Bio-based Materials in Construction: development and impact of prototype test buildings BaleHaus and HemPod
Submitting InstitutionUniversity of Bath
Unit of AssessmentArchitecture, Built Environment and Planning
Summary Impact TypeTechnological
Research Subject Area(s)
Engineering: Civil Engineering
Built Environment and Design: Engineering Design, Other Built Environment and Design
Summary of the impact
Over the past 13 years the University of Bath has been leading research
into low-impact bio-based construction materials, including the
construction and testing of two full-scale prototype buildings: BaleHaus
(2009) and HemPod (2010) built on campus. The research has directly
promoted: the development and wider market acceptance of award winning low
carbon construction products (ModCell® and Hemcrete®);
successful delivery of award winning buildings; and the wider sector
uptake of these technologies, including in a new school building in Bath.
The work has directly benefited industry partners working to meet UK
Government policy requirements to deliver low carbon infrastructure and
benefited society through the delivery of affordable sustainable
The research on crop based construction materials has been led by Peter
Walker (1998-date: Senior Lecturer, Professor) in the Building Research
Establishment's sponsored Centre for Innovative Construction Materials
(CICM), with input from Michael Lawrence (2004-date: Research Officer,
Lecturer), Andrew Heath (2003-date: Lecturer, Senior Lecturer), Andrew
Shea (2008-date: Lecturer), Katharine Wall (nee Beadle: 2011-13: Research
Officer), Christopher Gross (2008-09: Research Assistant), Kevin Paine
(2007-date: Senior Lecturer), Andrew Thomson (2012-date: Research
Officer), and Ian Molesworth & Edward Hirst (2007-2013: PhD students).
The research has also contributed to and benefitted from collaborative
national and international links, including: Yates (BRE); De Wilde,
Goodhew and Carfrae (Plymouth); Littlewood (UWIC); Morel and Arnaud
(ENTPE, France); MacDougall (Queens University, Canada); Dick (University
of Manitoba, Canada).
The research comprises two aspects: fundamental scientific
characterisation of material performance; and the development of
technically innovative construction solutions. The research covered here
considers two related fields of work: prefabricated straw bale
construction and the development of the test building BaleHaus; hemp-lime
construction and the test building HemPod.
Straw bale construction utilises a widely available agricultural
co-product to form highly insulated walls. Walker began by leading novel
research on developing the technical understanding of load-bearing straw
bale construction in 1999. Based on this initial work, in 2005 ModCell Ltd
approached Walker to collaborate in their development of prefabricated
straw bale cladding panels. Collaboration started with simulated wind
loading tests on panels for the award winning Eco-Depot project in York,
and has subsequently led to a series of UK Govt., and most recently EU
(EACI) sponsored research projects. At first this work focussed on
structural and durability aspects of the panels, leading directly to
refinements in panel design for enhanced structural performance (and
20-30% cost savings compared to the pre-research product design) and
better understanding of moisture transfer through panels and development
of improved specifications.
Directly as a result of this research, it was evident that the panels
could also be used to form low rise load-bearing walls. The BaleHaus
project included construction and performance testing of a prototype
two-storey house on campus at Bath . As well as structure and
weathering analysis, tests improved understanding of fire, acoustic and
thermal performance. Bath's direct contribution to the development of
straw bale construction during the REF period includes: leading grant
capture activities (total research investment to date exceeds £3 Million);
completing all constituent material and component design & performance
evaluations, including structural and environmental performance ;
developing computer design models; developing novel test protocols and
specifications; leading testing and monitoring of straw buildings [4,6];
product design development.
Hemp-lime is a novel bio-based composite formed from a mixture of hemp
shiv and a hydraulic lime-based binder. Walker began working on hemp-lime
construction in 2002, exploring effects of hemp-binder water exchange on
the properties of the composite [3,6]. A DEFRA sponsored project at Bath
has been undertaking fundamental work on hygrothermal (heat and moisture
exchange) and structural performance of hemp-lime materials , including
construction and performance testing of the HemPod building on campus.
This work has directly contributed to improving thermal modelling of
hemp-lime buildings, such as the Science Museum building at Wroughton
(2012), and the award of a British Board of Agrément certificate for
Hemcrete® (2011). Bath's research contribution to the
development of hemp-lime construction during the REF period includes:
leading grant capture activities (total research investment to date
exceeding £1 Million); completing constituent material characterisation
and development, including binder and mix design; establishing novel test
protocols and material specifications; product design development.
Kevin McCloud commented on the BaleHaus project at its opening in
November 2009: "Right now there are a number of exciting technologies
emerging in construction, but what we lack is the performance data of
the different technologies ... it will be really interesting to see how
this building performs" (see http://www.youtube.com/watch?v=7lLMevwSj84).
