Pete Walker, Dan Maskell and Aurélie Laborel-Preneron from University of Bath present their work on bale based SB&WRC prototype and the benefits to be found when construction and agriculture tightly collaborate.
Pete Walker: I am a chartered civil and structural engineer, and prior to joining the University of Bath I worked as an academic in Australia and Zimbabwe. I have been Director of the BRE Centre for Innovative Construction Materials at the University of Bath since 2006. I have been conducting research and development work on bio-based construction materials, including straw bale and hemp-lime composites, for around 20 years. I have collaborated with local companies in the development of an innovative prefabricated wall building system using straw bale insulation, leading to certification of the building system and a series of award winning buildings. At the university I also teach structural engineering and construction materials to undergraduate and Masters level civil engineers and architecture students.
Dan Maskell: I am a prized research fellow in Innovative Construction materials at the University of Bath, with interests in the use of construction materials for the improvement of indoor environmental quality, for the betterment of occupant health and wellbeing. He was awarded his PhD from the University of Bath in November 2013, followed by a three year post-doctoral Research Associate position, also at the University of Bath. I have a wide experience with natural building materials including earth, straw bale and other inorganic and organic materials. I have been researching straw bale straw bale construction for approximately 10 years. At the university I also teach structural engineering and non-conventional construction materials to undergraduate and Masters level civil engineers and architecture students.
Aurélie Laborel-Préneron: I have developed an interest in sustainable construction during my master in Civil Engineering, when I worked on a museum project built in rammed earth. After my graduation at the INSA of Toulouse in 2014, I chose to dedicate myself to research in eco-materials. I have then completed my PhD between 2014 and 2017 at the University of Toulouse. I have conducted an experimental research work about unfired earth brick containing various types of plant aggregates (straw, hemp shiv, corn cob, cork, rice husk). I studied these bio-based materials through a multidisciplinary approach including mechanical and hygrothermal properties but also durability properties such as durability to fungal growth, to climate and to fire. A holistic approach is, to my mind, essential when developing a building material to take into consideration as many parameters as possible.
University of Bath experience in bio-based materials: The BRE Centre for Innovative Construction Materials (BRE CICM) has been part of many projects about bio-based materials, especially about prefabricated straw bale panel systems and hemp-lime construction materials.
Pete Walker: We are developing a prototype made of wheat straw that we are re-designing as a straw bale specific for construction purposes. Straw bale building started in the UK in the mid-1990s and it has been developed significantly over the past two decades. In a context of reducing environmental impact of buildings, straw has various advantages. First of all, straw is a readily available and renewable material, which is biodegradable and can continue to store photosynthetically processed carbon dioxide throughout the lifespan of the building. Moreover, as a co-product, straw does not compete with food production. Raw straw is also a very inexpensive material that requires only little post processing in the case of baling.
Dan Maskell: Straw from wheat is particularly interesting for this project because of the significant quantities of this crop co-product are available in the Interreg (Channel) region of Northern France and Southern England: an estimation of about 3.3 million tonnes in the French Interreg area and about 2.3 million tonnes in the English Interreg area has been made. It is locally available. In this present project, the wheat straw has been sourced from a farm close to Bath (about 10 km).
Aurélie Laborel-Préneron: Finally, straw has also many favourable properties for construction. It is a good hygroscopic material, with a high moisture buffering capacity. This ability to respond to variations in environmental humidity is beneficial for both internal conditions and health of the building fabric. Straw also has good thermal and acoustic insulation properties, with surprisingly good fire resistance, and earthquake resilience, when the bales have been highly compressed.
Pete Walker: Most of the tests to characterize the prototype will be realised in the laboratories of the Department of Architecture and Civil Engineering at the University of Bath. Tests to assess thermal properties, hygric properties, such as water permeability or Moisture Buffer Value, mechanical properties or internal structure of the bales will be carried out. In addition to these tests, some specimens will be sent to Unilasalle in France for fire resistance tests.
Dan Maskell: Another part of the testing will be done at real scale on a pilot site. The monitoring at real scale will allow to determine the real thermal and hygric behaviour of the material. The deployment of this prototype will take place at the Building Research Park in Wroughton (about 45 km from Bath).
Pete Walker: Currently, the thickness of a wall made with straw bale is usually around 450 mm, which might be a barrier to the development of this insulating product. The objective of the developed prototype is to improve the thermal insulation of the bale, in order to be able to reduce its thickness and thus to be more competitive with other insulation products already on the market. To improve the thermal insulation, the solution undertaken is to change the straw orientation. However, in order to do so, new or adaptable baling machines would be necessary in order to be still able to produce the bale on field. This would allow not to increase the processing of the material. It would thus be still competitive in terms of price and low environmental impact.
Pete Walker: The University of Bath will benefit from this project by broadening the network and creating collaborative links with new research partners. More specifically, the BRE Centre for Innovative Construction Materials (BRE CICM) at the University of Bath, which is a leading research centre in eco-innovative construction materials, will be fostered by this project thanks to the production of new knowledge and expertise in this field of study. Moreover, some educational benefits will be observed such as new knowledge and experience feeds into existing and new courses.
Dan Maskell: To the wider area, the expected benefits will be the energy efficiency improvement in a context of limited resources, with the mobilisation of underexploited renewable resources such as wheat straw. The SB&WRC project contributes to the development of the bio-economy by the creation of sustainable solution for the valorisation of agricultural coproducts. This project is indeed in line with the European objectives of the framework programme Horizon 2020 from the point of view of energy efficiency and reduction of carbon emission.
Aurélie Laborel-Préneron: Finally, thanks to the online community, the different workshops and deployment of prototypes event involving various stakeholders, the project will reach a critical mass of stakeholders allowing to influence market trends.
Last updated on the 10-07-2018 by Sylvain Bosquet