[Greenbuilding] off-grid home

[Keith Winston]

On 12/7/2010 12:05 PM, Chris Koehn wrote:
> I've been asked to general contract a home on one of the B.C. southern Gulf islands without grid power. This is an architect designed, 1,600 s.f. home and while I have little influence with the over-all design, the owners have expressed desire to pursue some solar (evacuated tube and possibly PV) and have settled on wood as the primary heat source via a cook stove and separate fireplace.
> I am keen to find someone to help design an H/V system that meets B.C. code requirements, provides a modicum of comfort specific to the design of this home, consumes very little electricity and a minimum of propane, and can keep the home from freezing up when unoccupied. Anyone interested please contact me off-list.

I've been working on an off-grid home -- I was fairly involved in the 
energy side of the design from the beginning, it's a bit over 2000 sf. 
6 kW PV system, 80k kWh battery, geothermal heating. I'm not completely 
happy with it -- I went with the SMA Sunny Boy/Sunny Island combo that 
has some good and bad points, and we're just about to install a 14 kW 
backup generator which is necessary to equalize the batteries and 
address heavy loading periods in the absence of concomitant sunshine (I 
think if we'd installed the generator in the beginning, a few months 
ago, everyone would have been much happier, even though it will 
probably get very little use). The PV system (and probably battery) 
should have been bigger (!), because the house is all tricked out with 
modernistical stuff like dishwashers, clothes dryers etc. And an 
elevator... There's no wood or other biofuel backup.

Anyway, I'd recommend mini-split heat pumps. They can be almost as 
efficient as geothermal (26 SEER!), but they are completely zoned by 
nature (you don't have to turn on the entire house). Unfortunately, all 
the most efficient ones hang on a wall and have a noticeable visual 
impact. The Fujitsu RLQ series I like will pretty well heat down to 5F 
give or take, so they'll certainly keep the pipes from freezing. Of 
course, insulate the house like CRAZY, and put in GREAT windows. Be 
uncompromising about those points, since YOU are going to hang if it 
doesn't work in the end. You can get mini-splits in multi-head 
configurations (Fujitsu now has one that goes all the way up to 8 
indoor units), some of which give central control capability while 
still maintaining zonability, but the efficiency drops quickly even 
with just a second head (i.e. more like 16-17 SEER). Properly used, of 
course, a zoned 16 SEER system might be MUCH more efficient than an 
whole-house 16 SEER system (if you're willing to define efficiency in 
relation to comfort).

You can contact me off-list if you want consulting services, though I'm 
uncertain how available I am right now. Good luck on your project.

Warmly, Keith