References to the research
2. Wall, K.,
Walker, P., Gross, C.,
White, C. and Mander, T., 2012. Development
and testing of a prototype straw bale house. Proceedings of the
Institution of Civil Engineers: Construction Materials, 165 (6), pp.
377-384. DOI: 10.1680/coma.11.00003.
Awarded Howard Medal for best paper 2012.
3. Hirst, E., Walker, P., Paine, K. and Yates, T. Characteristics of low
density hemp-lime materials. Proceedings of Institution of Civil
Engineers: Construction Materials, v 165, n 1, p 15-23, February
2012. DOI: 10.1680/coma.1000021.
4. Carfrae, J., De Wilde, P., Littlewood, J., Goodhew, S. and Walker, P.,
2011. Development of a cost
effective probe for the long term monitoring of straw bale buildings.
Building and Environment, v 46 (1), pp. 156-164. DOI: 10.1016/j.buildenv.2010.07.010.
6. Lawrence, M., Drinkwater, L., Heath, A. and Walker, P., 2009. Racking
shear resistance of prefabricated straw-bale panels. Proceedings
of the Institution of Civil Engineers: Construction Materials, 162,
v 3, pp. 133-138. DOI: 10.1680/coma.2009.162.3.133.
The projects have often been conducted in close collaboration with
industry partners and research has fed directly into construction projects
prior to completion or publication of the findings. The research grants
listed below have had commercial impact in the REF period:
• ModCell: Prefabricated straw bale panels. DTi Technology Programme.
(£290k total contract). 2007-2009.
• BaleHaus: a modern innovative low carbon housing system using
prefabricated straw bales, Carbon Connections (£150k total contract).
• BaleHaus: manufacture of sustainable prefabricated straw bale houses,
Technology Strategy Board (£700k total contract). 2008-2010.
• Hemp-lime composites for low carbon building, DEFRA (UK Govt.) (£750k
total contract). 2009-2012.
• EuroCell. EU Eco-Innovation CIP (€1.6M total contract). 2011-2014.
Details of the impact
Overall Contribution: Our straw bale research has directly
contributed to the market development of ModCell, the award of UK and EU
patents and certification of the system [1 below]. The research has shown
that the excellent thermal insulation levels provided by straw bale and
hemp-lime construction can reduce operational carbon emissions by 70-90%
compared to 1990 best practice housing requirements. Using crop materials
in place of conventional cavity masonry wall construction can also save
around 30 tonnes of carbon per house (equivalent to 10-30+ years
operational impact depending on the heating system). These figures are
based on the Life Cycle Assessment of the BaleHaus project. The research
has supported UK industry in the development and adoption of novel
sustainable low carbon building materials and products. Research
contributions to new building projects have included BRE Information Notes
design guidance, expert advice on material specifications, bespoke
performance tests on materials and evidential data from research output to
support the building control approval process. Through the very close
collaboration with industry partners, research outputs have often had an
immediate impact. Over 300 building projects have benefited directly or
indirectly from the research (equating to approximately 9000 tonnes of
carbon saved) [2, 3 below], and these have won prestigious awards [4
Benefits and Beneficiaries: The benefits of the research stem both
from improved performance and lower carbon impact of new technologies
compared to existing solutions. The embodied and operational carbon
reductions of both straw bale and hemp-lime are significant. Direct
beneficiaries of the research include industry partners (both ModCell Ltd
and Lime Technology Ltd) through increased sales and clients who have
procured lower carbon buildings. Clients include: The Science Museum;
Marks & Spencer; Tesco; Hayesfield Girls School (Bath), May Park
Primary School (Bristol); Hengistbury Head Visitor Centre; University of
the West of England; 20 BaleHaus homes for LILAC Co-Housing (Leeds);
Inspire Bradford Business Park; Waterfoot Primary School; Think Low Carbon
Sustainable Centre; Barnsley College; Holm Lacey College Straw Bale Café;
Weydon Secondary School; and HAB (Kevin McCloud's development company).
Dissemination: The research activities have been undertaken in
close collaboration with industry (ModCell Ltd, and Lime Technology Ltd).
This has ensured direct and almost immediate uptake of research findings.
Wider dissemination routes have been through conventional publications
(journal), presentations (conferences, seminars) as well as CPD activities
to promote benefits of renewable materials (workshops; exhibitions). In
2009-10 BaleHaus received substantial media coverage, including on local
TV (BBC, ITV), international, national and local radio (BBC), national and
international print media and internet exposure [5 below]. McCloud
officially opened BaleHaus in November 2009, attracting significant media
interest (see quote above). The Lilac Housing scheme, using BaleHaus
design, has more recently featured on BBC national TV (The Culture Show;
10.10.12). The CICM's reputation as a leading centre for innovative
construction materials research has increased, attracting new staff,
students, researchers and visiting academics. In 2010-2011 the Centre
completed a Knowledge Transfer Account Fellowship with BRE, aimed at
raising awareness and promoting wider uptake of renewable construction
materials. This included a series of workshops in the South West at which
over 400 participants attended.
