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Community and Q&A

Island build with no grid power

Chris Koehn | Posted in Mechanicals on

I’m planning the build for a ~1,600 sq ft home on one of the southern Gulf islands, B.C. This particular island has no grid power. The owners would like to heat primarily with wood, via a wood burning cook stove and a fireplace. They are concerned about comfort in areas of the home that are a bit removed from the heat sources; namely the bathroom and a small second floor bedroom. They would like to incorporate some solar and are most interested in evacuated tube (water-to-water). Power consumption is a big deal, as it’s by propane generator only (and PV, if we choose to go that route). I’m thinking about heating (tile) floors in the bathroom, but I’m concerned with electricity consumption to run pumps.
A secondary issue is to provide back-up heat to keep the place from freezing up in winter and to satisfy code requirement.
I’m looking for potential solutions from folks who have faced similar challenges.
Thanks!
Chris Koehn
TimberGuides Design & build

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Replies

  1. Riversong | | #1

    I would try to talk them out of the fireplace, unless it's a Rumford with a gasketed chimney cap.

    Definitely incorporate all the passive solar possible in that locale, with sufficient direct-gain thermal mass for diurnal storage, as that will reduce fuel consumption.

    If you can find a wood cookstove with a water coil, you could thermosiphon hot water to the bathroom radiant floor above. Just make sure there's a pressure-relief valve in the system and large enough pipes to minimize head losses.

    If the house is that small and very tight (I imagine you're going to use those awful SIPS), then temperature stratification or variance should not be a significant problem. Make sure there's good air supply and return routes to all rooms and the second floor for passive distribution. A stairwell near the primary heating unit makes a good "supply duct" and an appropriate space geometry can help complete the convection route.

  2. GBA Editor
    Martin Holladay | | #2

    Chris,
    I think there is only one choice to provide backup heat and to prevent freeze-ups when the house is temporarily unoccupied: one or more propane space heaters with through-the-wall air intake and venting. Empire makes several models that do not require electricity.

    Whatever you do, don't choose any heating equipment that will require electricity to operate.

    Anyone who chooses to live off-grid should be willing to be flexible about indoor air temperatures in remote rooms on the coldest days of the year. You can minimize these temperature differences, however, by paying scrupulous attention to air sealing and by providing very high levels of insulation in your floors, walls, and ceilings.

  3. Lucas Durand | | #3

    Robert, what do you mean by:

    ... and large enough pipes to minimize head losses.

    Is there a way to quantify an optimal relationship between head and pipe size for a thermosiphon?

  4. Riversong | | #4

    Lucas,

    I haven't spent much time studying hydraulic engineering, but the head (or pressure) loss in a pipe system depends on fluid viscosity, fluid density, fluid velocity, static pressure (equivalent pipe length), gravity head, pipe roughness, and turbulence.

    The driving pressure in a thermosyphon system is the height difference (ft) times the density difference (pcf) between the hot and the cooler water (divided by 144 to convert to psi), and it ain't much.

    Bottom line is that thermosyphon systems don't have much pressure to push the water, so the larger diameter pipe the better. Old thermosyphon radiator systems used to use very large cast iron distribution pipes to allow sufficient flow.

    And the static pressure loss is largely a factor of the ratio between pipe volume and pipe surface area. I would recommend nothing less than 1" copper for any thermosyphon system.

  5. David Meiland | | #5

    Chris, I'm a few miles south of you in the group of islands that the Americans got. You can do quite well here if you have good southern exposure, design for passive solar, build a very well insulated shell, and generally minimize heating and electrical needs. Not sure about a fireplace, but a woodstove or two would be automatic for me in your situation, and if at all possible I would install the PV. It gets very costly floating the propane truck over to non-ferry-served islands on a landing barge, unless you have a lot of neighbors to split the cost, and listening to a generator run isn't that much fun either. You can get a lot of your DHW from solar thermal, and I would do that too.

  6. Chris Koehn | | #6

    Thanks for all the answers so far. Looks like we're headed toward water-to-water solar, with PV to run the pumps.
    BTW Robert, the home has no SIPs shown; the architect has drawn an insufficiently thick built up roof (doesn't meet code- 3 1/2" of rigid foam). In this case- but not all- SIPs will be a recommended solution.

