City buildings—Eco-labels and shades of green!

Available online at www.sciencedirect.com

Landscape and Urban Planning 83 (2007) 29–38

City buildings—Eco-labels and shades of green! John Burnett ∗ The Hong Kong Polytechnic University, Kowloon, Hong Kong, People’s Republic of China

Abstract The concept of the sustainable city seems to fall somewhere between the ideal of sustainability and the more pragmatic responses to environmental degradation that lies within the ambit of sustainable development. Buildings are significant in terms of the economic and social development of cities, as well as their environmental impacts. Eco-labelling has emerged to provide a measure of the environmental performance of buildings, but what shade of green, i.e. environmental friendliness, is manifest in a particular eco-label, and how does the assessment and certification of individual buildings contribute to a city that is more sustainable? This paper examines the extent to which a building eco-label, defined here as a certified performance grade under a building environmental assessment method (BEAM), characterises the performance of a building in environmental terms, and considers the link between the issues covered in BEAM assessments with the indicators for the sustainable city. Given their significant influence on cities, the discussion focuses on heavily serviced office buildings. © 2007 Published by Elsevier B.V. Keywords: Sustainable cities; Buildings; Environmental assessment methods; Eco-labelling

1. Introduction To appreciate the concept of the sustainable city it is purposeful to differentiate between the terms ‘sustainability’ and ‘sustainable development’, both used extensively in the literature, often in the same context. Rees and Wacknernagel (1996), writing on the subject of ecological footprints provide an insight when arguing why cities cannot be sustainable, and yet, why they are the key to sustainability. Their analysis shows that, “as nodes of energy and material consumption, cities are causally linked to accelerating global ecological decline and are not by themselves sustainable. At the same time, cities and their inhabitants can play a major role in helping to achieve global sustainability.” This idea of sustainability focuses attention on the ability of the human population to live within the earth’s environmental limits. Environmental sustainability requires that natural capital be maintained, both as a provider of resources and as a depository for wastes and is, arguably, a prerequisite for social and economic sustainability (Costanza and Daly, 1992; Goodland, 1995). On the other hand sustainable development, frequently quoted from the Brundtland report (World Commission on

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0169-2046/$ – see front matter © 2007 Published by Elsevier B.V. doi:10.1016/j.landurbplan.2007.09.003

Environment and Development, 1987) as, “development that meets the needs of the present without compromising the ability of future generations to meet their own needs”, has been interpreted to mean many different things, with a given conception tending to reflect the political and philosophical position of the proponent. Sustainable development tends to place emphasis on the economic and social dimensions of sustainability, whilst allowing a more manageable and incremental approach to environmental sustainability. It appears more attractive to the practical world of government and business than the more tangible concept of sustainability (Robinson, 2004), but as Willers (1994) observes, promoters of sustainable development tend not respect the environmental constraints, which are argued by some (e.g. Goodland and Daly, 1996) to be ‘non-negotiable’. Girardet’s (2000) concept of a sustainable city seems to lie somewhere between sustainability and sustainable development, i.e. “a sustainable city is organised so as to enable all its citizens to meet their own needs and to enhance their well-being without damaging the natural world or endangering the living conditions of other people, now or in the future”. Although Blassingame (1998) pondered whether sustainable cities are an inevitability, Girardet’s concept remains an ideal, and today’s reality is to strive for cities that are progressively more sustainable, with those entrusted with the overall responsibility for city planning, development and management able to offer only incremental approaches towards this ideal. Indicators for the sustainable city, such as those of the European Commission