Commercial impact: "The research carried out at the University
of Bath has been instrumental in the growth of ModCell" — Director
(ModCell Ltd). Since 2008 the commercial value of ModCell projects has
grown from £11k in 2008 to over £1.8 million in 2012; over the same time
ModCell staff grew from 1 FTE in 2008 to 10 FTE in 2012. The hemp-lime
construction market in the UK has grown from a few niche projects to over
250 completed projects, including Kevin McCloud's Triangle Project in
Swindon. Lime Technology's turnover has grown from £1 million in 2005 to
£6 million in 2012; over the same period Lime Technology's staffing
expanded from 12 FTE in 2005 to 57 FTE in 2012. "We could not have
developed as successfully as we have without our collaboration with the
University of Bath over the past 10 years" — Technical Director
(Lime Technology). These commercial developments have been directly
supported by the research outputs from Bath. Wider benefits of this impact
derive from employee spending into the local economy. Both main industrial
partners have also been developing export markets for their products. Lime
Technology has exported materials and technical expertise delivering
projects in USA and Australia; and ModCell, supported by the EuroCell
project, in Netherlands and Spain.
Societal impact: The research has directly supported the delivery
of new housing projects (Lilac community housing in Leeds) and public
buildings, including four new school buildings (see www.modcell.co.uk).
CICM has played a leading role in the Nucleus building, a new science
block for Hayesfield Girls School in Bath, the first commercial
loadbearing application of the ModCell straw bale panels. Walker supported
the school's development committee during the procurement process,
advising on technical details and using research data directly to provide
reassurance and clarification on performance where necessary.
"We won't get to an ultra-low-carbon built environment simply by
improving on the performance of the same old construction techniques.
The BaleHaus certainly hits that button, and could play an important
part in enabling house builders to meet their carbon targets." -
Director (Forum for the Future).
Sources to corroborate the impact
ModCell Patents: UK Patent GB 2457891B; European Patent
Modcell® building projects: UWE
Faculty of Environment and Technology (2010); Merrow Park & Ride
(2010); Weydon Secondary School (2011); Castle Park Primary School
(2011), Straw Bale Café (2011); Inspire Bradford Business Park (2011);
20 homes, LILAC affordable co-housing (2011-12). See: www.modcell.com/projects.
Hemcrete® building projects: Jennings
Business Park (2008); The Wine Society (2008); Orwell Housing (2008);
The Renewable House (2009); Welsh Institute of Sustainable Education at
CAT (2010); M&S (2011); 29 homes, Diss (2009-11); 42 homes, Swindon
(2010-11); 16 homes, Blackditch, Oxfordshire (2010-11); 15 homes,
Dormary Court, York (2011); 60 homes, Letchworth (2010-11); 16 homes,
Watford (2010-11). See: www.limetechnology.co.uk
References to CICM impact in built work: Thomas, C. The Genesis
Project: demonstrating sustainable construction, The Structural
Engineer 6 May 2008, pp. 39-46.
- Awards for building incorporating CICM research:
- BaleHaus: SWBE Award for Innovation (2010); British Construction
Industry Awards, Shortlisted (2010).
- WISE Building (Centre for Alternative Technology): Building of Year, Daily
Telegraph (2011); Favourite building of 2010, Architects
- Knowle West Media Centre: The South West C+ Carbon Positive Award for
Carbon Positive Communities, Bristol Civic Society Environmental Award
(2008); Green Apple Award Silver Award winner South Region (2008); RICS
Regional winner for the South West Community Benefit category (2008);
Shortlisted for the David Alsop Sustainability Award — IStructE Awards
- ModCell panels: The Offsite Construction Awards: for Best Product of
the Year & Best New Product (2008).
- Long Stanton Park & Ride: Green Apple Award (2012).
- Clayfields Sustainable Housing: RIBA Award (2009).
- The Triangle: RIBA Regional Sustainability Award (2012).
TV programmes featuring CICM work: Local BBC West TV news
(BaleHaus launch), Nov. 2009; Discovery TV — How do they do it, Nov.
2010; Kevin's Grand Design (Channel 4), Dec. 2011; Al Jazeera —
Earthrise, Aug. 2012; The Culture Show, BBC TV (Lilac housing scheme),
Oct. 2012; BBC 2 — Working Lunch Oct. 2012.