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Community and Q&A

Using hydronic in-floor heat in a superinsulated earth-bermed house

Grissom | Posted in Energy Efficiency and Durability on

I’m planning an earth-bermed house at the 4,000 foot elevation in the mountains of eastern Washington. it will be single story, 8 foot 6″ or 8″ ICF walls on the sides and back. Back fill to 6″ from the top of the wall.
The front will have a double 4″ ICF front wall 2′ tall and then double framed walls with thermal break to the top. This is south facing. front wall insulation is cellulose at about 18″ thick but mostly windows 140 sq.ft on a 340 sq. ft. wall.
The floor will be 2″ or 4″ insulation with 4″ concrete floor.
I will use prefabbed trusses with a 18″ heal on the wall with hard foam on the outside and cellulose in the attic to a depth of 2′.
Super sealed all the way around.
about 1400 sf on the floor plan. But the back 5′ deep 40′ wide will be unheated mechanical and pantry space.
I may put in a small gas fireplace for ambiance and some heating with the possibility of a small woodburning stove.
Temps in the winter are typically teens at day and single digit at night during the coldest months.
14 miles from the Canadian boarder.
Wrestling with radiant hydronic in floor for heating or not.trying to do off grid as much as possible.

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Replies

  1. User avatar GBA Editor
    Martin Holladay | | #1

    Grissom,
    You forgot to ask a question.

    One important point to remember with a earth-bermed house is providing emergency egress routes in case of a fire. Remember to include a properly sized egress window from every bedroom. All you've got is your south wall; every other direction is blocked.

    If you are building an off-grid house, you'll find it impossible to run a hydronic system off your batteries in winter, so I don't recommend hydronic heat. For more information, see How to Design an Off-Grid House.

  2. Andrew Bater | | #2

    Martin, I think your lack of love for hydronic heating is showing a bit here.

    Grissom appears to be in a heating dominated climate/scenario. He may not need a unit capable of air-conditioning (read heat pump or other type of compressor) that would trip up other off grid scenarios.

    Perhaps he could use a high efficiency wall hung propane fed boiler for his radiant heat source. Coupled with a little low wattage pump, that might do the trick for him.

    (I suppose he might need a dehumidifier too.)

  3. User avatar GBA Editor
    Martin Holladay | | #3

    Andrew,
    Like Grissom, I live in a heating dominated climate without the need for air conditioning. I live in an off-grid house. A wall-hung propane boiler requires electricity to operate -- most have powered venting -- and hydronic systems require pumps. When you need heat, the days are short and cloudy, so you end up operating this system with a gasoline-powered generator. It makes more sense to install a propane heater with through-the-wall venting -- a type of heating appliance that doesn't require electricity.

    Many of my friends who live off the grid have tried to install hydronic heating systems and have later abandoned the systems because the boiler and circulators depleted their batteries at the time of year when days are short and cloudy.

    But, hey -- Grissom can always give it a try. Report back here after five years.

  4. Andrew Bater | | #4

    Perhaps Dana Dorsett and Richard McGrath could be convinced to collaborate on an analysis whether this could work with today's ECM motors, storage batteries, etc.

  5. User avatar
    Dana Dorsett | | #5

    Hydronic heating is a TERRIBLE idea for an off-grid house- seriously! It's all pain for no gain, requiring a lot more battery & PV than would otherwise be needed.

    Heating with wood is a reasonable & reliable way to go in Okanogan, Ferry, Stevens & Pend Oreille counties, with plenty of nearby forest to cull from. The smallest woodstoves could handle the modest loads of a house like that, at a fraction of the installed cost of a hydronic solution and the off-grid power to support it.

