Hello Permies!
I have
Oehler's
books, yes, (as well as nearly every single book ever written on the subject of earth-sheltered construction, the collection takes up a whole shelf) and have been over and over it and read all the threads on it here and elsewhere. I am involved in a group project and heavily pushing for earth-sheltering in our buildings (as is one of my obsessions!). My best friend, who is also an experienced builder (of both standard modern structures and earthships) is completely NON-SOLD on
Mike Oehler's PSP method with the following (it seems to me quite valid) objections.
Firstly, he will never agree to the putting of posts directly in the ground, treated or otherwise. Clearly eventually such posts will rot, even with an absolute minimum of moisture, as
wood when exposed to soil WILL rot. Are we incorrect about this? For this problem, we can at least agree on the use of a foundation using
concrete and/or stone as a reasonable and acceptable solution either above or below the ground. Agreed?
Secondly, he insists that the wood planks of a PSP structure, directly in contact with plastic (or
pond liner or whatever specific kind of vapor barrier) will eventually rot due to condensation from LACK OF AIR-FLOW against the plastic. This seems to me a reasonable point, am I wrong?
This second issue is more of a problem, as I really otherwise quite like the simplicity of PSP, and going with a more "eastern school" (as Oehler puts it) paradigm of lots and lots of concrete is quite out of the question mostly due to high cost (among other reasons not worth getting into here).
Here is my proposed solution which I want you all to give me your thoughts on before I suggest it to my group. Basically a nice and thick layer of FELT between the wood and the plastic, to create BREATHABLE layer to prevent the wood from rotting. This would need to resist compression fairly well and yet be breathable enough to allow significant air flow allowing any condensation to evaporate and never reach the wood. It would probably want to be a SYNTHETIC felt to eliminate the possibility of IT rotting, though probably a very thick wool felt would work just fine.
Thoughts?
--Joshua