Friday, July 25, 2014

Timeline - Education on Earth Sheltering

This post is the first of two on the subject of Education on Earth Sheltering.

Early Influences
One of the first purchases after we decided to build an "off-the-grid" home was Rob Roy's informative book, "Earth Sheltered Houses". Although our ultimate design for earth sheltering is far removed from his, the take-away for me was that I could easily do the construction myself with very little professional help.  Also, it was the first time I had heard of a technique for building concrete walls -- dry-stacked cider blocks -- that I later considered several different times as I looked for ways to prune costs. 

However, I was totally turned off by a couple of things (a) his battle against water, both surface and ground water, using
increasingly sophisticated waterproofing systems applied to roofs and earth contact walls and (b) the probability that, in our climate, termites would feast on the wood decking supporting the soil on the roof.

Also, early on, I ran onto the works of a true pioneer in earth sheltering, the architect Malcolm Wells, who self-published a couple of handwritten manuals.  The take-away from him was that earth sheltered homes do not have to look like south-facing caves. He also advised against making the earth contact roof continous with the earth contact walls.

Hell-bent on Earth Sheltering
Being hell-bent on earth sheltering but still confused, I was elated when a friend gave me the 1st and 2nd editions of "Earth Sheltered Housing Design" written by Carmondy and Sterling at the University of Minnesota Underground Space Center (out of print).  It is a scholarly look at earth sheltering and provided a basis for evaluating information from other sources.

Most of the other references I found were scattered about on the web and were largely posted by companies selling concrete earth shelters or were talking about some unique and sometimes cool modalities such as Earthships ( whose earth contact walls are constructed from rubber tires filled with compacted dirt, which is certainly sustainable and adequate for the western high desert but unsuitable for our high water table and termite susceptibility.

State of Most Earth Sheltering Concepts Today - Not Good
Earth sheltering seems to have gained popularity after the oil crises in the mid-70s. With the exception of Earthships, most iterations seem to have been done along the lines of Rob Roy's homes.  The earth contact walls and roof (wood or concrete) were waterproofed with self-adhering elastomeric materials and insulated on the outside with sheet foam before backfilling. 
Southeast facade showing windows and deciduous shade trees.
Both my research and personal experience tell me that there are also many "earth homes", perhaps predating the '70s, that lack adequate waterproofing, have no insulation and often do not even face south.  The home pictured nearby is a good example.  Its structure is a large corrugated aluminum half-tube with at least three feet of soil on the roof and a mortared rock front and back walls.  It faces southeast with fewer sun-gathering windows than most passive solar homes of its size.  There is no insulation or substantial waterproofing between the metal and the soil.  It uses about 300 gal of propane a year but does well without air conditioning.  The owners are quite happy disappearing into a landscape which includes dozens of recently-planted trees and enjoying lower energy bills than most folks.
Northwest exposure.  The corrugated metal structure is exposed between the rock wall supporting the electric meter and the curved rock retaining wall above it that buttresses the soil on roof.