat at 78 where we might have to run it at 76 to get the same level of comfort we like. I have also discovered that since my home is so tightly sealed, I need to add in an Energy Recovery Ventilator that will periodically bring fresh air into the home and exhaust stale air. You might want to think about the ventilation part of HVAC - it is important. There are a lot of good posts on this forum about how ERV's work and the benefits. As far as hot water, I have two LP Rinnai tankless units that are connected in series. Normally only 1 unit fires, the second is only for when the demand is higher than normal like when we have guests. I like the Rinnai's for a lot of reasons - but my favorite is that I can run them off my backup generator so we can have hot water when the power goes out (which it does quite a bit where we live). Placement of tankless generators is key, and you have to be very careful since the venting requirements for these things may limit where you can put them. If you are planning to use tankless, you need to think about placement very early in the design - especially if you are thinking about a finished basement. We chose to put our units in the basement, directly under the master bathroom so we get instant hot water there. However, the kitchen and several other sinks are on the other side of the house - 88 feet away. We discovered that it was taking almost 5 minutes to get hot water at those distant sinks (88 feet of pipe holds many gallons of water which takes about 5 minutes to bleed out of a standard sink running at 1.5 GPM). Unfortunately, we could not place a tankless unit in the basement at the other end of the house due to venting issues. I would have prefered a smaller thrid tankless system at the distant end but instead wound up putting in small hot water recirculating system to eliminate that 5 minute delay at those sinks. I recommend pre-wiring the house so that you can add in a small backup generator later - even if you don't plan to have one initially. Have the electricians install a sub-panel in the basement near the location where you would likely put the generator - preferably on a side of the house down wind and away from the master bedroom. Have them wire your heat pumps, refigerators, well pump, septic pump, tankelss hot water, TV, Internet, some lights and outlets, freplace contoles etc. - whatever else you need to survive in an extended outage off that sub-panel. The delta cost for them to wire it this way during construction is very small and you will love it later if you decide to put a generator in since the wiring will be much easier. Best of luck in your new build!

Hello Your heat pump air-to-air sounds like the best options. If you dont need to use it for water the COP is quite high, usually COP-3-4. The COP means a ratio of what you get out vs what you put in. The COP of 3 is 3 times the heaat of what you put in. There are a number, some that get a COP of around 5 using source of 30F. Others list between 3-4 quite generally. Carrier is a maker of one type which has a COP of 3 and is a small size. When the source (outdoor temp) is low the COP goes down as does the output. (Below freezing especially). Its worth having an oil or wood or gas heater to go with the system as back up. Heat pumps that can heat water have to work harder as the water is warmer than the air used in buildings, so they use expensive CO2 heat pumps which will set you back about $5K easily. Therefore I would suggest keeping a boiler system, outdoor boiler. An indoor stove needs fresh air which is not ideal for heat pump system which works ideally with heat recovery on the ventilation system (extract heat from waste air at 90% or so efficiency). A neat approach may be to operate an air -to-air heat pump, aim for as high a COP as possible, but install a gas boiler if you have this. The smaller boilers, condensing systems, are surprisingly cheap. If you install a waste water heat recovery system which is just aa heat exchanger on you waste water from your shower, you can half the energy you need and thereby get by with a smaller boiler and consume only about 4-5kWh/day for shower water. A condensing boiler works most efficiently when working with water heating rather than central heating, and plus, the typical condensing system now heats so quickly that you dont need a hot water tank, reducing loses. You would still have at least 15KW available for heating the home. This can be done by putting in a heating loop into the air ducting that is shared with the air-pump. This could be a compact fan assisted system. There would be expense in heating controls for all the ducting. However, if you cannot put in ducting, then you can install a water radiator central heating system. To work with a heat pump, you can go for the super-efficient CO2 based systems that are emerging but expensive. The efficiency can be raised if the heat is needed at a low temperature, so requiring either under-floor heating or a 'fan assisted radiator' which extract more heat and can return the water to the heat pump much cooler than normal radiators, and require a lower temperature, raising COP. I would go with: Waste water heat exchanger ( I guess $500 est with capital cost $200-$300 plus basic installation if incorporated with a boiler installation and pipework anyway) -this will reduce the energy requirement of the condensing boiler, potentially allowing a smaller system. Condensing boiler - 15-25kW output, 90% efficient, capital cost $500 ebay Air-to-Air heat pump (in loft) - COP 3-5 (later figure seen in an Austrian GSHP but should work with airsource unless outside air is usually very cold?) cost? controls? Fan assisted radiator in ducting for backup (run off boiler)? Ventilation heat recovery

Thanks again. I feel we fall somewhere in the middle of your two descriptions. Our design was created with Southern exposure, solar gain, ample overhang, high efficiency, quality construction, etc. in mind. Architecture and aesthetics undoubtedly played a major role. I don't think we will be LEED certified but it is not your average house. That being said, we did not begin with our expected monthly utility bill as the basis for design. I think we have been reasonably responsible with our design choices thus far. Hence the Geo system. I, not knowing the trade inside and out, am just trying to get the most comfort (and pleasure) out of our system. I think that the higher end system will, without a doubt, provide the level I expect. What I am trying to glean is the sacrifices we would make if we spend less. I realize that the desuper heater and boiler will provide more consistent heat in the basement and that it will also be a more efficient back up/supplemental heat on the very cold days. The question becomes how much less comfortable will the basement be? How many days a year will we need the supplemental heat and is it worth the extra expense. How much better is an Infinity Carrier air handler than the Trane air handler? Will it be noticeably better? I need someone who knows to help me answer these questions. We are not against spending the money if the differences are going to be compromises we regret but we don't know how to figure that out before hand...