  7. GBA Editor
    Martin Holladay | | #7

    Chris Koehn,
    For an off-grid house, an active solar thermal system can make sense for domestic hot water, but rarely makes sense for space heating. Here's why:

    1. When it's cold and cloudy, a hydronic space heating system requires electricity to operate the circulators. This really is a deal-killer -- in the middle of winter, when you are cold, where is the electricity coming from? I have friends who built a new off-grid house with a hydronic heating system. They had to run their gasoline-powered generator all winter. The noise drove them nuts and the fuel cost nearly bankrupted them.

    2. If there's ever a need to leave the house unoccupied for a weekend, there's a serious chance of freeze-up. Draining hydronic lines is a real pain.

    The motto for an off-grid house should be: Keep it simple.

  8. Chris Koehn | | #8

    Hey Martin, KISS = good advice. I wonder though: is your friend's house in New England? We have significantly different conditions and demands here in the southern gulf islands..

  9. Lucas Durand - 7A | | #9

    We have significantly different conditions and demands here in the southern gulf islands..

    Are they though? One thing I don't miss about living in the Lower Mainland is the constant cloud cover and rain through winter.
    I guess some of the gulf islands benefit from a rainshadow...
    A friend of mine has a place on Salt Spring and I've spent some cold weeks there under cloudy skies. We even got snowed in once!

  10. Chris Koehn | | #10

    From New England? for sure. Avg. heating degree (F) days VT = ~8,000.
    Avg. in Vancouver BC (and we are a bit warmer than they) = ~3,000.

    It can definitely be cloudy and damp (= uncomfortable for us) but the heat loads are substantially less, making freeze-up less of an issue, and heating loads more manageable.

    I came here from Wisconsin (similar to Toronto in HV/AC loads) and my whole mind-set has had to change.

  11. David Meiland | | #11

    HDD base 65 is over 5000 here, how is it 3000 there?

  12. Lucas Durand - 7A | | #12

    Yes, sorry, of course it's much colder in New England than the SW coast of BC.
    I was refering more to the issue of cloud cover. In an off-grid scenario using solar thermal or PV, energy storage through long periods of cloud cover can be a significant issue - even in a location where heating loads are not extreme.

  13. Chris Koehn | | #13

    David & all- apologies, I thought I'd done the C to F conversion but I hadn't. We are ~5,400 (F) as well.

    Deviation from the mean temp is another relevant statistic which differentiates us from New England.

    I'd like to know more about cloud cover effect: can someone point me toward data?
    Cheers.

  14. GBA Editor
    Martin Holladay | | #14

    Chris,
    Yes, my friend's house is in Vermont. Yes, your climate is milder.

    Trust me, though, you often need heat when it's cloudy. And whenever your thermostat calls for heat, that little circulator is going to start draining your batteries.

    Off grid home = heating system that doesn't require electricity.

  15. Lucas Durand - 7A | | #15

    Chris, a previous post I made with links to some climate data got blocked by the spam filter...
    I'll try again.
    Go here for Canadian "climate normals":
    http://www.climate.weatheroffice.gc.ca/climate_normals/index_e.html

    Look at the bottom of the dataset for "Bright sunshine" and "Cloud amount (hours with)"
    Not all weather stations compile the same information so it may be that you have to look up a few different nearby stations to find the information you're looking for.
    A quick look at the data for Vancouver International indicates that roughly half of almost every month of the year, the sky is obscured by 8/10ths or more of cloud cover.

  16. David Meiland | | #16

    I think the southern Gulf Islands are a lot more like the San Juans than they are like Vancouver BC. According to the local realtors we get 247 days per year with partial or full sun. People are installing quite a bit of solar thermal and even PV here. PV is somewhat distorted because of the very nice feed-in tariff you get, which obviously wouldn't apply to Chris's project, but if the house is occupied during the summer and the shoulder season I bet he would get a good return anyway, and wouldn't be listening to the generator as much.

  17. Riversong | | #17

    According to the local realtors we get 247 days per year with partial or full sun.

    Realtors are not meteorologists, they are salespeople. Odd choice of authority to use for something as critical to PV design.

  18. Chris Koehn | | #18

    Martin et al,

    I'll re-state the design need: primary heat source will be wood. We are looking to provide a modicum of comfort in areas of the home that are not directly heated by wood, namely a bathroom/mudroom/foyer area, as well as a second floor bedroom. We'd like to design a solar system that will augment wood and work a bit when the house is unoccupied as well. Since the bathroom area will have a tile floor it seems natural (at least to this neophyte) to squirt a little heat in to the floor.

