As a conclusion to this first section of the chapter, for the future, offices should follow the example of the few and have highly insulated double skin facades with integral flexible solar shading. The space can act as a plenum or accommodate vertical ducts to carry supply and extract air. The exhaust air will pass through a heat exchanger, perhaps boosted by ground source heat pumps. Natural ventilation via an air handling unit (AHU) must be the norm, if necessary mechanically assisted by low power fans.Air is ducted through floors, for example, by using the TermoDeck system (Figure 10.14).
Flash floods will be an increasing feature of climate change. Swales or depressions to channel water to bunded tanks under landscaping and car
104 Building for a Changing Climate 15 14 13 12 11 10 9 5 3 4 1 23 22 20 19 18 2 17 16
1 Natural ventilation and light shaft 2 PV glass
3 Double skin facade with external ventilation and narrower air gap (prefabricated) 4 Double skin facade with internal ventilation and narrower air gap (prefabricated) 5 Vacuum double facade
6 Solar lighting for basement 7 Solar lighting for night 8 Artificial wetland 9 Curtain wall
10 Motored horizontal shading 11 Motored openable window 12 Motored vertical shading
13 Window with anti-bridge aluminium frame
14 Double skin facade with external ventilation and wider air gap 15 Elevated floor with phase-change material
16 Self-cleaning glass 17 Eco-cabin 18 Insulated window 19 Lightweight insulated wall 20 Chimney for natural ventilation 21 Green roof
22 Solar disc 23 Solar air collector
Source: Derived from the exhibition board in Building Energy Research Centre Photograph: Ruyan Sun
8 7
6
parks will be needed in areas increasingly at risk of flooding. Conversely, severe droughts are also in the frame, and therefore water conservation must take on a new dimension of importance with recycling and purification high on the agenda. The implications for foundations in clay soils must also be taken into account.
Not only because of climate change, but also because of security of supply, energy will increasingly become a matter of concern. The
building envelope should aim to be carbon neutral – even carbon negative – with the use of carbon sequestering materials. Its design should provide maximum opportunity for the installation of photovoltaic and solar thermal panels, especially with the prospect of much improved installed cost/kW of PVs in near future. Some sites will favour small scale wind power – bearing in mind that the load factor/COP of wind technology now has little room for improvement. On the Figure 10.12 Pujiang Intelligence Valley, Business Centre, Shanghai, China
other hand, there are claims that the COP of ground source heat pumps still has some way to go. Pile foundations coupled with GSHP loops are an economical option.
Whilst the energy requirement of the building envelope may continue to fall, uncertainty surrounds the future electricity demands of IT, which currently can account for 50 per cent of the total for the building. According to Max Fordham ‘in a low energy office building [IT equipment] will remain the largest source of carbon dioxide emissions (Fordham, 2007, p131). This is one reason why there should be an adequate margin in the supply of renewable energy, which probably cannot all be obtained onsite.
The harsh reality is that the bulk of offices and institutional/administrative buildings will never achieve zero carbon status even when the contribution from onsite renewables is taken into account. It has already been suggested that
zero carbon can be achieved by purchasing carbon credits under the European Emissions Trading Scheme. The extreme view of this device has been expressed by James Lovelock:
Carbon trading, with its huge government subsidies, is just what finance and industry wanted. It’s not going to do a damn thing about climate change , but it’ll make a lot of money for a lot of people and postpone the moment of reckoning.
(Lovelock, 2009) After the debacle of world economics since 2008 there are many who are sceptical about using the market mechanism to counter climate change. There is an alternative: a clean energy levy. In the case of most offices, there is not sufficient surface area to accommodate an adequate capacity of, say, PVs to qualify as zero carbon. The answer is for the calculated annual energy excess over zero to
106 Building for a Changing Climate
GSHP GSHP Fresh air Exhaust air Negative pressure Heat exchanger
be met by an equivalent contribution to utility scale renewable energy. For example, new offices in London could offer a lifeline to offshore wind power in terms of the cost of the Thames Array. In addition, where there is a significant risk of flooding from a storm surge, as in the Docklands development and Thames Gateway, there should be a special levy, as suggested in Chapter 5, contributing to an estuary barrage. Since this would also generate considerable power, the two levies could be amalgamated with an appropriate overall reduction in the levy.
As an example, current good practice suggests that the consumption for offices should be
around 150kWh/m2/year. Taking a modest size office of 10,000m2, if it can already be credited with 50kWh/m2/year from onsite renewables, this leaves a levy liability of 100kWh/m2/year. This adds up to 1000MWh/year. Taking the capacity (or load) factor into account, this liability could be fulfilled by meeting the cost of a 500kW wind turbine, or one third the cost of an industry standard 1.5MW machine.This would be a much more accurate method of subsidy than relying on the vagaries of the market. In the face of the twin crises that are looming – climate change and depleting energy reserves – such a levy system is the most appropriate.
