Posted By jimmyge on 29 May 2015 10:51 PM
  Is the concret slab floor ever poured at different levels to allow all the floor covering types to end up approximately at the same elevation? Thanks.

Generally, no.  What type of floor coverings were you considering?  If you have say 3/4" thick hardwood floors in one area and tile in another area, you would typically install 1/4" thick cement backer board or similar thickness uncoupling membrane under the tile.  The backer board (such as DUROCK) / uncoupling membrane (such as Schluter DITRA) serves two purposes:  1) it raises the typical 3/8" thick tile + 1/8" thick thinset up to approximately 3/4", and 2) it prevents movement or cracking of the subfloor from being transmitted to the tile.  Concrete will crack.  If tile is attached directly to the concrete, then the tile will crack as well.

Posted By jimmyge on 29 May 2015 10:51 PM
If I want good indoor air quality, is my only choice to use a fully ducted HVAC system? If so, how do I run ducts? ... Can the runs be put in the attic if they are insulated? How is that done? 

Putting insulated HVAC ducts in the attic is very common down here in the south.  It usually results in a significant energy cost penalty due to the ducts rarely being well sealed or well insulated.  In your case since you are having some spray foam applied in the attic, you could have uninsulated rigid metal HVAC duct installed prior to having the spray foam applied to your ceiling, then have the metal duct work sprayed with 2"-3" of closed cell spray foam to seal and insulate.  Keep the duct work low and close to ceiling and then have stabilized cellulose (generally better performance and lower cost than blown fiberglass) blown over the top of the ducts and entire attic for additional insulation.

Note that spray foam insulated duct work wasn't very common in the past, but is becoming more commonplace.  Google it for more info and examples.

You can't get R20 (whole wall) with studs and cellulose unless...

Space the stud wall away from the other wall and you can get any R value you want with 2x4 studs.

"Does a home require something in every room?"
Yes and No. We recently completed a 3300 Sf 10 room home which is comfortably heated and cooled with four mini splits.

I'd like to see actual data on a design day in Winter with the doors closed. Or with the sun streaming in in summer (again, with the door closed).

jonr - re wants to see data:
So would I, but the budget wasn't there for sensors. This very fussy client moved in around Christmas and is very happy with the performance of the house through the winter including the extremely cold (-10) temperatures throughout January and February. I do not have electrical date yet. This is the sixth house I've done with these and all clients have been very happy with the houses and the Mitsubishi units. As I have previously mentioned, I installed three in my 3000 SF 7 room two story old New Englander last year to get personal experience, used them through the summer and almost exclusively through the winter (we also used 1/6 cord of wood on cold days); our house has never been so evenly heated and comfortable. This year we'll be using the new Mitsubishi ducted units also. These are the future.

I should add that with non-ducted units the recommendation is that the doors be left open during the day. In my old house, one bath cools off a few degrees if the door is closed for long periods of time. In new houses, I've been in one vacation house where they keep the doors closed and have never noticed any temperature difference.

I'm not trying to give you a hard time, but I've seen so many claims of "my radiant slab designs never under/over shoot", "my passive solar homes never over/under heat", "my designs are wonderfully comfortable", etc and yet in all cases, no actual data is provided. A WEL (Web Energy logger) site would be nice.

That being said, I agree that centralized mini-splits in well insulated homes are a good option. Depending on the particulars, doors may have to be left open (sometimes).

I hope to start using data loggers, but seems like they'll be $1500 plus per house which no one wants to spend & is hard to budget, so all I can do is provide observed information on my work. What I can say about mini splits is what I have observed, and part of the reason I installed them in my house was to get first hand, personal knowledge of the units. I used one of the first high efficiency gas furnaces in the state in the early 80's, and have used many different kinds of heat including oil and gas, radiant, hot air, hydro-air, hydronic, solar rock beds, passive solar on slabs, geothermal and probably a few others so I have no specific allegiance to any of them & know that each has it's plusses and minus's. That said, nothing comes close to these in terms of sound quality, (radiant is pretty quiet) temperature quality, evenness of the room temperature and installation cost. This is a completely new type of system, which most people will not understand until they see one in use in a home. They are spreading like wildfire, especially in new construction like I'm doing; not because of my recommendations, but because it is a better mousetrap. They are widely used throughout the world; we're one of the last countries to learn about them.