  19. Lucas Durand | | #19

    I think the southern Gulf Islands are a lot more like the San Juans than they are like Vancouver BC.

    Yes, but Vancouver International is not in Vancouver, it is in Richmond. Though it is only a matter of 20 miles or so, the weather can vary significantly. Richmond recieves some of the rain-shadow effect from Vancouver Island like the gulf islands. It may not be quite as dry as the gulf islands where the arbutus trees grow, but I'm guessing it won't be far off in terms of cloud cover.

  20. Lucas Durand - 7A | | #20

    We are looking to provide a modicum of comfort in areas of the home that are not directly heated by wood, namely a bathroom/mudroom/foyer area, as well as a second floor bedroom. We'd like to design a solar system that will augment wood and work a bit when the house is unoccupied as well.

    I think Martin has already said it best:

    Anyone who chooses to live off-grid should be willing to be flexible about indoor air temperatures in remote rooms on the coldest days of the year. You can minimize these temperature differences, however, by paying scrupulous attention to air sealing and by providing very high levels of insulation in your floors, walls, and ceilings.

    In that climate, in a tight, well insulated house I'll bet you could easily stay toasty through the winter on less than a single cord of wood.

  21. Riversong | | #21

    I'll bet you could easily stay toasty through the winter on less than a single cord of wood.

    But how long does it take to collect a cord of driftwood?

  22. GBA Editor
    Martin Holladay | | #22

    Chris,
    No one who has ever lived in an off-grid house would consider heating the house when unoccupied with a hydronic heating system that uses a circulator.

    How many days will the owners be gone? Who will monitor the voltage? What happens when the voltage drops? Low battery = cold house.

    Yes, you can install a propane-fired generator with an auto-start feature -- one that comes on when the voltage drops before a certain point. But that means big bucks. And all for what reason -- because you don't want a propane space heater or two?

    You need to re-think your understanding of the ratio between the cost of electricity and the cost of fossil fuels. As we all know, fossil fuels are relatively cheap. (They may not always be relatively cheap, but that's a topic for another thread.) If you live off-grid, electricity is extremely expensive -- especially in winter, when it comes from a generator. Think $0.50 to $1.00 a kWh.

    Electricity in winter is like gold if you live off-grid. You don't waste it on trivial things; it's too expensive. If you can design a heating system that doesn't need it, you are home-free and happy. If you design a heating system that requires it, you are sad and despondent.

    If the homeowners will be heating mostly with wood, why would they ever invest money in a hydronic system?

  23. Chris Koehn | | #23

    Looks like we'll need to do a proper cost - benefit analysis. Back-up propane heat is certainly within the realm; indeed it's likely. As you mention Martin, it's cheap. Although "cheap" in this case is also relative: getting a barge to this island with a truck to fill the owner's 500 gallon propane tank is not cheap.

    This island has healthy second growth fir forests. The owners have several cords stock-piled from thinning and there's more coming. No need to drag driftwood up from the beach.

    BCBC requires a back-up heat source if wood is the primary. The owners have a desire to do some solar, they have a good solar exposure and I applaud their desire to invest in non-fossil fuel based energy sources. We have not committed to radiant.

  24. Mr. Greenguy | | #24

    If you're building on off grid house, the design should reflect this and if it has rooms with no heat source, it sounds like there is no architect involved. I may back up a little and refine the house design so that it reflects it's program (wood heat/off grid) and geographical conditions (gulf islands/heating degree days). Even at 1600sf, there is no reason to have cold/isolated rooms.

    However, as an alternative to a heat pump, one can always run hydronic heat off a wood stove with a liquid heat exchange. There is more than enough heat from wood combustion if you can move it where you need and being off grid, a hybrid system (wood/hydronic) with a small pump is all you need to move and heat and with the addition of a tank, could store a days worth of heat too.

  25. Chris Koehn | | #25

    There is an architect involved: unfortunately I don't think (IMHO) he did a great job designing for off-grid. There are other elements of the design that could have been done differently. The clients have a relationship with him and I am coming to this project late in the game.
    We are looking in to heating water with wood as well. Moving water is the bugger: pumps can be energy hogs. Although the new Grundfos ECM pumps are pretty dang good.

  26. Lucas Durand - 7A | | #26

    one can always run hydronic heat off a wood stove with a liquid heat exchange. There is more than enough heat from wood combustion if you can move it where you need and being off grid, a hybrid system (wood/hydronic) with a small pump is all you need to move and heat and with the addition of a tank, could store a days worth of heat too.

