The emerging principles of the circular economy are driving greater resource efficiency. Construction and the built environment is the single biggest user of materials and generator of waste in the UK economy. Effectively dealing with buildings at the end of their life has the potential to unlock significant economic value. However the value that can be extracted is very much dependent on how the buildings have been designed and built. Design for Deconstruction (DfD) looks at how decisions made at the design stage can increase the quality and quantity of materials that can be re-used at the end of a building’s life.
BRE, with support from the BRE Trust, have developed an outline methodology to assess the deconstruction potential of new build residential. Application of this methodology could lead to the reduction of CO2 emissions through the benefits of reusing and recycling materials and components from buildings at the end of their life, by addressing ‘Circular Economy principles’ in the built environment. The methodology involves a combination of using checklists and a scoring approach relating to a number of criteria, making use of information from design drawings and project specifications. Consequently, an overall deconstruction potential score is obtained for a residential building.
The methodology has been applied to a number of residential case studies including two modular constructions and a more traditional brick and block; and an office building and a ski-slope construction. The case studies describe the methodology, the deconstruction potential and recommendations for achieving an improved deconstruction capability.
This collection of case studies aim to raise awareness amongst architects, designers and contractors of the potential of deconstruction to create more sustainable buildings and some of the actions that can lead to better deconstruction outcomes.
Why is design for deconstruction important?
The built environment currently accounts for around 60% of UK’s material consumption and nearly half of all waste arising. By ‘Designing for Deconstruction’ (DfD) there are long term savings to be made in the amount of material used and related embodied carbon as well as reducedwaste arisings. This is by ensuring that components that are specified are fit for purpose and can preferably be reused rather than recycled at the end of their life, maintain their value. DfD is one of the key parts of the jigsaw to assist the construction industry in achieving higher levels of resource efficiency and embedding circular economy thinking.
There was an estimated 23.2 million dwellings in existence in England in 2013. Houses and other types of buildings that are designed and built now will at some point come to the end of their useful life (the accepted service life norm is 60 years), when they will be demolished or significantly altered. It is therefore important to consider how the buildings components can either be reused and/or recycled. Current recycling rates for demolition waste are very high; however the majority of these materials are often ‘downcycled’ (producing a lower value product than the original) and the reuse of components and products is minimal. This is in part due to the way the building has been designed and the materials that have been used – it usually costs more and takes longer to deconstruct than demolish. By undertaking deconstruction, products should be able to be removed for reuse as there is minimal damage to them. With demolition, the product is usually destroyed and the materials sent for recycling. Additionally, with the increasing use of composite products to assist in meeting higher thermal requirements, recycling rates are expected to be impacted as it can be difficult to separate these materials to enable their recovery. DfD enables a building’s resources to be preferably reused, therecycled in the most efficient and productive way. At its simplest level, there are two main considerations:
- The types of materials and components used; and
- The way the materials and components are put together (thus able to be taken apart) and deconstructed.
WRAP has defined Design for Deconstruction and Flexibility (DfDF) as one of the five principles for designing out waste within its Designing out Waste Guide. Consideration of DfD needs to be embedded within the key stages of the design process to ensure it is considered at the earliest stages of a construction project where the opportunity for influence is at its greatest. According to BS8895-2:2015 Designing for material efficiency in building projects , consideration of DfD should be given where feasible during the Concept and Developed design stages of the RIBA Plan of Work Stages.
There is some guidance available to help designers apply DfD thinking and principles such as the SEDA Design and Detailing for Deconstruction publication. However there is no accepted UK methodology, standard or test which designers can use to assess the ease of deconstruction of a building and the subsequent reuse and recycling potential of the building’s components.
BRE have developed an outline methodology to measure the ‘deconstructability’ of new build residential buildings. This methodology is intended as a developer/designer tool and should be applied during the design stage of a project, to inform the design process of where there is potential to maximise deconstruction opportunities, thereby contributing to reductions in overall carbon emissions. The methodology includes consideration of:
- materials and component choices;
- types of connections used;
- the accessibility of components and connections;
- the deconstruction process; and
- the level of project information relating to deconstruction.
The elements and components
A checklist is used to define the types of elements and components that will be used within the proposed building. The elements are grouped into: foundations and ground floor, other floors, roof, external walls, other walls and finishes, floor finishes, building services and sanitary ware. Fixtures and fittings are also considered, if information is available.
The elements are weighted using the relative impact of their embodied CO2e. These figures have been derived from an NHBC Study on operational and embodied carbon in new housing and BRE datasets. The weighting varies for the type of house: whether it is a masonry or timber house and whether it is detached or not.
DfD criteria are applied to each of the building’s weighted elements and a score is obtained for each element. The scored criteria are:
- Reuse and recycling potential of the key elements and components within;
- The connections between the elements and components (a checklist approach is used for connections for the first stages of design followed by the scoring approach);
- The accessibility of elements and components; and
- The deconstruction process.
Each of these criterion is scored either a 1, 0.5 or 0; dependent upon if it has been fully, partially or not considered within the design process for each element. The score for each criterion is then aggregated across the elements and presented as a percentage.
Appropriate project documentation is very important for DfD. When the building has reached its end of its life, sufficient information should be available for the demolition contractor to be able to deconstruct the building (i.e. take it apart), identify the components and materials that have been used and their potential for reuse and recycling. This is where the current development of Building Information Modelling (BIM), will make gains in the ability to document a project’s assets in a single location, with real time data.
DfD will also be influenced within the framework of BIM, enabling designers to model buildings more efficiently. 3D modelling of project data, design drawings and development of the project specifications enhances the knowledge base upon which a project is founded and therefore enables more resource efficient future uses. Data related to assessing DfD, such as the reuse and recycling potential of components, how they are connected and their accessibility could all be captured within a BIM model.
The intention is that this methodology is the first step in being able to measure the deconstruction potential. . There are a number of wider recommendations going forward:
- DfD principles should be applied throughout the design process and integrated into the BIM objects data and the main body of the design and specification details. It is relatively easy to score and provide recommendations for the reuse and recycling potential of key components and materials; suppliers may have to be contacted and reference guides used
- It can be difficult to assess the connections for DfD due to the amount of information required and the level of details on drawings. This isn’t always available at earlier stages of the project until detailed specifications are available and the opportunity for change is limited; making an early adoption of the DfD methodology is important
- Checklists for considering DfD within the project procurement and documentation should be used as part of the project planning process and where possible integrated into other systems/forms
- Dialogue with a demolition contractor will help in assessing the deconstruction potential, in the form of any special health and safety requirements, likely resource requirements and specialised equipment.
The methodology is likely to be further developed to include issues such as the lifetime of elements, BIM objects data, whole life costing and other types of construction projects.
- SEDA – Design and Detailing for Deconstruction
- CIRIA – Design for deconstruction. Principles of design to facilitate reuse and recycling
- WRAP – Designing out Waste Guides and Information
- WRAP – Design for Deconstructio and Flexibility
- BRE – Difficult Demolition Wastes: A Guide
Information on the reclamation and recycling potential