Building Underground

I just received an email in which a man asked about using bales below grade, as in an earth-bermed house. He wants to use bales due to their high insulative value, but is concerned about the effects of moisture on the bales. I too would be concerned about the moisture. We are trying to figure out a way to make it work as it would be a great marriage for sure!

I suggested that if he could find a way to use a material that would provide a break between the bales and the backfill, it may be possible. In other words, he would need to place the backfill against a structural element (what is yet to be determined, but perhaps concrete and a plastic waterproof membrane?) that would provide the strength and protection from ground moisture. He could then stack bales (the back side pre dipped in plaster for fire protection) slightly away from that wall so to leave a ventilation channel between the bales and the backfill assembly. That channel may need mechanical help in providing adequate air movement to protect the bales from moisture.

Seems a bit over the top to me, but I would like to see what other options you may have for such a job. I would really like to see this as a possibility in the future. Thanks for any input you are willing to share.

13 Responses to Building Underground

  1. Frederik Thu, January 26, 2012 at 12:14 am #

    In his book “The New Ecological Home”, Daniel D. Chiras describes the house he built for himself. It is partially earth-sheltered, with an above grade, strawbale facade on the south side covered with a metal sheeted roof and solar panels. On the north side however, it has walls made of rammed earth tires and is below grade, with a green roof. He is apparently very satisfied with the results, although he acknowledges that making walls of rammed earth tires is very time consuming. I love his solution of an earth-sheltered house + green roof on the cold side, with a southern strawbale facade + solar panels on the sunny side. That pretty much perfectly combines the best of both systems in my opinion.

  2. Lot S. Sun, January 29, 2012 at 4:13 pm #

    I was thinking of using ferro cement as a break between the straw bales and the backfill. It then could be done very thin and on the cheap. Create some kind of verticle ribs attached to the cement for the bales to rest up against for the air space. If those ribs had holes through them, they could be used to stitch up the bales as they’re laid.

  3. Jeff Richardson Mon, January 30, 2012 at 3:48 pm #

    The main reason for an earth berm house is to take advantage of the natural regulating and insulating effects of the ground. Depending on location anything about 5 feet down or more maintains a pretty constant temperature. Therefore lots of insulation isn’t required, and might actually work against you in these locations. Myself, I would skip it, find a nice South facing slope and just use the straw bale at the exposed daylight walls.

  4. Nic Moodie Mon, January 30, 2012 at 6:50 pm #

    very interesting!
    Ive been mooting the idea for a few years for my ‘one day i will build” house. The introduction of green roofs to the mass market has created some pretty exciting membrane solutions that would create a high quality seal but the void gap sounds tricky.

    In my minds eye i had been toying with the idea of using earth ship style tyres and paacked earth to create Retaining walls with indoor/outdoor enclosed terrace below ground, with hay bale on outside facing walls and intensive green roof with membrane. not as “underground” as the picture above but moving towards… And a similarly low impact on the landscape and thermal properties.

  5. dirtdiver 5050 Mon, January 30, 2012 at 10:50 pm #

    What about earthbags wraped in 6 m poly. Then the bales on the inside. Would give you a frame and then you just complete the wall. Finnish by completly covering the structer!

  6. Andrew Morrison Fri, February 3, 2012 at 11:16 am #

    Indeed. This is a good, natrual material and the insulation value of bales really isn’t needed since the ground wil provide the insulation. Good idea.

  7. Spencer Wed, February 8, 2012 at 12:00 pm #

    It is my understanding that while earth berming provides a great system for regulating external conditions…as in mitigating the effects of wind and water and seasonal temperature changes, it isnt a great insulator. The ground can leech away heat. In the project I am planning at the moment I will be using passive solar heating as my main heating source. I am concerned that earth berming would reduce the effectiveness of the passive solar heating. I have read that a fair bit of heat can even be lost through the foundation!

  8. Michael Mc Cann Thu, February 9, 2012 at 11:58 am #

    Ok then, here’s one for you. I’m about to build this year following the Mike Renolds “Earthship” principals. However, instead of the earthen berm on the north side I plan to build with an adobe interior wall and strawbale exterior wall. Any suggestions on how this might go together and weather there might be moisture issues arise?
    Great blog by the way:)
    Taos, New Mexico

  9. lyle Wed, February 15, 2012 at 3:16 pm #

    Read the book Serious Straw Bale; filled with good information including some on this very subject. Roy-Brassard home in Quebec will prove of interest.

  10. Russ Tue, February 21, 2012 at 5:31 am #

    I am a sprayfoam contractor and I spray the standard concrete walls and even below the slab with 2 lb density CLOSED cell polyurethane foam. It would work great on the straw bales and create a monolithic water/vapor barrier at thicknesses above 2″. It would also give a very high insulation value. I would recommend spraying the foam below the slab and then spraying the foam against the walls and tying into the foam sprayed below the slab giving the full barrier.

  11. Marco Pombo Fri, February 24, 2012 at 12:52 pm #

    A hybrid underground/strawbale house is a beautiful thing…but like any good thing, the better the prep, the better the result.I think the cost/time benefit of bales below grade is not favorable but some things have been done with “vertical crawl space” (a chamber between back wall and hillside)which may work for you…obviously a roof sytem needs to extend back beond the cavity to a retaining wall or “foundation” of some sort.Tire footings with a pier and earthbag infiil might be nice for this “envelope”.

  12. Walt Dutton Tue, March 6, 2012 at 9:04 am #

    I’ve had a little experience in trying to prevent water from getting at or into structures built partially surrounded by dirt. The problem really is that water doesn’t give up, and what may seem watertight one year may be soggy the next. The absolute best idea seems to be to keep that water running away from your structure, not toward it. You can do more good by careful grading uphill of your building than you can by trying to outsmart the water at your wall or foundation.

    The natural tendency is to select a side hill location so three sides can be against the dirt and one side can be open for access. But water runs down hillsides all the time, and you have to select a patch of ground that is naturally dry. Another approach is to build above ground and then ramp the dirt up around three sides. Still another approach that has worked is to allow not just inches but two to three feet of space between a retaining wall (which could be a dry stone wall) and the wall of the building, with a tile or perforated pipe curtain drain laid at the bottom of the free space. This allows air to circulate and also gives you acces to your building wall for maintenance, and if you have water around you will have maintenance.

    Having the wall exposed to the air in this way does rob you of the insulating properties of dry earth, but the wall will be protected from the wind and any dead air space will give you some insulating effect.

    Finally, I like to have any banked up dirt waterproofed near its top surface, as by a thick poly film covered first with coarse river rock that will stay put and not cut the film, topped with fine gravel or dirt. A dirt bank that will shed water will eventually dry out and remain stable, and will make a good secondary insulator. In any construction that is surrounded by dirt, it will be better insulated after a full year than it is at first, because it takes time to get it really dry.

  13. Ricky DeMonia Sun, April 1, 2012 at 5:52 pm #

    You might check out the techniques described in “The $50 and Up Underground House Book” by Mike Oehler. They may be most useful for rural areas with less strict building codes, but definitely affordable.

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