Passive solar + pole + bermed all rolled into one?

Hi

My wife and I have been planning for years to get off the grid and live a simpler life on a small farm. We just spent the first year on our new property. It's been hard work living and learning to survive off the grid. Except I've had to cheat a little using my electric generator. lol. But we have a clear water creek that never dries up. So rain catching is unimportant. At this point, I am ready to begin constructing our house. I am pretty much a DIY guy with a construction background. So I will be doing it all by myself with occasional help from my wife and daughter. I am posting a photo that shows where we are. The top left of the photo shows where the main country road is. Our driveway comes down and around to meet where our camper is sitting. It can continue on down to the valley below. So we are actually setting midway down a hillside. We have a large pad roughed in. Our camper is setting on the entry way and I have a small temporary porch built onto the side for last winter. The rest of the pad is big enough to easily build a 24x36 home. We decided on a single story with a gambrel roof. With 4 bedrooms at one end and the rest open (vault style). It will most certainly be a post frame set up. And the roof will be rafters. The reason why I am posting here is because I want the house to be passive solar WITHOUT A CONCRETE FLOOR. I am new at the whole passive solar idea. But being off grid is important here. In the photo my camera is pointing East. So the hillside behind us is actually facing South. We have a host of trees around us. Pretty much a whole mountain behind us.

I was wondering if there is a way to build a pole building home into the hillside behind us, bermed in. Even if it meant the need to build a concrete wall on the bermed side as a "retaining wall" to make things safe. Does this make sense? Or would it likely be unnecessary in designing a passive solar setup?

PHOTO

What's your location, and soil type?

Hi Jake..... Yes you can build your home into that south facing hill..... your soil looks like it has a lot of gravel (small rocks) in it... so it should drain well. If you are NOT in an area that gets a lot of winter sunshine..... then having passive solar heat collection will not be of much help... because it depends on the sun shining in from the south (at a low winter angle) and warming a large mass that holds heat. Most passive solar heating setups require lots of windows (glass) on the south side of the house..... and if MOST of your winter days are cloudy and grey then you would actually loose a lot of heat ..... through all that glass.
About berming into the hillside..... I have built many barns, greenhouses and hobbit homes, dug into hillsides or bermed.... I always do a cement block (with rebar driven into the ground, coming up through the holes in the blocks, and filled with cement)... or a mortared stone wall or poured concrete wall with rebar or heavy wire mesh..... this is to hold back the soil when it is totally saturated with water and wants to move downhill. It is important to put a good French drain (perforated pipe at least 4" dia, surrounded with gravel, UPHILL, at the base of the retaining wall..... before you back fill it with dirt... If I am doing this in a rainy climate (more than 24" annual precipitation), I put a waterproof membrane (pond liner) against the wall on the uphill side, curving it under the French drain and then back fill with the gravel (around drain) and dirt to the top of the wall.... I have built an underground Mandan Indian Earth Lodge.... in rainy western Oregon, this way...... and there were often small streams of water flowing out of the down hill end of the French drain tubes.....during heavy rains.....
Be sure to find out how many average days of winter sunshine you get there.... you need at least 20 days of sun out of every 30...... if it is mostly cloudy... then you could mortar stone all around your wood stove (except the door and the flat cooking top).... or you could build a stone wall behind your stove and put the stove right up against it............ thus the stones absorb all the heat and slowly release it during the night.... this is also a form of passive, massive heating...... We live in the southwest with over 300 days of sunshine a year..... most of the rain 24", in the summer as monsoons...... and we have an adobe (clay, sand & finely chopped straw) Floor..... it hold the heat nicely..... and we have a stone wall behind the wood cook stove..... all of this helps hold heat.... that is released at night... I hope this is helpful for you... best of everything to your family, Sunny

You don't necessarily need a *concrete* floor, but you do need heavy mass exposed to the solar input in order to be passive solar.

This can be done with water-filled barrels or the like, but with plenty of land and presumably a decent amount of stone judging by the terrain, I would think masonry would be very practical.

What is the reason you don't want a concrete floor? If it is comfort underfoot, you could limit the masonry floor mass to a smallish area near the southern exposure, and maybe even have a wood-framed and insulated floor a step or two above this level so any cold air would tend to flow down to meet the thermal mass.

If you just don't want Portland cement for ethical reasons, there are traditional earthen and stone masonry methods that will serve the purpose. Earthen floors with appropriate finish are said to be very comfortable, though I think they wouldn't stand up to the abuse that a wood floor could take.

Whether or not you can combine a pole structure with berming may depend on how dry or moist your climate is. Where the soil tends to be dry most of the year it may be practical (see the wofatis at Wheaton Labs), but if you have damp soil and groundwater, I would keep all wood above ground or thoroughly separated. Another consideration for berming is longevity. Do you want to build something that will serve for your lifetime, or for many generations? You can do a lot of things if you accept a finite lifespan for a structure.

At our school, all the buildings are passive solar heated only, and most are bermed into the south facing slope. I think it's probably really nice for the coolness in summer, but I suspect that that infinite cool mass at the back of the house makes it a little harder to warm the houses up in winter, and in particular, a little harder to keep the evenings toasty warm rather than just warm enough.

Our bermed walls are made of stone retaining wall, and the houses are made of earth, thick enough to be good thermal mass in their own right. They face precisely south, and are mainly heated by having greenhouses attached from October to April.

