Outpost                            SBE0104

Written evidence from Outpost

Outpost Architecture + Design:

Response to the Environmental Audit Committees inquiry into Sustainability of the Built Environment

Outpost is an architecture and design studio based in South London. As a practice we have a specific interest in building with natural and low-carbon building materials. In the summer of 2020 we participated in the Government Homes of 2030competition, and our proposal was short-listed as one of the final six competition entries. Our response to this inquiry is based on the research and design work done as part of our competition entry.

The competition submission was based around the principles of inclusivity, human health, and low environmental impact. The strategies used to achieve these principles have been condensed into the following headings: Relationship between building + landscape, resource resilience, building performance, and planning policy + regulation. This explores a new model for development which achieves deliverable homes with a focus on low carbon, and challenges recent changes which permit developers to build with less guidance than previously, and no focus on sustainable development.

Relationship between building + landscape

In current planning policy there is not a strong enough relationship between development and land-use, whereby land is not only used to accommodate homes but also to contribute towards sustaining a community through food production, recreation space, and physical beauty, to name but a few. The proposal takes a landscape-first approach, demonstrating that landscape can contribute to healthy urban spaces, human health, and lower net carbon

The Environment Agency report Health, People and the Environmentclearly highlights the enormous financial, social and health benefits of taking our greenspaces seriously. For example, during flooding in England between November 2019 and February 2020, 4,600 properties were flooded, causing physical damage but also an estimated bill of £20 million in mental health costs[1]. Well-planned green and blue spaces can contribute significantly to flood risk mitigationa problem set to increase as the effects of climate change become more severe. The landscape design explored in thehomes of 2030 proposal prioritises water management, introducing a large network of swales that feed back to the existing watercourse on the east side of the site, alongside several new water features of ponds and small lakes. An effective water management strategy with sustainable drainage and healthy water systems will mitigate flood and drought risks posed by climate change and help to create environments that are attractive to people and wildlife[2].

The impact of high-quality green and blue infrastructure in urban areas can ameliorate the warming effects of climate change with studies demonstrating cooling of up to 2.5 degrees C under the high emissions scenarios based on UKCP02 predictions. The use of landscape design in a holistic way will also contribute towards summertime solar shading design strategies. Food production represents 20%[3] of our greenhouse gas emissions[4] so our design proposal allows for all soft landscaped areas to be capable of growing food alongside the more dedicated food production allotment areas. Residents will be able to engage in foraging as well deliberately growing of part of their food if they so desire.

The benefit of nature to our health is also becoming better understood. A growing body of evidence suggests that interacting with nature improves psychological wellbeing and can even reduce the risk factors and burden of some types of mental illness[5]. A study of over 19,000 people in England looked at the effects of spending two hours or more a week in or around open green spaces. The results showed a significant increase in the likelihood of people reporting good health or high wellbeing[6].  A study in 2017 assessing the benefit of London parks calculated that the relative value of mental health benefits was 7% of the total economic benefits of London parks, a large fraction amounting to ca. £6.8 billion over 30 years[7]

An additional bonus of a varied landscape inclusive of water, marshland and a diversity of trees and vegetation is that the landscape actively sequesters carbon, helping to balance out any carbon cost involved in construction. Current building design and development models tend to include a high percentage of hard landscaping, and poor (if any) examples of green infrastructure, which offers little opportunity for building resilient communities. Green infrastructure must become a priority for new developments, with water management, temperature control, biodiversity and human health both mental and physical playing a larger part in our drive to provide homes and urban spaces.

Resource resilience

In 2017 more than 100 billion tonnes of materials were extracted from the earth. This is nearly four times the amount extracted in 1970 and only around half of that predicted by 2050[8]. Construction and infrastructure projects around the world are accountable for around half of all extracted materials. Our reliance on finite resources, and resources from far afield, is unsustainable and will to lead to global material shortages. This is already being demonstrated in the recent shortages of timber and steel within the construction industry[9]. We must be able to source materials more locally in order to absorb global market changes, which will no doubt become more dynamic as our climate continues to change.