    I would advise against this. Getting some heat for DHW is one thing, but a woodstove is not the right appliance for running a hydronic space heating system - unless it's been especially designed for that purpose.

  27. GBA Editor
    Martin Holladay | | #27

    If the wood stove is running, you've got heat. No need to complicate a perfectly good wood stove by trying to connect it with a hydonic heating system with circulators.

    Has the architect talked to people who actually live off the grid?

  28. Riversong | | #28

    As I noted in the very first response to this thread, a woodstove with a designed-in water coil (don't add one or use a flue pipe coil, which interferes with exhaust flow and increases creosote formation), then there's no reason you can't thermosyphon hydronic heat to the bathroom above without a circulator.

    You can also use the woodstove, then, to heat or preheat your domestic hot water tank and this will effectively "store" the wood heat for slow return to the living space.

  29. Gord Schiller, Sooke, B.C. | | #29

    I like what everyone has suggested. My take on a couple of points:

    If you are going to be using beach wood as your source of firewood, your new stove will have a shortened life expectancy because the salt in the beach wood will corrode the stove and the flue (dispite the flue pipe being SSteel). Burning beach wood will void the manufacturers warranty. I highly recommend a Blaze King which is the stove I am currently using. It has long burn times and is one of the most environmentally friendly stoves on the market. So instead of your stove lasting you say twenty years, you will have to replace it more frequently along with the flue. Also, don't make the mistake that so many people make when heating primarily with wood and that is you have to prepare in advance for your next years wood requirements. It would be a good idea to incorporate a good size wood shed into the design of house, one that is not part of the house but adjacent to it with a covered roof between the wood shed and the house with doors at convenient locations to allow for provision of wood from your wood shed into the house. The wood shed should allow you to separate one years wood from the next. Burn times of the stove and efficiency of the stove will reduce the amount of wood that you burn and therefore the trickle down effect of not having to spend too much time cutting wood. Get yourself a gas operated wood splitter, saves your back and also makes it a lot safer when splitting the wood. Remember, accidents happen and being on an island you have to be extra cautious to work safe at all times. You should anticipate having to clean the flue yourself. Design your roof access so it is user friendly and as safe as possible. The flue should if at all possible be a straight flue from the top of the stove to the exit point through the roof. Zero bends equal efficient gas exhaust and easier cleaning.
    Please check out two articles in Fine Homebuilding, Jan. 2010 on energy-smart walls and also Mar. 2010 on Zero-energy homes.
    The long and short of it is, you have to do your homework, pick the building type that best suites you and go for it. It is amazing how much free advice is available out there, but it doesn't necessarily make it right. Remember, the building code is still required on islands and is in place to protect everyone.

  30. David Meiland | | #30

    Great point about roof design and access to the woodstove chimney. Getting to my chimney-top is roughly equivalent to the Hillary Step. I probably wouldn't have altered the building, but it makes for some annual excitement.

    I doubt the OP means to burn beach wood. Fir is probably plentiful and he shouldn't need much.

  31. R from Sooke | | #31

    Plan for the worst, hope for the best, plan on redundancy, have backups to each system, weather and sunshine in partcular are not something we have when you most need it, wood can also be a premium on a island. Design in "thermal mass", you might want to seriously look into ICF construction, for many good reasons, insulation, thermal mass, and being on a island, fire control. With a wood fireplace, position is extremely important, do not have it on exterior wall, much will be lost. Aside from the requirements, with the proper construction it is possible to build to a level that requires very little addtional heat to keep the whole place warm. A higher concern in this area, is humidity, venting and recapture of the heat loss in this area is very important, think heat exchanger, put with the power issue, passive air exchanging is important, heat in air rises, and will draw cool air with it, use it. Seasonal heat storage and exchange works, even here, luckily and mainly because we have only a short period time where heat is needed. As for power, look into wind power, in this area it generally is more prominent when power is most needed. Design two systems of electricity 120VAC AND 12VDC, think like a camper or motor home, not like a regular house, heat can be added by body heat, cooking, even a methane generator or ... other creative spots, don't waste it, keep the ceilings low, no wide open spaces to waste energy, doors on every space to close when the room is not needed or when the room is being used and the other side isn't. Look at designs from years ago when most houses only had wood heat, there were reasons they did things they way they did. You don't have to reinvent the wheel, just use it all to your advantage.