I was building for someone who refused to consider them until he ate at a restaurant and noticed one on the wall above him. The next day he called to say he wanted them in his house.

Posted By jonr on 31 May 2015 01:29 PM

You can't get R20 (whole wall) with studs and cellulose unless...

Space the stud wall away from the other wall and you can get any R value you want with 2x4 studs.

You can do that, but you would need ~6.5" of interior wall (3.5" for 2x4 section + 3" gap for additional insulation) + 8" of poured concrete (8" is typical poured wall thickness) for 14.5" thick overall wall to equal an 11" thick ICF wall (2.5" EPS on each side of 6" concrete core).  And with all of the insulation on the interior side of the mass wall, you lose most if not all of the benefit of the wall mass.  And then how do you attach anything to the exterior concrete wall?  If you want a stucco type finish, that is easily accomplished, but if you want anything else it gets time consuming to make attachments.

You can do that, but you would need ~6.5" of interior wall (3.5" for 2x4 section + 3" gap for additional insulation) + 8" of poured concrete (8" is typical poured wall thickness) for 14.5" thick overall wall to equal an 11" thick ICF wall (2.5" EPS on each side of 6" concrete core).  And with all of the insulation on the interior side of the mass wall, you lose most if not all of the benefit of the wall mass.  And then how do you attach anything to the exterior concrete wall?  If you want a stucco type finish, that is easily accomplished, but if you want anything else it gets time consuming to make attachments.

Here is a fast way to install insulation boards, furring strips, etc. to block, concrete:
http://www.ramset.ca/admin/pdf/201301251211Insulfast_Brochure_RdFinal_lowres.pdf

Operates off of a battery and a gas canister.  Can attach insulation boards up to 6" thick.  No need for a stud wall when insulation is attached directly to concrete.

jimmyge - the standard ICF is more than enough. We are in Calgary Alberta and our 2 storey house performs at about R52. There are plenty of ICF houses built in Alberta with the same results. 11 to 12 inch ICF walls, foam under the slab and R50 in a well sealed, vented attic and you will have a home you can be proud of.

Also remember that you are in Minnesota, not New England or Arizona so other peoples experience with mini splits may not be your experience with mini splits. From the data available, mini splits have come a long way in the last few years but not sure they will handle your design temperature yet.

Posted By jimmyge on 29 May 2015 10:51 PM
  ....I have hydronic radiant floor heat experience, ...

What do you intend to heat the water with?  Natural gas available?

No natural gas, rural lot. Propane is most cost effective until it costs over 3 bucks a gallon.

Geothermal is so great, but from what I have read, the less heat you need, the longer the payback period. With only 2000 square feet and well insulated, I fear that it would not pay back in my lifetime (I am 56). Also, I hear from guys who have a dozen or so years on their go systems and they loose a scroll pump or mixing valve. Another five years added to the payback period.

Crawl space suggestion... if doing that, I have the expense of the floor system. Most of the way to a full basement, which i just proved is too much money. AGREED it offers ducting possibilities, but adds too much money. If there is another way, I'd prefer it. However, I may be coming back to this idea yet.

I am leaning toward the mini splits, with HRFH tubing in floor fired by a modulating propane water heater for the cold winter days when the minis couldn't run. Also, plumbing in a loop from an outdoor wood burning boiler, for the coldest months when I might feel like building a fire to lower the propane bill. Of course I need a HRV, so am thinking of how I'd be able to duct that from kitchen, laundry, bath, and return fresh to livingroom, and bedrooom.

I am meeting with two local HVAC companies this week to discuss. These guys both bid the original plan. Now we will see what ideas they have. All your great information will make me an informed consumer. THANKS!

I agree with your feeling about the crawl space. Be prepared that a lot of HVAC companies are not well versed on mini splits, or residential HRVs. Commercial HRVs are common but much different. A Mitsubishi rep may be able to locate a dealer in your area. If possible, locate the HRV in the top of a closet where the duct runs to the living spaces & baths will be fairly short, and where the 6" intake and exhaust can exit the building at least 48" above the ground so they don't get buried by snow. A minor adjustment in the truss design where they give you a space above the ceiling but within the envelope would work well.

