Environmental performance and sustainable architecture a critical review in the context of singapore public housing 2

It is observed that current literature on these aspects is grouped into three mainstreams of study: interrelationship of housing policies and socio-economic factors, housing design built

Part II Environmental Performance of Singapore

Public Housing – Empirical Construction

Chapter 6: Public Housing Development in Singapore

6.1 Prelude

This chapter starts with a brief summary of Singapore public housing, followed by its literature review In the context of this research, the literature review will focus on three aspects – socio-economics (including housing policies), housing design and environmental performance It is observed that current literature on these aspects is grouped into three mainstreams of study: interrelationship of housing policies and socio-economic factors, housing design (built-form) and social aspects; and housing design and environmental performances These three mainstream studies will then be positioned against the Integrated Framework for Sustainable Housing Design and Discourse This will reveal some issues that have not been explored by existing literature, which limits the understanding of sustainable development of Singapore public housing

6.2 The evolution of public housing development – a review

6.2.1 Public housing in the 1960s

Emerging in the midst of acute housing shortage, rapid population growth and extensive slum living conditions, public housing was initiated with the vision of being a prior condition to economic success The housing policies in the first five years were to ‘provide low-cost housing for the lower income groups at rentals which [were] within their capacity to pay (HDB Annual Report, 1961) In 1964, when the acute housing shortage was eased, Home Ownership Scheme was introduced to target lower middle income group, enabling and encouraging them to own their own homes (HDB Annual Report, 1964); followed by allowing residents to use their Central Provident Fund to purchase public housing In order to

reserve public housing for the needy residents, household income ceiling and household size and composition were controlled under housing policies

The dominant housing type during that period is the 1-room flats arranged linearly along a loaded common corridor 2- and 3-room flats were also built in a smaller portion, 25% and 30% of total housing built respectively in 1967 As a result of mass construction, the quantity of public housing grew, enabling 32% of the population housed towards the end of 1960s

double-Figure 6-1: Typical 1-room flats arrange along a double-loaded-corridor housing block in the 1960s (Source:

HDB (1970) First Decade in Public Housing 1960-69)

6.2.2 Public housing in the 1970s

The second decade of public housing development was associated with high demand and change in the citizenry’s perspective and expectation of public housing as a result of resident affluence As a response, housing policies were amended by raising the eligible household income ceiling and allowing smaller household size to qualify for public housing (HDB Annual Report, 1972) Furthermore, the Board extended its activities to cover housing for the growing

Corporation (HUDC) Housing regulations were also lifted, e.g allowing resident to install condition in their flat with written permission from the Board (HDB Resident Handbook, 1973)

air-During this period, the construction of emergency 1- and 2-room flats gave way to the more spacious 3-, 4-, and 5-room flats The design and construction process were improved with the introduction of standardisation and modularisation of building materials and elements (HDB Annual Report, 1975) The linear housing block design of the 60s was succeeded by single-loaded-corridor slab block and point block designs Principles to self-efficient neighbourhood and new town were established and consolidated

Figure 6-2: Typical slab block and point block housing design in the 1970s

6.2.3 Public housing in the 1980s

Public housing in the 1980s was developed with the emphasis on promoting a sense of community and identity (Perry et al, 1997) Over the years, the socio-economic characteristics

of HDB residents and their lifestyle had undergone substantial changes Incomes increased Household structure, size of families and demographic profile of the population, was constantly in a state of changes These social changes required the implementation of new

policies Major areas of review included the need to preserve the Asian tradition of grandparents living with or near their married children and grandchildren The policies also have to meet the changing demands of Singaporeans and certain categories of Permanent Residents as well as non-citizens for housing at reasonable cost The relaxation of rules on mutual exchange of home ownership flats to give greater resident mobility In addition, the qualifying household income ceiling was constantly under review These policies kept the percentage of population living in public housing constantly increased, reaching to 88% of total population in 1989 (HDB Annual Report, 1989)

Public housing flat designs in this period were marked with new design of 3-, 4-, and 5-room model A with larger areas and quality Executive apartments were also introduced to cater for the upper-middle income group On the other hand, improving quality of existing housing was continuously carried out since the early 1970s In promoting the identity for housing estate, the design of high-rise housing incorporated local traditional architectural and building elements In promoting a sense of community, common public spaces within housing estates were given more attention Public housing embarked upon new role of enhancing social integration in this decade

