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Building with bale and cob in hot, humid climates

 
                                              
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I am from Southeast Alabama.  80 degrees plus from march 1 to nov 1.  Maybe 15 degrees and very few frosts every year.  Average of 45 in of rain a year.  My biggest battle is finding housing that keeps things cool and dry.  I have thought and seems the best option I have is to build a house 3 ft underground and then on top of that build 5-6 ft cob inside, straw outside wall (bout a foot thick each) so the house is sunken a little.  The ground's mass will keep the air cooler.  Face the house south with a northern berm and grape or kiwi vines on a trellis in front of an overhang so sun out in summer sun in in winter.  I don't know how effective this would be at heating but I have been in a south-facing basement with lots of windows in alabama when it is 100 outside. Plenty of light and it was 77 degrees in the basement with the door open.  I don't know what would be best for flooring or roofing but I think this is the best option for my climate so far. Any experience or suggestions?
 
Emerson White
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Location: Alaska
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If you are building a house underground in the deep south be sure that you have a French drain around and below the entire perimeter that goes to sunlight.

The humidity will shorten the lifespan of the straw, and the straw must be raised up and isolated from the well drained ground, and you may have termite problems. I do not know about the engineering involved.

You might consider a Monolithic Dome, maybe with some extra insulation and a solar run ground source heat pump. Alabama has ground water that sits at anywhere between 55 and 65 f year round, a heat pump on a loop running under a tree covered lot (or even better a tree shaded lilly covered pond) can give you a lot of wiggle room, hook up an ERV (Energy Recovery Ventilator) and use the winter time to evacuate the heat from your ground source and you will have a relatively environmentally responsible home that will stay that way for 100 years,

Take a look at the "Hybrid" designs. Add a green roof and some earth berms and you would have the coolest, driest hobbit house imaginable. Also think carefully about window direction. South or west = bad.
 
                                              
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I was planning on putting a pond liner under the whole house before laying anything else down.  The cob and straw bales would be off the ground one foot and cob plastered on both sides.  If I can't point the house south then how would I heat the house efficiently on our coldest winter days?  Without having to run anything maybe.  Going to have solar power and already planned for tube skylights in non-sunlit rooms.  What would this change?
 
Emerson White
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Location: Alaska
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You live in a cooling climate, you only need a very tiny amount of heat, build a solar hot water heater on the south side maybe and heat the home hydronically when you need it. Also pond liner under the house will be the equivalent of building your house in a pond.
 
                                              
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So build a massive well-drained trench around the house but how do i keep the water out from underneath? Would I have to build concrete slab?  Finding out more than I barganied for on building into the Earth.  What's the best solution for lighing in a north facing house?
 
                                              
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Also, if a pond liner keeps things in what could I put down to keep things out? Is there nothing I could put in place to repel water and then put the foundation on top of?  Would building  northfacing house with Southern berms with the northern wall being bale cob be a better solution?
 
Emerson White
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Location: Alaska
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If you have a french drain in a ring around the house then the groundwater level cannot rise above the level of the loop unless it is coming in from the top (which it wont because your house is there, shunting water off to the sides. Running to daylight lets you evacuate the water in the trench at high speed, where as a sump pump would be slower.
 
Emerson White
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Location: Alaska
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You want an impermeable barrier shaped like an umbrella not like a cup.

you will still want a vapor barrier under the house, something like visqueen but just as a flat layer under the floor, tyvek works too, The idea is to stop any vapor that might be floating up from under the house, and this is about percentage of area covered, and you do not want something like a pond liner that water will pool in, because pooled water will make more vapor than you could ever want to stop.
 
                                              
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So, I've got a ring of deep french drain with my gutter capturing all my rain runoff and I've put a impermeable barrier under my 3 ft sunken foundation?  Should keep things dry if the french drain is deeper than my foundation?  I am new to all this just trying to integrate thermal mass for cooling. It seems difficult to find something in the middle.
 
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