  32. Riversong | | #32

    Design in "thermal mass", you might want to seriously look into ICF construction,

    ICFs are one of the least effective configurations of mass and insulation. Thermal mass in an insulated structure has little value unless it is contiguous with the conditioned space.

    The most effective dynamic mass wall has at least 4" of dense, high specific heat mass (such as concrete) insulated only on the outside. Second best is a CIC wall (concrete, insulation, concrete) such as the ThermoMass system. The worst performing mass walls are ICI (insulation, concrete, insulation like ICFs) and interior insulated concrete walls.

  33. jim slack | | #33

    Ive built off grid and using ICFs. My current house is ICF and has radiant heat.

    ICF construction is feasible if concrete is available. It may be a great idea if building directly on exposed rock as the blocks can be scribed to meet the landform, and its a much better idea than piers. An ICF basement will not freeze in southern Ontario. PEX pipe in loops under 250 feet are the ideal way to transfer heat. Antifreeze can be added for freeze protection and the best installation method is to install the PEX in 1.5 inches of concrete. For a pump, I would think something wind powered would be ideal. I like the idea of a woodstove with a water jacket reservoir to heat the house, but to be effective a pump really is needed.

    PEX will be more resistant to cracking in the case of a freeze. I would certainly have all the pipes run thru interior walls and installed on a slight angle for draining.

    With the house oriented to the south, lots of energy efficient windows, and dark stone / ceramics to act as a heat sink, solar should supply most of the heating requirements in a well insulated tight home.

    A simple solution to leave a bit of heat on during an absence would be to leave a propane burner running. I think I would look at buying multiple 100# propane tanks and removing them for filling before paying to have a tanker barged over.

    Most off grid houses use a combination of solar and wind power generation, batteries, and minimal use of a backup generator to charge the batteries. I would suggest using larger than normal PEX piping for the domestic water supply, and instead of a pressurized system, have your water reserve at a high point in the house, and use gravity.

  34. GBA Editor
    Martin Holladay | | #34

    Jim,
    You wrote, "Most off grid houses use a combination of solar and wind power generation." In fact, most off-grid homes do NOT include a wind turbine. Almost all include a PV array.

    Good wind sites are rare.

  35. Riversong | | #35

    If you want to use ICFs, I would recommend Durisol which is made of recycled wood fiber and Portland cement - no petrochemical foams, fire and termite resistant, vapor-open and can be cut with a saw or accept a screw at any point. They are available from 6" to 14" thickness, and with mineral wool inserts to create up to R-28 mass walls with the insulation to the outside of the concrete cores. They accept any finish, including plaster and stucco, directly on the rough surface with no prep. And, because the material is self-draining, you can use a high-slump concrete with no loss of strength.

  36. GBA Editor
    Martin Holladay | | #36

    Robert,
    Are you sure that an R-28 Durisol wall is possible?

    Here are the Durisol R-values I have -- as provided by the manufacturer:

    Durisol WF30 Wall Form with 3.5” insert, plastered inside and out - R-20.6
    Durisol WF30 Wall Form with 3” insert, plastered inside and out - R-19.01
    Durisol WF25 Wall Form with 2” insert, plastered inside and out - R-15.4
    Durisol WF25 Wall Form with 1.5” insert, plastered inside and out - R-13.8
    Durisol WF30 Wall Form with no additional insulation, plastered inside and out - R-9.1