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(2005), include enhancements to environmental performance, i.e. reducing ecological footprint, sustainable land use, reducing noise and air pollution, the availability of amenities and open places, improved mobility and transportation, as well as reducing atmospheric emissions. Given their environmental, economic and social impacts, buildings are clearly a significant part of the sustainable development debate. So-called green buildings are contributors to cities that are more sustainable. This discussion considers the performance standards of green building eco-labels, defined here as a certified grade (or rating) of performance achieved under a building environmental assessment method (BEAM), and the extent to which performance relates to the indicators for the sustainable city. Because of their significance to the economy of a city, and their wider social and environmental impacts, the focus is on BEAM eco-labels for heavily serviced (e.g. air-conditioned) office buildings. 1.1. Green buildings A succinct definition for a green building, one that is echoed in other texts, is provided by ASTM International (2001), i.e. “a building that provides the specified building performance requirements while minimizing disturbance to and improving the functioning of local, regional, and global ecosystems both during and after its construction and specified service life”. Furthermore, “a green building optimizes efficiencies in resource management and operational performance; and minimizes risks to human health and the environment”. Whilst not defining targets for environmental sustainability the notion provides a goal for improved eco-efficiency, and by emphasising performance requirements and human health, it also embraces economic and social dimensions of sustainable development. Conceptually, the definition can be presented as a life cycle ‘efficiency’ ratio: life cycle eco-efficiency =

indoor environmental quality(IEQ)+services+amenities resource consumption+environmental loadings

The aim is to provide satisfactory levels of specified building performance whilst minimising consumption and environmental loadings over a buildings life cycle. Kilbert and Grosskopf (2005) argue that the ideal green building should have five major features; integration with local ecosystems, closed loop material systems, maximum use of passive design and renewable energy, optimised building hydrologic cycles, and full implementation of indoor environmental quality measures. Whilst a few exemplary buildings may be getting close to this ideal, for the majority of so-called green buildings the performance enhancements over conventional practice are incremental. The relative ‘greenness’ of a building in a given jurisdiction is discernable by the extent to which the performance standards achieved are an improvement over prevailing standards of building environmental performance, i.e. the customary baseline/benchmarks (e.g. compliance with regulations), as well as the extent to which they meet the standards required for environmental sustainability. Fig. 1 contrasts the levels of environmental

Fig. 1. Reducing environmental impacts through green building targets.

performance of the baseline/benchmarks, the targets for environmental sustainability, and the incremental improvements in the performance standards of green buildings. Conceptually, Fig. 1 can apply to a particular performance issue (e.g. annual energy consumption), a building, or a stock of buildings. As indicated by the double-headed arrows the absolute levels of performance of the baseline/benchmarks, as well as the targets for environmental sustainability, are largely unknown, although there are indications that significant performance improvements are needed, such as 75% reductions in energy consumption (von Weizs¨acker et al., 1997), and even more for other resources (Rob`ert et al., 2000). As performance standards rise (more buildings become ‘greener’) the baseline improves, so that over time the green building standards should be raised incrementally (as indicated by the staircase and the single-headed arrows). This illustration also highlights the debate about the legitimacy of using relative or absolute performance levels in BEAMs (Cole, 2003), as it has been argued that in order to adequately assess environmental sustainability only a limited range of absolute performance criteria need to be considered (Kohler, 1999). 2. Building eco-labelling BEAMs emerged in the early 1990s to provide some measure of the environmental performance of buildings, and now some 20 or so such tools are in use world-wide. Of these assessment methods some are well-established, such as BREEAM (Baldwin et al., 1990, 1998), HK-BEAM (CET, 1996; HK-BEAM Society, 2004), and LEED (US Green Building Council, 1999, 2003) and some have been introduced relatively recently, e.g. CASBEE (Institute of Building Environment and Energy Conservation, 2003), and Green Star (Green Building Council of Australia, 2005). The outcome of a BEAM assessment is an eco-label, e.g. BREEAM-Excellent, HK-BEAM-Platinum, LEED-Gold, etc.,

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based the sum of points (e.g. BREEAM) or credits obtained (e.g. LEED), or on a more complex calculation incorporating weighting factors (e.g. CASBEE). The BEAMs referenced here have developed independently as voluntary instruments to provide a catalyst for market transformation (Cole, 2003). They can be differentiated by • the life cycle stage(s) covered by certification; • the environmental aspects (performance issues) covered and their categorization; • the performance requirements (criteria, levels, standards, etc.); • assessment methods demonstrating compliance; and • the scoring system that determines the final grade (eco-label). A method (see Table 1) may include one or more tools to assess new and/or existing buildings, and might target particular types of building. BEAMs for new buildings and major refurbishments can provide for assessment and certification

