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Last edited 15 Nov 2020
Design for deconstruction, office building
This is the fifth in a series of case studies that use a new methodology to assess the deconstruction potential of new build properties. The case studies and methodology have been funded by the BRE Trust to raise awareness amongst architects, designers and contractors of the potential of Design for Deconstruction (DfD) to create more sustainable buildings and lead to better deconstruction outcomes.
This building was built as the first ‘Energy Efficient Office of the Future’ and represented a major advance in the design of low energy buildings. It was designed to demonstrate techniques which can be used in future low energy and environmentally-friendly offices.
The building is naturally ventilated and uses its thermal mass to moderate high summertime temperatures. Water is abstracted from a borehole and used as a very energy-efficient source of additional cooling for the building. The offices have a high proportion of glazing to make maximum use of daylight, together with solar louvres to limit solar heat gain. Other features include a super-efficient lighting system, sophisticated controls, photovoltaic panels and the extensive use of recycled materials.
The concrete building consists of two parts – approximately 1,300 m² of offices for about 100 staff and about 800 m² of seminar facilities. The building is approximately 2,040 m² total gross area and 1,470 m² of net usable area. The stack face of the building faces almost exactly due north south with the main seminar room on the north side of the offices. The offices are 30 m x 13.5 m with the long axis running east-west, with the west wall connecting to the entrance atrium. The stacks and the solar shading are on the southerly facade of the offices.
The offices are on three floors and are on a regular grid, 4.5 m north zone, 1.5 m corridor zone and 7.5 m south zone. The ceilings of the ground and first floors are 3.4 m high at their peak. The second floor has a southerly facing sloping roof which varies from 2.5 m up to 5 m in height. The building specification is summarised in the table below.
No project-specific deconstruction information is available. However, detailed construction drawings are available. This will enable the demolition contractor to develop a suitable approach for deconstruction.
Score achieved 91%
External and internal walls: External brick leaf of the cavity wall was installed using a cement mortar, making it difficult to remove the bricks for ruse without considerable damage. The plastered internal wall would have to be demolished. Plaster boards screwed on to timber stud walls can be manually un-screwed. Skirting boards nailed to plaster boards can be removed.
Roof: Aluminium roofing is fixed using self-drilling and threading screws to the metal framing which can be dismantled. All other elements fixed using bolts, screws and nails such as steel columns, metal decking, timber tongue and groove boards, timber panels, eaves, aluminium louvre blades, coping, flashing, gutters can be removed. Figure 2 shows drawings of the roof construction.
Score achieved 69%
Services in the building are minimal and run along the raised access floors or via ceiling voids which can be easily accessed for maintenance or removal. The plant rooms in the ground floor, conference hall roof and the first floor allow a good level of access to service and dismantle/ remove any machinery.
Score achieved 64%
Recycling of the concrete foundation and ground floor is possible depending on whether it is possible to separate and sort the steel and concrete cost-effectively. The PIR insulation could be sent for energy recovery, rather than recycling.
Plasterboard used in the ceiling and partitions are recyclable. Internal and external timber battens for installing plaster board and cladding is recyclable and partly reusable; similarly the external untreated cedar cladding is also reusable.
OSB boards, mineral wool insulation, breather and vapour control membrane in the ground floor and roof are currently non-recyclable or re-useable. Glulam beams and purlins, and composite aluminium/timber framed windows although non-recyclable could be reused if they can be removed intact.
Score achieved: 74%
Internal floor finishes, doors and fittings can be soft stripped manually, with hand tools to minimise damage caused by large machinery. Following this, it is possible to strip off building components such as the roofing, cladding, windows and finally framing and foundations with excavators or cranes. This may have to be followed by more detailed manual separation of individual fixings and components (either on-site or off-site). Timber floors and fittings may require soaking with water to avoid splitting prior to removal.
The kitchen units are built in and are made of chipboard and stainless steel handles. Recycling is possible, but the more likely route is to become a fuel source. The worktops are manufactured from recycled plastic coffee cups. All the wardrobes doors are ply faced and these could be successfully reused. The main staircase is constructed from steel sections with steel balustrades, which can be unbolted and reused.
The office scored 72% overall for its DfD potential. Elements which had greater potential for DfD are the services which run along the raised access floors or ceiling voids making them accessible, the roof and the upper floor. The connections criteria (91%) and the optimisation of the deconstruction process (74%) scored the highest and reuse and recycling potential the lowest (64%). Most of the components could be dismantled using non-specialised equipment, as mechanical fixings are commonly used.
Key issues summarised are:
- The use of lime mortar rather than cement mortar for the reclaimed brick external wall would enable future reuse.
- It is preferable to fix the hardwood parquet flooring using nails or other mechanical fixings rather than glue, which could limit the reuse potential.
- Consideration of materials that have a potential recycling route (if reuse is not appropriate). Products that are difficult to recycle currently include the OSB boards, mineral wool insulation, and breather and vapour control.
- Reuse of precast concrete products, e.g. the raised floor panels, can be reused, however it is likely that information would be required with regard to their service life, structural integrity and load capacity etc. It could also be difficult to find another suitable application, without having to alter the dimensions of the panels.
- Due to considerations given to access for the services and the stack during the design – it makes them score highly for accessibility at the end of life.
This article was written by Katherine Adams. It was originally published on BRE Buzz in February 2016.
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