Design for recycling v design for durability

Introduction

The UK government waste strategy, as set out in the 1998 Department of the Environment Transport and the Regions consultation paper Less Waste More Value ⁽¹⁾, promotes a waste hierarchy, which prioritises the reduction of waste followed by reuse of waste, recycling and finally the disposal of waste. Waste minimisation initiatives are well under way in the UK and recycling is now being considered. To enable reuse and recycling in the building industry, buildings should be designed to allow for dismantling of building elements. The ability to dismantle is however sometimes at odds with the principles of designing for durability.

Waste minimisation and recycling

The UK building industry is increasingly adopting waste minimisation strategies in construction and demolition projects to achieve both environmental and economic benefits. A number of waste minimisation approaches are currently being implemented. In construction, modularization is expected to reduce waste through more efficient use of standard sized materials and prefabrication has been found to minimise waste through the enhanced and more controlled working conditions of a factory environment. In demolition the reuse and recycling of demolition waste has proved to be economically beneficial where the demolition waste can be reused on the same site in lieu of primary materials, be it roof tiles, concrete aggregate or hardcore ⁽²⁾. In both construction and demolition work the segregation of waste has also proved economically beneficial by resulting in reduced disposal costs for the separated waste and the elimination of disposal costs for recyclable materials.

With the evidence of possible economic benefits of recycling, recycling is increasingly being considered as a viable way of reducing the environmental impacts of building. The environmental benefits of recycling materials are extensive. The energy benefits of recovering building elements for reuse or for recycling can be as much as a third of the total energy use of a building ⁽³). Further environmental benefits of recycling and reusing building elements include reduced depletion of natural resources, reduced destruction of natural habitats and the resulting extinction of plant and animal species and reduced waste and pollution generation.

However the scope for recycling building elements and materials in existing buildings is often limited by technical constraints imposed by the construction of the building itself. In order to maximise the potential for recycling in buildings in the future, buildings should be designed to facilitate the reuse and recycling of building elements and components.

But should all elements of a building be designed to enable dismantling and reusing or recycling? Should all buildings be constructed for recycling? Or should certain building elements or building types be designed for maximum durability?

In the UK numerous buildings currently in private and public use are more than 200 years old. The municipal offices in Twickenham (ca. 1650), St.Bartholomew’s hospital in London (ca. 1730), numerous London stations built in the early 1800’s and a substantial number of the country’s dwellings of the same period are some of the many examples of long life buildings. Building for durability still does appear to have a place in today’s culture and could have a more targeted practical function in future.

To determine where designing for recycling and designing for durability is most appropriate the nature of building work being carried out to existing buildings in the UK was investigated. A survey was undertaken of UK architects to establish the nature, frequency and motivation for refurbishment, alteration and replacement work to buildings and building elements.

The survey

The work reported as part of the survey was divided in five main different types of work.
1/ Decoration
2/ Internal remodelling (included repositioning of partitions, doors etc. and internal fitouts)
3/ Replacement of services (including heating and ventilation, electrical services etc.)
4/ Replacement of external non-structural elements (including windows, roofing, wall cladding etc.)
5/ Conversions and extensions.

None of the work reported included substantial structural work. In most cases the basic building structure was kept fully intact.
The average frequencies of the work (Fig. 1) varied according to the type of work, work to the building interiors occurring more frequently than work to the exterior, and according to the type of building. (Fig. 2) Retail buildings, bars and restaurants were found to have the shortest turnover of internal fitouts and shopfronts and public buildings on the other end of the scale had the longest periods between interventions.

Generally the work frequencies were well below the potential life of most building elements. Internal remodelling would generally involve removing walls with a life expectancy of 30-60 years in plasterboard and 60+ in solid masonry construction ⁽³⁾. A remodelling frequency of 10 years would therefore reduce the life of the building element life to a third or less of its potential. This shortfall could be reduced by either reusing the building element or recycling the material.

What appears significant is the motivation for the building work. Most work to existing buildings was not motivated by requirements for maintenance, but rather by the wish to enhance the appearance, increase space or improve the economic value of the building. The survey results showed only one fifth of the work was regarded as maintenance and another 5% of the work was aimed at upgrading to current technologies (Fig 3).

Fig 1 Average frequency of building work

Fig. 2 Frequency of work to building elements of existing buildings



Fig. 3 Motivation for building work

Reuse, recycling or durability

Reuse is preferable according to the above-mentioned waste hierarchy, but may not always be the appropriate waste solution. Considering the work done in connection with services, we find that services are often removed due to their technological obsolescence and could therefore not be reused, but should be dismantled and tdhe materials recycled. Designing for recycling would therefore seem essential for building elements that have a shorter life than the rest of the building. This would apply to services, but also most finishes in buildings.
Reuse does appear appropriate where building elements have a longer potential life than the time for which they are neede in one location. Internal building elements such as the previously mentioned plasterboard wall are prime examples. Here building technology currently prevents plasterboard walls to be reused. Even recycling of the materials is hampered by the contaminants.

However design solutions for reusable partitions exist for offices and similar solutions could be developed for other building types. While the majority of building elements that would benefit from reuse are not reclaimed, there are, in fact, numerous building elements that can and are currently reclaimed and reused, roof tiles, bricks, doors are only a few.

A further point highlighted by the survey was the fact that work to structural elements was minimal. Whether because of an absence of any need to change the structure to achieve the desired results or due to the high cost of structural interventions, the fact remains that it appears possible and very common to work within existing structures.

Conclusion

As a result of this study the following building format is proposed as a possible way forward for waste minimisation, recycling and reuse in buildings.

The proposed format would provide a durable structure that would allow changes of finishes, secondary building elements and service. It would also be designed to allow changes of building use, which may require the structure to be over-designed in terms of structural loading and sizing (e.g. floor to ceiling dimensions). Internal and external secondary elements should be designed for reuse, many examples are already available on the market. Services should be able to be dismantled and the components reconditioned or recycled.

Finishes should be designed for reuse and recycling, possibly following the examples of companies such as Interface, which leases floor coverings and recycles used carpets. The proposed format is not limited in terms of building type.

While some technologies aimed at producing durable buildings preclude the recycling of the same, this is not necessarily always the case. The durability of building elements can in fact contribute to the recyclability of those same elements. The challenge is not to make buildings recyclable rather than durable, but both recyclable and durable.

References

(1) Coventry, Woolveridge, Hiller 1999: The Reclaimed and Recycled Construction Materials Handbook. CIRIA C513
(2) Case Study Report, Waste minimisation in housing construction. CIRIA RP582/1
(3) P.Crowther Design for disassembly to recover embodied energy PLEA 1999 Conference
(4) Shiers and Howard 1996, The Green Guide to Specification Post Office Property Holdings