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at different stages (e.g. CASBEE certifies pre-design, design and construction), at the completion of design and specification, or upon completion (e.g. HK-BEAM). BEAMs intended to assess existing buildings can be used at any time postoccupancy, and may cover the whole or just the core of a building. In addition to building performance emphasis will be placed on the quality of management, operation and maintenance practices. Climatic conditions and the environmental priorities in country of application influence what issues are included, the performance criteria, assessment methods and the weighting (scoring) of the issues. The environmental impacts covered may be grouped in different categories, such as global, local and indoor, but as Table 1 illustrates issues that relate to the specified building performance (shaded) can be separated from issues that relate to the external environmental impacts. The boundaries of assessment are generally limited to the site and interactions with adjacent properties. Assessments will focus on the appropriateness of a building and its engineering systems to meet the

Table 1 Framework of building environmental assessment methods (BEAMs)

Notes. Shaded area indicates ‘external’ environmental impacts and non-shaded area indicates ‘internal’ (indoor). a Used in the early BREEAM and HK-BEAM versions. b Similar categories used in LEED and latest HK-BEAM versions. c % score not applicable to CASBEE which uses a ratio that translates to a grade. d Used in the latest versions of BREEAM for offices.

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Fig. 2. BREEAM ‘98 new offices (Building Research Establishment, 2005).

needs of users and operators, separate from the impacts of the users themselves (e.g. waste generated), although assessment of provisions to better manage these impacts is included (e.g. facilities for waste sorting and recycling). The assessment of a building complex comprising several building types is usually based on separate assessments for each, with the overall grade based on individual assessment scores weighted by floor area (e.g. CASBEE, HK-BEAM 4/04). Figs. 2–4 highlight some of the features and relative weightings of three tools, BREEAM-98 for new office designs based on the 2005 check-list (Building Research Establishment, 2005), LEED-NC (new construction) Version 2.1, and HK-BEAM 4/04 (new buildings). These illustrate similarities and differences

Fig. 3. HK-BEAM 4/04 ‘New Buildings’ (HK-BEAM Society, 2004).

Fig. 4. LEED NC-2.1 new construction (US Green Building Council, 2003).

between tools used on a continent (North America), in a country (UK), and in a city region (Hong Kong). 2.1. Overall standard and market penetration Although they are sometimes specified by city or state governments and by large organisations to meet policy goals (Cassidy, 2004) BEAM assessments are generally being undertaken on a voluntary basis. In the broader market, the perception that building green requires a substantial additional initial investment and risk has been widespread (Portland Energy Office, 2000; Bartlett and Howard, 2000; von Paumgartten, 2003), and with owner-occupiers rarely considering life cycle costs or undertaking a cost–benefit analysis, in the absence of financial incentives the take up of a voluntary labelling scheme depends on the benefits perceived by the client in terms of marketing advantage and/or enhancements to building performance. Consequently, in the development of most BEAMs a key consideration is to balance overall difficulty against achieving market penetration. In order to encourage take-up most of the performance criteria included tends to focus on what the client and the project team can accomplish in the given circumstances although to enhance credibility, issues that are outside the client’s influence are also included. For example, the location and nature of the land used (Greenfield, Brownfield, reclaimed), decisions about which are dominated by economic realities when land is in short supply, will be included, but given relatively less weight within the overall assessment. Without additional inducements, the extent to which standards can be raised within a BEAM depends on how the label is valued by investors, developers and building owners, but will need to be incremental and over a time frame which allows industry to assimilate new demands (Fig. 1). In any event, performance

