Cob or Strawbale? hybrid earth sheltered/earth bag/straw bale/cob home

This is a post I've already posted in other topics, but just so I don't miss anyone...

First time poster, long time fan here...This site is a GOLD MINE. My wife and I just purchased 10 acres and are building an earth-sheltered home this spring as soon as the ground thaws on the south shore of Lake Superior in NW Wisconsin. I've been planning the house for months. We were originally planning to build a dome home and came across Simon Dale's site during our research and fell in love with the idea. Although we've had to alter many parts of the design to try to stay within the confines of the building code, we have decided to do the timber frame and reciprocal roof living roof, rubble trench/frost protected shallow footings with 20 foot wing insulation on the south side, leading to the drain tile that encircles the entire umbrella of the building. We plan on using earthbags to build a retaining wall for our earth berm on the north, east and west sides and using them for the foundation/stem wall on the south side. Everything inside will be on a gravel pad with a cob floor (similar to slab-on-grade) for thermal mass. My question (if anyone can help) is whether or not to use strawbales with cob plaster or just plain cob on the south side? We have long, cold winters and we'll have a LOT of windows on that side of the house, so I don't know if there will be any REAL advantage as far as insulative value (not to mention the cost of shipping and trying to find them this time of year) to using straw bales as per my original design. We also plan on building a green house on the outside of that wall probably next spring. With cob, we could run a rocket mass heater through that wall...Anyone have any insight? Thanks for reading!

Hi Jason
I've built a number of rocket stoves and a couple of mass heaters and am contemplating a house like yours on our farm in central illinois so I'm very interested in following your progress and learning from you and would be happy to exchange ideas as you and we move forward.

You might want to try mixing some vermiculite into the south facing cob to get some air into the wall which would lighten the mass but decrease the transfer which in your case is the cold. I'm sure you'll find ways to increase your insulation in the coldest months-- straw bales stacked up temporarily against a cold outside wall, curtains blankets or panels inside-- but vermiculite should help. I've bought mine at Menards. Any way you can trap air into your mass, maybe even beer bottles. Good luck with your work, sounds good.

Michael

michael Egan wrote:Hi Jason
I've built a number of rocket stoves and a couple of mass heaters and am contemplating a house like yours on our farm in central illinois so I'm very interested in following your progress and learning from you and would be happy to exchange ideas as you and we move forward.

You might want to try mixing some vermiculite into the south facing cob to get some air into the wall which would lighten the mass but decrease the transfer which in your case is the cold. I'm sure you'll find ways to increase your insulation in the coldest months-- straw bales stacked up temporarily against a cold outside wall, curtains blankets or panels inside-- but vermiculite should help. I've bought mine at Menards. Any way you can trap air into your mass, maybe even beer bottles. Good luck with your work, sounds good.

Michael

I repeated this post in the Cob forum as well, which is turning up some discussion on the topic.

I've looked into the vermiculite idea, and it sounds pretty good.

I am also very interested in the exchange of ideas...when are you starting construction? Do you have any experience in this type of building, outside of the rockets?

Best of luck to you as well! I'm sure we'll be in touch.

If you need any help with labor I also live here in Wisconsin. Free labor!!!