Heating load target 20kWh/m2/year
Electrical load target 25kWh/m2/year
Air tightness <3m3/hr/m2
Daylighting 100% to BS 8206 Pt2
Artificial lighting controls Luminance and person detection
Dimming controls with building management system override Heating/cooling Dual action ground source heat pumps
Active chilled thermal mass
Additional cooling Ground source water cooling for rooms with high internal heat gains Evaporative cooling where viable
Solar thermal circuits below car parks for seasonal heat storage
In areas prone to flooding, surface water storage tanks below car parks, terraces, etc. Alternatively, permeable surfaces to all hard areas
Insulation U-values: W/m2K
Walls 0.10
Average for windows 0.8 (triple-glazed)
Roof 0.10
Ground floor 0.10
Plan Narrow floor plate to maximize daylight and cross ventilation. Where possible include an atrium
Ideal orientation: north–south
Appendix
108 Building for a Changing Climate
Structure Design for wind load of 150mph storm
Design for 50°C peak summer temperature re expansion joints and materials stability
Floors Hollow concrete planks with fairface soffit with cavities facilitating flow and return of ventilation/warm/cool air, for example the Termodeck system
Facade Double skin facades with integral flexible solar shading, the cavity acting as a plenum for heat retention in winter and cooling in summer. The exhaust air will pass through a heat exchanger, ideally boosted by reversible ground source heat pumps. Natural ventilation via an air handling unit (AHU) (Figure 10.14), if necessary boosted by low power fans
Roofs Green roofs where possible with Monodraught ventilation units
Alternatively, 30° south facing pitch is ideal for PVs and solar thermal. Thin film PVs are promising for the future
Materials Insulation materials
No petro-chemical-based insulants. Insulants from renewable sources, e.g. sheep’s wool, cellulose, cork
Structure Low carbon concrete via pulverised ash aggregate
(example: Persistence Works, Sheffield by Feilden Clegg Bradley) Design for dismantling and reuse of elements
Recycling Maximize prefabrication to minimize waste and facilitate recycling bricks bonded with lime mortar for ease of recycling
Steel Better recycling potential than concrete
Timber Should be from certified renewable forests Onsite composting of vegetable matter and paper Building management
systems
User-friendly BMS design with intelligible instructions All-staff training in optimization of BMS performance Biodiversity Tree planting with appropriate species offering solar shading
Wide range of plant species around buildings Pools for wildlife and evaporative cooling Green facades where possible
Appendix
Some of the most environmentally advanced buildings are to be found in various buildings designed for community use. One of the leaders in the field is Jubilee Wharf, Penryn quayside, Cornwall (Figure 11.1).
The genetic code of Bill Dunster and the Zedfactory is clearly evident in Jubilee Wharf, Penryn, Cornwall, UK. Its shapes are unconventional, yet architectural critic Jonathan Glancey considers ‘It fits, in an appropriately ramshackle way, into the higgledy-piggledy fabric of Penryn … somehow it all fits together’ (Guardian, 11 January 2007) (Figure 11.1).
This is a mixed development beside the river in Penryn consisting of two buildings. One comprises 12 studio workshops with six maisonettes above. The other accommodates a Sure Start nursery, the ZedShed public hall offering community facilities and a café that already has a renowned reputation. The two buildings enclose a courtyard establishing a public walkway along the quayside that has already proved a successful social space. It is already a ‘lively and bustling space’ which, in due course, should accommodate a farmers’ market. The design of the waterfront block roof ensures that the brisk winds on the harbour are deflected over the courtyard.
It has been described as a ‘state-of-the-art example of green architecture’ (Buchanan, 2006). The environmental features of the building are encapsulated in a characteristic architectural/services drawing, Figure 11.2.
The Jubilee Wharf maisonettes are super- insulated and airtight with glazed sun spaces.
The floors are concrete, adding to the thermal mass. Natural ventilation is by means of wind- orientating cowls designed to cope with the often extreme wind loads. The workshops have low grade underfloor heating, as do the maisonettes and community spaces. However, the combination of high insulation and solar orientation plus solar thermal panels on the higher roof means that it is hardly ever needed. A wood pellet biomass boiler ensures comfortable conditions in winter. Local labour and materials were used, most notably western red cedar and larch from the vicinity. All wood used in the construction was from sustainable sources and therefore accredited by the Forest Stewardship Council.
Four wind turbines are located on the quayside, and are able to rotate to exploit any wind direction. There are plans to mount photovoltaic cells, which should enable the complex to be a net contributor to the grid.
Jubilee Wharf is a milestone in green design and sets a new example for how small towns can develop, intelligently and economically.
(Peter Buchanan, 2006)
Health
The primary cancer health care and treatment centre at the Churchill Hospital in Oxford is the first major hospital in the UK to be entirely heated and cooled by ground source heat pumps (GSHPs).As such it is deemed to be an exemplar