Hey folks. . . I'm looking for your expert opinions.

I'm going to be building a small single car garage with a guest apartment above it on my land here in Maine.     I'd like to heat the place as efficiently as possible, ideally avoiding the use of heating oil, gas or propane.    But I'd also like the system to be automatic, not requiring a hopper to be filled with wood pellets every two days, or a stove be refilled with firewood.     The system needs to be streamlined, automatic, and reasonable in cost.     I'm not sure what my options are.

Putting radiant head in the slab of the garage itself is quite appealing, but doing so will probably lock me into going with radiant heat in the apartment.   I could be wrong.    I'm not married to the idea of radiant if it's not the most efficient.   I also won't have space for a mechanicals room, given that a W/D will need to go beneath the stairs in the garage.

The structure will be 939 sq ft, equally divided between both floors.    Most likely, the structure will be built using SIPs and triple glazed windows.     Both floors will be heated, although the garage itself will only need to be kept at 60F in the winter.


Given this list of variables to be met, how would YOU heat this place?




Exterior View:








First Floor Plan:



Second Floor Plan:



Thanks in advance for the advice . . .


John

Answer: with a "fazer" set on "humanoid comfort mode".

The real answer: condensing domestic water heater with plate heat exchanger and hydronic sub-system. Radiant floor in the slab is best, as you suggest, and Europanels for the second floor. This is the most cost/space/energy efficient gas-fired system available today unless you have cheap electricity and low consumption.

The gas-grid in ME is pretty sparse, and they're specifically looking for a non-fossil solution, although I agree that high insulation levels and tapping off a gas-fired HW heater is a cost-effective approach.

Daikin's hydronic air-source heat pump & radiant floor/panel would probably get you there. (paging Rob...)

Going all-out PassiveHouse style on the insulation levels and electric radiant (or resistance elements in the ventilation air stream) could also get you there (possibly for similar money to a hydronic heat pump solution, if designed in from the get-go.)

Dana:

I've concluded the smartest approach isn't necessarily to avoid fossil fuels, but to make sure that if they're being used, they're being used incredibly efficiently.   

Badger Boiler's response got me thinking and I spoke with a few people on the phone today about how they would address the heating needs of this tiny 939 sq ft structure.    I'm likely to go with the following set-up:

1)   An Elite EL-220 Ultra High Efficiency, Condensing LP Gas-Fired Heater/Boiler
2)   An SSU-119 Superstor Ultra Stainless Steel Coil Booster Storage Tank
3)   A couple small, wall-mount hydronic radiators within the apartment, sufficient to keep the place at 72F in the dead of a Maine winter, and at little cost. 
4)   A Rehau radiant floor heat system, primarily for the slab in the garage floor, but also as a supplementary source of heat (and guaranteed warm floors) in the apartment.    It would be mounted between the floor joists beneath the apartment.

Given that the Elite boiler has a turndown ratio of 6-to-1, it could easily heat the water for the radiant tubing at temps much lower than that being heated for the hydronic radiators, and by using propane incredibly efficiently for both.   The Elite could also ramp-up to produce an endless amount of hot water for the 5-head shower in the bath (which will use up to 12.5 gpm.)    Since this structure will be super-insulated and airtight, and because I'd always have the supplementary radiant heat beneath the apartment floor, the hydronic wall-mount radiators would likely only come on in really cold weather.   

I'll also likely add a small ERV to the mix, so a structure this airtight and well-insulated will breathe properly.

With these systems in place, this place should cost a pittance to heat.



John

You are on the right track but I would like a private word with you.

I wouldn't use Onix. But then I would never use Onix. I've seen too much.

I'm a little stunned you're doing a 5 head shower. how unlike you John

Posted By NRT.Rob on 05 May 2010 09:12 AM
I wouldn't use Onix. But then I would never use Onix. I've seen too much.

I'm a little stunned you're doing a 5 head shower. how unlike you John

Heya, Rob!

I'd like to at least use the Onix as a staple-up product beneath the apartment floor (and go with the Pex in the slab.)    Aside from cost, what's the drawback to going with the Onix beneath the apartment floorboards?


John

I've seen a strange, mysterious black gunk in some Onix systems. There is only one thing in the system I can see that would cause such a thing.... so I will never use or recommend that product for anything.

Posted By NRT.Rob on 05 May 2010 11:08 AM
I've seen a strange, mysterious black gunk in some Onix systems. There is only one thing in the system I can see that would cause such a thing.... so I will never use or recommend that product for anything.

Rob:

I'm not real keen on 'mysterious black gunk.'    I appreciate the heads-up.


John

The only advantage I can see to using Onix pipe over pex is that it will cost 4 times as much as pex pipe and will not fit any affordable heat transfer plates on the market.
Try looking at some other pex pipe, Onix is like using bendy radiator hose, cant get behind it.
Dan

I've not heard great things about the Onix over the past couple of days, so I'll likely be going with Rehau RAUPEX® O2 Barrier Pipe in the concrete slab, and Rehau RAUPLATE™ Joist Space Heating below the apartment itself.    The latter is a system recently introduced by Rehau that offers higher conductivity with the aluminum plates, as well as reduces expansion noise of the tubing by keeping a firm grip on it.  

I'm in the process of having a local outfit price out both for me.

Thanks for the feedback.



John

I re-read the original post to look for something. Radiant in the slab was mentioned, but is heating the garage below a necessity? If not, then why not just insulate really well between the garage & apartment & use baseboard heat or something?