  6. Grissom | | #6

    Thank you for the prompt on not posting a clear question.
    I do have an access point that will come in through the back. Yes I'm in a dominant heat area and A/C is unnecessary. I'm a contractor and have built many homes some with radiant but never with this configuration. it is my own home.
    I appreciate the answers so far.
    the question is what type of heating is best. I've leaned towards In Floor Hydronics but not sure if that is actually needed after reading many of the forums on it.
    This house will be of a Passive Solar design. the burming is more that the house will be buried in a ridge with southern exposure and a super insulated roof.
    Cost is an issue and I do have grid power but don't want to rely on it and transition to offgrid.
    Looking for suggestions on the best way to keep this comfortable for my wife and others. I understand that the floor won't be warm to the touch necessarily but it may also be too much for the amount of insulation capabilities I'm installing.
    As a side note, when I back fill there will be a 1' sealed area of sand and gravel next to the house walls a vertical 2" foam board and then a waterproof membrane on the outside of that going up to the top of the foam board and back to the house under the eaves to seal out any moisture. this will provide an additional layer of mass and insulation barrier. Yes I will be waterproofing the outside of the ICF walls too.
    as you can see the amount of insulation and heat sink will be significant. Heating may not require much.
    I'm looking for suggestions on the best way to heat. been leaning towards hydronic and believe its the best with proper mass but may be over kill for how we are building this.
    Yes bedrooms have egress windows built in and will be using a whole house HRV.
    LPG range, maybe that for dryer and HW.
    thankyou for all your input.

  7. User avatar GBA Editor
    Martin Holladay | | #7

    Grissom,
    Your decision about the best heating system will be based in part about how serious you are about going off-grid. I have lived in an off-grid house for 43 years, and I can honestly say that there is no advantage to making your own electricity. My electricity is far more costly than grid power, and is very limited. In the summer, when my photovoltaic panels produce more electricity than I can use, I can't sell my surplus power or get credit for it. The extra summer power is wasted.

    Grid power is also more environmentally friendly than off-grid power, which depends on gasoline-powered generators or propane-powered generators, as well as nasty lead-acid batteries.

    So anyone who can hook up to the grid should do so, with gratitude, and should stay hooked up.

    If you are serious about going off grid, you should take the advice given by Dana Dorsett and me and drop the idea of hydronic heat.

    For more information, see this article: All About Radiant Floors.

  8. Richard McGrath | | #8

    Most well thought out off grid homes are designed with a generator of some sort on site . He stated that he is trying to go Off Grid as much as possible . How off grid do you want to be ? In your location , would Lp be readily delivered if you ran out ?

    Grissom , what fuels are available at your site ? Does the Sun shine in this crazy off grid place , how often if so . Martin will undoubtedly say you should go with solar pv panels to make electricity and will then say that solar thermal to produce hot water and heat is a waste of time or to quote , " Solar thermal is really , really dead " . Problem with that statement is that this is just plain wrong , most systems that he refers to were poorly done for any number of reasons , most because some early installers and those still around make fatal mistakes thinking they were / are intelligent .

    Let us not forget what type home is being built , my gut tells me that this is a lowest possible load house due to it's construction . Unlike solar Pv , it is relatively inexpensive to store heat energy year round and use it as you need it while taking into consideration that the system may need help occasionally and designing accordingly . Living off grid should not and does not have to just accept comfort consequences which by the way can lead to health issues .

    I for one would rather enjoy an honest debate on this topic without all the horror stories of days gone by and systems designed and installed by those who believed they were the one that could fool Mother Nature .

    As far as boilers and circulators draining or depleting batteries , that is where it gets circuitous . There is just no need to utilize these types of equipment anymore . Envisioning the loads that this house will experience , any one of these circulators would be bigger than necessary while being among the smallest , least power consuming .
    .

    Imagine how much energy would be required to move 1-3 gpm through some tubing embedded or even in the ceiling from a tank full of stored water . See , Sunrise House in Fairbanks , Al . Due to location , size I am not suggesting that you need a 5000 gallon tank nor that it must be inside the envelope

    Wondering how this homeowner will feel after 3 more years , not off grid , but very happy with comfort , first cost , and fuel usage of his radiant , concrete floor . 4000 sf , heat , hot water , cooking , clothes dryer , 4 adults . Those hydronic radiant floors sure do suck terribly .

    Let ne be clear , I have the utmost respect for both Martin , Dana and others here who are just misinformed or have not found the right people to assist them in the proper uses of hydronic systems .

  9. User avatar GBA Editor
    Martin Holladay | | #9

    Richard,
    You may think I'm misinformed. But I have lots of practical off-grid experience under my belt.

    Most people who opine about off-grid systems haven't lived that way for decades, as I have.

    If Grissom wants to keep his new house connected to the grid, it's entirely reasonable to install a hydronic heating system if he wants to.

  10. Richard McGrath | | #10

    No need to get salty Martin . That was not a personal attack .