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requirements need to adjust because of changes to regulations (e.g. the ban on chlorofluorocarbons), new benchmarks (e.g. minimum requirements for energy efficiency), and assessment methods, and adjustments to weightings and scoring in response to changing priorities. Flexibility may be incorporated to allow clients to submit additional and/or alternative criteria. Although the standards set by a BEAM must rise, else it will become irrelevant; client concerns about the currency of an eco-label over time can restrain enhancement. A building originally assessed to be ‘Excellent’ using an earlier version of a BEAM is unlikely to achieve the same grade if the current ‘existing building’ version is far more stringent, unless significant allowance is made for performance issues that are largely outside the control of the building managers, e.g. constraints imposed by the original design, change of use, etc. Likewise, an existing building simultaneously achieving a particular grade may not be on a par with a new building achieving the same grade unless the performance criteria in the ‘new’ and ‘existing’ tools are similar. Greater emphasis on final testing, commissioning and handover of new buildings does allow for closer alignment with the assessments for existing buildings. 2.2. Performance criteria and assessments Performance criteria, i.e. the requirements for the award of points or credits may be defined in various ways, and include quantified performance targets, compliance with particular standards or codes, compliance with certain conditions (e.g. as specified in a check-list), or provision of certain features. Prerequisites, i.e. performance requirements that must be satisfied, can be specified, either for a part of the assessment (e.g. energy use), or for particular points or credits. Pre-requisites normally include compliance with regulations, but may endorse a particularly important part of the procurement of a new building (e.g. basic commissioning in LEED-NC). Third party certification is important for businesses which seek to declare higher performance standards, so BEAM assessments are generally carried out by independent assessors based on various submittals, i.e. a combination of declarations, specifications, site measurements, etc., with verification by independent third parties, and/or site visits by an accredited assessor. Support material; be it in the form of guides, on-line tools, advisory notes or consultations with assessors is an essential part of the process. Because of distances LEED requires extensive and detailed submittals (US Green Building Council, 2001), whereas BREEAM and HK-BEAM can take advantage of closer proximity to enable consultations, allow for interim assessments and to undertake site visits. Whatever the approach, it is important that outcomes can be assessed in an objective manner; else, there can be disputes between project teams and assessors, and inconsistencies in assessment outcomes. The ability of the assessors to arrive at consistent judgements is important but in the final analysis much depends on the integrity of the client and his representatives, as it is not possible to verify all claims (e.g. the amount of recycled material used).

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3. Specified building performance The emphasis on providing the specified building performance in the definition of a green building cited above recognises that a product (building) cannot be green if it fails to satisfy its intended purpose. For office buildings, of importance are those aspects of building performance that impact on the occupants and on productivity. Clearly, indoor environmental quality (IEQ) is significant in respect of health and comfort (Sensharma et al., 1998). In most BEAMs IEQ is expressed in terms of indoor air quality (IAQ) and/or ventilation, thermal comfort, lighting quality, acoustics and noise, as well as provisions for maintaining hygiene (e.g. prevention of bacteria in air-conditioning systems). The building and engineering services should provide for the needs of users in terms of quantity, quality, controllability and flexibility that allows for changes on use. IAQ is a complex issue, relating to both odour comfort (manifest in the levels of carbon dioxide—CO2 ) and extent to which pollutants are below acceptable limits. CO2 levels are determined by the adequacy of ventilation to match occupancy. Ventilation also provides for dilution of pollutants, be they from outside, from the ventilation system or from interior finishes and furnishings. IAQ performance criteria in BEAMS require that detailed specifications for materials emissions are met, or tests are carried out on the building (see Table 2). For testing, the criteria, measurement methods, sampling, locations and conditions need to be defined, but need to be limited in order to avoid excessive cost. This need not be a significant requirement beyond what should be specified for commissioning heavily services buildings. Criteria and standards that define thermal comfort vary between countries, but whichever the criteria chosen and delivered to a space, not all building occupants will be satisfied. For example, meeting ISO recommendations (ISO, 1994) for temperature, relative humidity and air movement may satisfy only 80% of occupants, because of individual preference and because these three parameters may not adequately address the thermal comfort experienced by individuals. Lighting performance needs to consider not just quantity but also quality in terms of glare, colour rendering, etc. Daylight penetration and views to windows are important health and comfort issues, as well as provided potential for energy saving (Boyce et al., 2003). Notwithstanding, post-occupancy evaluations of office buildings (BOMA, 1999; Bordass et al., 2001) suggests that, within bounds, it is not so much the set points, be it for thermal comfort or lighting, that is the main issue, rather it is the control over that users can exert, and how they can compensate for deviations outside their preference. Mitigation of noise from outside sources, from building services equipment, airborne noise between rooms, and impact noise between floors are all design issues that warrant inclusion as a part of the IEQ assessment if not already adequately covered by building regulations. Compliance may be demonstrated by appropriate calculations or on-site tests. Performance assessments of other building services (e.g. vertical transportation) and the provision of amenities (e.g. for recreational purposes) tend to be limited because the focus has been on indoor environ-