There is a global surplus of straw, and in England approximately 5million tonnes per annum[10] are produced surplus to requirements. Much of this could be redirected towards straw panel factories without altering agricultural practice - enough to build 650,000 houses annually. Lime render is produced from naturally occurring limestone and clay from clay beds, both of which are plentiful in the UK. Timber can be sourced from sustainable forests, some within the UK, and others from continental Europe

Instrumental in sustainable resource management is the reduction of material waste. It is essential to limit the use of virgin, non-renewable materials, to look to plant-based and renewable materials that can eventually return to the earth, and to use, and re-use non-toxic materials in their original state where possible. It is possible to deliver buildings that achieve or better the target of limiting the building volume made up of petrochemical materials to maximum 10%, as demonstrated at Acharacle[11] primary school and Tulshill Neighbourhood Hub[12]. Included in the 10% figure are all mechanical, electrical and plumbing installations, with any use of concrete or steel substantially increasing the percentage, even in the case of high performing, environmentally friendly buildings.

Building performance

Thanks to the progress made since the start of the environmental movement, we occupy a time where our understanding and scientific advancement of plant and clay-based materials is such that we can now use them to build in ways that outperform petroleum-based materials. These readily available, low impact, hygroscopic, non-toxic, long-life, zero waste and beautiful materials offer us the opportunity to think afresh about how we construct our built environment to help meet the challenges we face.  These are the materials that are most effective at reducing embodied carbon. 

The building system proposed - comprised of modular straw bale panels by EcoCocon[13] - involves only four layers, the fewest number of layers of any system on the market achieving PassivHaus performance levels. This simple and more monolithic construction ensures longevity, as illustrated by extant examples such as Feuillette House (France), built in 1920 of lightweight timber frame with strawbale infill, which shows no deterioration after 100 years of life[14] and Pilgrim Holiness Church (Nebraska) where the baled straw is loadbearing (no wood framework required).  Here in the UK, we have a vernacular type of building called cob - a monolithic wall structure of unfired earth plastered with lime- which lasts for hundreds of years, with over 100,000 such houses still surviving throughout the UK, mainly in Devon and Dorset.

Modelling of the proposed building typologies as part of the 2030 submission using the design PH Passivhaus software and Passivhaus Planning Package (PHPP) demonstrated that an efficient form factor and overall energy balance within Passivhaus standards is achievable with this modular straw system, principally where the space heating and cooling demand is at or below 15kW/m2a. Figure A illustrates an embodied carbon calculation (using the OneClick tool) which analysed an EcoCocon wall in comparison with a Structural Insulated Panel (SIP), both with a U-value of 0.12W/m2K. The calculation demonstrates the reduction in embodied carbon that can be achieved by using the timber and strawbale panels as the primary (insulated) structure of the dwellings with potential savings of 70 KgCO2e/m2 identified. This equates to a 68% reduction in embodied carbon, largely due to the significantly simpler manufacturing process, which tends to be the most energy intensive stage of a products lifecycle.

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Figure A.

The use of minimally processed natural materials is a key design feature to achieve these carbon savings. The EcoCocon system uses an airtightness layer to further increase the already excellent airtightness achieved through the straw wall system. The design of the EcoCocon panel system means no sheathing layer is required as the panel itself resists racking. The wood fibre insulation layer that wraps the building reduces thermal bridges and also forms the substrate for the lime render. The proposed lime render system is a one-coat product that does not require a plastic mesh which helps to eliminate any end-of-life waste and carbon. Another key reduction is in the embodied carbon of the insulation when compared with conventional systems. EcoCocon panels contain a combination of straw and wood fibre, which emit 23kgCO2e/m2 whilst the SIP panels emits approximately 57kgCO2e/m2.

The carbon cost of materials should unquestionably include their manufacture and delivery to site, thereby encouraging local use of materials.  In this aspect, straw carries a distinct advantage over most complex building components, since, with sufficient pre-planning it is possible to obtain straw locally in most UK locations. This was demonstrated by Nottingham University[15] who constructed Europes largest strawbale clad building using straw from their own land adjacent to the building site. Straw is also an annual crop and abundantly available as a waste product from farming.

As Figure B.  demonstrates that whilst a house built to Passivhaus standard using conventional materials will have a net carbon cost of 115 tons, a house built to Passivhaus standards using plant-based materials would have a net carbon cost of just 15 tons.


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Figure B.

