We are building a house soon and I need help deciding on the heating system. Zone 4C (Vancouver Island, Canada). 2100 sf house on 1 level. Slab on grade. Passive solar design (long wall facing south). Will have a wood-burning stove for backup heat (we live on forested acreage). We don't have natural gas access here. Currently use propane which I would like to not use anymore. Plan to hook up PVs at some point but it is not very sunny here in winter. But for now, electric heat is first choice. I hate forced air and am trying to avoid any ductwork. In-floor radiant heat is expensive and may be overkill in our climate if we insulate well (thoughts?). What about radiant wall heating? And I've just learned about radiant cove heaters, though I sure don't like the look of them. Everyone here loves heat pumps, so I'm considering minisplits but they also look ugly and are they loud? Am wanting to do "better than code" insulation, but not sure what the balance is between comfort and cost (see my thread in the design forum about wall structure). Any suggestions on heating systems would be much appreciated. TIA!

They do make mini-splits with cassettes that go in the wall or ceiling. There are also ducted mini-splits so that all you would see would be the vents. We are using Mitsubishi HyperHeat units, and they are very efficient. They are also nearly silent- I like to challenge new visitors to see if they can hear the unit running. That includes the outdoor unit. I used the ugly wall-hung indoor units, and you don't 'see' them after a while, but I can see where they wouldn't be everyone's cup of tea. Our house is ICF in hot, humid South Carolina, and our A/C load is only 9K BTU; heat is 12K BTU. In the 4 years I have been here, I have seen temperature extremes from -16 C. to nearly 42 C.(!) One feature I like about the Mitsubishi units is that they have a dehumidifier mode, which we use in the shoulder seasons when A/C isn't needed.

I build in New England and also use mini splits; they have worked so well I installed them in my old "New Englander", tightened up the house and stopped using my fossil fuel units. They heat better, are far quieter and work much better, in addition to having the drying cycle (dehumidification) and AC. They are less "ugly" than baseboard heat and are so quiet and inconspicuous in use that we forget about them. The "cost vs comfort" is a false issue; additional insulation and air tightening will give you far better comfort and less expense - year round - for the life of the house. With homes similar to what we are building, the mortgage with all of that additional cost, plus utilities is still less than a "code" house.

We have designed radiant floors in your area. Electric boiler and PEX tubing in the slab. Nothing better. Most will go without AC in the Pacific NW but a mini or high velocity would could work for you. I have both here in Minneapolis.

Thanks so much all of you! Good to hear they can be used with "cassettes" in the ceiling. That might be less obtrusive. Also very pleased to hear they are quiet (I have a thing about fan noise, drives me batty!). I will have to look around and see what is available.

With slab on grade, radiant might be less expensive than you expect. With the availability of wood, a wood boiler could heat the floor with the thermal mass being a benefit.

A single wall or ceiling cassette isn't going to be a great solution for a slab-on-grade 1-story, and multiple ceiling cassette would require way to much compressor and be oversized for the room loads. But a ~1.5 ton ducted mini-split would probably do it.

Even though you hate ducts, the duct sizes and air volumes of a fully modulating unit that was right-sized for your low loads is NOTHING like the rattle & blast of a propane hot air furnace- it's quieter than your refrigerator. You'd likely be looking at 8" x 12" or 6" x 18" trunks 4" - 5" round hard piping to the register ducts.

With slab-on-grade you have to plan the duct routing in advance to run it in soffits or service-chase fully within both the pressure and insulation boundary of the house. (DON'T run them in the attic, above the insulation!).

There are a few hydronic output air source heat pump solutions suitable for slab radiation, but they're expensive- more than 2x as expensive as ducted mini-split solution.

First thing to do before designing any heating solution is to get a handle on the actual heat loads, but taking a wag at it...

Your 99% outside design temps on Vancouver Island are pretty modest- +20F/-7C in Nanaimo, +26F/-3C in Victoria. A tight IRC 2012 code-min 2100' house would have a heat load of around 20,000-25,000 BTU/hr @ -10C/+14F, a well designed slightly better than code house would come in under 20K. Let's assume that you can tweak the design and detail it to duck under 20,000 BTU/hr @ -10C

The Fujitsu 18RLFCD mini-duct unit is rated at 21,600 BTU/hr in it's HSPF efficiency testing, which means it has to put out at LEAST that much at +17F/-8C with a 70F indoor temp (per the HSPF testing protocol). I'd have to look up the extended temperature capacity specs to tell you what it delivers at -15C and -20C, (temps rarely but sometimes seen in your area) but it's probably going to be a good fit. The thing can modulate down as low as 3100 BTU/hr @ +47F/ +8C, and it's very quiet, particularly at low and mid speed where it will be almost all the time. Unlike most of the competition, this series an be mounted vertically, which give it a bit more flexibility on where to mount it and how to route the duct work. (You could mount it in or on a wall in the utility room to make filter swapping easier, even if the ducts were running in the ceiling.)

http://www.fujitsugeneral.com/PDF_0...mittal.pdf

http://www.master.ca/documents/1Fuj...RU_RLF.pdf

http://www.btureps.com/fujitsu/fujitsu-literature/2014-rlfcd-rlfcc-brochure.pdf

There are others.

