Thank you for the responses! Brian Knight ~ Our home is one level (on a slab) with three bedrooms. It will be an open floor plan, just over 2,000 sq.ft. When I said "relatively" air tight/energy efficient I was referring to our quest to balance efficiency with using healthy materials (not a fan of spray foam for example). We do want to be mindful of proper ventilation/air exchange and have looked into doing something like this (copied from http://homeenergypros.lbl.gov/group/1000homechallenge/forum/topics/panasonic-whisper-green-w-ductless-heat-pump?xg_source=activity): "Some minisplits may have a small ducted system. Dave Robinson, www.GreenEarthEquities.com buys foreclosed homes in central California that he renovates, using two,1 ton Fujitsu mini-splits. He ducts one to the bedrooms and bath with very limited ductwork located in the hall ceiling. The other unit is ductless, and conditions the living room and kitchen of the one-story ranch homes. There are significant cooling loads with lots of 100 degree weather. His approach of combining ducts and ductless results in simple systems and homes with low energy bills. Dave has case studies posted on his website." Reply by Dave Robinson on August 31, 2011 at 10:12am "To be more exact, we use one outside unit (2 ton is the smallest they make in this model - so we use it on everything). One inside unit is the conventional mini split high on the side wall in the main room ... the one that everyone associates with mini splits. The other inside unit is mounted on the ceiling at the mouth of the hallway & delivers air to all the rest of the rooms thru a small duct system that we mount on the existing ceiling of the hallway. So the unit and all the ducts are inside the envelope. Then new drywall is added, reducing the hallway height about 10 inches. We throw the factory filter away and allow a 20 x 30 filter grille right under the air handler to provide a lot more filter area as well as access to the unit without breaking the building envelope. You can see pics of this hybrid duct design at A Good Business? How Long? Plus Ducted MiniSplit Update (Click the right arrow on the photo in the center of the page and it will take you thru a few other slides from that webinar and you'll get to the Mini Split photos). You'll notice we use galvanized pipe. That, along with the oversized return keeps the static way down which is essential for efficiency on these units. This unit has now been in two years. The owner loves it. Zero problems. Has utility bills less than half of his neighbors. This job also used a Panasonic ERV. We mount the ERV very close to the return of the ducted system and in the pick-up area of the wall mounted unit so all fresh air is circulated by the main system with no additional equipment needed. It works well for us and we have adopted this as our main system. It's the one we specify every time unless we are keeping old equipment that's not too old or too over sized for after our renovation. You'll also notice that we mount the outside unit on the roof instead of on the ground. Lots of reasons." We are thinking this might work with our floor plan: Kirkhall ~ Thanks for sharing your personal experience. I have read more on the HVAC forum. My interest in posting here was to see if ductless mini-splits were at all a preferred choice by those building new homes versus just being used for retrofitting/new additions. Niteshadepromises ~ "Based on all my research the operating costs are pretty substantially lower which we're looking forward to and hopefully might offset the initially higher install cost." This is in line with what we are thinking too! Good luck with your build! David Cary ~ The tax credits are wonderful, however, there is that pesky problem of having to pay upfront. With some budget reworking, this may be possible. However, my concern relates to your comment, "But I'm not sure getting all fancy is worth it.... R20 net walls, good southern exposure with some thermal mass. You won't need that much heat and you shouldn't need a/c." We don't want to pay for more than we need. The difficulty for us has been determining what our need is when factoring in the passive solar. I also agree with: "I've thought about this a lot and I don't know how cold you get but if you have total control of design and southern exposure, your best bet is lots of solar planning, tight house with thick walls. Cover the windows well at night. Then put the money in PV. Code will require too much of minisplits to be cost effective." To satisfy code, what would your recommendation be for a thermostatically controlled system that is reasonably efficient and cost effective (presuming we could swing the PV)? With good solar planning, another viewpoint is to put in some baseboard heaters to satisfy code. Is this reasonable or silly? Dekeoboe ~ I'm interested to know what you chose and why? Flgargoyle ~ As our heating and cooling days are very similar, it's good to know that you think it's a viable option. Though it seems I'm in the minority, I don't really mind the look of the wall units. Maybe it's because I don't find vents and returns all that pretty! Lori in the NW ~ Thanks for your opinion ~ they certainly are not for everyone! This post was edited by daisyblue on Fri, Feb 22, 13 at 17:45