Many common materials include toxic substances. The Substitute it Now policy outlines three categories of chemicals and 800 individual chemical groups that we should aim to avoid. Amongst the cause for concern are groups of chemicals that can cause cancer, alter DNA or damage reproductive systems, or those that do not easily break down and so accumulate in the food chain.  The EcoCocon straw wall panel is 98% plant-based fibre requiring no added chemical treatment to the straw, with the adhesive used in the plywood structure making up the remaining  2%. Unlike some other fibre-based insulation products that require fire retardants such as boron and biocide, straw, through its dense compaction and high naturally occurring silica content, does not require any additional fire retardants. The internal clay renders are fully organic materials that contain no chemical additions. The hygroscopic qualities of both clay and straw provide an intelligent interior finish capable of regulating humidity levels and improving internal air quality with many associated health and wellbeing benefits[16], as well as reductions in operational carbon.  

Globally and in the UK, the oldest remaining buildings are built using natural materials. We have learnt from the work of master builders who were able to design and build houses with lifespans of several centuries. To this mix, we have added the knowledge that we now have about the causes of climate change and how to mitigate them, the causes of unhappiness and disaffection with homes and habitats, and the tools at our disposal to increase well-being. It is impossible to argue that natural materials do not have the potential for a very long lifespan, when we are surrounded by evidence of their longevity (the House of Commons being a prime example). Our palette of materials is the same as that of the master builders of the past: straw and timber for structure and insulation, and lime and clay plasters for finishes, which prevent toxins, regulate humidity and are naturally anti-bacterial avoiding condensation and mould growth.

Given the simplicity in construction, low embodied carbon, high performance, longevity and benefits to human health, it is impossible to argue that nature-based materials are not essential in achieving the Governments net zero targets, and beyond.


Planning policy + regulation

Building regulations will imminently be in place to limit the height of timber frame or mass timber buildings from six storeys to effectively three storeys. This will put the UK housing sector on an entirely different path to the rest of Europe and North America where suitably certified timber frame and mass timber construction is becoming ever more prevalent and continues to reach new heights. We believe this decision is premature and that more could be done to underpin the safety of timber frame and mass timber construction as the basis of the new regulations. The Timber Trade Federation itself notes that:

Following the Grenfell Tower Fire, the government has rightly put great effort into making buildings safer. As the timber industry we support the creation of high quality, safe and sustainable buildings in the UK. However, we are concerned that by failing to differentiate between external cladding and the structural wall, the current approach to combustibles legislation will not achieve its aims[17]. We are proposing the use of natural construction materials as the key to delivering sustainable, affordable, healthy and safe buildings and we share the concerns of the Timber Trade Federation that the recommendations regarding proposed changes risk missing the opportunity to deliver safe combustibles legislation for ALL housing by failing to distinguish between cladding and structure, and failing to consider the risks of off-gassing from some non-combustible materials. There is already substantial evidence that some natural materials including timber have very high fire ratings.

Contrary to popular belief, straw and wood buildings resist fire very well. The straw in the panels is compressed at a density of 110kg/m³, leaving insufficient room for oxygen to fuel a fire. Moreover, straw contains high levels of silica, a natural fire retardant. When burning, both materials form a surface charcoal layer that protects them from flames. Combined with clay plaster, the proposed panels are rated to withstand two hours of intense fire according to the REI 120 and REIef120 certifications, meeting strict fire safety requirements. In fact, after two hours of over 1000°C (1832°F) on one side whilst the other side showed an average temperature increase of only 17.7°C (63.9°F).

Current planning policy and regulation does cover material re-use. Recording the location and nature of materials and components within the construction cycle using digital materials passportsenables them to be re-used in the future. When integrated with building information modelling (BIM), blockchain and digital twinning, it is possible to create a complete digital record of a building. The value of this is greatest at maintenance and disassembly stages, at which point information on materials and components can be accessed easily and used to guide decisions. This approach also records the inherent value of materials and components. The data will be saved centrally for future reference and intentions for reuse, recycling and maintenance and shared through home-user guides so that occupants understand how their homes are built. Options include the Madestar organisation and the BAMB platform.

The key impediment in stopping the industry adopting a natural material such as straw  is the increase in clauses within PI insurance making it difficult to specify anything non-standard. Additionally, there is a huge knowledge gap in the construction industry whereby contractors/planners/building control are not trained in the use of natural materials.  This requires both an attitude shift but also a shift in regulation towards encouraging the widespread use of natural materials.


