R-Value of earth bags

Welcome! If you could talk about ways to increase the R-Value of earth bags, perhaps with partial rice hull infilling or vermiculite? Also, earth bag suitability for foundations. Thanks!

C Smitty wrote:Welcome! If you could talk about ways to increase the R-Value of earth bags, perhaps with partial rice hull infilling or vermiculite? Also, earth bag suitability for foundations. Thanks!

There is a lengthy discussion about all of this in the book. The use of rice hulls, vermiculite, pumice, perlite, and crushed volcanic stone as filling and for insulation are possibilities; they are best kept pure and separate from soil for optimal insulation. Earthbags can provide their own foundation, as well as a foundation for other techniques, such as cob, strawbale or cordwood construction.

Consider adding biochar to the list of materials that could be used for insulation.  It's as insulative as polymer foam insulations when dry.

Greg Martin wrote:Consider adding biochar to the list of materials that could be used for insulation.  It's as insulative as polymer foam insulations when dry.

That is a very interesting idea that had not occurred to me. It is rather expensive to buy in my vicinity, but I suppose one could make their own.

Greg Martin wrote:

Consider adding biochar to the list of materials that could be used for insulation.

How might this affect the building as a fire hazard?
One of the reasons I'm interested in alternative building systems (other than the longevity and sustainability those alternatives usually imply) is that we've got an awful lot of housing in wild-fire high-risk areas in North America - think California last year and areas of BC and Alberta in the last 10 years. Would you expect that so long as the external finish was fire resistant, biochar as insulation wouldn't be a problem?
I like the idea because as long as the biochar is made in an environmentally sound manner, it's a renewable resource. Some of the other insulations mentioned, such as vermiculite, are not renewable. In a building that will last a hundred years and survive floods and fires, I'm totally willing to compromise, as most of what's being built today wastes huge resources and is designed to last only ~70 years and doesn't cope with either fire or flood at all!

How might this affect the building as a fire hazard?  

 That was the first thing that came to mind as well when considering biochar as a building material.  With a good layer of stucco or cob or whatever, it will probably be fine, but if a creeping coal got into your wall... yikes!

Jay Angler wrote:
How might this affect the building as a fire hazard?

My thought has always been that one would pack biochar in a space between two walls made from earthbag, masonry, rammed earth or other nonflammable thermal masses.  At the top one would seal the biochar cavity off with a nonflammable layer as well.  Because all the volatiles have been burned off in the making of the biochar it takes a bit to get it started, but you definitely don't want it to have a chance to get going.

I use an open pit method to make biochar.  It takes me about 5 hours to make 1 cubic yard plus the time needed to gather and cut the wood.  I'm still plotting out ways to get the cost down to the minimum possible, but for the projects I have going on this provides an ok method of production at the moment.

One last thought on the flammability of biochar....it's no where near as flammable as wood, which is the vast majority of what my house is made from.  Charcoal briquette manufacturers add sawdust to the briquette to enable them to light, for example (the wood gives off flammable gases when you heat it while the charcoal has already given up all those gases when it was created).

OK, if it needs to go between two thermal masses, it may not be worth the trouble if there are other reasonable alternatives. I've got Kelly's book on order from our public library, so I'll read the relevant parts in it before doing any experimentation.  I have read in the past that earth bags are not the best for the Pacific North Wet Climate as we get so little sun in the winter and we lack the swings of day vs night temps that earth bags excel at moderating. I'd totally try one of Paul's Wofati concepts but our local council is waaaayyyyyy too conservative to bother going there!