    I have always just wanted for truthful information to be shared wit those who can benefit from it . That being said , as in damned near all industries nowadays , technical savvy , proper design and install is always in question .

  11. User avatar GBA Editor
    Martin Holladay | | #11

    Richard,
    Not to belabor a point, but I was quoting you. You wrote that Dana and I are misinformed.

  12. User avatar
    Dana Dorsett | | #12

    The wintertime insolation in that neck of the woods is quite robust, and passive solar works really well, even on less-insulated homes with less thermal mass than the one described. A friend of mine (now in his early 80s) sold his 70 acres of spruce & cedar on the Colville res a few years ago that had two off-grid cabins, one an old geodedic survey line cabin near the bottom of a mostly shaded ravine, the other a newer passive solar cabin, built in stages during the 1980s & 1990s a hundred or so yards up the hill on the sunny slope of the ravine. The woodpile at the passive solar cabin went basically un-used. This was no PassiveHouse and not even close to the performance of at 4" + 4" ICF.

    The rainy season on the northern tier counties of WA is primarily the spring, peaking in late spring. Winters tend to be clear and dry, with VERY good sun, with solar uptake often enhanced by snow cover in the late-December through late February time frame, particularly at altitude (4000' is high enough.) It can be overcast in winter at 2000' but often enough it's "bright clouds" type of overcast. There are many days when the top of the cloud deck will be BELOW 4000', with back-scatter insolation from the tops of the cloud layer boosting the passive solar.

    Building a heating system with the complexity of a hydronic floor with solar thermal stored in tanks just doesn't make much sense, to manage the pipsqueak load of a well designed passive solar house in that location. Many or even most days the average heat load will likely be negative, even in winter.

    Even at 4k' there is likely to be a significant peak air conditioning load- lots of sunny days with peak temps in the low 80s, with sun until well after 9PM near the solstice, but in that location it can be managed by night time ventilation + day time window shading, without mechanical cooling.

  13. Richard McGrath | | #13

    You cannot stop at misinformed and not include the rest of the thought in this effort Martin , it becomes a misrepresentation of my comment and thought .

    "Let ne be clear , I have the utmost respect for both Martin , Dana and others here who are just misinformed or have not found the right people to assist them in the proper uses of hydronic systems ."

    The full comment offers more than me saying you and others are wrong , there was an alternative

  14. User avatar
    Dana Dorsett | | #14

    Just curious, but for purposes of possibly getting extremely local weather profiles, got a ZIP code?

  15. Jon R | | #15

    You need to be clearer about the priorities you put on being green, convenience, comfort, avoidance of grid power, up-front cost, operating cost, etc.

    For example, the designer found hydronic quite useful.

    It's possible (but not likely practical) to build hydronic systems that distribute heat with no power (just convection).

    ICFs aren't very effective in terms of internal thermal mass.

  16. Grissom | | #16

    So it seems like I've created a little firestorm here.
    Here is the point; I've spent a bit of time designing this house and thinking it through. While along the lines of a passive design it is not a complete passive house. I've made it as insulated as reasonably possible.
    I'm just looking for input on whether I need in floor heating or what type of heating might make the most sense.
    Summer is no problem our current three bedroom above ground does fine with open windows at night and closed during the day. well insulated but not near as well as the new house.
    the floor will be completly insulated from the ground and and cement walls.

  17. Grissom | | #17

    So it seems like I've created a little firestorm here.
    Here is the point; I've spent a bit of time designing this house and thinking it through. While along the lines of a passive design it is not a complete passive house. I've made it as insulated as reasonably possible.
    I'm just looking for input on whether I need in floor heating or what type of heating might make the most sense.
    Summer is no problem our current three bedroom above ground does fine with open windows at night and closed during the day. well insulated but not near as well as the new house.
    the floor will be completly insulated from the ground and and cement walls.

  18. Andrew Bater | | #18

    This is ChevyCamaroLovers.c*m, you have asked a Ford Mustang question.

    There are very few proponents of hydronic heat on GBA, and largely for good reason. These systems are often expensive, complicated, and difficult to implement. I am quite surprised that no one suggested you use a mini-split, that is the most common response, and rightly so.

