Building Revolutions

Applying the Circular Economy to the Built Environment

David Cheshire

• Verlag: RIBA Publishing
• Jahr: 2019
• ISBN:
  9781000701555
• Auflage: 1
• Thema: Architecture
• Thema: Architecture General

The construction industry operates within a linear economy of make, use, dispose. Buildings are stripped out and torn down with astonishing regularity while new buildings are constructed from hard-won virgin materials. But raw materials are becoming scarce, and the demands for them are exploiting fragile ecosystems, even as the global demand for resources continues to rise.

Policy makers and organisations are beginning to look for a more regenerative, circular economy model. The construction industry demands over half the world's extracted materials and generates around a third of the total waste generated in the EU, making it a prime candidate for applying the circular economy. Yet there has been little focus on how construction industry professionals and their clients can contribute towards the movement.

Drawing on illustrative methods and examples, Building Revolutions explains how the principles of a circular economy can be applied to the built environment where resources are kept in use and their value retained.

10. Selecting materials and products

Buildings are gold mines of materials just waiting to be harvested.

Ellen MacArthur Foundation

In a circular economy, each material in the building and its components has to be declared and defined, the composition has to be as pure as possible and it has to separable from other materials. These requisites ensure that buildings can become materials banks (see Chapter 11) where materials are effectively stored for future use, rather than consumed and lost.

One of the defining principles of a circular economy is the distinct split between 'biological materials' and 'technical materials', as explained in Chapter 1. Biological materials, such as wood and sand, are used in products that are free of contaminants and toxics, so they can be returned to the biosphere at end of life. Technical materials, such as metals and plastics are retained within industrial loops that ensure they are not lost to the economy or returned to the environment. These technical components should be reused as far as possible and the constituent materials recycled as a last resort.

Matching Lifetime to Material Selection

The idea of 'building in layers' (proposed in Chapter 6) aims to differentiate between components with a shorter lifespan (e.g. carpets) and those with a longer lifespan (building structure). The likely lifespan of each component should be carefully considered and the materials selected accordingly. The lifespan of internal fixtures and fittings is often over-estimated and designed for a long lifespan that is not achieved, leading to significant waste. Components that are likely to have a shorter expected lifespan can either be made from biological materials that can be returned to the biosphere or designed to be readily returned to the manufacturer for reuse, remanufacture or recycling. Components with a longer lifespan, such as the structure and fabric, should be designed to be durable and resilient, whilst ensuring that they can be maintained, upgraded or disassembled, as required.

'Project XX', Delft

Project XX is an experimental office building design in Delft, Netherlands. The aim was to design a building with a limited lifetime, on the basis that office buildings often undergo major refurbishment every 20 years. So rather than designing a building that is supposed to last for 60 or 100 years, why not design one that just lasts for 20 years? The name ‘Project XX’ represents the design life of the building in Roman numerals.

Each of the building elements and materials were classified according to their lifetime and their ability for reuse. The main elements of the building were chosen to last for the required 20 years and then the following criteria were applied:

• simple to reclaim as uncontaminated raw materials, such as sand or untreated timber
• reusable without any alteration, in general applications
• reusable with minor alterations, in specific applications
• fully separable and recyclable.

Jouke Post of XX Architecten says: ‘Materials should be matched to the expected lifespan of a building. That means that components with differing lifespans should be mounted so that they can be dismantled separately.’

The building uses some simple techniques to increase the potential recovery of materials and components:

• the façade is independent of the structural frame
• all the connections (e.g. steel plates, pins and bolts) can be dismantled and avoid the use of glue, putty or sealant
• the insulation is not bonded to the prefabricated ground slabs or the roof membrane
• the internal timber cladding panels are left unpainted, and
• the carpet is not glued down.

Figure 10.01: Project XX, Delft, showing interior.

Dry methods of connection are used between different elements, such as:

• the façade frame and the glass panels
• the steel plate connections between timber columns and primary beams, and
• the connections between floor panels and beams.

The building also uses biological materials that can be returned to the biosphere at end-of-life, so the ventilation ducts are made from cardboard, the structural frame is laminated timber (see Figure 10.01), and a sand fill is used in the first floor to provide acoustic insulation.

The building was constructed in 1996 and has proved so popular with the occupants that it remains standing at the time of writing.

Biological Materials

Biological materials are those that can be returned to the biosphere and allowed to biodegrade. The circular economy model proposes that the use of biological materials can be ‘cascaded’ through various uses, rather than used just the once. An example of cascading might be where solid timber is used in a building and then chipped for use in panel products.

