I'm in the planning stages for a cob/straw bale house I'm going to build next year. I thought I would post some thoughts here to get some input, since I love reading this forum and I have gotten a lot of ideas from you all!!
I live in central NC, and there's plenty of clay around here. The climate is temperate (leaning towards the warmer side). It's also very humid. My parents have six acres they were dong nothing with, so my husband and I moved in with them and started a two acre permaculture forest garden (well, it will be two acres when it is finished). Now we want the eco house to go with it! (We're pretty tired of living with my parents, anyways) The site is at the top of a gentle slope that is a big open, grassy field (the field we are filling in with the forest garden)... I'm really scared of digging down and hitting bedrock, since the property is sort of half floodplain and half rocky outcrop.
I own the $50 and Up Underground House Book and the Cob Builder's Handbook... as well as this old book I found at a used bookstore called Passive Solar Energy written something like 30 years ago. That and the two cob houses I have been in are my source of info of how to build something like this. I thought I was going to have $3,000 to spend on the house... but I just had a baby and long story short... my savings have been depleted more than I thought they would be (thank you insurance company). So now I have to do this house on as little as possible.
I have a friend who recently finished building her own house this year. Here is a link to a big set of photos of the build start to finish (or I guess there is still some plastering left to do, so there may not be "finished" photos yet!): http://www.flickr.com/photos/danielleackley/sets/72157623078007101/
One of the guys who helped her build this place has taken workshops with Ianto Evans in Oregon... boy am I glad he flew all the way out there so I don't have to!! He is currently building a cob/conventional home hybrid for his parents to live in. He is blogging about it here: http://cobandon.blogspot.com/
I'm thinking I want to start with just one room.. with a loft space above. I think the loft space will open it up and give the downstairs a big, open feeling even though it's a small space. I also know that roof/foundation are the biggest expenses, and building up takes advantage of that. I'm thinking upstairs can be a nice cozy sleeping loft in the winter, when warm air rises up. But in the summer, I was planing on trying to create a solar chimney effect... is there anything wrong with this plan? Or is this just "strategically placed vents" and not a solar chimney?? See attached photo. Notice my roof slopes downhill... thank you Mike Oehler!
For the roof, I understand pond liner is a huge expense, so I don't want to do a living roof... but that is by far the most attractive option. I don't mind just a tin roof, but will I have to replace it often? Can I put a layer of dirt under the tin roof (for insulation)? Or a layer of straw? Is that a stupid amount of flammability?? I would rather have a living roof for the strength and insulation, if there is an affordable way to do it. How does evaporative cooling work with pond liner? And if it does, how does it not drain the house of heat in the winter? I do have plenty of woods on my land, so I can harvest some trees for the roof.
I want the bale walls to be load bearing, because I don't want the expense of timber/nails/labor (I am no good at woodworking so would have to hire someone). Does this mean I have to have straight walls?
I want to build a rocket stove... is there an advantage to putting the heated cob bench on the south vs. north walls? Can I run the exhaust pipe through a straw bale wall or does it have to be a cob wall? I'm thinking most of my walls will be straw bale since it gets pretty hot here and I don't want the thermal mass of the cob overheating the house in the summer. Or is cob supposed to cool in the summer as well? My friend's cob house is straw bale only on the north wall, and it gets a bit toasty in there this time of year. There is not sufficient overhang though, so I'm not sure what it causing it exactly.
Also, if I have some leftover dirt, I was wanting to make a cob wall sun trap. My understanding is that it's just a cob wall in a cupped shape, facing south. And then you plant stuff in the curve on the south side. Right?