Hello Tom,
Congratulations and best wishes on your project! Looks like you are putting a lot of time and thought into your design, including how it will perform and how it will actually be built and maintained, not just how you want it to look or how "cool" a particular material or method may seem. This is of
course essential, yet seems inexplicably absent from the design process for so many owner/builders. I am a first-time straw bale owner/builder/designer myself, and have over the years met many others aspiring to projects like ours. Perhaps it has just been my bad luck to meet these people during the early, conceptual phase of their projects, but they almost never fail to impress me as being woefully uninformed and unprepared for what they are getting into. Most have seen a few pretty pictures in
books and said "ooh, I want that!" Few have started with a methodical, introspective design process addressing the key questions: What are my design goals - practicality? economy? longevity? aesthetics? low energy consumption? resale value? What lifestyle do I plan for myself that this building will support, and why will one design or building material be better than another to do that job? Do I have a realistic and informed time frame/budget/pool of labor? Even fewer have even the tiniest inkling of the magnitude of research, planning, and hard work that will be required, or of the problems they will encounter along the way.
In any case, you are clearly not among that crowd. Again, congratulations. You clearly desire to produce a superior product ...and if the natural buildings we create are not actually superior to the industry-standard mainstream options already available to us, often for less cost and certainly for less effort, then I consider that a failure.
I will admit that I'm far better versed in straw bale architecture than I am in earthships, but I share Tom's stated surprise at your design. Or at least your nomenclature. I had actually caught on way further up in this thread, based on the look and placement of the ground level front door on your north side, that your design does not include earth berms. So I echo Tom's question: if it is not built into a hill, bermed up, or otherwise earth-integrated, why do you call this an "earthship" as opposed to simply a passive solar straw bale structure? I had thought that was part of the definition of earthships, at least in practice, if not according to your six principles.
Having myself also designed (and mostly built) a passive solar straw bale home with a metal roof and an
RMH for supplemental heat, I am of course inclined to appreciate your design. (BTW, buy the metal direct from the factory and install the roof yourself - it is easy to pick up the proper technique if you have a drill with a clutch, and you will save so much money!) I also agree with your statement that a well-built straw bale structure should be no more inherently susceptible to moisture damage than a home built of wood. Wood rots when wet just as completely as straw; it only takes a bit longer. Of course, wall systems based on stone or masonry (or tires) don't share this problem. Bill is correct of course that straw bale must be "detailed impeccably" ...but shouldn't any owner-built structure be? It is only the mainstream construction industry that knowingly builds poor detailing into its product. And I don't even fault them for this; they are giving their customer exactly what he wants, which is low sticker price above all else, including longevity. I would have agreed with Tom that a straw bale wall has no business against an earth berm, no matter how well vented, but of course you are not planning to do so.
I must take issue with one thing you wrote, however, and that is "Getting rid of the tires also gets rid of the labor issue. Strawbale houses are fast and easy to build in comparison!"
Oh, don't even be tempted to think so, good sir! And don't believe any of the books you have read that suggest as much. I read all of the same books, and they are false advertising. Straw bale walls are extremely labor intensive to raise and finish. Perhaps not as much so as monolithic
cob, but make no mistake: the man-hours required to complete a straw bale structure will boggle your mind once you are actually into your project. I will concede that a VERY small, VERY simple, load-bearing design could be built reasonably quickly and economically, compared to the standard stick-built house. But this assumes 1) meticulous and flawless preparation of the site and materials and day-by-day schedule that will be used, and I'm talking about a quality of planning that no first-timer should ever expect to achieve; 2) a large and dependable force of free labor to aid in the initial bale raising, keeping in mind that "free" and "dependable" are often mutually contradictory terms; and 3) damned good luck.
In any case, from studying your schematics above, none of these apply to you. Your house is not very small (two bedrooms, a stair well, a separate kitchen, and a separate living space ...I am guestimating just over 1000 sq ft, plus the greenhouse?), it is not very simple (two stories, two roof lines, and an attached greenhouse), and I can only assume given your location that it is a non-load-bearing design. Modified post and beam? That is what I chose, and it is a good system (including good for selling your design to code officials), but it means a lot of extra work compared to load-bearing.
BTW, if you were to say that you actually do intend load-bearing straw bale, I would emphatically advise against. Builders in the desert or Great Plains attempting a well-organized blitz on a maximum 500 sq ft, one story, simple square floor plan can get away with load-bearing designs. They can reasonably expect to get from bare foundation to completed roof sheathing within one month, and are accustomed to longer stretches without rain. You have no such luxury in Washington, nor I in South Carolina. Even those desert builders would still take additional weeks to finish up the first coat of exterior plaster, until which their walls are still somewhat vulnerable, even beneath a roof.
If you would like to provide more details of your design and construction plan by PM, I would be willing to make further comment based on what I've learnt through hard experience. I'm sure many other permies would have good advice for you as well, if you posted in the straw bale forum rather than the earthship forum.
As for the attached greenhouse, I share Jay's concerns over the basic design, though I can claim no first-hand experience in this area. But one of my
PDC instructors gave me the exact same warnings that Jay has given here, and she should know: she lives out west and she is old enough to have been around the first generation of earthship architects as they pioneered the concept, and to have observed the results 30 years later. She called those early attempts at passive solar design "solar brutal," claiming they only resulted in unusable living spaces that were too hot during the day and too cold at night. You live in a more moderate climate than those earthship pionneers (PNW vs SW), with milder winters and much less solar exposure in the summer. This is surely in your favor, but still I would crunch the numbers rather than rely on such anecdotal logic. And/or design in features to mitigate temperature extremes, such as exterior shutters/louvers for reducing exposure on sunny days, and heavy interior drapes for insulating against cold nights. If manually actuated, such features shouldn't be too expensive. Even better, so long as you prepare for them in your design, you could plan so that they would be left as a possibility for retrofit only if proven necessary by the first year's experience.
And/or you could detach the greenhouse from the dwelling structure as Jay suggested, or at least place an insulated wall in between the two. With ducting through this wall, you could set up a blower system to transfer heat from one area to the other as needed, but under your control.
Some things to consider.
Again, best wishes! And thanks for posting your excellent schematics.
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