Hemp Houses


The Suffolk Housing Society in UK undertook a project to build homes out of hemp and to compare their performance to brick and block built houses. This project has since gained international attention. It all started when Ralph Carpenter, a local architect, took a trip to France and saw, in Rene, a collection of houses made of hemp. The construction material was developed by Madame France Perier.

There is an interesting story behind the development of the hemp construction material. France Perier was a conventional chemist. She developed skin cancer and searched for a cure. She found that hemp oil was effective and cured her skin cancer. She then set out to research the amazing properties of hemp. Coincidentally she saw a bridge that was constructed in the Metrovingian period (Roman period) and that used hemp in the mortar between the rocks. France Perier investigated the uses of hemp in construction and developed a product she called Isochanvre (Chanvre means hemp).

Isochanvre is flame-proof, non-toxic, 1/9 the weight of cement concrete, has excellent insulation properties, unpalatable to rats, termites or insects, and is flexible and strong. Because of its strength and flexibility it is an ideal building material in areas prone to cyclone and earthwakes.

Ralph Carpenter brought the idea back to St Edmundsbury Borough Council and Suffolk Housing and convinced them to seriously consider hemp housing. The project was funded by the society with grants from the Housing Corporation and St Edmundsbury Council. The project commenced to build and test four houses – two hemp houses and two traditional brick and block houses. Two houses (one hemp and one brick) were occupied when they were completed and two were left unoccupied for three months to monitor their environmental performance.

Summary of the Findings from the Suffolk Housing Project

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. It was discovered from an examination of the composite images of the front and rear elevations of both houses that there was significant heat loss through external walls and windows from the traditionally build masonry house in comparison with the hemp house.

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 minimization

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.

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.

Other countries eg Australia and Ireland are taking on hemp house construction projects. In Ireland it has been found to be non-economic at the present time, because hemp has to be imported. The solution, of course, is to grow hemp close to the construction site.

Copyright 2005 - Last Updated October 2005