  37. Jim Tornillo | | #37

    I've recently completed an off grid second home in upstate NY and spent two months living in it from 22 October to 14 December. The keep it simple idea, along with a willingness to be flexible about heating, and electrical use is key.
    On thing no one has talked about yet is lighting. I incorporated gas lighting in every room. It works quite well even for reading, but it also provides heat. I have two lights in both the mud room and bathroom. The light(s) in the bathroom is on 24/7 in the winter. While I was there in Dec. the temp went to 3 degrees F., both lights were on that night. On the more temperate days, fourty degree range, the lights were the only source of heat in the entire building. As far as providing heat to a bedroom, you could locate it next to a room that had a space heater or gas light, and use hot air ducting work to move air between the rooms; don't forget a return.
    For electrical power I have a 7 KW generator and a pair of 2.4 KW inverter chargers. The battery bank is small, only 4, 115 Amp batteries connected in series parallel. Both the generator sense, and the well require 220 volts, hence the two inverters. While the batteries when full can fill the well tank (82 gal), most of the time the generator will come on. You might want to consider a cistern to store water (fill with the generator)and a 12 volt or 110 v pump to move water to your pressure tank.
    You also need a propane refridgerator, being off grid, an electric one just wont work. Another thing to consider is a propane stove, with pilot lights, not electronic ignition. The resistive load needed to operate the oven can be a problem. While a wood cook stove is quaint, they are hard to control and will overheat the home in both summer and winter. Also make sure your microwave and toaster are low wattage.
    For hot water I used a tankless propane system, that way when I drain the water, I don't put 50 or so gallons of hot water down the drain. Draining the water, and shutting down the electrical system will cost you a lot less than running the heat and electricity, and less chance of something going wrong and you comming back to a catastrophe.
    For heat I used a small wood stove and have three small non-vented propane heaters distributed throughout the building. One heater is in the basement and only used on exceptionally cold days to keep the water from freezing. The other two rarely come on when the wood stove is in use.
    During the two months I stayed at my "camp", I used 126 gallons of propane. The major users I believe were the refridgerator and the bathroom light, using about 60+ gallons of propane over the 54 days I was there.
    Good luck on your project.

  38. Riversong | | #38

    Martin,

    According to their 2007 size chart, they have a 5" insert that can offer R-28.

    Also here

  39. GBA Editor
    Martin Holladay | | #39

    Jim,
    You wrote, "You also need a propane refrigerator; being off grid, an electric one just won't work."

    I've lived off-grid for 35 years. For the past 18 years, I've had a Sunfrost electric refrigerator (model RF-12). It runs on 12 volts DC, has massively thick foam insulation, and runs on a small Danfoss compressor that uses 24 amp-hrs a day at 12 volts (equivalent to 0.29 kWh per day at 110 volts) when the room is at 70 degrees F. I charge my batteries with a PV array, supplemented during the dark months with a Honda gas-powered generator.

  40. Riversong | | #40

    Jim,

    A tight house should not have unvented combustion appliances, and gas lights are also unvented combustion appliances that will produce CO2 and water vapor and produce unwanted heat in the summer.

    A wood cookstove was traditionally used for space heating in small dwellings, and an outdoor summer kitchen for the warmer weather (especially for canning season).

  41. GBA Editor
    Martin Holladay | | #41

    Robert,
    Thanks for the links to the Durisol information. I wasn't aware of the R-28 option.

  42. Anonymous | | #42

    No one has suggested a masonry fireplace, which come with the option of preheating water, and also ovens, and efficient woodburning.

  43. Keith Turner | | #43

    Enjoying the discussion. We live in Harvard, MA. A large Shaker built, 3 story dormitory building in our historic district has a series of pipes running in a chase built within the chimney of a large Rumford fireplace. These pipes supply hot water to the second and third floors. Could such a system be adapted to your application?

  44. Chris K | | #44

    I'm interested to learn more about masonry heaters. Can they be configured to heat water or forced air?

  45. GBA Editor
    Martin Holladay | | #45

    Chris,
    Yes and yes, although the more pipes, pumps, and blowers you install, the more you violate the KISS principle.

    Masonry heaters are centuries old, and their main virtues are simplicity and dependable performance, without the need for bells and whistles.

  46. Chris K | | #46

    We need to figure out a way to get some heat squirted in to small areas of the home that are not close to the fireplace (which hopefully becomes a masonry heater..) location. In a perfect world I'd configure the floor plan to put the masonry heater central.. but it's at the opposite gable end. Thanks Mr. architect.
    So if we can find a way to efficiently move some hot air or water around we can keep from resorting to propane heaters.

  47. Riversong | | #47

    I agree with Martin. Masonry heaters are, ideally, centrally located in the house (they can also serve a structural purpose), and heat by radiation.

    But it's also easy to incorporate warm air or hot water systems as well as cookstoves and hot water gravity tanks. My old friend, Jonathan Von Ranson in Wendell MA, was one of the first builders of masonry heaters in the US (and he wrote the first article on them for FHB in the early 80s).

    The one he built for himself was triangular in cross-section. The side facing the living room had a true Rumford fireplace. The side facing the kitchen had a cast iron firebox, a built-in oven, a cast-iron cooktop, and a stainless steel water tank with a spigot. The top of the flue had a movable cap to seal in the heat once the fire was burned down to coals. A quick morning fire would generally heat his small house for a day or more. On very cold days, another quick evening fire, or a small fire in the fireplace would keep the house warm all night.