Figure 6-3: Incorporating local traditional architectural element and the focus on community development

(Source: HDB, 1988)

6.2.4 Public housing in the 1990s

The emphasis of public housing in the 1990s was on service and quality development and environment (Yuen et al, 1999) The socio-economic characteristics in the 1990s were the continued decrease in household size, rapid increase in resident affluence and resident mobility Housing policies were transformed to both meet and shape these changes, through raising the qualifying household ceiling income, allowing singles to own a 3-room or smaller flat, and allowing second air-condition to be installed in public housing flat

As a response to the trend of smaller household size, public housing design in the 1990s had their flat size reduced twice in 1993 and 1997, resulting in smaller flat size of up to 20 square metres compared to those in the 1980s The prominent activity of public housing in this decade was taken up by upgrading programmes, which were proven successful in providing better living environment in older housing estates without the need to relocate residents and break up their established community ties

Figure 6-4: Upgrading programme in older public housing estate and the use of Space Adding Item (Source of left

picture: HDB, 2000)

6.2.5 Public housing in the 2000s

Public housing after the year 2000 has been marked with the attempt to create sustainable

living environment The vision of HDB is to research and develop ‘HDB Eco-Town’ that

would strive for the best practices to meet environmental and community needs (HDB Annual Report, 2002) Along side with this vision, public housing was facilitated with lighting dual circuit system in the public areas of housing blocks, to be automatically switched off after midnight to conserve energy (HDB Annual Report, 2001) Rooftop garden, equipped with a wide range of recreational facilities, was introduced with purposes of (1) greening, softening and reducing urban heat island effects of the densely built environment (Wong et al, 2002), and (2) providing comfortable communal areas for the residents Furthermore, experiment on increasing the height of public housing (up to 40 storey height) has also been being carried out, to be higher land-use efficiency Studio apartments with elderly-friendly design features were introduced as a respond to the aging population and wealthier senior residents

In brief, the trend of public housing development since its inception can be traced in a process of being merely providing sheltering for low-income residents, to better respond to resident affluence and aspirations, to enhancing social integration, and finally toward sustainable development

Figure 6-5: Higher high-rise living and better environmental responsive housing design

6.3 Literature on public housing – a review

Existing literature on public housing covers many aspects related to public housing development, i.e socio-economic aspects, housing policies, housing design, construction methods and techniques, management, real estate, environmental performances, etc In this research, the literature review, besides concentrating on HDB activities in public housing development, focuses on 3 aspects – socio-economics (including housing policies), housing design and environmental performance Literatures on these aspects can be grouped into three mainstreams of study: the interrelationship of housing policies and socio-economic factors, housing design (built-form) and social aspects; and housing design and environmental performance

6.3.1 Interrelationship of housing policies and socio-economic factors

For the last four decades in Singapore, there has been a progressive integration between economic growth, social stability, and urbanisation process through public policies (Castells et

al, 1990) Public housing policies, as both responding to, and preventing the extremes of, the socio-economic variables through times, have been under constantly reformations There are two levels of public housing policies At macro level, the policies address the physical environment, i.e high-rise high-density development and comprehensive planning of new town, and the national interest in promoting home ownership At micro level, housing policies are concerned with estate management, i.e ‘maintaining the housing estates and educating the occupants of its housing to the requirements of high-density high-rise living’ (Tan, 1998)

Developing mass public housing towards high-rise high-density direction aims at ‘achieving as high a residential density as possible, within the limits of social acceptability, environmental amenability and economical constraint’ (Yeh, 1975) This policy has resulted in social characteristics that are distinct from traditional landed property residents In the early stage,

social transformations due to high-rise living were quite pessimistic The main problem was the weak bond between the individual and social structure, associating with little sense of neighbourhood and pervasive sense of insecurity (Riaz, 1977; Spiro, 1977; and Tai, 1977) These social issues, however, have gradually been alleviated as indication of higher sociable interactions in public housing estates (Tai, 1989; HDB, 2000)