Re Mike: You might be mixing me up with âÂÂTigerâÂÂ; IâÂÂll take that as a compliment. âÂÂThis an elaborate system to heat water.â An elaborate system to inexpensively heat water and heat/air-condition your home. This will be about the most expensive way to go up front but the life cycle and operating costs are extremely low by comparison when executed properly. Think about it this way, per equal volume, water delivery is 3,500 times more efficient than force air delivery and the HP will have a COP of about 4 irrespective of outdoor conditions. In the case of the OP, their entire distribution system can be kept as is if in good repair, no money spent on tearing it out and replacement. Given the size of the property, perhaps a horizontal ground loop might be possible for less than the cost of vertical drilling. When they complete their new addition another zone can be added to the existing geo HP system for VERY little money. It would hardly be more than another manifold and either a pump or zone valve plumbed into the existing buffer tank (see linked manual again). Water heated to about 120F instead of 140F with free DHW when in A/C mode. You always have to look at the total cost differential between conventional and geo, including rebates & tax credits, along with life cycle and energy costs. If gas isnâÂÂt used as an alternate backup fuel, the cost of installing the gas line could be put into the ground loop. In the end everyone does what they perceive is best for them. Were the installation manual plumbing schematics clear and helpful? IMO SR

heat pump, central air and heat and a mini split as far as cost of operation? heat pump same as central air and heat except that the heat pump provides the bulk of the heat. this is what I recomend to my clients based on savings compared to electric strip heat. with heat pumps the electric strip is emergency heat and for when temps are 30 degrees..which is not that often for us. central air is electric strip heating only. the most expensive way to heat your home. (espically if you have entergy for your utility provider) mini splits are pretty cool. expensive but fit a lot of needs and great for tight retrofit spots. the condensing unit goes outside like with any set up, but this is where it changes. in each room the air is provided by a wall mounted air handler unit. the condensing units are up to 3 tons. each room would have the ahu..this is what they are calling zones. cost is higher, but you don't have ductwork, so it evens out a little better. with the foam insulation & low e windows your tonnage of ac required will be less. although I don't recomend 'rule of thumb' sizing instead of the ususal 400 to 500 sq ft per ton, your house will be more in the range of 600 to 700 sq ft per ton. oversizing will cost more to operate, wear the equipment out sooner, and will NOT dehumidify. be diligent in finding out what is being spec'd for your home and what options are available for you. some systems will qualify for tax credit, and it is always a good idea to do better than the legal minimum allowed by law (code). in what part of La. are you building? best of luck.

Thanks for the feedback, all. Two reputable contractors came up with roughly the same load calculations, resulting in 7 - 8 tons. The 2600sf is deceptive... The layout of the house is reminiscent of raquetball courts. Lots of vertical everywhere, if measured in cubic footage you might get a more reasonable perspective on this strange house. I might just do an energy audit as klaire2001 suggested and see if that tonnage can't be downsized. But for now let's assume 8 tons is the right figure. So how much should I expect to pay for top-grade high-SEER matched heat pump systems like Carrier Infinity 16? (Assume no additional furnace is added.) Keep in mind that there is no existing ductwork, and the house does not make ductwork particularly easy to install. My current plan was to run exposed spiral ductwork along one of the cathedral peaks to reach the upstairs rooms... Knowing we could box off the peak if it looks too crazy. Without seeing a floorplan that probably doesn't make sense to you, but you'll have to trust me on it. :)