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

Hello, Would like to know how many BTUs (for 1 wallmount system)would I need for two floors of 690 sqfeet (each floor). The Unit will be on the 2nd floor in the middle between 2 bedrooms and a washroom (over washroom door facing master bedroom). It will be a dual split system. ------------------------------------- Also would like to know which is a safe reliable cost efficient brand, example of wall mounted (split systems) air conditions I've heard of: Fujitsu (they give 10 years warranty parts and labour) Mitsubishi (6 yrs parts and labour however been making them longer) Daikin (6 yrs parts and labour) Igloo York Carrier Grey All about the same price... ----------------------------------- Finally, is it better to get a dual system (with heat pump), from my understanding they are almost the same price and the advantage is that it has a variable BTU which may save some $$. Since the heat pump will be at the higher level then it wont heat as much however it is coming at about the same price. Then again more electronics in a system more chances of malfunctioning sooner? Thank you, Stelios

Hi ionized. Our issue with running actual ducts is that our house is very, very, very old and the original very, very, very old part of our house is solid one foot thick log walls. Going through them at any point is a nightmare for anything. We have a new addition, which would be fairly easy to run duct work, but working it into the old part of the house, which also has only 7' ceilings which are completely open ceilings with timber joists (bark still on them), which we plan on leaving open. We plan on adding some sort of insulation in the flooring between levels but between solid walls, no actual ceiling space and of course no basement, a "ductless" system is seeming the better way to go. Also, no we have no natural gas. Not knowing a whole lot, I would guess I need to run it into 6 rooms. 3 bedrooms, living room, dining room/entry, and kitchen. Right now our coal heat is actual a free standing base burner coal stove, so not central heat. Real turn of the century stuff, but believe it or not seriously efficient and the more insulated the house gets the less I think I need heat other than it, except for the fact I am living in the turn of the century stoking a coal fire daily. Because of the log wall set up the only room that is left out is our new MB. It is on the outside of the log house in the new addition and not on the same level as the stove. So the circulation just doesn't get there very well. There is also the more temperate times of year like Oct. when it would be nice not to be running the stove and have easy access to heat at night if it gets to 30 like it did the other night. My few real questions are do I need to have an additional heat source like baseboard heating for this type of unit? I saw a Youtube video that said if it gets too cold they don't run right. Would my coal stove be OK (we have no plans on getting rid of it and will continue to burn it in the coldest months of winter), or would I then have issues in my MB if I didn't get enough heat up there if the temp dropped? Aslo, I read somewhere and now I can't find where, that there were 35' maximums on the length you can run from the compressor outside. Is this true of all systems or did I read this on one site or someone talking about one manufacturer? If so I am thinking I need two compressors to service different areas of the house, is this how the cost starts adding up quickly? And do I need to hire a professional to install it? I promise we are not average DIYers. We would not be ready to install the entire system at once at any given time. I was hoping to educate myself, decide on a system, buy the parts we need as we go room to room. We are slowly working our way through the house, but we are probably looking at a 8 year total project.

Assuming your looking at inverter model mini splits there's no problem with oversizing somewhat as the unit will "throttle back"...reduce compressor output and air handler fan speed to meet the heating or cooling needs being called for. This is unlike typical AC/Heat pump systems that are either on or off and when oversized in AC mode may not allow the room to dehumidfy enough...so no problem oversizing with a mini split as long as it's not grossly oversized. Also,many mini split heat pumps can exceed their nominal rated btu's in both cooling and heating...so a rated 18,000 btu in A.C. mode might be able to put out 20,000 btu. You'll need to check the specifications carefully to find this out but many models nominal ratings are actually lower than maximum actual output capability. It's been my obeservation that a mini split will provide more cooling and heat for it's rated size than a typical ducted system. As there are no losses due to duct work in attic or in crawl/cellar space you get higher efficiency not just in energy ratings but in actual output when comparing the similar size traditonal system. Also, you might want to check out a few other brands of mini splits besides the Mitsubishi (which is very good one). I'd also look at Futjitsu which has 18,000 and 24,000 models that qualify for the tax rebate. Sanyo is another good one. I'd stay with the Japamese brands and only buy from an authorized dealer for the brand who has installed a bunch of them. I'd leave the bathroom door open or ajar a bit and you'd probably be OK. If you've got a lot of money you could buy an inverter model mini split that can accomodate two wall air handler units and put one in the bathroom...but that would be overkill for 48 s.f. in my opinion. I've got a 15000 btu model in my sunroom (wall to wall 6' windows) which is L shaped and 400 s.f in Columbia, SC. It does a great job even though a manual J calculation said I needed 17,000 btu. I work as construction coordinator for a facility that has 50+ mini splits so I'm very familiar with these units.