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Table 2 Examples of IAQ-related performance criteria in HK-BEAM 4/04 [10], LEED NC [11] Intent HK-BEAM 4/04 new buildings (for A/C offices)–IAQ/ventilation specifications Ensure that building ventilation systems are not contaminated as a result of residuals left over from construction activities Demonstrate that airborne contaminants from outside sources will not give rise to unacceptable levels of indoor air pollution in normally occupied spaces Demonstrate that airborne contaminants, predominantly from inside sources, etc. Ensure ventilation systems provide for effective delivery to occupants in normally occupied spaces Prevent exposure of building occupants to concentrated indoor sources of pollutants LEED-NC 2.1–IAQ/ventilation specifications Provide capacity for indoor air quality (IAQ) monitoring to help sustain long term occupant comfort and well-being Provide for the effective delivery and mixing of fresh air to support the safety, comfort and well-being of building occupants Prevent indoor air quality problems resulting from the construction/renovation process Reduce the quantity of indoor air contaminants that are odorous, potentially irritating and/or harmful to the comfort and well-being of installers and occupants

Avoid exposure of building occupants to potentially hazardous chemicals that adversely impact air quality

mental impacts, but are being given greater attention as BEAMs develop embrace wider dimensions of building performance. Given the high rates of churn (change) in offices, ever changing IT requirements, etc., performance criteria may include the ease and speed with which change and/or provision of new services can be undertaken. Design issues such as adaptability, serviceability and maintainability are performance criteria that can be assessed using qualitative criteria derived from standards (e.g. ASTM International, 2005), albeit with less objectivity than for issues for which quantifiable criteria can be specified. 4. External environmental impacts BEAMs generally include criteria for the most significant external environmental impacts, global and regional impacts such as greenhouse gas emissions, ozone depletion, deforestation, NOx, SOx, particulate emissions, river pollution, etc., local impacts including waste, water and local air pollution, and neighbourhood impacts, such as overshadowing, noise from building equipment, etc. Although not usually a high priority for investors, owners or even tenants (Sayce et al., 2004), energy used by buildings is significant and obviously a key concern with regard to global warming. Assessment of energy use and emissions is generally a significant part of most BEAMs (Figs. 2–4). Performance criteria usually includes an estimation of energy efficiency of air-conditioning and/or heating systems, lighting systems, and equipment such as lifts, the inclusion of features (e.g. meters),

