Anemia Infantil

In the simplest sense, design for deconstruction (DfD) means considering end of use scenarios during initial building design (Institution of Structural Engineers’

Sustainable Construction Panel, 2011a). Good design can ensure less damage to components and higher material recovery rates, thus maximising the volume and value of material that can be reused, ensuring high recycling rates of the remainder, and minimising waste to landfill. When considering embodied carbon, component reuse can displace the need for virgin material production. In this regard, deconstruction is preferable as it preserves the invested embodied carbon of materials, reducing the input of new energy in reprocessing or remanufacturing materials (Kibert, 2003).

The DfD concept emerged during the early 1990s (Kibert, 2003), and has been applied on a wide range of predominantly steel and wood-framed structures (see Densley Tingley (2012 pp. 14–18) for examples). Extensive guidance for designers has emerged, such as the checklists proposed by the Institution of Structural Engineers’

Sustainable Construction Panel (2011) or the principles outlined by Kibert (2003).

Davison & Densley Tingley (2011) identify 33 commonly cited design strategies

for deconstruction, summarised in Table 9. DfD can be supported by a range of software tools outlined by Densley Tingley (2012 pp. 13–14), including Sakura – a whole life carbon appraisal tool that incorporates end of life options, intended for use at the conceptual or scheme design stage (Densley Tingley & Davison, 2012).

Despite the clear environmental benefits and associated credits within environmental assessment schemes (Davison & Densley Tingley, 2011), the application of DfD is subject to a number of constraints, outlined by Guy (2002).

Chief amongst these is the “difficulty in convincing clients to pay slightly extra for their project to be designed for deconstruction, when the benefit is not incurred until some point in the future when the project is deconstructed and then the value of the salvaged materials can be claimed” (Densley Tingley & Davison, 2012). Without the common use of whole life costing and confidence in a future reuse market, it is difficult to make an economic case for DfD.

Over recent years, demolition has also become increasingly preferred to deconstruction due to time constraints, health and safety concerns and financial considerations. Although recycling of construction materials has increased during the last decade, reuse has declined substantially (Kay & Essex, 2009). For example, of the one million tonnes of steel arising from UK demolition in 2007, only 30,000 tonnes were reclaimed for reuse (3%). Meanwhile, only 1.5% of 2007 new build steel demand was met by reclaimed steel (Kay & Essex, 2009). By comparison, other estimates have suggested that across the EU between 10 and 37% of steel is reused, depending on section type (Addis, 2006). Cooper and Allwood (2012) have suggested that up to 50% of many common steel and aluminium construction products could be reused, though this is subject to a number of barriers (Densley Tingley & Allwood, 2014). There is clearly significant potential for greater reuse of high value and carbon-intensive metals within UK construction, with steel reuse the subject of two Innovate UK funded research projects at the time of writing (Gateway to Research, 2015). The potential also extends beyond steel, with an estimated 10 million tonnes of construction materials that could be reused each year (Kay & Essex, 2009 p. 6).

One means of exploiting this potential is encouraging greater use of novel ownership structures. For example, the leasing of major structural components such as roofs. In such a scheme, occupiers would lease out the roof for a long period corresponding to the anticipated structure life (such as 40 years) after which time the roof owners and installers would dismantle and reclaim the materials for reuse on a similar project. This approach has already been adopted by a small number of firms providing steel portal frames, temporary bridges and event staging. This model could potentially be applied to elements of many more structures with short anticipated lifespans and standardised designs. Component level precedents already exist in established take back schemes for plasterboard and PVC windows.

Table 9: Strategies for design for deconstruction (from Davison & Densley Tingley, 2011)

1 Ensure there is an integrated set of 'as built' drawings

2 Design building so elements are layered according to anticipated lifespan 3 Use connections that can be easily removed

4 Avoid use of adhesives, resins & coatings which compromise reuse potential 5 Develop a deconstruction plan during the design process

6 Design components and joints to be durable, so that they can be reused 7 Provide identification of component types

8 Use a standard structural grid

9 Design for maximum flexibility - to preserve the building as a whole 10 Whole design team, client & contractor need to be on board

11 Ensure structural systems can be easily deconstructed 12 Identify the design life of different elements

13 Provide access to all parts & connection points

14 Use the minimum number of connectors and limit the different types 15 Minimise the different number of materials used

16 Design the geometry to be simple

17 Allow extra time to ensure DfD is incorporated 18 Train contractors in DfD, where required

19 Establish targets for the percentage of the building that can be reused 20 Where possible design in passive measures instead of active service elements 21 Provide a full inventory of all materials and components used in the building 22 Size components to suit the means of handling

23 Use prefabrication and mass production where possible 24 Select easily separable materials, with good reuse potential 25 Avoid composite systems

26 Plan service routes so that they can be easily accessed and maintained 27 Designation of ‘fixing free zones’ to maximise lengths of material for reuse 28 Use modular design

29 Design for locally produced materials 30 Allow for safe deconstruction

31 Provide adequate tolerances for disassembly 32 Provide spare parts & storage for them

33 Avoid secondary finishes that cover connections

More projects could incorporate the reuse of existing foundations. Foundations are often responsible for the largest environmental impacts of a structure, requiring high volumes of concrete and steel. A wide range of reasons restrict their reuse in practice but many of these can be overcome (Addis, 2006 pp. 89–93). The last decade has seen the dissemination of extensive best practice guidance from CIRIA and the BRE (RuFUS, 2006; Chapman et al., 2007). This not only includes advice on reuse of existing foundations but steps to enable future reuse of new foundation designs. An

estimated fifth of global steel production is used in foundation rebar (Moynihan &

Allwood, 2012). Simply leaving this material in the ground at the end of a structure’s life is a tremendous waste. The development of technologies that can enable more effective recovery of this steel, or more frequent reuse of foundations, could significantly reduce new material demand.

In the long run ongoing efforts to develop fully reusable structures for common project types represents the next milestone for DfD. For instance, the RE-Fab project intends to create a framework for the development of Flexible Life Buildings (ASBP, 2015). Following a successful feasibility study and development of common protocols, the intention of the RE-Fab project is to develop a fully adaptable and demountable house for repeated deconstruction and reuse. The increased use of BIM also offers opportunities to maximise the benefits of DfD through comparative assessment of deconstruction strategies (Akbarnezhad et al., 2014). In the meantime, as summarised by Kestner & Webster (2010): “market forces are not sufficient” and “a combination of green building rating system incentives, price increases for new materials and possibly tax or regulatory incentives” will be needed to drive demand for DfD. Rios et al. (2015) highlight a range of state policies implemented in the U.S. that could support DfD; however, it is unlikely that comparable policies would garner sufficient support in the UK parliament at present. In addition to regulatory drivers, increased testing and re-conditioning facilities will be needed to support greater reuse.