Not that you'd EVER need it (except for this year :-) ), they provide high efficiency air conditioning too.

If you're pouring the slab it doesn't cost much to install the PEX to leave that option open, but an electric boiler would cost about 3.5x to run as a better-class mini-split in your climate. (I have several relatives a bit south of Juan de Fuca heating with mini-splits now, some of whom had previously been heating with resistance electricity- the super high efficiency is real.)

But not nearly as comfortable as radiant floors. My mini goes off and I gladly pay 3x to keep my cold feet warm. We will have inverter hydro heat pumps in my lifetime and you can convert later if you can't afford the $200.00 per month to have 'real' comfort.

Dana, I've been browsing through the threads here and I just want to thank you for taking so much time to answer posts in such detail. I really appreciate it!

We are closer to Victoria in temperature, being located about halfway between there and Nanaimo. A super crazy cold day here in the Cowichan Valley might get near - 7, but that is really rare. So if I understand you correctly, the one you recommended would be more than sufficient here.

I've spoken to many people here with heat pumps and they all say that once it dips a bit below 0 C, they really can't cut it. So most people have a backup source of heat. I'm hoping to get away with the wood stove, but regs here may require we put in a couple of baseboard heaters (which we will rarely, if ever, need, or so I'm told).

You nailed it on my dislike of ductwork, rattle and blast well describes it! We currently have a propane forced air system and I hate it for the noise, the grates in the floor that get in the way of furniture, and we have 3 furry family members, so when the air starts blowing there is often a dust-bunny whirlwind! Stuff falls in them, and they can make a great highway for mice (we are out in the country and critters are just a reality here). I also think if we can avoid duct work it cuts down a great deal on the cost of installation, and as you pointed out, the duct work can't go in the slab or in the attic, so it's a bit of extra work there too. My thinking was save on installation of heat system and put that savings into added insulation. Does that make sense in my situation?

Thank you for estimating the heat load. I've only just become familiar with this term and no idea how to measure it, so I appreciate you doing the math. And thanks for recommending the Fujitsu. I plan to visit our local heat pump guy and it will be helpful to have this information on hand.

Badger: as someone with chronically cold feet, I hear you, I really do. But I'm a knitter and between my hand-made wool socks and a great pair of wool slippers, I've managed well so far without it. The cost of in-floor plus the boiler, etc is really high here and given I'm on a tight budget, I'd like to forgo that luxury for other things.

I've also read that if you insulate your slab and home properly, the slab should take on the same temp as in the room, and therefore should not feel cold to the touch. Given our mild winters, that seems reasonable...or am I dreaming? ;-)

Although it does bring up the question of flooring (e.g. concrete, hardwood, etc), but I'll start another thread on that!

What electric boiler do your use? I haven't been able to find any and therefore did not think that they existed.

That is a good point and probably her best beat. I use a wood fired boiler to heat the floor in my shop and it also sends the hot water to heat my home. That is the best way to go for anyone who has a source of wood and does not mind the effort involved in the harvesting, transporting, and stacking of cut log pieces.

Yeah, the harvesting, etc is not something I'd like to have to do beyond the odd cold day when a fire would feel good. Also, we only have 4 acres, so not really enough to support something that needs to be fired all the time. More a backup, ambience type of thing!

"once it dips a bit below 0 C, they really can't cut it". All heat pumps are not equal. We use the Mitsubishi Hyper Heat; our winter temps go to -15 and the mini splits work fine, although they are less efficient. Last winter hovered around -0- for most of two months. In terms of air tightness, you can keep the heat you make inside the house, or let it escape through unintentional leaks; just a function of how much fuel you want to use and how much moisture you want traveling through your wall and roof assemblies. The majority of moisture traveling through the envelope travels on moving air. Keep in mind that there are hundreds of places that air escapes, so sealing them is mainly a matter of paying attention and then using high quality tapes and caulks that will last. Even if there are a few failures, a massive failure of all the tapes,caulk and other measures is unlikely.

The Hyper-Heat is a good choice. I would tube the slab for future, the least of a typical radiant job. You Canucks make one of the best ,Thermolec, that we use here along with our own Electo Boiler made in Minnesota.

