the earthship concept
The earth houses in Olst are inspired by Earthships by architect Michael Reynolds. The first Earthships date from forty years ago and have been extensively tested in use. Waste - where possible - and local building materials - as much as possible - are decisive in construction. An earthship is designed to be self-sufficient.
Architect Michel Post of Orio Architecten has adapted the principles to the Dutch situation (precipitation, annual temperature and subsoil).
12 houses have a north wall of car tires - filled with rammed earth - that partly supports the roof. In the 11 other houses we have replaced this with straw bales - the roof is leaning on a timber frame. The roof has a slope of 9º to optimally catch the sun: in the winter to the back of the house, in the summer little or no sun in the house.
Characteristic is the orientation towards the sun - the houses have a glass facade on the south side. The shelter of the north wall of car tires, a slope of earth and a green roof are important for thermal mass. An earth house is well insulated. The energy performance coefficient is zero or almost zero (this varies per house/household). Earth houses require much less heating than conventional houses. Additional heating can be done with a clay stove or a (particularly energy-efficient) wood stove or heat pump.
The houses have grilles in the front and skylights in the back. The difference in height creates natural ventilation in all rooms. Additional measures were taken where necessary.
In Olst we pump up groundwater to purify it into drinking water. We guarantee quality with regular tests - monthly.
Wastewater from households (only “grey” water) is filtered into clean surface water for the entire district via the helophyte filter.
The homes have varied solutions for wastewater. Most residents have a compost toilet. This saves many thousands of liters of drinking water on an annual basis and prevents “black” water. In addition, it also keeps valuable minerals available locally. The carefully obtained compost is used on the property.
The Middenhuis has a connection to the normal sewerage system.
The total of 274 PV panels on the 23 homes and the Middenhuis provide an estimated 63,300 kWh annually, more than enough for energy-neutral living. The households have a regular connection to the grid; which is used as a battery: in sunny weather we deliver back, on dark days (in dark months) we get green energy back. We are currently looking at how we can pass on the generated energy at district level.
The installations such as PV panels, hot water and helophyte filter also result in higher costs in the construction budget. On the other hand, residents have much lower fixed costs than in conventional homes.
Due to the embankments on the north side and the layout of the neighborhood with nature trails and varied plantings, the earthen houses will make the transition between built-up and rural areas very gradually. Bags of compost have been sown with a slope mixture to make the roofs greener. This is further supplemented by seeds that blow in from the environment. Edible greenery makes the neighborhood even more enjoyable. The combination of nature trails and semi-paved surfaces provides an attractive alternative to a paved residential environment and makes an important contribution to water management in the district. The chosen lighting protects the natural value of darkness.
Self-build was a conscious choice. Since the start of construction, at the end of 2011, we have been guided by construction coordinators, who supervised the quality. In this way we became more handy and more educated in what was needed. At the end of 2013, we started working in specialized teams.
During the construction period, we received more than a thousand volunteers from home and abroad. They came to learn about (aspects of) earth house construction, such as building with straw, constructing a helophyte filter or mud for walls. Often they also came to bring skills and thus helped our construction move forward.
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