Carbon, though a main focus of this inquiry, cannot be considered in isolation. Much of the evidence provided in this submission demonstrates that there is need for a holistic approach towards sustainable development whereby human, ecological and wider environmental consequences are all considered. Only with this approach will we achieve development which is truly sustainable that being socially sustainable, ecologically sustainable, and environmentally sustainable. Our suggestions for change are outlined below:

We want to see England acting to instigate a natural and biotechnology circular economy-based industry. We would welcome a government led initiative enabling the UK to act as a global leader in this emerging industry. Exemplar strategies towards mobilising this include:

-          Financing in-depth independent testing and verification of safety of key natural construction materials which would allow the many emerging businesses to expand and enter mass market adoption.

-          Supporting UK production of plant and earth based materials

-          Investing in training and skills across the industry (Architects, Contractors, Engineers, Building Control, Planners etc)

-          Building Regulations reform that prioritise the safety of all materials guided by data that take into account carbon, toxicity and safety in use.

We want to see radical not incremental environmental standards embedded into planning policy. Over the past decades the ability of the local council planning departments to fulfil the vital role of setting standards and enforcing these standards has been completely eroded through underfunding. Rather than further dismantle the powers of the planning and building control systems we want to see these vital public institutions strengthened and given teeth to go after those who do not adhere to the new standards.


To establish these new standards, we would like to suggest:

-          A citizens assemblymodel comprised of architects, engineers, planners, manufacturers and suppliers, building control and developers, for creating and amending policy

-          The introduction of a minimum energy standard based on ASBP Silver Standard or PassivHaus standards[18] or similar.

-          A maximum of 15-10% petroleum-based materials per dwelling by volume

-          Embodied carbon in line with achieving ambitious targets such as the LETI (London Energy Transformation Initiative) 2030 target of 300kg CO2e/m2 and 200kg CO2e/m2 including sequestration[19]

-          For toxicity to be designed out of all building components and follow the Substitute it Now design criteria[20]

-          A 200 Year Design Life

-          Independent On-site Quality Monitoring

-          Digital material passporting

-          Transitioning from a SWM waste plan to Material Conservation Plans, and penalising developers that do not comply with waste and reuse policies

May 2021

[1] https://www.gov.uk/government/publications/state-of-the-environment/state-of-the-environment-health-people-and-the-environment

[2] A clear response to climate change, the necessity for such interventions are laid out in the National Design Guide. Planning practice guidance for beautiful, enduring and successful places (Ministry of Housing 2019)

[3] https://www.carbonbrief.org/uk-could-cut-food-emissions-17-per-cent-by-sticking-to-healthy-diet

[4] .https://www.businessinsider.com/food-system-role-in-climate-crisis-possible-solutions-2019-8?r=US&IR=T

[5] Gregory N. Bratman et al. Nature and mental health: An ecosystem service perspective. Science Advances 24 Jul 2019: Vol.5

[6] https://www.nature.com/articles/s41598-019-44097-3    

[7] . Vivid Economics, Natural Capital Accounts for Public Green Space in London (Vivid Economics, 2017)

[8] https://www.businessgreen.com/news/3085100/business-as-usual-is-dead-global-resource-use-smashes-past-100-billion-tonnes

[9] https://www.architecture.com/-/media/GatherContent/Whole-life-carbon-assessment-for-architects/Additional-Documents/11241WholeLife CarbonGuidancev7pdf.pdf

[10] https://www.dropbox.com/s/uefh584fja44pcn/v2_LCA_Data_UK.Gov_stats.xlsx?dl=0

[11] .http://www.gaiagroup.org/projects/project/26

[12] https://strawworks.co.uk/projects/tulse-hill-neighbourhood-hub/

[13] https://ecococon.eu/gb/

[14] This house It is currently being extended by the French strawbale Association as their base, through the Interreg funded Up Straw project. http://cncp-feuillette.fr

[15] https://www.nottingham.ac.uk/news/pressreleases/2012/february/uks-largest-prefabricated-straw-bale-building-opens.aspx

[16] https://asbp.org.uk/all-resources?tx_category=briefing-paper

[17]  https://ttf.co.uk/combustibles-legislation/

[18] https://www.passivhaustrust.org.uk/

[19] LETI Embodied Carbon Primer: https://b80d7a04-

[20] https://chemsec.org/business-tool/sin-list