Public housing policies related to home ownership and housing allocation aim to promote economic stability for the residents and to act as a political instrument The concept of homeownership has been understood as providing residents not only a sense of pride, but also the incentive to look after their home (Sim et al, 1993) In discussing political legitimacy and housing, Chua (1997) juxtaposes Singapore’s public housing programme to those of the US and the ex-socialist central European countries While the US programme characterises its housing

socio-as a consumer good and the ex-socialist European countries idealise housing socio-as a social right, Singapore public housing avoids the drawbacks of the two system and is able to ‘institutionalise universal provision without eliminating the ability of market forces to exercise discipline on housing consumers’ (Yuen et al, 1999 in the summary of [Chua, 1997])

The mutual interaction between socio-economic factors and housing policies is brought up in Yeh’s study (1985), which highlights the interrelationship among household changes and housing policies That is the patterns of household growth directly affecting housing demands, which in turn has policy implications for housing supply (Yeh, 1985)

Housing policies related to estate management associate more to the requirements of density high-rise living ‘Such restrictions are imposed either for the protection of the common property, preservation of the outward appearance of the buildings, safety of occupants of other flats, safety of the buildings, or for the preservation of the peaceable

high-These estate management policies have, however, socio-economic consequences to the residents For instant, the Estate Renewal Programme since the late 1970s has been considered successful in terms of safeguarding resident community ties, social stability, and infrastructure utilisation through reducing resident mobility (Lau, 1998 & HDB Corporate Newsletter, June 2000)

In general, housing policy started with restrictive rules and regulations to safeguard the housing provision to the right categories of residents This aimed to maintain certain orders and principles in public housing estates during the confusing stage of resident in their lifestyle transformation These housing policies and regulations have gradually been lifted and relaxed

as a response to socio-economic changes, e.g alleviation of acute housing needs, the continuous growth of Singapore wealth, more and higher educated residents, and household structure changes

Pugh’s paper on ‘Housing and Development in Singapore’ commends the effectiveness of housing policies and traces these successful policy transformations:

Firstly, ensure a flow of resources and finance into housing from the saving of the

community; secondly, create a statutory development corporation, complete with

powers and resources to plan and build social housing; thirdly, relate the access to

that housing to a wide range of income group; fourthly, use home-ownership for

general social, economic, and political purposes; fifthly, do not be too perturbed by

some orthodox economists argument; sixthly, ensure an adequate supply of

low-priced land in growing urban areas; and finally conceive and operate housing policy

and other social policies as an integral part of the development (Yuen, 1999 in the

summary of [Pugh, 1985])

6.3.2 Housing design and its social impacts

In line with Churchill’s statement that we shape our dwellings and aft erwards our dwellings shape

us, many scholars and researchers are interested in studying the public housing physical built-form and social impact relationship Field (1992) argued that ‘by design and planning of new towns on

a hierarchical basis, in which the distribution of activities nodes such as town centre, neighbourhood centre and sub-centres and precincts are defined, Housing and Development Board has provided not only shelter but also a way of life for Singaporeans.’ Many literature discussions

in such relationship focus around the impacts of high-rise housing built-form to its residents

In responsing to the concern of monotonous appearance of public housing estates in Singapore, the relationship between high-rise high-density housing and sense of place has been explored Two separate studies in the same year by Teo, P & Huang (1996) and Teo, S.E.(1996) reveal that residents' sense of belonging is not very clear, despite of the efforts on creating distinct identity for housing estates – using highly visible designs and providing different focus activities for each precinct such as courtyards, walkways and pavilions for resident interaction, and thus developing sense of bonding and belonging The papers suggested that residents’ perspectives

on this issue should be consulted before taken into estate planning and housing design

Experiences of social problems associated with high-rise living from other countries have also been compared to Singapore public housing development (Lim, 1979 & Chua, 1994) In this aspect, Chua (1994) pointed out that negative experiences with high-rise public housing in other countries are not applicable to Singapore context mainly owing to Singapore climatic condition The tropical climate ‘encourages the use of public space as a way of escaping the confinement of the flat, while indirectly increases informal surveillance of the residential environment as a whole The high level of pedestrian activities is essential to generate community sentiments in high-rise estates.’ (Yuen et al, 1999 in the summary of [Chua, 1994])

