I am building a 1100 sq/ft bungalow with a walk out basement in NW Ontario Canada. Walls will be 2x6 with cellulose and 2" closed cell foam on the exterior. R60 cellulose in the ceiling. The windows will be tri-pane low e argon with either vinyl or fiberglass frames (I haven't chosen a supplier yet). Careful attention will be paid to air sealing with the aim of >1 ACH; there will be a HRV. The front of the house with walkout faces east

Heating and cooling are the issue.... I have considered GSP but its too expensive, I am told that the payback on the $25000 investment would be looooooooooooong in a small energy eff house so I "think" I have a solution. I am considering a system that uses either a Mitsubishi Mr.Slim heat pump or the Daiken heat pump, these are designed to both heat and cool. However it gets considerably below those units minimum temps (-25c for the Mitsu, not sure of the Daiken) for several weeks each winter.  The heating guy I have spoken to has what he says is a simple and elegant solution.....

He advocates using a single interior unit installed in the highest part of the sloped great-room (floor plan is fairly open). This heated or cooled air will be circulated through the upper and lower levels of the house using the DC variable speed fan on the electric furnace that will provide heat during the winter when the mini-split is off line (-25 or colder). This "mixed" system; he says, will provide me the advantages of up to 4/1 efficiency to-25 before the electric furnace takes over at 1/1.

He quotes about $5500 for the mini-split and another $1100 for the furnace; duct work is extra.

I have few heating alternatives, oil is expensive and getting more so every day, propane is just as expensive and electric in the=is region is big bucks too. Natural gas is not available.

Any thoughts on this heating cooling plan with a mini-split?

The heating guy I have spoken to has what he says is a simple and elegant solution.....

Has he implemented that solution anywhere else? If so, maybe you could talk to the owners and see how it works out for them.

Not that the above can't work, but an air to air ducted heat pump is the more obvious choice.

Yes an ASHP in the ducted system makes more sense, that said $6,600 for mini and air handler + duct work is how much?
You take 30% tax credit off geo and the gap gets narrower. Your payback may not be as long as you think.

BTW who is taking care of the filter on your minisplit in the "highest part". Does price include the scaffold needed to get to it?

Lots of builders in the northeastern USA are using minisplit heat pumps successfully, so they do work. It obviously doesn't get as cold here so backup heat is not as important - and is often left out entirely. I wonder if a direct vent gas unit would be a better backup; probably depends on the amount of time the minisplit is off.
One suggestion I do have is to increase your wall insulation to R-40. While R-28 will work (R-20 less studs= R15+ R13), the added insulation will help hold the heat to let the house coast through cold spells and decrease your use of back up heat. A superinsulated house is also very receptive to solar gain so cold clear sunny days can provide enough heat.

I have spent some time thinking about this, and I should have some actual experience by July. Control is the potential flaw as I see it. But if your great room is half or more of your square footage, the problem boils down to equalizing the temps in the two halves. My approach is low speed continuous circulation, which raises a second problem. I'll have limited ability to address areas that need extra conditioning. What Bob said. Super insulation will narrow differences.

You'll have an easier task with a variable speed air handler. Put a second stat in the unconditioned half so the handler will pick up speed as it falls behind. Faster circulation will make the minisplit run harder. My backup is a radiant slab.

No problemos with filters. I am putting a Merv 12 filter in front of my continuous fan. If you have a fan running all the time, no reason not to have the cleanest house on the block -- and limit your step ladder minisplit trips to once or twice a year.

Posted By ICFHybrid on 27 Mar 2012 09:40 PM

The heating guy I have spoken to has what he says is a simple and elegant solution.....

Has he implemented that solution anywhere else? If so, maybe you could talk to the owners and see how it works out for them.

He is currently heating and cooling a 1000 sq/ft shop/office with basement with a single Mr Slim. It is very well insulated (R40 walls and R60 ceiling). It has several rooms which are kept closed (like bedrooms or bathrooms would be in a home). The temperature (he relates) is uniform throughout the building (I visited his shop to see it in operation when it was about 10f, too warm to "prove" his point). He sets the Mr Slim to maintain 70f, and the elctric backup furnace to start at 68f. He went on to say that he selected spring/fall on the electric furnace as opposed to the winter selection to prevent the electric furnace from firing on all elements.
He added that since the DC variable speed motor is used to circulate the conditioned air through the building constantly the higher cost of the DC motor is soon saved by its lower operating cost ( he says saving about $200/yr in electricity for that fan alone). He also has an HRV that runs on a schedule.

Posted By jonr on 28 Mar 2012 07:05 AM
Not that the above can't work, but an air to air ducted heat pump is the more obvious choice.

They seem much more expensive, but I agree.... if they were even close to the price of the Mr Slim plus electric furnace I would be all over it.

$5500 for the mini-split is about right, and a ductless will usually blow the socks of ducted air-source heat pumps on average efficiency.

In a relatively open floor plan, electric baseboards would be as-effective a backup as the ducted electric furnace, but without the wind-chill and noise.

