Example of a minimal holiday cottage
designed by Angela Elliss Design
Dematerialisation is a critical aspect in sustainable development - some would say the most critical. This is not only because of the resource savings provided by reduction of any individual element in a project, but because of the multiplying factor - the ripple effect - created by these reductions. Here Neville Cowland of NOWarchitecture explores the potential before steps are taken to build anything.
What dematerialisation means
At the basic level dematerialisation refers to the reduction in the quantity of materials required to serve economic functions in society. In building terms, dematerialisation means doing more with less, or better yet, no material consumption to deliver the same level of functionality to the user. Choices are available in the way buildings are constructed to significantly reduce materialisation to a point where carbon neutral development is achievable.
Dematerialisation strategies for environmentally sustainable design that guide architecture include:
- Efficient logical structures & rational building forms
- Reduction of secondary finishes
- Economic use of materials
- Consideration of life cycle costs & embodied energy
In any approach to dematerialisation, planning decisions and material selections are augmented by consideration of passive energy systems which respond to climatic conditions:
- Solar orientation for warmth in winter and natural daylighting
- Even cross ventilation and induced passive ventilation
- Night purging systems for summer cooling
- High levels of exposed thermal mass to reduce temperature fluctuations
- Intelligent interplay of natural light
These initiatives are further supported by strategies for building services which provide reduced energy requirements:
- Low energy heating and cooling systems
- Efficient artificial lighting
- Integration of renewable energy sources
- Integration of rainwater harvesting systems
- Integration of passive cooling systems
The first strategy in dematerialisation is the planning of the project. Carefully define the size of the project, because at the basic level dematerialisation refers to the reduction in the quantity of materials required to serve a function.
- How many spaces are needed? Be conscious of the difference between required functions and desired functions and frequent and infrequent functions
- What space is required for each function?
- What size does each space need to be?
- Can the same space provide for multiple functions?
Ensure that room sizes are appropriate to their function, character and comfort levels based on:
- Floor space
- Room volume
- Proportion: enclosure area to floor area ratio
- Functional relationships: proportion of circulation space (wasted space)
- Spatial psychology: make spaces look larger than they are; consider window size and positions to allow external views to increase the sense of space and use mirrors to multiply views to enlarge the visual space
The number of spaces can be minimised by designing them to provide for more than a single function. For example, an appropriately designed and fitted garage can function as a rumpus room or home gym; a study can function as bedroom for infrequent guests. For easy transition provide storage options which allow the space to provide for different uses without limiting other functions.
Bigger is not better
If we look further in relation to housing, size becomes critical. Not only do larger houses require more materials, but there is a multiplying effect. Larger houses require more land which in turn dictates that there is more road for each house. As a result, service provision such as stormwater drainage and water and power supplies are spread over a larger area, requiring longer runs which requires larger pipe sizes, larger power cables and increased losses in the distribution grid. In itself, increasing the density of housing provides a substantial flow-on in dematerialisation of basic infrastructure.
Designing buildings around efficient structures provides a basis for reducing the materials required. Aesthetics of a project should be designed around an effective structural system, rather than the inverse. By considering the structure as integral to the aesthetics during the design process it is possible to reduce the structure to a higher efficiency and even to use the structure as the aesthetic element to reduce the requirement for cosmetic materials.
Structures can be made more efficient by taking a three-dimensional approach. For example, 3D strutting can significantly reduce beam span, thus the size, and reduce the number of columns required. The choice of materials used for the structure also affects the amount of materials required. In poor foundation conditions consider using void former tanks as structure to replace extensive concrete footing systems. This not only reduces the extent of material required, but provides a secondary purpose in providing water storage and can also provide a third purpose in providing a direct thermal source for cooling ventilation air. Select materials with less environmentally expensive alternatives. Concrete and steel can easily be replaced with timber or engineered timber which, when used appropriately, can also create a high quality aesthetic.
Make efficient use of materials; reduce elements to the thinnest possible. Generally favour lightweight materials but be aware of their embodied energy and reduce materials by designing efficient enclosure of spaces.
Make everything perform more than one function; eliminate walls if storage units can provide divisions, and make divisions and balustrades thin by using materials such as plywood, steel or glass instead of normal framed and lined walls. This reduces the required building size and can also provide for sharing light or simple reconfiguration of spaces.
Where masonry materials are required, consider using natural stone in place of brick or concrete. Use cladding as structure (walls) and use masonry as an internal thermal mass material rather than as a non- structural cladding. Use plywood bracing to reduce the extent of materials in structural walls or use insulated panels (SIPs) capable of long spans to allow portal structures to reduce framing.
An understanding of systems can provide a means for dematerialisation beyond the bounds of a project, even if more than the minimum infrastructure is provided at the site.
Water harvesting with on-site retention provides a benefit on site, and reduces infrastructure beyond the site by lowering the peak loads on public storm water systems and reducing demand for public water supply systems. On-site power generation (distributed energy systems) reduces grid infrastructure and distribution losses. Energy and water efficiency also aid the reduction in infrastructure: if less is used then less infrastructure will be required for supply.
Efficiency of design and installation is important. Avoid replicating services in the building. For example, the boiler for domestic hot water can also provide for heating in hydronic systems. Improved insulation and reduced air leakage reduces the requirement for heating and cooling systems. Materials which do not have secondary finishes reduce chemical loads and require less maintenance.
Learn more by buying the entire book
This article is one of many useful articles in the book entitled "How to rethink building materials". The book can be purchased online as a hard copy or soft copy (e-book).
Table of contents - "How to rethink building materials"
- Part 1 Overview: What it's all about
- 1.01 Creating sustainable change - Barriers to getting the message through.
- 1.02 Choosing materials from an early design stage - Questions to ask at the beginning of a project.
- 1.03 Managing change - How to avoid the downside of the building industry's inherent aversion to risk.
- Part 2 Forethought: A look at the issues behind the choices we make
- Part 3 Planning: Unfamiliar but essential considerations
- Part 4 The Great Debates: Contested ideas about material impacts
- Part 5 Uncommon Solutions: The fast-approaching horizon
- Part 8 A-Z of Building Materials