    It says a lot to Martin's and site owner Taunton's integrity that they discourage folks from making impractical decisions, even though there are advertisers of some of those products on the websites and in the magazines.

    Personally, I think what you want to do is possible, but I am clearly biased having come out of a commercial environment where water based systems are the most effective mechanism for moving heat. Coupled with that I live in a passive solar home with radiant heat, well it's obvious I am going to root for you.

    If you want someone to do the pumping and heat source electrical load calculations, your man is John Siegenthaler, P.E. You might even be able to convince John to do it for free; he likes interested challenges that he can feature in his articles in PM Engineer magazine.

    PS Grissom, the electrical grid is wonderful. I endorse using it if possible!

  19. User avatar GBA Editor
    Martin Holladay | | #19

    Grissom,
    Andrew Bater correctly described the usual GBA advice: If your new house will have grid power, it's hard to beat one or two ductless minisplits.

    If you are interested in information on heating a house that is connected to the electricity grid, here are links to two relevant articles:

    Heating a Tight, Well-Insulated House

    Choosing HVAC Equipment for an Energy-Efficient Home

  20. User avatar
    Dana Dorsett | | #20

    Hydronics are definitely an efficient way to move heat (by FAR superior do ducted air!) but when the amount of heat that you need to move is miniscule (as in a SUPERINSULATED house )the expense & complexity cease to make financial or even comfort sense.

    Then there are the carbon-emissions and other environmental costs of fossil burners vs. leveraging grid power with heat pumps. An electric boiler can be low carb (especially in hydro and increasingly wind-heavy WA) , but expensive to operate, ridiculously expensive in an off-grid environment. It would be nice if there were more small-scale air to water heat pump solutions to choose from, and the local expertise to design and install such systems. (It would be nice if $100 bills grew on my houseplants too. ) But from a practical point of view even ductless air source heat pumps are a stretch in some locations due to lack of local support, despite being easy to design around for low-load homes.

    But for off grid heat pumps don't make sense either. I'm sticking with optimizing the passive solar aspects and heating with wood for this one, if the goal is to be able to eventually cut the umbilicus with the utility.

  21. Grissom | | #21

    Thank you Andrew and Martin. I will look into both of those resources. And you also described the issues that I have faced in resolving this issue of how to efficiently heat a home.
    There seems to be so much conflicting information and many have their soapbox that they honestly believe is the correct approach.
    There needs, in my opinion, to be a group that can lay out the different options that are available and how they fit within the different design parameters. Obviously with changes in technology there will be changes in the approach to heating.
    Some people honestly want to be off grid and not be hampered by design restrictions of a passive solar house. As a former builder I realize what i'm bringing up is not necessarily as simple as it seems. But there should be a comprehensive discussion of all the different methodologies for heating and living in a home that would incorporate grid and off grid.
    Too many people go one way or the other and don't consider all the information and how it can be utilized in concert with good design and living style.
    Someone posted that the cost of Solar was actually more than grid. I understand this and agree when you consider all the initial cost and design and then add in the maintenance and replacement through the life. But looking at efficient ways to change how we live without compromising design and livability and restrictive lilving spaces seems like an area that hasn't been fully explored and or presented.
    A book would be outdated by the time it got to press with the changes in technology. For someone like me having a way to look at all the options incorporating geography, climate, design options, living options.....etc. while daunting, would provide most individuals with a great source to start with, who may not know anything other than they want to make a change.
    Thank you all for your input. I will continue this quest.

  22. User avatar GBA Editor
    Martin Holladay | | #22

    Grissom,
    I can assure you that GBA strives to be the resource you seek: a web site that honestly "lays out the different options that are available and how they fit within the different design parameters."

    The two articles I linked to in my Comment #19 present the advice of John Straube, a respected expert, and me on the best ways in heat a low-load house. Since those articles have been written, the performance of ductless and ducted minisplit units has gotten even better, strengthening the argument in favor of minisplits. Minisplits work well with a grid-connected PV system, and allow designers to prepare for a fossil-fuel-free future.

    Going off-grid introduces many complications to the picture, however, which is why fewer than 1% of Americans live in a off-grid house. It's tough to live in an off-grid house, which is why I devoted a special article to the challenges of anyone willing to scale that cliff. Here again is the link: How to Design an Off-Grid House.

