Scheme Summary

The scheme consists of 4 three bed and 1 four bed self-built earth sheltered homes. It is the first earth sheltered development in the UK, and is built on sustainable and self-sufficient principles with net zero CO2 emissions, and very low environmental impact.


Scheme Details

The Hockerton Housing project formed in 1993 with the brief to develop five houses on a 25 acre agricultural site outside Hockerton, Nottinghamshire. Planning approval was granted in 1994 subject to a Section 106 Agreement, which delayed construction considerably. Construction took just over two years.

The project was completed in October 1998.

The homes go beyond sustainable construction to form the focus of a sustainable community. It was on this basis that Newark and Sherwood Council agreed to the development.


Design and Environmental Features

The houses were designed to be simple in construction, but with high level thermal performance. A single storey modular layout enabled constant spans and economies of scale for door and window fitments. The materials used were selected to meet a range of criteria:

  • structural integrity and high thermal performance
  • minimal embodied energy
  • use of non-toxic materials to minimise environmental and health hazards
  • environmental policies of manufacturers
  • readily available low to medium technology
  • local suppliers, where possible
  • minimal impact on land and resources

The homes have high thermal mass construction which stores and releases heat over long periods of time. Concrete block, slab and beams and clay tiles provide the bulk of the thermal mass. Energy to heat the houses is sourced from the sun, human bodies (equivalent to a 100w bulb), and electrical appliances, eg cookers. The heat is retained in the houses due to:

  • high insulation to all external surfaces (non CFC expanded polystyrene - 300mm)
  • a solar store buffer zone between the inside and outside
  • earth covered roof, rear wall and end walls - 500mm depth
  • low heat loss double and triple glazed windows (low e-argon filled)
  • a mechanical ventilation and heat recovery system

Together, these maintain temperatures in the 18-22°C comfort zone, and reduce the need for space heating. 60% of a conventional house's energy use is saved by the removal of space heating. The homes are designed to optimise sunlight and warmth. They are SW facing, with an emphasis on afternoon light. A glazed frontal roof allows winter sun to penetrate to the rear of the buildings. Conservatories provide a seasonal living area, maximise passive solar gain and promote good levels of natural daylighting. Excess heat from them is used to heat water stored in very large insulated tanks. The design provides self-shading during summer, reducing thermal gain and internal brightness.

Hot water is produced efficiently via a heat pump, using just 25% of traditional energy levels. Low energy appliances and light bulbs reduce energy consumption even further. A wind turbine is planned to produce electricity. Planning permission has been granted and erection is expected during 2001.

Overall the houses use about 10% of the energy used by a comparable traditional house - 8kWh instead of 80 kWh. All water is sourced and treated on site and stored in underground tanks. Potable water is produced through filtering to remove small matter and chemicals and ultra violet treatment to kill bacteria and viruses. A reservoir stores non potable water which is filtered and used for all other uses. The resevoir contains enough water for 100 days use. Water is conserved as much as possible through the use of low flush WCs, flow restrictor shower heads (baths are limited), and detergent free clothes washing (removing the need for second rinses).

A reed bed treats sewage. Bacteria in the water are fed by the reeds, and in turn feed on the pathogens in the sewage. The lake itself forms a wildlife habitat.

To be completely self sustaining, Hockerton has developed its own community business to provide employment for community members. Visits to the development can be arranged.


Costs

After land acquisition, the second problem often associated with self-build is securing funding. The Co-operative Bank and the Ecology Building Society worked together to form a solution. Initial loans from the bank were eventually converted into mortgages with the building society. The homes cost, on average, 485/m2. Cost per home can be broken down as follows:

 
£
Basic construction
51,000
Conservatory
24,000
Landscaping/infrastructure
9,000
Set up costs and supervision*
20,000
Total
92,000

(*high due to planning and construction delays).

The Co-operative considers these costs to be good value for money.


Developer's Comments

The houses at Hockerton are a successful experiment in low-energy design. They are attractive and pleasant to live in. The design of the site enables a sustainable life style with self-sufficiency in water and food while also providing a high level of amenity for the residents.

Elements such as high levels of insulation, high thermal mass and sustainable energy supplies from a wind turbine, or by purchasing energy on a green energy tariff, could be replicated in more mainstream developments.

Some of the weaknesses of the dwellings could easily be addressed. Early problems with damp and humidity were caused by residents failing to use the mechanical ventilation system in an attempt to minimise energy consumption.

Contact: Nick White,
Hockerton Housing Project,
The Watershed,
Gables Drive,
Hockerton,
Southwell,
Notts. NG25 0PQ
Tel: 01636 816902
Email: hhp@hockerton.demon.co.uk
Website: www.hockerton.demon.co.uk