With reasonable air-communication between floors, putting the mini-split head at the top of the basement zone and distributing the heat via convection is probably going to work, without ducted air distribution. My uncle heats a 2 story house that has a fully height great room open to both floors, mounting the mini-split head just a bit above floor level of the second floor. His is not a high-R house, but his outs design temp is only about -7C, not -25C. Still,room to room temperature differences are quite small with the doors open- he intentionally keeps the sleeping quarters cooler by closing the door.

Design temps near me are about -15C, and homes with R25+ whole wall values and reasonable windows have relatively low room-to-room temperature differences when using a single head mini-split as the only heating source, no ducts or remix. The room to room temperature differences will only become an issue for you at cold to very cold temps, and if rooms have their own thermostats & baseboards, temperature balancing with baseboards just becomes the backup heat pretty seamlessly. Set the temp on the mini-split a few degrees above that of the doored-off room T-stats, and set the baseboard T-stat in the main zone with the mini-split head a bit below the mini-split. It's easier to dial in room-to-room temperature issues that way than with any ducted system and if the mini-split is bumped up a few degrees above the baseboard T-stats the baseboard won't run until it's cold enough to produce a significant delta-T between rooms.

Just don't site the compressor unit where it'll get dripped on or buried by snowdrift or roof avalanches, eh? (Bracket mounted on walls well above the snow line, protected by the eaves or rake of the roof usually works, but they can be ground-mounted under decks and mini-shed roofs too.)

Posted By Dana1 on 28 Mar 2012 06:18 PM
$5500 for the mini-split is about right, and a ductless will usually blow the socks of ducted air-source heat pumps on average efficiency.

Why is a mini-split much more efficient than a ducted air-source heat pump?

Even better, add: "when a fan + ducts are being used to circulate the air from the mini split".

In my case, a minisplit would be half unducted and half ducted, preserving some of the ductless efficiency. As well, the ducted part is completely inside the envelope and driven by an ECM fan that costs less than leaving your porch light on. Entering the realm of speculation, low speed distribution, if it works, would keep the minisplit on the most efficient side of its variable speed.

That said, Kenora's focus is capital cost, and so is mine. I can buy a 1.5 ton Mr Slim for about $2k, complete with charged lines. Haven't cross threaded a fitting for 30 years.

Posted By Bob I on 28 Mar 2012 10:36 AM
Lots of builders in the northeastern USA are using minisplit heat pumps successfully, so they do work. It obviously doesn't get as cold here so backup heat is not as important - and is often left out entirely. I wonder if a direct vent gas unit would be a better backup; probably depends on the amount of time the minisplit is off.
One suggestion I do have is to increase your wall insulation to R-40. While R-28 will work (R-20 less studs= R15+ R13), the added insulation will help hold the heat to let the house coast through cold spells and decrease your use of back up heat. A superinsulated house is also very receptive to solar gain so cold clear sunny days can provide enough heat.

I am interested in how to get R40 in the walls!

Posted By toddm on 29 Mar 2012 10:47 AM
In my case, a minisplit would be half unducted and half ducted, preserving some of the ductless efficiency. As well, the ducted part is completely inside the envelope and driven by an ECM fan that costs less than leaving your porch light on. Entering the realm of speculation, low speed distribution, if it works, would keep the minisplit on the most efficient side of its variable speed.

That said, Kenora's focus is capital cost, and so is mine. I can buy a 1.5 ton Mr Slim for about $2k, complete with charged lines. Haven't cross threaded a fitting for 30 years.

YES! Capital costs are very important to me like most I sure, every dollar I save can go elsewhere in the building or reducing debt. Where pray-tell can a guy get a 1.5 ton Mr Slim for $2000? I am not sure what size I will need but that price seems very attractive

Posted By kenora on 29 Mar 2012 03:21 PM

Posted By Bob I on 28 Mar 2012 10:36 AM
Lots of builders in the northeastern USA are using minisplit heat pumps successfully, so they do work. It obviously doesn't get as cold here so backup heat is not as important - and is often left out entirely. I wonder if a direct vent gas unit would be a better backup; probably depends on the amount of time the minisplit is off.
One suggestion I do have is to increase your wall insulation to R-40. While R-28 will work (R-20 less studs= R15+ R13), the added insulation will help hold the heat to let the house coast through cold spells and decrease your use of back up heat. A superinsulated house is also very receptive to solar gain so cold clear sunny days can provide enough heat.

I am interested in how to get R40 in the walls!

With 2x6 cellulose fill the basic structural wall comes in at ~ R14.  By adding 2" of closed cell on the exterior (~R13) you're up to R28.  If you went with 4.5" of exterior iso (~R27) rather than the closed cell foam you'd be at (R13+R17=) R40.  That's actually a reasonably buildable thickness for exterior rigid foam, beyond that gets a bit awkward though.  Rigid iso, assuming typcial scrap rates about $1.50 per R per square meter of surface area, installed, so at R27 you're looking at ~$40/m².  At 2" of closed cell you're already talking ~$40+ per square meter installed, but only getting R13 performance, or about $3/R/m².  