6.3.3 Housing design and environmental performance

In recent years, there have been increasing numbers of researches on the environmental performance of public housing design Most of these researches are carried out at the Department of Building, National University of Singapore There are two types of researches

in this aspect The first research type is the relationship of housing built form and individual environmental performance, e.g natural ventilation (Wong et al, 2002; Soemara & Wong, 2001; Rajagopalan & Choeng, 2001) daylighting performance (Liaw, 2001), energy consumption in corridor lighting (Khoon & Choeng, 1999; Joo & Ullah, 2000) The second research type is the relationship of public housing built form and a system of environmental performance There are currently two established system of environmental performance in literature – the Total Building Performance (TBP) and the Building Environmental Assessment Method for Resident Building in Singapore (BEAM)

Total Building Performance assesses 6 mandatory performance aspects of building, which are

‘spatial quality, thermal quality, acoustic quality, visual quality, indoor air quality and building integrity’ (Hartkopf et al, 1983) Data for evalu ation are obtained by three methodologies: expert walk-through or assessing through observation, objective measurement on site, and subjective measurement or questionnaire survey the occupants The three sets of data are then compared and compiled to conclude the evaluation TBP approach was applied for evaluating and comparing study of total building performance of two HDB housing blocks built at different times – early 1980s and middle 1990s (Khalequzzaman, 2001) The study concluded that: – the outputs from objective and subjective measurements were fairly coherent;

– the newer building block has better performances across the six performance mandates compared to the older one; and

– thermal comfort, indoor air quality, acoustics and spatial quality of the two housing blocks are satisfactory, while visual quality is relatively less acceptable

In another study, the bioclimatic architecture through evaluating HDB flats (Chowdhury, 2000), TBP methodology was applied A framework to define bioclimatic architecture was proposed, and it includes: orientation, natural ventilation, daylight, solar control and thermal capacity Three selected HDB flats were evaluated against the above framework through three data gathering methodologies of TBP The study confirmed and recommend that

– North South is the ideal orientation,

– windows provided on two opposite walls facilitate good daylighting and natural ventilation, – increases window height can enhance cross ventilation, and

– effective shading should be provided to reduce excessive glare and to prevent driving rain into dwelling units

wind-Lee et al (2001) developed a the Building Environmental Assessment Method for Resident Building in Singapore (BEAM) as a tool to evaluate the environmental performance of Singapore public housing BEAM’s framework includes 11 criteria, organised under three categories representing 3 scales of environmental impact, which are global, local, and indoor issues (Lee et al, 2001) Benchmarks for criteria in BEAM were established based on TBP methodology to gather and analyse data Weighting among criteria were formed through a survey of experts in the field

In another study, BEAM model was justified and applied to study the environmental performance of two HDB flats as case studies (Liu, 2001) Case study one is a 3-room flat in a slab block built in early 1980s The case study two is a newly-built 4-room flat in a ‘hybrid’ housing block layout Data gathering method is objective and subjective measurements The study result shows that both case studies achieve relatively high score The study has also identified the major different scores between the two blocks is the indoor issue, i.e case study one has better score for indoor issue due to the building’s slab block configuration and

In summary, these researches contributed insights to the environmental performance of public housing design through relating environmental performance to physical features of housing design These endeavours also indicated a new phase that public housing is heading towards – the ‘HDB Eco-town’

6.4 Public housing from sustainable housing perspective

Briefly from literature reviews of Singapore public housing in section 6.3, there have been extensive studies on the interrelationship between housing policies, socio-economic conditions, and housing built-forms Furthermore, there have emerged more studies on the relationship between housing design and their environmental performances In order to understand the sustainable development of Singapore public housing, the above topics in literature review are arranged in line with the structure of the Integrated Framework for Sustainable Housing Design and Discourse (Figure 6-6)

Figure 6-6: Diagram of topics covered in existing literature on Singapore public housing

The topics, covered in existing literature on public housing, provide fragmented knowledge (within each field of study) in understanding the sustainable development of public housing The accumulation of all the fields of knowledge, as summarised in Figure 6-6, does not

Socio-economics

6.3.2 6.3.1

provide a holistic perspective to the sustainable development of public housing Rather Figure 6-6 implies a process, in which housing policies and socio-economic factors have influences and interactions with housing designs that sequentially have impact on the environmental performance Environmental performance is, in turn, implicated to be the springboard towards sustainable housing performance The role of socio-economics domain (including housing policy and resident behaviour), architectural design domain, and the interconnectedness of the two domains and environmental performance have not been discussed (Figure 6-7)

