Scheme Summary

This is an EU Thermie funded project which is due to achieve practical completion in September 1997. This is a new build scheme of 58 housing units. The main aim and objectives of this project are to demonstrate that a fully integrated and qualitative design package of energy efficiency measures in the construction of housing can:

  • Reduce heating, lighting and ventilation costs by between 43% and 75% over and above current national (European) minimum standards.
  • Reduce energy use and CO2 emissions associated with space and water heating by 44%.
  • Reduce the embodied energy and environmental impact of the building materials, the construction process and the maintenance of buildings by the careful design of buildings and selection of its components, construction process and system.
  • Show (by comparison) that energy efficiency measures over and above national minimum standards are cost effective for both private and social housing schemes and in all cases demonstrate positive internal rates of return on investment.

Scheme Details

Grey water recycling

The project involved the demolition of a High Alumina cement tower block and erection of 58 low rise dwellings comprising 40 sheltered flats for the elderly and 18 general needs flats and houses. The scheme was designed by Fielden Clegg architects and the thermal performance of the whole scheme will be monitored during its first year of occupation by the Bristol Energy Centre. A primary aim of the scheme is to provide affordable warmth which is defined by Dr Brenda Boardman as energy charges not exceeding £0.09/m2/week for low income housing.

Improvements on existing regulations are achieved by:

  • Maximising natural day and sunlighting
  • Better thermal performance of building fabric - buildings achieve 10 under NHER
  • Increasing the efficiency of the heating system.
  • Utilising low energy lighting.
  • Constructing "airtight" buildings to minimise filtration.
  • Providing passive means of natural ventilation.
  • Selecting materials and processes with the least embodied energy.
  • Recycling materials wherever possible.
  • Selecting materials and processes with the least environmental impact.
  • Constructing with durable low maintenance materials.

Energy conservation measures in the Bristol project include:

  • Low `U' values for roofs, external walls and floors.
  • Solar orientation.
  • Floors and internal walls of high thermal mass materials.
  • Low `e' gas-filled windows.
  • Airtight construction.
  • Fresh air supply by Passive Stack Ventilation (PSV).
  • Thermal storage group heating.
  • Solar preheating of communal domestic hot water.
  • Low energy lighting.

An independent study of the design has shown that the superstructure has a level of embodied energy which is below average.

All ground floors are precast or in-situ concrete with 75mm of rigid insulation under a 75mm screed. Precast construction is also used for the upper floors of flats.

The external walls consist of a 100mm thick outer leaf, a 200mm cavity filled with two 100mm mineral fibre bats and a 100 or 140mm dense block inner leaf. The two leaves are built independently and incorporate 100mm rigid insulation cavity closers at all external opening reveals.

In the loft spaces a 200mm layer of sprayed cellulose fibre is applied and maintenance walkways are installed.

Material from the demolished tower block has been crushed and re-graded on site for use in the new development and also to be used in a nearby major engineering project, the second Severn crossing. This reduces site traffic and also the extent of landfill and quarrying activities associated with the project.

Cost Implications

The whole project cost approximately £200,000 more to include the energy efficient measures than it would have cost without them. Typically, remembering these figures are two years old, the costs would have been £556/m2 and at Rockingham it actually worked out to be £616/m2. It is important to emphasise that these additional costs are for the construction only and do not include the additional costs associated with investigation, planning, monitoring etc. These additional costs are approximately £3,000 per unit.

Developer's Comments

One aspect that The Guinness Trust feel that they would repeat is the recycling of materials from demolition. As said earlier some of the details from the demolished flats were reused on site, other material taken to the second Severn crossing.

"Perhaps we need regional centres to collate information on materials available and materials required to ensure most efficient practice - possibly local authorities" - Clare Hawley, Area Development Manager, The Guinness Trust.

Contact: Clare Hawley,
Area Development Officer,
The Guinness Trust,
1-2 Osprey Court,
Hawkfield Way,
Hawkfield Business Park
Bristol BS14 0GT
Tel: 02475 766300
Fax: 02475 769000