    In a very tight house, however, I would avoid the fireplace and simply use the airtight firebox - and provide it with outside combustion air.

  48. GBA Editor
    Martin Holladay | | #48

    Chris,
    It's tempting to generalize about a certain profession, but I'll restrain myself. Suffice it to say that a masonry heater, as you pointed out, does not belong at the gable end of the house, but right smack dab in the middle.

  49. Riversong | | #49

    Chris,

    A masonry heater cannot be exposed on the outside of a gable wall, like so many fireplace chimneys are, or it will be a heat loss element.

    If there's any way to reconfigure the house, I would do so.

  50. GBA Editor
    Martin Holladay | | #50

    Chris,
    I'm mulling this over. I want to be sure I understand the situation.

    An architect has designed an off-grid house, but hasn't yet figured out how to heat it? Moreover, the plans are so advanced that it is too late to locate the masonry heater in the center of the house -- because the architect has determined that the masonry heater belongs against a gable wall?

    And now you, the builder, are looking for advice on the Internet to figure out how off-grid homeowners usually heat their homes? In hopes, presumably, that an off-grid-friendly solution can be discovered before the house is finished?

  51. Chris Koehn | | #51

    Not too far off Martin..

    I am looking to many different sources for info and help with this; the GBA being one source among many. I am also working with solar folks, electricians and plumbers with off-grid experience, HVAC designers and contractors, etc. My strategy is to gather info from as many sources as I can, learn as much as I can, and move forward with proposing what I think is a viable program.

    I have been asked to G.C. this home, designed by an architect. I am being very wary of suggesting major changes to the clients as their relationship with the architect is long and much time and energy has been invested in design before I became involved. The supposition, until recently, has been that the home will be mostly heated and powered by propane, with a wood fired cook stove and fireplace. The owners wish to minimize propane usage and I am keen to help them with that.
    We are planning to do some PV. Wood heat will suffice for all of the major public spaces in the home, with a bathroom/mudroom and small second floor bedroom being too far from the wood heat sources for effective service by them alone.

    The wood cook stove is quite centrally located and one potential solution would be to change it to a Tuli Kivi / masonry heater type burner: big solar mass combined with central location and the ability to heat water or air might just solve our dilemma, while honouring the KISS principal..

    We have not begun construction yet. I am currently preparing a budget along-side these recommendations.

  52. Riversong | | #52

    As Dr. Joe once said: "energy conservation has the potential to destroy more buildings than architects."

    Though he might have gotten that backwards.

  53. Dan | | #53

    Does anyone know of any small wood cook stoves that are sealed combustion units? Does that even exist? I am designing a small tight house and would like to use a wood cook stove but I would rather it had it's own air source and didn't use mine.

  54. Chris K | | #54

    Dan I haven't run across one. But it's relatively common to have a custom bit of sheet metal fabricated and attached to the stove to accomplish this. Just want to be sure it allows plenty of air flow so draft isn't inhibited.

  55. GBA Editor
    Martin Holladay | | #55

    Dan,
    I don't know what you consider to be "small," but many manufacturers make airtight wood-burning cookstoves. Just Google "airtight wood cookstove."

    Here are a few links:
    http://www.chimneysweeponline.com/htoval.htm

    http://www.northerncookstoves.com/

    http://marginstoves.com/

    http://www.elmirastoveworks.com/fireview.aspx

    http://www.qualitycountryproducts.com/

  56. Mary Jacob | | #56

    I'm not a builder or an architect, just a remodeler, but my family has had an off-grid home in the Blue Mountains of eastern Oregon for decades. It is now seasonal; but my grandparents lived there year-round back in the 30's & 40's, with several feet of snow all winter. We still use it into the snow seasons for hunting, dealing with many conditions. I'll throw in my two cents, as we have loads of just practical experience...

    Sorry, but it would be dumb to put a tile floor in anywhere. Tile is cold, hard and not welcoming in the best of times, and surely not worth heating here. Put in wood or some waterproof flooring with rugs on it, period. This isn't the Hilton! Architects get way too fancy and unrealistic for off-grid. As has been said - K.I.S.S.!!