  23. Grissom | | #23

    Thank you Dana
    If I had the budget I would do this design with a basement level for mechanical. A wood burning stove with a very large heat storage unit in the basement to store as close to 100% as possible and let it either radiate up through the live floor or utilize the natural convection principles with floor grates or ductwork. No fans or mechanical and a fire every few days. Kind of like a heater, Kang, fireplace or modified Rocket mass heater.
    A large super insulated HW storage system with wood and solar HW heating.
    Thank you all for your input. I hope I've stimulated some conversation as well as collecting more information for my project. Looking to help others as well in the future.

  24. Grissom | | #24

    Thank you Martin

  25. Richard McGrath | | #25

    What you just described is EXACTLY what I am talking about . Solar thermal , highly insulated
    ( coccoon tank ), and a DC ECM circ probably using about 13 watts to move the fluid . Store , Sip and stay warm . When necessary light a fire to replenish . Multi source ! Maybe even radiant ceilings as opposed to floors , capable of same work using 40% less area and tubing .

  26. Grissom | | #26

    one area that has been overlooked and maybe isn't practical is Solar Air Heating. many years ago it was experimented with and even a book written which is out of print and I have a copy of.
    The problem was that they didn't have an efficient storage method with it. You can do similar with Solar water and heat transfer.
    Using a Solar Air Heater with ductwork and a basement or lower mass storage unit you can use the natural convection and gravity dampers/check valves, to move the heated air through your heat mass storage unit. using ducting in the house you can move the heat out of there and circulate using the same natural convection principles. or just let the heat rise out of the unit to the floor of your home.
    they heat up quicker than solar water and with the proper ducting will move air without pumps or fans. A heat storage can be a concrete box with larger washed gravel or rocks with inlets and outlets top and bottom for convection. Theory and facts combined. It all can run with no electircity and supplemented with wood heat. I think it would work well in a Super insulated home.

  27. Malcolm Taylor | | #27

    Grissom,

    I had several of those books in the 70's too. Saunders Super Solar Houses and others. They were immensely interesting and part of the reason I became an architect. The reason they are out of print, and that similar ones have not replaced them, is that the approach they suggested has been supplanted by other much simpler more effective ways of achieving the same result. Saunders himself moved away from mass storage solar and instead concentrated on super-insulation.

    A well insulated and air-sealed house has a heating and cooling load that makes the large scale investment in mass storage and passive solar features unnecessary. That's why you are getting the advice you do here in GBA. At this point using small heat pumps or investing in PV panels appears to make a lot more sense. In the future this approach will no doubt be supplanted by something even more efficient, but it's a safe bet it won't be hydronic systems or mass heat storage.

    From an architectural point of view, a welcome outcome of abandoning the Saunder's type approach has been that the houses don't have to be modified to be efficient. You don't end up living in a large machine designed to store energy, and can use the space for other things, or eliminate it altogether.

  28. Grissom | | #28

    Great points Malcom and understood.
    I think for me as I ponder all of these comments has been to realize that there is a small section of society that wants to be off grid as much as possible. But still wants to maintain a somewhat modern, easily maintained lifestyle and living standard without the intense work of collecting and burning wood and all else.
    it's having our foot in both worlds of "off grid" and convenience that is the challenge.
    I appreciate the patience and input of all on this forum. First time to really dive into this type of communication format.
    My take a way's so far are: energy evaluation by a competent advisor on my structure with climate 1st. Based upon this evaluation look at the different options for the BTU's needed.
    At that point the work begins with determining the system to use. this forum has helped me to narrow it down immensly. while I like radiant floor, I think budget wise it doesn't make sense.
    thank you all especially Martin for your valuable articles and experience. Not to disrespect any of the rest of you and your expertice either.

  29. User avatar
    Brian Knight | | #29

    Consider me a typical GBA reader who agrees with staying in grid and away from hydronic heating. Your passive solar ideas seem outdated, troublesome and needlessly expensive. All you need is well designed windows and maybe some extra mass in the floor.

    https://lakesideca.info/blogs/dept/guest-blogs/cost-effective-passive-solar-design

  30. Grissom | | #30

    Thank you Brian. your points are noted.

  31. Malcolm Taylor | | #31

    Grissom,

    Good luck with your project. If you put as much thought into the design of your house as you are doing its energy use, you will end up with a delightful place to live.

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