Criteria/assessment Implementing a construction IAQ management plan; building ‘flush out’ or ‘bake out’; and replacement of all filters prior to occupancy Demonstrating compliance with appropriate criteria for CO. NO2 , O3 , RSP—as specified e.g. IAQ Certification Scheme or similar Demonstrating compliance with appropriate criteria for VOCs, HCHO, Rn Outdoor air ventilation rate—as specified; air change effectiveness—as specified Adequate ventilation for rooms/areas where significant indoor pollution sources are generated; local exhaust of premises undergoing fit-out and redecoration Install a permanent carbon dioxide (CO2 ) monitoring system that provides feedback on space ventilation performance in a form that affords operational adjustments For mechanically ventilated buildings, design ventilation systems that result in an air change effectiveness ≥0.9 (ASHRAE 129-1997) Implement an indoor air quality (IAQ) management plan for the construction and pre-occupancy phases of the building—details specified The VOC content of adhesives and sealants used must be less than the current VOC content limits—as specified; carpet systems must meet or exceed the requirements of the Carpet and Rug Institute’s Green Label IAQ Test Program; composite wood and agrifiber products must contain no added urea–formaldehyde resins Design to minimize pollutant cross-contamination of regularly occupied areas—as detailed

and actions (e.g. commissioning, energy management manual, etc.) that will assist with energy management during operation. Computer simulation using appropriate software (ASHRAE, 2001) is used to estimate how efficient a new building design is in comparison with a benchmark design, i.e. one meeting basic or minimum local code requirements (Lee et al., 2001a). The assessment seeks to quantify as a percentage the extent to which the enhancements included in the design of the assessed building improve on the defined benchmark, rewarding improvements on a sliding scale (e.g. up to 10 credits for up to 45% reduction in HK-BEAM 4/04). As energy use depends on the variability of the weather and building use, the modelling will assume a typical weather year, and use an appropriate occupancy density and schedules for both designs (Lee et al., 2001b). For example, in the case of HK-BEAM the benchmark building assumes a design lighting power density of 25 W m−2 (Electrical & Mechanical Services Department, 2002), and performance of air-conditioning equipment that meets minimum code requirements (Electrical & Mechanical Services Department, 2002), whereas the assessed building would use actual design data (e.g. 15 W m−2 for lighting). An estimate of the reduction in electricity maximum demand may be included in the assessment. However, such simulations, no matter how sophisticated, are unlikely to reveal actual consumption during building use, which can be some 50% higher in large commercial buildings (Sat, 2003). Assessment of water use generally follows a similar approach as for energy use, i.e. quantifying savings from, or provision of,

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water efficient fixtures, the provision of meters, etc. Coverage of materials aspects can be quite diverse, such as reuse of structures, use of recycled materials, timber from sustainable sources, waste sorting during construction, provision of recycling facilities in the building, etc. 4.1. Site and neighbourhood impacts BEAMs rarely explicitly refer to urban planning although, through assessments associated with land use, ecology and interactions with adjacent properties and open spaces, can help promote good practices. If not already covered by planning requirements or building regulations assessments could give credit for designs that provide control over relief and diversities in height and the massing of a development, and/or the protection of view corridors and breezeways, etc., but this is rarely done. Given that greenery and access to it physically and visually are important to health and well-being (Jackson, 2003) assessments of related issues should be incorporated, especially for high-density neighbourhood designs. Relationships between buildings, when viewed as ‘neighbours’, varies depending on the types of building involved. Redevelopment of urban areas with a mix of commercial and residential buildings is a good planning model in cities like Hong Kong, given the opportunity to enliven communities and reduce travel needs, but locating heavily serviced buildings in close proximity to residential and other buildings can be confrontational, with the former the more antagonistic. A ‘good neighbour building’, one that limits as far as practicable negative impacts on the neighbourhood would be more agreeable. An exceptional building, one that provides in addition some positive impacts to the neighbourhood, would be more welcome. So, issues such as overshadowing of adjacent properties are often included, even thought may be an unreasonable requirement in a dense, highrise urban setting. The provision of open spaces and amenities for use by neighbours, pedestrian walkways and thoroughfares, etc., though difficult to weigh up against issues such as energy use, appears to be reasonable and legitimate considerations. As positive impacts they can be counted as part of ‘services and amenities’ in the life cycle eco-efficiency ratio. Assessments of buildings on Brownfield sites seek to encourage inclusion of measures to improve the site ecology in terms of soft and permeable landscaping. For Greenfield sites, the focus is on minimising ecological impacts and conserving heritage, either by preservation of existing features or appropriate substitution, e.g. replacing existing vegetation with native plants and trees, or through relocation to another site. For high-rise buildings, there is opportunity to improve the ecology of a site with green roofs, sky gardens, etc. but there remain concerns about cost, safety and ongoing maintenance. Respondents to a survey by Calkins (2005) cited complexity as an issue when attempting to respond to green building design. Ecological mitigation strategies, increased shade, and minimizing paving have a low degree of complexity and low cost, and a relatively high degree of use by respondents, whereas green roofs, permeable paving and some infiltration strategies have a higher level of complexity, and were used less.

