I want to install earthen floors in as many rooms as I can, in my small cabin, that I eventually want to take off the grid.
The living room is south facing, and I will install a rocket mass heater there, so I would have all the benefits of an earthen floor there. But, before I redo the living room, I will make the bedroom. It already has a big window facing north, I use papercrete as insulation and I will change the current wooden exterior with a stone wall. It will be around 30 cm thick, and then 12 cm papercrete.
I'm also planning a big window facing west - I will catch some sun there, so the stones will heat up, but not a whole lot, and the earthen floor will catch some sun, and give a lot more heat than the stone walls, but again, not a whole lot.. I have been living i hut made of stones, with no insulation, and in the summer its great, but in the winter it's a problem. It takes a long time to heat, and I have electric heating there in addition to a small woodstove. That is nothing like a rocket mass heater though - that said I have no personal experience with rocket mass heaters yet.
I also plan on fitting a window in the ceiling, I will put grass on the roof. So, the room will be well insulated, and since the hut is quite small, around 45 m2, I'm (..is this wishful...) thinking that the heat from the rocket mass heater in the living room will be enough - and that all the windows won’t matter too much - although we do get cold winters here, with snow and sometimes minus 20 degrees.. But that is not too often, since it's a costal climate - it's more than anything a very wet climate..
Some more details, the "deepest" part of this room is about 70 cm (from where the floor will be, down to the current rock/soil). On the north side it's about 30-40 cm, it's sloping to the east. There used to be a wooden floor, but all the materials were pretty rotten, it was built about 60 years ago. In the east I will build a new foundation, the kitchen will come next to the bedroom - but I plan on installing a wooden floor there, and see if I can’t have a small root cellar. All in all the room will be about 9 m2. I'm sure that it will work great in summer - but I'm a little worried that it could be too cold during the winter.
Best thing I have seen in these cases is in-floor heating. One roll of PEX tubing placed before you place the earthen floor. Heat the water by solar and/or the RMH. In-floor heating only needs 80-110 degree F water, easy to do from setting a tank near the RMH. Small circulator pump running from 12v. It is not "cheap" but it is a good solution that also helps dry the floor to prevent mold issues in wet climates.
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I agree with Scott. Pex or PVC laid prior to the floor finish is a extremely efficient way of heating via radiant floor heat and the benefits of keeping the floor dry if your going earthen are awesome as he stated.
Our design for the Rocket Stove Mass Heater will be a copper tube wrapped around the barrel portion and again as Scott pointed out a 12V Circulatory Pump and 12V Zone Valve will help to regulate the temperature. Excess heated water can be stored in your water heater and circulated to provide a adequate amount of piping hot water for showers or baths as well. The PEX or PVC tied into copper is fine for domestic use so even though you are using it for heating you can easily divert unused heated water to supplement your domestic use.
Our design will divert the excess water to a large 8 foot round 4 feet deep hot tub in the bathroom area and remain isolated from our domestic water simply because we love bath's, soaking and hot tubing. Also the area of our build gets a over abundance of sunlight so a small solar water heating panel and distilling chamber will do well for dishes, laundry and domestic uses. In a colder climate I would use the water heater for circulating the excess like I mentioned. Just a side note if the excess seems to be heating more than you need and reaching temps of say 200 degrees you might also install a few old retired water heaters inline to allow more flow and a increased storage capacity.
A small area set aside for say 3 side by side tanks (1 active 2 storage only) would not only give you a great storage capacity in a relatively small space but if insulated well be able to sustain a even temperature even as the stove runs down on wood throughout the evening. Also pressure relief valves do go bad and with three (1 on each tank) the likelihood of a rupture would be greatly diminished if the temperature of the water rose faster than you anticipated.
One last note on radiant floor heat... If your toes are warm you are warm... Its been my observation that homes heated this way can maintain a air temperature of 65 degrees or less and still be quite comfy... We all tend to have PJ's or some clothing on while relaxing but normally kick off the shoes and let the feet air out. A warm floor means a warm body so I am 100% convinced for efficiency and comfort warming the floor is imperative.
Since it's raining most days of the year here, water is an issue. Here are some pictures. To start with what you can't see, the room is facing west, and it will be covered with natural rocks on the outside (about 45cm) and then insulated with papercrete (about 10 cm - same way as in the hallway (pic)). I plan to use tadelakt as the final internal layer, which should make it waterproof. I reason that is a good idea, so moist will only be able to enter the walls from the outside. I will have one vent(but I'm not sure if I need one) since the window facing north has small built in vent - and I'm also planning another window facing west, and one in the roof.. The idea is that it will be very comfortable in summer, cool, with plenty of light, but still warm from the evening sun. I plan to fortify it, so I can install a grass roof.
How can I ever explain these pictures.... I will remove the rest of the chimney, and the concrete "thing" in the middle of the picture was there to keep the floor up. I will make that a part of a wall, to separate the bedroom from the kitchen. The exhaust from the rocket mass heater will exit through the small window. I will pass the heat through a bed, and then under the kitchen and bathroom floors. To make the floor I'm planning to start by placing big rocks at the bottom, then gradually smaller rocks, before I put gravel/sand. But from there I'm not sure, I'm actually contemplating using papercrete, and to make the floor with tadelakt as well, since it's waterproof, and papercrete insulates. I'm thinking that as long as moist is not coming from both directions, outside and inside (walls) and only from underneath (floor), then it should not be a problem. I've been studying the ground where the floor going to be, and no water is entering through the walls - same with the papercrete, it is never moist, and that is without the planned 45 cm of stones to protect it from the outside..
To try to connect the dots - the north of the house is in an inclination, behind an artificial dam made about 100 years ago. Further up there are marshlands - some tall trees are growing there and when we dug out the floor we removed several roots We have the well on this side of the house, about 10 meters higher than the ground level of the hut, and I have never seen it dry.
Regarding the topic of this thread, I'm not considering an earth floor anymore. The plan is to make the a wood floor in the center of the room, and tiles next to the walls. I would love to have hot water circulating in the floor, but things are taking so many years I might settle for an electric cable instead, since I've given up on the idea of going completly of grid. I still want the house to function prefectly without adding any elctricity to heat it etc - even when we are not there - but when we are there, I want to be able to heat the floor in what will be like a path, leading from the bathroom through the bedroom, passing the kitchen and finishing in the livingroom. Since the hut is very small, and I will insulate it very well, I hope this will be enough to live there comfortably most of the time.
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