I'm designing a house which I would like to utilize radiant warming in the earthen floors. Does anybody have experience with laying PEX tubing or other radiant technologies within earthen floors? All of the literature online only discusses burying the tubes in cement or under floorboards. Ianto Evans' 'The Hand Sculpted House' discusses hydronic heating within cob floors as an option for heating, but doesn't dive into the specifics of the process. There are many companies online who now install these technologies with conventional materials, but I haven't found anything regarding natural floors. Other than the flooring material, I would like the rest of the system to be the same as other contemporary systems: Water heated by a tankless water heater enclosed in separate loops throughout the house.
Radiant heat is a great choice. For starters, the best thing to do is utilize the sun from sun facing windows, floors and walls that has high heat-cool, moisture holding capability such as earth coupled to the winter sun, over hangs, trees, awning's, etc to block the sun on hot summers. Looping the micro-coils won't change from concrete standards to earth, just tie them down and apply a scratch coat with a higher binder content to hold it all in place, along with fasteners...that is the easy part.
Depending on how air tight you build, how many people will be coupled to the radiant heat sources of walls and floors, how much hot water demand, heat and cooling loads, that is hard part. Another free source are solar thermal tubes that are easy to build yourself, coupled to PV more costly upfront.
I'm not sure where you getting that a tank-less system will handle your demands fast enough, but a good start would be do offer a system diagram including loads and capacities for review. Not impossible, but some with the right efficient envelope in cold climates like PA I have seen need very little to no HR, solar enough, no mechanical s. I'm thinking the best approach is to design a passive system(solar thermal panels, walls, floors, etc) and build it with active provisions in place, including ventilation, hybrids, determine the unit capacitys if any after the build and some testing.
One thing is for sure I don't subscribe to "HR is Dead" popular today, that designs HVAC to buildings, not people. When you factor in people some mini-splits tied to PV does not show better. Solar thermal to electric resistance makes more sense.
Here what I was talking about from the link I provided....Look how many BTUs are required for a high performance building vs low, almost 3/4 less.
"Therefore, when we use the term Radiant Based HVAC Systems, please understand we are talking about the body’s radiant heat transfer to and from the built environment (see Table 1.) and controlling it first with architecture then with mechanical solutions.
As illustrated below, low performing buildings using traditional heating systems need high fluid temperatures in heating (and low temperatures in cooling) but only a high performance building can use low temperatures in heating and high temperatures in cooling. In fact with high performing buildings, using radiant cooling and heating, conductive floors and close tube spacing, fluid and surface temperatures operate close to the core body temperature and enable maximum efficiency from the heating and cooling plant. How "close" the tubes are does not have to be an exact science, but I'd put them closer for a concrete slab than earth since earth has a better thermal and hygroscopic property or effect.
here it says to get the tubes around 12" OC. For bare feet, the more dense the mix the hotter. Use concrete as a guide. The specific heat and conductivitiy is not that far from it I know of.
Radiant panels outperform in-floor radiant heat designs because heat travels in all directions equally, but the amount of heat transfer is directly proportional to the temperature differential. So if you have your heat source right on the ground, a large portion will be dissipating into the earth. Radiant panels however, are inside the homes envelope, so they deliver all of their het to the home and it's occupants.
The other issue I have with your design is using a tankless water heater for heating is a disaster waiting to happen. I like to use a standard 40 gal. water heater if you want to heat on the cheap. This will require a stainless steel flat plate heat exchanger to separate the hydronic fluid from the hot water. A better system is to utilize solar gain as well with an 80-120 gal tank with 2 heat exchangers already built in.
The thing most people don't understand is that the tankless water heater also has standby losses in heating itself up and electrical usage by fans, motors and cpu. The efficiency gain stated on the unit is not going to be your efficiency, because that is only when the unit is condensing and operating at peak efficiency. This will be rare, most of the time the 40 gal tank will outperform a tankless.
If you want to discuss this further, post more details and we can go over this difficult subject that is filled with corporate misinformation.
One of the great things about hydronic heating is the zones. With a turn of a valve a zone is turned on or off. Maybe because my parents house had hydronic floor heat I’m biased. I grew up walking on cozy warm floors. The cat loved it. So I added hydronic floor heat to the house I remodeled and then to my Motorhome. And I plan on it for my Skoolie. Like nearly everything doing it well isnt as simple as it sounds. I read a textbook called Modern Hydronic Heating. But PEX pipe sure helps. My Dads house had copper in cement I’m assuming. It may have corroded long ago. I’ve seen it done in cob at Ray Kelleys. In a downstairs room that was always cold so they added a cob floor with PEX tubing.
Check out www.electrodacus.com . He is going to run and heat his Canadian house with all solar but will add 13,000 watts of solar. There’s no reason why hydronic couldn’t be all solar with enough panels.
I’d like to design a Permaculture wagon wheel shaped community for nomadic vehicles or tiny houses in zones around a central space. In the middle would be a big dome greenhouse with a RMH central boiler. Hydronic heat would be pumped to each zone on demand.