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Site aspects also focus on the mitigation of air, land, water, and noise pollution both during construction and during building use, and light pollution from buildings has also been given attention. Transport-related issues include the provisions for car parking, alternative transport (e.g. facilities for cyclists), and providing suitable access to buildings to avoid congestion and reduce nuisance. Transport needs and impacts can be significant if a building is located remotely and has been given significant weight in some tools (e.g. BREEAM). 4.2. Weightings and grades The assignment of weights to the various performance issues is the most contentious part of the framework of any BEAM. Whilst it is desirable that the issues included and the relative weights assigned (credits, points, weighting factors) reflect the significance of their environmental impacts, in the absence of easily assimilated and reliable data to quantify impacts over the building life cycle, weightings are determined by consensus through a survey of stakeholders who provide their views on the relevant importance of the environmental issues to be included (Cole, 2003). Life cycle assessment (LCA) methods are becoming increasingly relevant to inform on external environmental impacts and therefore their relative weightings, but LCA alone cannot determine the weightings for IEQ issues (J˝onsson, 2000) and other performance issues that fall under the guise of services and amenities. In the context of the definition of green buildings given above it is interesting to note the relative weight given to IEQ when compared to the external environmental impacts (resource consumption and environmental loadings). Figs. 2–4 give the percentages for the latest versions of BREAM, HKBEAM and LEED which were arrived at through consensus through a survey of stakeholders. Life cycle costing (LCC) may also have a role by demonstrating the worth of increasing the weight for issues that are environmentally significant but do not provide significant benefit to developers. Subject to meeting pre-requisites, and the absence of any adjustments to weightings, grades are generally determined from the summation of points/credits ‘earned’. 5. Shades of green Greenness implies reduced external environmental impacts over the life cycle, but BEAM assessments cover both attributes of building performance (particularly IEQ), and a mix of real and potential external impacts. This, together with the lack of absolute performance standards and scientifically defined weighting factors, makes it impossible to quantify the greenness of an eco-label in absolute terms. With differences in the range of environmental issues covered, the performance standards and assessment methods, it not easy to compare or benchmark labels. Furthermore, BEAMs assessments indicate only the potential for better performance. Certification at the design stage implies that the coverage will be less, or outcomes less certain, than when certification includes assessment of the completed building, since assessment of construction performance and commissioning

