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Off-grid part-time house -- avoiding winterizing? Options
Pat Miketinac
#1 Posted : Thursday, December 31, 2009 3:44:35 AM
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I think it would be possible to put everything within the house envelope that is freeze sensitive, especially since you plan on passive solar and an earth berm. The solar hot water panels could be under a skylight on a roof angled and oriented for solar gain, with shades to prevent overheating the panels when not being used. I had water boil in mine when a circulating pump quit! A thermosiphon hot water system might be another option.

If you have an uninsulated concrete floor and an earth berm, with good insulation above grade, freezing should not be a problem. My earth shelter never drops below 65 degrees with no heat, but I am in Florida with a 72 degree ground temp. My well and pressure tank are in an insulated building that will not freeze due to the warmth from the ground, even when we had a 17 degree low.

NicoleC
#2 Posted : Thursday, December 31, 2009 3:09:11 PM
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Thanks for the reply, Pat.  That's an interesting idea on placing the hot water panels under a skylight.  I'm not sure the reduction in gain would be efficient here -- we don't get nearly the direct sun that Florida does -- but if there is electrical backup losing a bit of efficiency may be an acceptable trade-off. 

It is considerably warmer where you are.  Our ground temperature gets down to about 45F here, and with a periods sometimes of a week with highs of 20F (and possibly lower depending on the location of the property), I'm not sure a partial berm and the design alone could keep the pipes from freezing during these periods.

The obvious solution would seem to be a small tankless system, but it would require a much larger PV array.  This is not only a cost issue -- especially since it must be oversized for our sub-optimal sun anyway -- but any large and conspicuous PV array left unsupervised routinely and predictably for a week or more might not be there when I get back!

davisonh
#3 Posted : Friday, January 01, 2010 12:50:44 AM
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I think now,if I were to do this all over again I definitely would put water lines and such on the interior portions of the walls and most definitely if there were to be any such water system,to put the pump in or under the house.You do not say where you are,but definitely would run a 12 volt either main or backup system water pump and well insulated.Passive solar would require lots of stone.Hot water definitely an on demand system,electric or gas or forced hot water.You may luck out with an air to air heat pump setup for heat,along with the passive solar.Wood stove can heat your hot water with a coil in the firebox.

NicoleC
#4 Posted : Friday, January 01, 2010 4:35:02 PM
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The problem with an on-demand hot water heater is it forces the PV array to really be up-sized.  They pull anywhere from 80-150 amps.  For a tri-phase 220v unit, that's a whopping 30000 watts.

I have heard you can heat water with a wood stove, but I don't see firing up a wood stove to wash the dishes in the summer when it's 105 outside.

I'm starting to think an in-wall heat pump, setting the thermostat down to 40F or so in the winter when I'm gone.  I installed one as a backup heat source in an old condo that had a 45 year old furnace and it worked great.  Many pull as little as 3-4 amps -- only 1300 watts.  We get plenty of sun in the winter, so the PV array could just keep it ticking along.  I'd still insulate the pipes and such against outages, as an added safety factor, so the hot water tank would be the only likely casualty, and even then the cabin might perform well enough to say above freezing.

Plus it means cutting less wood... although I think I'd have a wood stove as a backup anyway.

For thermal mass, I'm thinking ICF.  It's simple to build with, will be strong enough to hold the weight of the berm and is easy to water proof.  Also strong enough to be tornado resistant.

 

davisonh
#5 Posted : Friday, January 01, 2010 10:03:44 PM
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Oh no,I did not imply firing the stove up in summer to do the dishes,no thats what solar hot water collectors are for. A tank outside painted black is more than enough to suffice for hot water in summer,or you could do panels with them piped in parallel with a hot water heater.The woodstove with the helicoil can be used to space heat the building as well as domestic hot water piped in parallel with the hotwater tank.That way if all else fails to keep the cabin above freezing the hot water heater will act as a space heating unit to keep it above freezing.You can get on demand heaters in lp gas too.120 volts x 4 amps=480 watts,so even better!

