Press Release: September 2002

Sustainable hemp homes project paves the way for viable alternative

Building environmentally sustainable housing comes at a cost, that is the conclusion of a study into a unique 'green homes' project that has been underway in Suffolk.

The project in Haverhill has allowed analysts to examine the environmental impact, energy use and other factors including comparative building costs involved in the construction of four identical houses. Two have been built using specially processed hemp, lime and timber as the principal materials, the other two are of 'traditional' brick and block construction.

The publication of the report coincides with renewed Government interest in 'green homes'. Reports from the Earth Summit indicate that Prime Minister Tony Blair wants to see 1 million green homes built in Britain in the next decade. It is thought that tax incentives - and penalties - could be used to encourage environmentally sustainability and energy efficiency to be built into new homes and home improvements.

The Suffolk project is the first time that complete houses have been built using hemp in Britain. The principal conclusions are that while the hemp homes have far less impact on the environment - they use less energy to build, create less waste and take less fuel to heat - they cost about 10 per cent more to build than brick and block houses.

It is estimated that the cost of hemp construction was £526 per square metre compared to £478 for the brick and block houses. This differential might be reduced if hemp construction was to be adopted on a commercial scale, with the efficiencies that that would bring.

"At the moment it comes down to what the building industry regards as being the most important factor when it comes to deciding on future construction methods, financial cost or environmental cost," said Steve Clarke, chief executive of Suffolk Housing Society, of Bury St Edmunds, who commissioned the project.

The research into the two building methods has been conducted by the Building Research establishment (BRE) paid for in part by a £60,000 Innovation and Good Practice grant from the Housing Corporation.

The BRE studied the two systems for:
  o Relative structural, thermal, acoustic, permeability and durability qualities;
  o Reduction in waste generated on site;
  o Environmental impact;
  o Construction costs.

The hemp houses are built in a terrace alongside their brick and block counter parts as part of a £1.5 million 18 unit social housing development on a 1.2 acre site in Park Road, Haverhill. A social housing grant of £675,000 was provided by St Edmundsbury Borough Council who nominated the tenants for the new homes. The four properties in the project cost £176,000 to build.

The first tenant to move into a two bedroom hemp home was Amanda Collenette, 21, with her baby daughter, Jasmine. They took up residence in December 2001 and for three months their lives were closely monitored by sophisticated instruments measuring qualities such as insulation, energy efficiency, sound proofing, structural stability, resistance to water and condensation factors.

The second 'hemp home' remained empty until Jessee Mulcock and her five-year-old son Vinni moved in during the spring so that its properties as an unoccupied house could also be monitored. The same occupation pattern applied to the brick/block houses.

The BRE's full research findings have been published on its web site at www.bre.co.uk/pdf/hemphomes.pdf. Suffolk Housing Society has published a summary of the findings that is available in hard copy or from its web site www.suffolkhousing.org.

"I believe the findings will be of interest to both public sector and private house builders," said Steve Clarke. "The hemp system does have advantages over brick and block construction and, if adopted, could mean a change in the way houses are built in future."

The hemp was supplied by a French company Chenovette Habitat which specialises in processing the material for use in buildings. It was combined with hydraulic lime before being poured into wooden shuttering which when removed revealed the walls of the new timber framed houses. The ground floor screed was made up of a hemp, lime and sand mix.

The hemp homes feature the use of natural materials such as wooden window frames and clay tiles on the floor of the kitchen. The whole effect gives the buildings a more natural, warmer feel than many of today's modern homes.

"This project has the potential of changing the way we think about building homes in a more environmentally friendly way," added Steve Clarke. "There is a growing interest among public sector homes providers in building properties in a more sustainable way and we have had interest from around the world from people who are keen to know more about our project."

Inspiration for the experiment came from local architect Ralph Carpenter of Modece Architects, of Bury St Edmunds, who saw the successful use of hemp in house construction in France and proposed the idea. A visit to France in 1998 convinced Suffolk Housing Society and St Edmundsbury Council that the experiment would be worthwhile.

Although hemp mixtures have been used in partition walls before, the hemp homes are the first houses to have been built this way in Britain.

"The houses have a terrific natural feel to them," said Ralph Carpenter. "Because the hemp and lime mixture breathes there is no condensation and they are warmer to the touch. People instinctively find them cosier."

Summary of findings
Structure & durability
The qualities of hemp homes were found to be at least equal to those of traditional construction.

Thermal comparisons
Heating fuel consumed by the hemp homes is no greater than that used in the traditionally constructed houses.

Acoustics test
Hemp homes did not perform as well as the traditional houses but they did meet the sound resistance requirement.

Permeability
Both forms of construction appear to give complete protection against water penetration. However, the hemp homes generate less condensation.

Waste minimisation
There appears to be little difference in the amount of waste produced by each method. Although the waste is of a different nature in each case both are likely to have an environmental impact.

Environmental impact
The advantages that the hemp homes display are:
The use of renewable materials, particularly the hemp
Low use of energy in producing the principal materials
Reduced excavation of subsoil for foundations
The materials are recyclable
Minimal amounts of energy will be required to demolish the buildings compared to brickwork and concrete.

Construction costs
It is estimated that the true cost of hemp construction was £526 per square metre compared to £478 for traditional construction.


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