HRV can be run in the concrete slab as can forced air with a counter flow furnace. As with radiant, if it goes in the floor, insulate under it. The advantage is that it is within the building envelope.

But I agree with Bob. Have the trusses (over the hallway?) constructed as for a tray ceiling. Run your poly (air barrier) continuous from wall to wall so that none of the hvac is outside the sealed envelope and then after the hvac is frame in and complete what would have been a tray ceiling.

I spoke with both local HVAC designers today. One said they always duct townhouses (which are single level homes like my new plan), with sealed and insulated ducts in the attic. Per code they must be sealed, in the attic they must also be insulated and seal tested and report shown to inspector. And he offered to hang them 2 feet off the bottom cord of the trusses so we could spray foam and blow insulation in.
The other HVAC guy said they'd probably opt for ductwork under the concrete floor and a counterflow furnace (I didnt get to ask him if they have done this before and what the ducting is made of and insulation, etx, but i will get to ask eventually). I mentioned mini spits and they both felt I would be happier with a system that was able to fully recirculate and filter all the homes air. Without the benefit of ever having lived in a home with a minisplit, I also feel more comfortable buying a system I am more familiar wiith, meaning something ducted with a DC blower to run on low. It also greatly simplifies the home, because I would leave out the RFH tubing, pumps, set point controllers, manifolds, water heater or boiler, and all the related plumbing. Cost is about the same, with all the above RFH stuff and labor, probably cost approximately $7000, plus the three or four mini splits plus install, guessing $5000 for those installed. And the ducted system with hepa air filter, ecm blower, ruud ac, hi efficiency furnace, and a hrv, plus a coil in the plenum to bring in hot water from an outdoor boiler when I want will also cost about $12000 complete. Also, the floor does not become so touchy, since no tubing, so it can be nailed to for wall plate attachment and base cabinet attachment at will, I can cover it with whatever floor covering I want, etc. It just seems less stressful to duct it above or below. I kinda like the ducting below if they have a good system with insulation for that. Assuming the ground is about 48 degrees year round (possibly even a bit warmer under the house with excellent perimeter insulation), it seems like a better environment than the attic which goes from 25 below zero to 150 above. Then the trusses can be simple. The home is a t shape, with trusses both directions, so adding the tray feature is not simple.
I will keep you posted what the bids offer when I see them.

Some truss designs that allow overhead ducts to be part of the building envelope are here.

Are there ducted furnaces that can turn their fans down so low that they are acceptable alternatives to separate HRV/ERV ducting? Ie, the furnace fan would run all the time.

I'm a huge fan of the mini splits from world travels, but in MN aren't there days cold enough that mini splits can't be your only heating? It seems a waste to have redundant systems.

HRV need ducts too. Am I reading this correctly, you can combine HRV with heated and cooling ducting?

What's the plenum and outdoor boiler system?

At least part of the HRV system can be plumbed into the main HVAC ductwork. The HVAC contractors seem to bid the lowest they can to get your business. To keep it lower cost they put in the code - required HRV for a balanced system by plumbing it into the main ductwork completely. However I have read that it will perform much better and save more energy if it is plumbed seperately from the main ductwork. A good compromise I can make and afford to pay them to do is to at least install the outlet points (which gather the air to be expelled from the home), from the bathrooms and kitchen, ducted seperately from the main ductwork. The replacement air still dumps directly into the cold air return, for distribution everywhere. I guess the plenum I was talking about is the ductwork just above the furnace where they install the ac coil. In addition to that coil, I am going to install a copper coil which I can plumb up to an outdoor wood burning "boiler". In this system, water is heated in a water jacket surrounding a metal fire box, all located in a cute little dog house like building out in the yard, keeping the mess and danger of burning wood far from the home. The water is pumped thru insulated buried plastic tubing, recirculated. I know this method loses maybe 25% of the heat because of the extended distribution plumbing, but the other factors out weigh the losses. I will probably only use this system when it is really cold. Otherwise building a fire each day will get old. Wood supply in my area is virtually unlimited.