I just finished my office and shop with a twin head Fujitsu, the house already has the same in Mitsubishi, and have also tubed the floor and allowed for propane and electric service so we can demonstrate the advantages of each. The main being comfort and future choice of fuel. We an currently by split dry oak for nearly the cost of NG so wood boiler may in our future and the radiant floor always a viable option. Floor temperature sans radiation is more function of window size and quality than heat source or insulation.

> The cost of in-floor plus the boiler, etc is really high

I'm curious, how much? Looks like a Thermolec boiler is around $900.

This looks interesting. Seems to be saying that it can be used to add hydronic heating (or cooling) to a Mitsubishi Hyper-heat heat pump. Now if it were only affordable. Maybe Fujitsu will do the equivalent...

Thank you for the suggestions of "tubing the floor". I will look into the cost of that.

Also great to hear that today's heat pumps can handle lower temps. I must say, the more I learn about them the more impressed I am with them!

But since some of you are pushing the radiant argument, and since the idea of toasty feet is somewhat alluring (and I want to make in informed decision!), I'd like to ask a few more questions:

Is it true that you have to keep an in-floor system on all the time because it takes so long for it to heat up the slab from cold?

Is there any risk of the tubes freezing if you went on vacation in the winter and turned the heat off, or does the concrete around it protect from that?

Is it true you actually need MORE sub-slab insulation when using radiant heat compared to not using it in a slab?

What happens if there is a breach or leak in one of the pipes - is your only choice to jackhammer your slab open?

Is it crazy to think that solar PV could ever power such a system in the near future, especially in a climate where the sun rarely appears in winter?

Is it true that you could use a heat pump to heat up the water that circulates in the floor (or at least boost the heat a bit), thus providing a more energy efficient system? I think that is what johr linked to above?

thank you.

The only people who do not want radiant heating are those of whom have never experienced the incomparable comfort.

2" of XPS is the practical standard weather you radiate the slab of not.

A properly designed radiant slab will operate on outdoor reset controlling supply water temperature according to the outdoor temperature. There is rarely a lead or lag more especially where sun is not a factor.

For those who worry a lot, anti-freeze is an option but I prefer a Wifi thermostat such as the EcoBee or Nest for security since the plumbing in the house, and every house, would burst before the heated slab cooled off.

Leaks are fixed like any plumbing leak in a slab. Rare.

Solar hydro is crazy except in southwest US. PV is not in the cards as the panel to output ratio is simply too high to be practical with massive storage tanks the first hurtle.

Unfortunately there are really now practical/affordable air-to-water heat pumps available for modest residential applications at this time. One could argue the same is true of ground source heat pumps though for larger homes with high electric rates the numbers fall closer to practical.

In special cases (like off-grid), solar PV + oversized heat pumps + large hydronic storage might make more sense than the alternatives (batteries?). It can be made to work for space heating/cooling, refrigeration and domestic hot water.

Thanks, everyone. I will price out some systems, but the cost savings between going with heat pump vs. radiant is a pretty substantial fraction of our overall budget. But you've convinced me to take a closer look at both (esp. the idea to put the tubing in anyway), and I thank all of you for the information and time!

Posted By Bob I on 25 Jul 2015 09:31 AM
"once it dips a bit below 0 C, they really can't cut it". All heat pumps are not equal. We use the Mitsubishi Hyper Heat; our winter temps go to -15 and the mini splits work fine, although they are less efficient. Last winter hovered around -0- for most of two months. In terms of air tightness, you can keep the heat you make inside the house, or let it escape through unintentional leaks; just a function of how much fuel you want to use and how much moisture you want traveling through your wall and roof assemblies. The majority of moisture traveling through the envelope travels on moving air. Keep in mind that there are hundreds of places that air escapes, so sealing them is mainly a matter of paying attention and then using high quality tapes and caulks that will last. Even if there are a few failures, a massive failure of all the tapes,caulk and other measures is unlikely.

 Actually, some heat pumps ARE equal! (Let's parse the English with correct logical structures, eh?  )

"Not all heat pumps are equal." is what you meant to say. Now that the peeves have been properly petted...

In this case, who cares about what happens at -15F, a temp not seen in Victoria since the last ice age?

The 99% temperature bin for Victoria BC is  -3C/+26F, and almost any mini-split will still be operating efficiently and with reasonable capacity at their winter temps, meeting or beating it's HSPF numbers in that climate, (even if a lot of PTHPs and old school ducted heat pumps crap out at 0C.)

I'm not saying that a Mitsubishi Hyper Heat would be inappropriate (most of my relatives in that region heating with mini-splits are using them), but the palette of mini-splits that can work is much broader in coastal BC than in New England.