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outcomes can only be based on specifications and contractual arrangements. It is possible to appreciate the greenness of a particular ecolabel relevant to conventional buildings by taking into account the proportion of the BEAM assessments that have been satisfied (e.g. 55% for ‘Silver’), the standards of performance achieved, the rigour of the assessments, and the relative weighting of each issue in determining the grade. Obviously, the higher the grade the greater the number of performance criteria that have been met. However, unless there are restrictions, such as the requirement to satisfy certain pre-requisites or minimum score in one or more categories (e.g. HK-BEAM), the performance outcomes can differ for the same grade within a BEAM, e.g. satisfying IEQ criteria as opposed to satisfying, say, energy use and emissions. The additional (real or perceived) cost may dictate which criteria are met. A client targeting a particular grade may seek to determine the initial cost premium, so project teams often scrutinize each BEAM point/credit to determine the feasibility and cost of achieving compliance, targeting the lowest cost issues first (Scheuer and Keoleian, 2002; Green Building Alliance, 2004; Calkins, 2005). Other points/credits thought to be attainable would then be considered in order to ascertain that the target grade is achievable. The performance criterion for each point or credit achieved also has a bearing on greenness. For external impacts, it is about the extent of the performance improvements, such as quantifiable reductions in energy use, water use and construction waste, beyond local benchmarks, as well as the provisions that help facilitate efficient building management. Requiring up to 45% reduction in predicted annual energy use is significant, but more so when equipment is properly sized, can be properly controlled, maintained and monitored during operation. The quality of assessments, i.e. tangible verification of the ‘evidence’ that demonstrate compliance, is also relevant, with assessments based on measurements implying greater rigour than those based on simulation or the use of check-lists and specifications. With the prospect of inherent design faults and inadequacies of construction, and because green buildings require ‘green’ operators and users to avoid ‘grey’ performance (Browne and Frame, 1999) persistence in green performance post-occupancy is more likely if certification includes compliance with the requirements of full building commissioning and handover (maintenance manuals, training, etc.) to the facility management team. Notwithstanding, it is apparent that not all issues are equal in terms of difficulty, cost or relevance to life cycle environmental performance, so in the final analysis the allocation of points/credits (the weightings) and their aggregation to determine the final score (grade) has a significant influence on the relative ‘greeness’ of a building eco-label. For the BEAMs listed in Table 1, the grade ‘Silver’ or ‘Very Good’ requires only 55% of the available points or credits, i.e. compliance with roughly half of the assessment criteria, reinforcing the point made by some observers (e.g. Portland Energy Office, 2000; Green Building Alliance, 2004) that such an achievement is neither a significant enhancement nor incurs a significant cost penalty over conventional practice.

Perhaps achieving ‘Gold’ or ‘Very Good’ can be regarded as a noticeable enhancement, and achieving ‘Platinum’ or ‘Excellent’ can be regarded as being exemplary relative to prevailing norms. 6. Concluding remarks Neither cities nor city buildings are sustainable, but can significantly contribute to global environmental sustainability. The environmental performance of cities is being given increasing attention, but remains secondary to economic and social priorities, so environmental enhancements tend to be rather modest and incremental. The intent of BEAMs has been to enhance the environmental performance of buildings, by identifying significant environmental impacts, mitigate as much as possible the negative impacts, and promote positive impacts over a building’s life cycle. Given that assessments are generally voluntary, the standards set need to take account of the business interests of clients, so the performance demands and enhancements tend to be incremental also. Building eco-labels provide a measure of environmental performance, but greenness in the context of global environmental sustainability is confused by combining scores for building performance with those for external environmental impacts. Whilst buildings are major contributors to environmental degradation they are, at the same time, important in sustaining businesses and the city economy and, given that city folk spend some 80–90% of their time indoors (Chau et al., 2002), can contribute positively to the quality of life. IEQ is clearly germane to sustainable development, but assessments can be more relevant when coverage of additional social and economic issues is included, a trend now seen in the development of some BEAMs (Cole, 2003). The development of cities is a matter for governments through land use planning, standards and guidelines, but much city land is for buildings, mostly private buildings. The interface between BEAM assessments and urban planning imperatives is currently rather limited since most BEAMs concern themselves with impacts on the immediate neighbourhood. Likewise, coverage of ecological impacts is usually confined to preservation or conservation within the site boundary, rewarding mitigation of impacts on Greenfield sites, and remedial actions on Brownfield sites. All new office buildings of any size and/or complexity are prototypes, and high performance requires a well-informed client brief, good design integration of the building and systems, co-ordinated and quality construction, and comprehensive commissioning. Where financial and other pressures conspire to reduce the time allowed for quality work the outcome will likely result in a building that performs below expectations. Post-occupancy evaluations (Federal Facilities Council, 2003; Yik and Lee, 2002) reveal problems that can be traced back to design failures, poor co-ordination during construction, and inadequate commissioning, especially where buildings incorporate new features and technologies unfamiliar to contractors and building operators (Stum, 2000). In general, management, operations and maintenance staffs are not provided with the resources

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