The difference is that with the iso you'd be needing to pay more attention to air-sealing details, but if you used foil-faced goods you can do a pretty good job with FSK tape and a bit of 1- part foam. But with foil facers you'd be well advise to use a variable-perm vapor retarder like Certainteed Membrain on the interior rather than poly, lest you build in a moisture trap.  (With fiber faced roofing iso you can probably use poly.)  SFAIK Canadian building codes still require poly unless the exterior foam is such that the sheathing stays below the interior dew point even at heating DESIGN temp, which is quite stringent compared to IRC levels.  You'd be close @ 55% of the total center-cavity R on the exterior in southern Ontario, but probably not in the colder NW part of the province.

The other difference is that the carbon-equivalent greenhouse gas emitted in blowing the iso with pentane is only about 1% that of the HFC245 used with the closed cell SPF.

Posted By kenora on 29 Mar 2012 03:23 PM

Posted By toddm on 29 Mar 2012 10:47 AM
In my case, a minisplit would be half unducted and half ducted, preserving some of the ductless efficiency. As well, the ducted part is completely inside the envelope and driven by an ECM fan that costs less than leaving your porch light on. Entering the realm of speculation, low speed distribution, if it works, would keep the minisplit on the most efficient side of its variable speed.

That said, Kenora's focus is capital cost, and so is mine. I can buy a 1.5 ton Mr Slim for about $2k, complete with charged lines. Haven't cross threaded a fitting for 30 years.

YES! Capital costs are very important to me like most I sure, every dollar I save can go elsewhere in the building or reducing debt. Where pray-tell can a guy get a 1.5 ton Mr Slim for $2000? I am not sure what size I will need but that price seems very attractive

How's about a 2-ton 2-head multi (one head for upstairs, the other for downstairs) for $2.5K? (I recently saw a non-superinsulated ~750-800 square foot ski condo heated with the 20KBTU version of that , in a place with design temps a bit below 25C.)

If you're up for the DIY approach, the hardware isn't very expensive, and the industry has gone way out of their way to make installation dead-easy.  Stick to a manufacturer that has reasonable local support for you, and unless you really screw it up you can probably get someone to commission your DIY install for not big money.

I'd always want somebody with the right tools & experience to test and fully commission the thing.  The factory pre-charge isn't 100% guaranteed to be dead-nuts-on every time (especially with a 10 left-thumbed installer) and may need to be adjusted. They can "work mostly" with pretty miserable efficiency if not set up correctly, and even alleged "pros" with minimal experience can miss stuff.  Factory certified installers, and installers that put in dozens per year are preferable to those who have only installed a handful, and are selling them as a sideline.

There are two tested often used methods to achieve R40. Dana1 explains one above. The other method is double wall construction - two 2x4 walls or 2x6 plus 2x4 on the interior. Leave an air space of 1-2" between the walls & fill with dense pack cellulose. A total depth of 11-12" should do it; foam not necessary.

http://www.ebay.com/itm/18000-BTU-Mitsubishi-MR-SLIM-Ductless-Mini-Split-Air-Conditioner-19-2-SEER-COOL-/230757513714?pt=Air_Conditioner&hash=item35ba3839f2#ht_8317wt_912

The same people have a 2.5 ton for $2,341. You'd get the mitsubishi warranty but you'd expect some attitude from the local dealer. Minisplit service isn't critical in my use. (multifuel as in active and passive solar, wood stove boiler, electric tankless and minisplit.) One of the advantages of having a toolkit is no one piece is critical.

toddm-

It looks like the unit that you referenced is for cooling only, while the original poster is looking for heating and cooling.

When I went down the mini split path (have since given it up) I was looking at the Mitsu hyper heats with electric base board backup. The planned house is roughly 1700 sqft main level with 1700 basement, (about 1200 finished eventually). Was going with r40 double stud walls and ICF basement wall. I was planning on putting a 1 ton head on each level. However by the time I added the cost of those up, added the HRV, added the dedicated ducting for the HRV, added the cost of the baseboards with the cost of the wire and install...I was close to hitting $10k. In my area, a 2 ton vertical well geo unit can be had for right around 20k with ducts and HRV installed. Take off the fed credit (obviously you do not have this being in Canada) and other rebates from local power company, it brought my down to around $10,500 net. Obviously I am going the geo route. (COP 5 Waterfurnace). I have since changed to ICF from footer to roof too, with additional foam on the exterior to bring my total foam thickness about r30. Interesting enough, due to my help from local reps, this makes the price of ICF the same as a double stud wall including the cost of dense packed insulation (about $3500 right there). I do not think many people will argue against ICF being a superior structure, despite the lower r value. My heat load simulations indicated very little btu difference between r30 and r 40 however. At that point the loss was driven by the windows sizes.

However back to your situation at hand, when I was down that route, the solution for distribution was to use the HRV as the fresh air distribution. Pump the heated air from the mini split and allow the HRV to circulate from room to room. Something else to consider is alot of "modern day" hvc guys are concerned about air distribution and forced air units being to all spaces. In tight, well insulated homes this necessity drops off quite a bit. But one argument to have is how the homes with radiators, infloor radiant, and other non forced air heating methods works just fine at heating spaces.