Also, an unexpected issue I can mention after living in these houses for 20 years, is that, not having a fridge, I can't find a shaded cold spot for food storage outside, or an unheated cold northern storeroom! Until we built an underground root cellar, we didn't have anyplace to keep fermented pickles for the winter.

Thank you all for such good advice. In my area, most people still use traditional methods of construction which of course all require costly methods to heat and cool. I am open minded with alternative methods. But my experience is limited to traditional construction. So I guess there's more for me to look into before I begin. The reason I don't want a concrete floor is because it would require bringing in trucks and workers to do the job. Frankly, I want to do it all myself. And the cement and labor costs in this area are outrageous. Thus, I am looking for alternatives. We originally contemplated just building an underground concrete home, dry stacked, filled, and stucco. But the cost involved doesn't fit with our budget. This is all out of pocket. And we no longer deal with credit or banks. The whole idea is to be self sufficient, off grid, and "no longer part of the system". At least as much as possible.

We do receive a fair amount of sun low in the sky throughout the winter. But there's no doubt we get plenty of gray too. I was indeed thinking of the idea of putting up a wall of mass and letting the sun come into the front windows to hit it during the day. I just did not know if it would work incorporating it into the South facing wall, or if I needed to just put it up in the middle of the house. Possibly around the wood stove as mentioned before. It would certainly be much more economical for us to just put up a pole house using this method and foregoing the bermed hillside idea at this time.

this is also what i would like to build. you can see my stumblings,
ideas and research here --> greenhouse/cabin.

i am still dreaming of this, maybe can actually work out trying to build this in the next couple of years....i have a couple of good leads on possibly where. looking for the right south facing hillside =) and atm, maybe even a few possibilities.

i have been drawing that again, started over from scratch though. the footings i drew were a bit too large, and i want to try to shrink it smaller, again.

anywho i think you would be interested to research the PAHS umbrella house ideas, geothermal, and
Subterranean Heating and Cooling System (SHCS).

if it is the costs associated with ready to pour concrete that makes you shy away from it, you could do it considerably cheaper by learning slipform stone masonry, how to make stablilized earth, or by using only minimal amounts of concrete/cement in essential areas, combining them with earthen plaster walls and floor.
and/or with wood, but only for the part not bermed.
light clay straw is one method of making earth walls, which works with post and beam.

if you have a large area of rocks, gravel, sand and clay for free you can work out mixes with your local materials, adding small portions of bag cement and various masonry mixes, so that the costs of the materials is significantly cheaper. in this way you could use what comes out of your hole, and other nearby areas, to then supplement the cement and /or lime /etc...purchased bag materials.

however "free" does not consider the costs of this kind of work for your muscles and back!!! even some small earth mover can make this more realistic.

Leila

Thanks for the great info. I like the straw/clay idea. I could probably make that work. We have virtually unlimited rock gravel, and sand where I live. Our clear water creek runs all year long. And never runs out of rock and sand. I never thought about the idea of making my own cement.

hopefully this wont come across as being a stickler, but just to be informative - you would be striving to make your own CONCRETE, not cement.

although those words could seem to mean the same thing, cement is one part of concrete, the other parts being sand, gravel, and sometimes other things. the cement is the part that *cements* it together!

some people want to use as little cement as possible, and make something thats called stabilized earth, or soil crete, or perhaps other names as well. this is sand, gravel, and your local soil (subsoil actually) clay/loam/whatever your subsoil consists of....added to cement from a purchased bag. some people prefer to use lime, other bag mixes, and a lot of variation...and are trying to get the cement portion to be as little as possible (like 5-15 percent cement, 85-95% other things)...but maybe more like 20-30 percent cement, and the rest from your land, should be easier to pull off a nice solid concrete, or soil crete.

this is already cheaper than buying bag concrete, as the sand/gravel is "free" ...and a lot cheaper than getting a ready made concrete mix delivered by truck.
doing something like slipform masonry with rocks, is going to be much cheaper than doing all concrete, as the rocks will be filling up the volume and stretching your bag cement further.

If you are in Georgia, you have more cooling than heating to worry about, and a mass wall may be appropriate. But I suspect light straw clay exterior walls could give a good balance of mass to insulation for your climate, and big overhangs will serve multiple functions. I would suggest investigating rubble trench footings and a raised earth floor, which will give coolth in the summer, and an interior masonry mass wall surrounding or incorporating an RMH and exposed to winter sun. I suspect any wood in the ground (unless treated with nasty chemicals, or an extreme rot-resistant wood like black locust) would have a short lifespan. A solid stone plinth to support a timber frame (could be simple joinery, not necessarily all mortise-and-tenon) could last several lifetimes if built well.

Slipform seems like a great idea considering we have unlimited rocks and stones of every size here. I've never done it before. But would gladly learn the trade.

I am also toying with the idea of using a TROMBE WALL for the passive solar. We live in KY. So we have equal amounts of warm and cold. Sometimes more cold. Although I realize that sunlight may be limited at times. But its just my thinking to cut back on wood burning whenever the sun is shining. And also using the windows to heat up various objects in the house. I wonder if a slipform wall would still work as well for a trombe wall? My wife loves the idea of doing slipform for the whole house. Similar to this. https://upload.wikimedia.org/wikipedia/commons/4/4b/Finished_Slipform_Stone_House.jpg