NHBC Report Advises Cautious Approach To Organic Materials

Source: greenbuildingpress.co.uk

A study by the NHBC Foundation has found that the use of natural crop-based building materials – such as hemp and straw – is a growing trend in the construction of new buildings across the UK.

Adnams hemp and lime block built distribution warehouse The report based on the findings, 'Cellulose Based Building Materials (NF55)' advises that there are risks associated with using such materials and highlights that at the current time relatively little robust evidence exists to support their long-term performance as currently used. Crop-based materials have been used historically in the construction of houses and farm buildings in the UK – typically for cob walls and cellulose-based materials such as straw and reed for thatching roofs. The use of these materials has declined, but recent years have seen a renewed interest in the use of traditional cellulose-based materials including hemp, reed and straw, in walling and roofing for their renewable, low embodied energy and insulation qualities. Recent work on embodied energy has seen traditional cellulose-based materials being re-examined as potential low impact construction materials. There are many examples of using crop-derived materials in construction, both traditional ones such as thatch and cob, and more recently hemp and lime in addition to straw bale construction. There has been increased interest in using these materials. Early examples of cellulose-based construction, such as a social housing development for the Suffolk Housing Society at Haverhill in Suffolk, the Renewable House at the BRE Innovation Park and the BaleHaus at Bath University, have been surpassed by much larger social housing and commercial projects. The 3000 m2 Adnams Distribution Centre (hemp and lime), the project at Denmark Lane, Diss, Norfolk (114 homes using hemp and lime), and the Waddington project in Lincolnshire (straw bales) are examples of completed developments. There have also been developments in off-site construction using cellulose materials. Developments using straw bale panels and hemp and lime panels have been used to construct around 20 buildings in the UK including the Cheshire Oaks Marks & Spencer retail store near Ellesmere Port. If use of these materials is to reach its full potential then questions on buildability, long term performance and risks need to be reviewed, assessed and evaluated. This report uses the latest findings from BRE, BBA and other sources, as well as from some of the cellulose-based material companies themselves, to provide a balanced overview. The broad aims of the report are to: clarify the nature and role of cellulose-based building materials review current developments describe the major factors to consider when using cellulose materials. The study drew on the activities of BRE and their partners enabling access to representatives of the natural fibre building sector, associated supply chains and other research programmes. BRE undertook the role of technical lead through its existing expertise and that of the BRE Centre of Innovative Materials at the University of Bath. The Centre for the Built Environment (CBE), part of the Adapt Low Carbon Group at the University of East Anglia, provided a focal point for contact with supply chain partners.