NicoleC
#6 Posted : Saturday, January 02, 2010 12:41:10 AM
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Yeah, but I won't be there all the time to feed a wood stove to keep the pipes from freezing!

When I am there is not the problem -- trust me, if it's below freezing inside, I'm moving out.

practicalman45
#7 Posted : Monday, January 04, 2010 7:20:15 AM
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Design all of your supply plumbing so it can be easily drained. Valves and faucets opened up and the slope of things makes it all drain out easily. Traps such as the sink and toilet must get antifreeze added, or be sucked out dry somehow such as a wet or dry vac.

MichaelK
#8 Posted : Friday, January 15, 2010 3:57:17 PM
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Hello Nicole

I am exactly in your situation right now.  Our homestead is at 5000 feet in the Sierra Nevada, and the winter lows here drop into the teens.  Freeze damage is one of the things I have to focus on.  We have a well and 5000 gallon storage tanks situated up the hill from our cabin.  We run a generator to produce 220V power to pump water into the tank, but get gravity flow back down with the generator off.  If the tanks are full, their thermal mass keeps them from freezing in winter, but that's with the pipe to the cabin drained.

I'm just in the process of finishing the inside shell of our cabin now, and only now am I running PEX pipe through the walls to bring water inside to the kitchen and bathroom.  PEX is good because it can handle freezing, and can be pushed through completed construction.  Our source of winter water is just 5 gallon buckets that I fill up at home and bring with me.  I find that I can get by with about 10 gallons a day, which includes cooking/cleanup, a few toilet flushes, and a shower.  I'll heat hot water on my gasoline stove, put it in 1 gallon plastic jugs, and shower that way.  Two or three gallons will get you satisfyingly clean.  I use about 3 gallons to flush the toilet.  I just dump the water straight in the bowl.  The weight of the water starts the siphon that performs the flushing process.  When I leave, I leave standing water in the toilet and tub drains.  It doesn't get cold enough INSIDE the cabin for water to freeze.  What we could do though is flush the line with water/antifreeze if we thought the weather would get so cold it might freeze inside.

For long term, I bought a propane powered tankless heater for hot water.  That will only get plumbed in once I build a utility room around our well so all the pipes from the well can be inside from the weather.  I won't use the TWH till we get our solar panels installed because it has an electric igniter.  I also plan on having a solar batch heater for summer hot water.  What I've already done is laid the pipe for it, but instead of the batch collector, I spliced in 200 feet of regular garden hose.  Carefully laid in the summer sun, it collects enough heat for a several minute hot shower.  I may also plumb our wood cookstove for thermalsiphin hot water, but that again would only be for winter hot water.

So many ideas, and so many projects.  I am right now installing the chimney for our woodstove, then it's finishing the bathroom, then it's finishing the kitchen, then it's finishing the solar panels, then its.....

Well, you get the idea.  Things take a long time to complete when they're getting finished peicemeal, one by one.

Good luck to you, and definately make your land purchase as soon as you can.  I doubt if prices will get any better than right now!  If you can finalize a deal this winter, you'll have time to break ground and get your first garden and fruit trees in the ground.

Michael

NicoleC
#9 Posted : Friday, January 15, 2010 3:57:17 PM
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I am in the early stages of planning a small off-grid house on 10+ acres that will be used for weekends and, someday, full-time living.  I am not going to choose a property until I do some more planning, but there are plenty of candidates in my price range.  I plan to buy the property and then build myself as time and cash flow permits.

My current thinking is:

electricity - PV array
water - well or rainwater collection, depending on the site
sanitation - composting toilets, greywater (or the county may require a septic tank)
hot water - solar hot water + electricity from PV array
heat - passive solar design + partial earth berm + wood stove

Since I expect to use the cabin during the winter, too, I don't want to have a lengthy winterize/de-winterize process each weekend.  The winters are mild, but we do have periods in the winter where temps may stay below freezing for several days at a time.

I have considered a pump which only pumps water up out of the well or an underground cistern on demand, and also the possibility of burying the pipes underground.  (The ground never really freezes here.)  However, that still leaves the hot water heater tank. 

Does anyone have any thoughts on this, or has a system they are using successfully?

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