    A good woodburning cookstove (ours is a 1920-30 era South Bend Malleable Range, where we make the BEST sourdough pancakes!) with internal water heating coils going to an external hot water tank (with pressure relief) is a superb solution. This is to be plumbed into a good-sized, like 25-30 gallon tank, not just a 'bin' on the side of the stove. Every time you have a fire for a while, you have HOT water. Share the tank with solar pre-heated water and you have a real winner. We have a shower in our cabin, nice and toasty. BUT train the kids NOT TO JUST RUN the hot water, it's a precious and limited commodity! There's not enough to waste it trying to heat a floor with it, or heat from the stove, leave the heated floor out.

    The hot water tank also radiates heat when there is no fire, so don't hide it away in a closet, leave it in the open near the stove. A cookstove has a very small firebox, so is generally not made to hold a fire for hours. You can find good cookstoves in Amish country, they still make and sell them. Search the internet. The Amish are a good resource for lots of practical information for living off-grid. They have lived that way, full time, forever. Or, you're not too terribly far from Portland, call Buck's Stove in Portland.

    You will also want some other, "cool" method of cooking in the summer, as burning a fire in the cookstove for a couple meals will make the house unbearable in the summer. (Go swimming instead of taking a shower on these days). Put in a simple propane cooktop (vented), or have a propane camping stove to use outside, or a burner on the side of the BBQ. Wood fires are lovely in the cool weather, not in the heat. If they think they must have a microwave - maybe they shouldn't be looking at off-grid...

    The other stove should be a free-standing airtight heating stove, not a fireplace. It will maximize the radiant heat and hold a fire all night and will way more than adequately heat a 1600 sq ft house, when sized correctly. You won't need supplemental heat. Wood shed is a definite must, as suggested. DRY, seasoned wood is critical. We live on Mt. Hood, buried in snow, and a good woodstove is more than plenty here. In fact, it's usually too much and you'll have the doors open. That's all you need, and a little patience to get it warmed up.

    On to the electricity part - we have NO electricity or generator in our off-grid cabin, but we have a propane refrigerator, and it works great, even has a good freezer. Takes a little fine tuning to get the temperature just right, but works like a champ. And we have many propane mantle-lights overhead. Not exactly bright halogen bulbs, but more than adequate for a 'vacation' home, even enough for reading. Why do you need all the expensive, noisy generator, etc.? If they think they seriously NEED electricity for daily living, I'll repeat - maybe they shouldn't be looking to build off-grid....?? Leave the computer and TV behind. And yes, it's easy to add the generator just in case, I'm just saying there are many good, simple alternatives for some of the other utility needs. An off-grid home should be about taking advantage of everything that's natural - gravity feed, solar, wind (there is fairly reliable afternoon wind in the islands), gas, etc., before you start thinking you need pumps and electrical 'stuff'. BTW, speaking of pumps, where does the water come from?

    On to water - back to K.I.S.S. The water should just be drained every time they leave the home when it's likely to freeze. Keeping a remote home warm in the cold weather when you're far away is ridiculous - a constant worry. A HUGE unnecessary expense and risk on many levels - fire risk, or run the propane tank dry and the generator quits, or the space heaters quit, and you've got beaucoup water damage, etc. WHY TAKE THE CHANCE? A propane tank to service that without constant fills would take up half the property. Again - make it simple and easy with a simple plumbing system designed to be easily drained and easily turned back on. That's what we do, and it couldn't be easier. Make sure the water coils in the cookstove get drained as part of the system to avoid breakage, and make sure NO ONE BUILDS A FIRE IN THE COOKSTOVE WITH THE COIL-PIPES EMPTY!!!! That will ruin them.

    I would suggest that if this house is somewhat accessible and will frequently be empty, that the windows have locking shutters of some sort and good steel storm/screen doors over the entrance doors. We've had our cabin 'invaded' a few times and it is not accessible by road to the public, past our locked gate. They still walk in.

    Of course, all of this depends on how often these folks intend to use this house/cabin/retreat. If they live there full time, things change. If they don't brave the cold water and blustery winds to get out there for most of the winter, then this is the way to go. And if they do, this still works well. Tell the architect to actually live off-grid before designing cutesy-high tech things they will hate or find take up too much money and time to tinker with when they just want a vacation. Living this way is very relaxing and rewarding, and the simplicity of getting back to basics is the best part and should be the focus.

    Best of luck on this cool project. I spent my childhood sailing through those islands with my family (Dad built sailboats), and this area in the "sun belt" is a great place! They're lucky, and if done right, they'll find the simple pleasures and have a functional, easy to manage retreat for decades to come...

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