Design - A Journey Taken

This post is a brief summary of the evolution of earth sheltering since the oil embargo days of the mid-70s and how our project fits in.  It was originally written to supplement sit-down discussions during group visits to our home, especially when the level of interest in the details of passive solar is likely to be average or less than average.  I post the document here thinking that bloggers with only a casual interest in sustainability might find it interesting enough to pause.  Spoiler alert:  A meaningful telling of the story still requires some technical details, so hang with me.

(Click on any photo to enlarge it for better viewing.)

Early Research

Our early research, beginning several years before breaking ground (including visits to several Midwest earth sheltered homes and one of special significance located in eastern Washington state), revealed the following typical attributes of early earth sheltering:

--  South-facing slope in a rural location built in the 70s and early 80s; probably more prevalent in northern US and western mountain regions than in the hot/humid midwestern and southern climates

--  Concrete roof covered with earth; concrete north, east and west walls buried in earth with insulation and waterproofing on the outside then backfilled with earth; concrete floor with insulation below it.  The amount of useful thermal mass for moderating inside temperatures limited to concrete in the walls, ceiling and floor to the total exclusion of any adjacent earth

--  Most, if not all, of the south wall conventionally constructed but with more than average insulation and lots of windows to maximize solar gain during cool months

--  Commonplace reports of water infiltrating living spaces through both roof and walls; a problem that was hard to manage with complete earth sheltering

--  Heated with winter solar gain through south-facing windows but invariably supplemented by wood-, cob-, sawdust-, or corn-burning stoves

--  No air conditioning, at least in cool climate locations; most of the houses we visited in our lower Midwest area had AC if not actually full blown HVAC

--  Limited floor space -- usually one story and often one room deep

Further Research

More research radically influenced our understanding of earth sheltering:

--  Considerably less earth contact suffices but still sited on a south-facing hill, no dirt on the roof!!

--  No insulation behind earth contact walls or under the floor; soil becomes principal thermal mass

--  Extra-thick conventional insulation for the exposed non-earth-contact exterior walls and roof

--  Winter heat provided mostly by summer sun and stored in the thermal mass supplemented by winter sunshine through south windows; dubbed "Annualized GeoSolar" by an early advocate (see "Featured Post on the left sidebar); main features of AGS...........                    

Early concept drawing.  Black line below floor level depicts the conduit linking
the solar collector in front of the house with the solar chimney behind the house.
  The orange lines in front and in back of the house depict the insulation/watershed
 umbrella.

1.  Solar collector for harvesting the heat during the long days of summer

2. Conduits under house to distribute the heat to the soil, exiting in a "solar chimney" behind the house

3.  Insulation/watershed umbrella to increase the amount of dry and insulated thermal mass

--  With no insulation between living quarters and earth contact walls and floor, heat flows freely in and out of the thermal mass – out during cold weather, in during warm weather

Our Iteration 

--  Our design utilizes everything listed above under "Further Research" with these additional features:  
     1.  Larger house -- almost 3,000 square feet -- and multi-story

     2.  Town location rather than rural; readily available utility hookups

     3.  No conventional HVAC system

--  Strict adherence to sustainability practices -- from groundbreaking to present -- regarding location, design and construction  (in fact,
over-qualified for Energy Star or HERS certification (see the recent post on blower test results))

Two of five rain gardens after a spring downpour, located behind a
berm running the breath of the property that directs runoff to the gardens

--  Blower door test (that measures the rate of air leakage through the building envelope) recorded 1.1 air turnovers per hour, a score, according to the consultant administering the test, much lower than any he had seen in 20 busy years of testing

One of several native gardens; notice in the background
the southern extent of the eastern red cedar shelter belt 

--  Surrounding grounds utilize berms and rain gardens to hold surface runoff until it soaks in and leaves underground and purified                      

--   Landscaping largely limited to plants native to the Midwest 

-- Cold west and north winter winds slowed by a red cedar shelter belt rimming the property on the west and north sides