Buildings

penetration at certain times of day (rather than switching on the air conditioning) to putting on a sweater when the external temperature drops (rather than turning up the thermostat). On balance, green buildings require a more proactive engagement between occupier and the environment, which reflects the degree of “active” or “passive” environmental design techniques available in individual buildings, to which the report now turns.

Design and technology The greatest opportunities to achieve a higher environmental performance for buildings can be found in the early stages of their design. An integrated design methodology of green buildings combines environmental principles and technological inputs at various design stages. It requires a multidisciplinary approach and broadens conventional building design by including rigorous assessment procedures to comply with performance targets (Baker and Steemers 1999). Designing buildings based on environmental considerations implies continuous feedback between different design components, as decisions regarding building form, orientation, components, other architectural aspects as well as building systems are entirely integrated.

There are two basic paradigms of green building. The first is based on the concept of “passive” design where buildings respond to their local site context by using natural elements (such as air-flow and sunlight)

to

limit the effect of external conditions on the internal environment. Many traditional buildings with thick walls and small windows in hot climates, or with natural through-ventilation with courtyards and terraces in humid areas, belong to this category. Passive design aims to provide a comfortable environment while eliminating or reducing the need for space heating, cooling, ventilation or artificial lighting. The second paradigm is based on a more “active” approach that uses newer technology and state-of-the-art building management systems to reduce the energy load of buildings. Solar screens, lighting scoops, environmental flues, photovoltaic cells (PV), wind turbines and other devices are found in most state-of-the-art high-tech buildings. Both paradigms can be applied to new buildings as well as retrofitting existing building stock.

Many passive design techniques are finding their way into a new generation of building designs across the developed world, while new forms of green energy generation are being integrated in building projects in the developing world (Baker and Steemers 1999; Hawkes 1996; Herzog 1996). The field is littered with examples of how both passive design and technology have successfully reduced the energy footprint of buildings. A recent study of 5,375 commercial buildings in the USA showed that in new buildings the use of energy-efficient

lighting, heating, ventilation, air conditioning and shading can achieve a 64 per cent reduction in energy use (Griffith et al. 2006). In the UK, energy consumption guidelines indicate that the introduction of natural ventilation can achieve 55-60 per cent

reduction in

energy consumption in office buildings, compared with fully air-conditioned and fully glazed office buildings (CIBSE 2004).

Greater attention is now given to the impact of sustainable environmental design solutions on the running costs of buildings and how much energy is embodied in construction materials and processes. Increasingly, life-cycle assessments (LCA)2 applied,

which include not only operation

are being and

maintenance, but also the manufacture of construction materials (McDonough and Braungart 2002). In addition, a new generation of building guidance is focussing on the total energy costs of buildings, from the design stage through to completion, including considerations about their recyclability (Anderson et al. 2009; Hammond and Jones 2008).

Beyond the fabric and construction of the building, a more holistic approach to the design of buildings and their use also requires consideration of all energy-related components, including appliances and equipment used in buildings. Their relative energy use varies from country to country, based on climatic and cultural differences. The following listing of appliances and equipment by residential and public or commercial categories demonstrates the range of supplier industries involved.

Residential building sector

• Space heating and cooling • Mechanical ventilation • Hot water systems • Appliances (incl. cooking, washing, refrigeration, entertainment and cleaning)

• Indoor lighting

Office and commercial building sector

• Space heating, cooling and ventila- tion, air conditioning (HVAC)

• Indoor lighting • Outdoor lighting • Office equipment • Servers and data centres

In commercial buildings, office equipment comprises the fastest-growing area of energy consumption. In residential buildings world-wide, a growing proportion of energy consumption is associated with household appliances, including televisions, DVD players and home computers. Implementing the best available technologies can reduce their energy consumption by

2. Life-Cycle Assessment (LCA) is a tool devised for evaluating the

environmental impact of a product, process or a service across its life cycle, also referred to as the “environmental footprint”. All inputs and outputs of material, energy, water and waste over the entire product life cycle and their relative impacts are accounted for, including the extraction of raw materials, processing, manufacturing, transport, use and disposal. The main objective of a LCA is to compare the impacts of several alternative processes in order to chose the least damaging one.

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