Figure 6-7: The yet to be explored issues in comprehensively understanding Singapore public housing in terms of

sustainable development

Through the setting of Singapore public housing, critical review of the practice of environmental performance from sustainable housing perspective in this research will explore the above issues and contribute some knowledge of Singapore public housing from sustainable housing perspective

?

performance Socio-

6.5 Conclusion

This chapter has briefly recaptured the evolution of Singapore public housing There have been different agendas in public housing development in each decade It started with the response to the emergency shortage of housing and the providence of standard living environment in the initial decades, promoted community development in the 1980s, provided quality housing environment in the 1990s, and has been progressing towards sustainable housing development in current decade

Literature on Singapore public housing in the three domains – socio-economics, housing design and environmental performance – has been reviewed and grouped into three mainstreams of study – interrelationship of housing policies and socio-economic factors, housing design and social aspects; as well as housing design and environmental performance After grasping with the overview issues related to Singapore public housing, the three mainstream studies are positioned against the Integrated Framework for Sustainable Housing Design and Discourse This has revealed some issues that have not been explored by existing literature for a comprehensive understanding of sustainable development of Singapore public housing This research, through using the setting of Singapore public housing development to critically review the practice of environmental performance, will also shed insights to these yet-to-be-explored issues These discussions will be covered in the empirical discussion of 'From Environmental Performance to Sustainable Housing Performance' in Part III of this thesis

Chapter 7: 'Green Building Challenge' and Singapore Public Housing 7.1 Prelude

This chapter is a preamble to acquiring empirical data for the research, i.e the environmental performances of Singapore public housing over the decades through case studies Firstly, a comparative study of existing prominent building environmental assessment methods will be carried out, through which Green Building Challenge (GBC) is selected to derive primary data for the study Secondly, GBC will undergo a process of localisation and customisation for suitable application in Singapore high-rise high-density public housing This localisation and customisation are divided into two sections: one for adjusting the parameter of the environmental performances, and the other for establishing the weighting system

7.2 'Green Building Challenge' for public housing – rationale and setting up

7.2.1 Rationale for the selection of Green Building Challenge

The selection of a building environmental assessment method to derive empirical data in this research lies on the appropriateness and ability to assess environmental performance of high-rise high-density housing in the tropical region and other requirements of primary data The first main requirement is the environmental performance of housing designs in the condition

of their respective period This will facilitate the chronological analysis of the evolutionary housing designs However, some case studies, especially those in the 60s and 70s, have been modified and renovated by both residents and Housing Development Board’s various upgrading programmes These modifications, without doubt, affect the case studies' environmental performances To minimise this defect, the case studies will have their environmental performance evaluated based on their design or as-built drawings as well as

main requirement to derive primary data is a building environmental assessment method being sensitive enough to dictate the minor design differences in the environmental performance results among case studies Table 7-1 juxtaposes the main building environmental assessment methods together and against the requirements from primary data

to facilitate the selection

Requirements

Suitable for

Table 7-1: Comparing building environmental assessment methods based on requirements of primary data

In comparison among the main building environmental assessment methods listed above, GBC and BEAM have the advantages over others for this research While the advantages of GBC are its features of being the second-generation building environmental assessment method over the first-generation methods, BEAM has the advantages of being a local-constructed method with benchmarks, criteria, and weighting system ready for application in assessing Singapore public housing

In comparison to BEAM, GBC lacks of local-context criteria, benchmarks, and weighting However, GBC has the advanced features of a second-generation method, which can meet the two main requirements set out by the attribute of primary data – evaluating building environmental performance based on design parameter, and providing outputs with fine interval results among case studies GBC is, therefore, opted to be a methodology to obtain primary data in this research

7.2.2 Green Building Challenge – applicability and setting up

As mentioned earlier, GBC is established to be flexible with its benchmarks and weighting system that can be customised to make the method more appropriate and applicable in accordance to the regional climatic and practice conditions Therefore, prior to its application, GBC's environmental criteria have to be re-evaluated and adjusted for the suitability in this study context, benchmarks have to be established, and weighting system has to be formed

The framework of GBC includes 6 environmental issues to be considered However, at the present, GBC operates only 4 environmental issues: resource consumption, environmental loading, quality of indoor environment, and quality of service The other two issues, Economics and Construction Management, have not fully been established and their present in GBC is for crude view into the issue (Cole, 2002) Furthermore, the two issues are beyond this research scope, which focuses on public housing design, and thus will not be included in this study

