BBCDC extends learning facilities with energy-efficient 'Earthship'

Rising enrolment at Bethel Business and Community Development Centre (BBCDC) and lack of space compelled us to augment facilities over the last year.  In October 2021, ground was broken for a 200m2 Earthship, that would serve as a lecture theatre and hall.  Earthships are associated with the work of Michael Reynolds, an American architect and designer, who pioneered use of old tyres and earth sheltering in the United States.  His purpose was to reduce life cycle costs of homes, employ waste materials and reduce long term energy costs.

The building includes over 60m² of tyre walls on the south and west sides, which were then backfilled with soil.  During construction, a gravel drain was installed on the perimeter to allow excess moisture to drain down and away from the subsoil.  The earth-facing wall of the tyres was also waterproofed with heavy polyethylene.

An advantage of this construction system is that no foundation was necessary as the base of the tyres rests on highly compacted subsoil.  The tyres were stacked with a slight repose, staggered joints, and connection of subsequent layers to those beneath with screws.  End thrust is contained by two reinforced stone masonry columns at opposite corners.

Screws prevent movement of the tyres while they are filled with soil and compacted.  A few special tools were made to enable easier filling of the sidewalls. The interior face of the tyres was plastered while plastic bottles were filled with water and embedded in large cavities to add thermal mass, recycle waste and reduce the use of cement plaster. 

The interior space includes male and female toilets, a social area served by a food services counter, and a large open area used for teaching, lectures and educational activities.  The structure will double as a hall and facilitate a broad range of uses for theatre, drama, events and singing.

This Earthship is part of a cluster of solar energy applications at the south end of the campus, which includes a solar lab, a solar farm and demonstration solar water heaters.  The new Earthship also includes a new biogas system for toilet waste.  The windows and orientation take advantage of solar gain winter and thus far perform admirably, along with a daylighting feature.  

The entire project provided excellent experiential learning for BBCDC students. This included surveying and earthworks, concrete technology, stone masonry, carpentry, roofing, and interior finishing.

The use of discarded tyres is also drawing much interest.  The technique lends itself to construction on sloped sites, where bench terracing and earth sheltering make better use of space.  The Earthship concept utilises a large volume of soil, which will conserve energy by retaining cool temperatures in summer, and warmth in winter.

The number of women entering the industrial subjects at BBCDC is increasing each year.  On the 1st of August, a new school term began at BBCDC with 75 new female students and 75 new male students entering their first year.  As usual, the solar course will be well attended, and it is a relief to have the additional space provided by the Earthship for lectures and activities.  Power for the building is provided by the solar lab and farm next door.