Biodegradable materials are those that can be broken down by microorganisms in the biosphere. Sassi proposes that biodegradable materials can be grouped into four categories:¹

1. Natural materials that can be used following minimal processing (e.g. timber, bamboo, cork, hemp).
2. Natural materials bonded with a resin or mesh (e.g. clay, hemp and straw mixtures for external walls, strawboard for internal partitions, jute carpet backing, linseed oil and natural resin to make linoleum).
3. Natural compounds used in manufacturing products including adhesives and other polymers (e.g. natural protein to manufacture biodegradable plastics).
4. Biodegradable synthetic materials (biodegradable plastics).

Materials in the first category require only to be shredded to allow them to be composted. For materials in the second category, the aim would be to ensure that biodegradable material is not bonded with non-biodegradable materials (e.g. natural fibres used in concrete or cement products or chemical, non-biological bonding agents), as this will inhibit its ability to be returned to the biosphere. Non-toxic bonding agents can be used in minimum amounts, but this would restrict the potential uses for the resulting compost.²

Natural biodegradable plastics can be made from polymers such as cellulose, starch, protein and sugar molasses extracted from plants.³ Biodegradable synthetic plastics have been developed and have some limited use for disposable packaging and plastic bags.

Substituting biodegradable materials for technical materials is one way to reduce the end-of-life impact of components, particularly those with a short lifespan or those that currently have poor reclaim or recycling rates. Examples are shown in the following case studies.

Adaptavate – a Biocomposite Plasterboard

Fit-outs and refurbishments often involve stripping out plasterboard partitioning and drylining. All too often, the plasterboard is scrapped and sent to specialist landfills, despite it being technically and commercially viable to recycle the gypsum into new plasterboard. There are alternative wall boards on the market, but there are very few truly natural products that can be composted at end-of-life.

Thomas Robinson researched biocomposites during his MSc at the Centre for Alternative Technology and his idea for a natural wall board product was selected for the UK Climate-KIC Accelerator Programme based at Imperial College London. This allowed him to raise enough funds to set up Adaptavate and to start the product development of a biodegradable board called ‘Breathaboard’ (see Figure 10.02). The board is made from a biocomposite with the aim of providing the following beneficial properties:

Figure 10.02: Breathaboard biocomposite plasterboard alternative.

• Hydroscopic, meaning that it will absorb and release moisture from the air. This will help to reduce mould growth and the impacts this can have on the health of occupants. It should also help to reduce the impact of moisture on the building fabric.
• Entirely compostable at end-of-life, meaning that offcuts or the whole board can be returned to the biosphere.
• Lighter than other wall boards, making it easier to lift and handle.
• The binder has been proven in other applications to absorb VOCs. Robinson is hoping to be able to demonstrate that his wall board will also absorb VOCs from the internal environment.

Plasterboard is an example of a ubiquitous building component currently made from a technical material that is often not returned back to an industrial process. Products like Breathaboard represent an opportunity to substitute a biological material for a technical one, providing multiple benefits in the process.

GatorDuct – Cardboard Ductwork

Building services typically have a shorter life than the buildings that house them. Systems and components that service floors and occupied areas are often stripped out as part of a refit, particularly in office and retail environments. Perhaps in these situations, the local services could be considered as consumables. So ductwork could be made of readily recyclable materials instead of using durable, engineered metals and plastics. There is ductwork on the market made from fabric and even from cardboard.

Tri-wall cardboard ductwork has been developed by GatorDuct, which has a coating made from a water-based solution with a water dispersal polymer, fire retardant minerals and a final hydrophobic finish (see Figure 10.03). The coating can be recycled with other water- and oil-based printed paper. The cardboard is high strength and can be used by recyclers for other substantial cardboard products. Cardboard ductwork requires less insulation than steel ductwork as it has some insulating properties. It is also considerably lighter, making it easier to handle and install.⁴

Figure 10.03: Cardboard ductwork.

Architype and The Enterprise Centre

Biological materials can be used to create lighter construction that uses fewer resources, as well as providing materials that can be returned to the biosphere.

Architype’s desire for simplified designs can be traced back to its roots in self-build housing. Designing for lay builders means everything has to be as simple and pared back as possible. The practice has carried this philosophy through its projects and has designed buildings that use less resources through a combination of lean design and careful materia...