Environmental criteria are reassessed based on the responsiveness to local tropical climate, the suitability to the context of high-rise high-density housing, the consideration to current practice and available information Weighting will also be established based on an analysis of hierarchy of importance among environmental categories and issues in Singapore’s climatic and public housing context

7.3 Localisation and customisation of environmental criteria

Regarding about setting benchmarks, GBTool User Manual suggests that benchmarks shall be the typical practices of the country In accordance to statistical data, the current highest number of public housing flat type is the 4-room flat (Figure 7-1) The popular housing block

is a combination of 4-room model A and 5-room improved A housing block of this design type is opted to facilitate the establishment of benchmarks for GBC in this research It is noted that the environmental performance output of case studies through GBC are relative to the selected housing block as benchmark to serve the purpose of this research only They are not the environmental performance results relative to the official environmental performance practices of the country

Figure 7-1: Number of flat types from 1960 to 2002 (Source: compiled from HDB Annual Report, various issues)

There are a number of considerations in localising and customising environmental criteria

of GBC to suit the local context Firstly, criteria that are not applicable to residential building will not be considered, e.g assessments relating to HVAC system Secondly, criteria that are not appropriate to regional tropical context will be modified for suitability Thirdly, some input data required by GBC, which are not available in local practice, will

not be included in the study, e.g embodied energy of building materials (see scope of

discussion in section 1.5.4) Table 7-2 presents the localisation and customisation of

environmental criteria and customised benchmarks of GBC for the suitability of Singapore public housing and the research context

GBC’S CRITERIA MODIFIED CRITERIA FOR SUITABILITY AND

R.1 Net life-cycle use of primary energy

R.1.1 Primary energy embodied in

materials, annualized over life-cycle Important criterion but not assessable Not applicable

Lack of local information and too complicated for crude calculation as most building materials are imported from different countries R.1.2 Net primary non-renewable energy

used for building operations over the

life-cycle

Net primary non-renewable energy used for building operations over the life-cycle 189 MJ/m

2/year

Benchmark is the current residential average energy consumption Figure is calculated from statistic information (Department of Statistic, 2002)

R.2 Use of land and change in ecological

quality of land

R.2.1 Net area of land used for building and

related development purposes Net area of land used for building and related development purposes 0.2 m

2 land per m2 net area in a total site area of 4820 m2 Benchmarks are derived from calculation of the

baseline housing block

R.2.2 Change in ecological value of the site Change in ecological value of the site The net ecological value of the site is expected to undergo some deterioration from

the predevelopment condition

R.3 Net consumption of potable water Net consumption of potable water 74.1m3/occupant/year

Benchmark is the current residential average water consumption Figure is calculated from statistic information (Department of Statistic, 2002)

R.4 Re-use of existing structure or on-site

materials

R.4.1 Retention of an existing structure on

the site Retention of an existing structure on the site 0% structure of an existing building on the site retained as part of the new building

R.4.2 Off-site re-use or recycling of steel

from existing structure on the site Off-site re-use or recycling of steel from existing structure on the site 0%

R.4.3 Off-site re-use of materials from

existing structure on the site Off-site re-use of materials from existing structure on the site 0%

Off-site re-use or recycling of steel and other materials from existing structure on the site are not managed and recorded by HDB The practices are varied dependent on different contractors (Source: informal interview with senior HDB staff)

R.5 Amount and quality of off-site materials

used

R.5.1 Use of salvaged materials from

off-site sources Use of salvaged materials from off-site sources 0%

R.5.2 Recycled content of materials from

off-site sources Recycled content of materials from off-site sources 0%

R.5.3 Use of wood products that are

certified or equivalent Use of wood products that are certified or equivalent 100%

(Source: informal interview with senior HDB staff)

R ENVIRONMENTAL LOADINGS

L.1 Emission of green house gas from building production and operations

L.1.1 Embodied emissions of materials,

annualized over the life-cycle Not assessable Not applicable Lack of local information

L.1.2 Green House Gas emissions from all

energy used for building operations

over the life-cycle

GHG emissions from all energy used for building operations over the life-cycle 36.3 kg/m

2/year Benchmark is calculated from energy used for building operations through formula provided by

EC-ASEAN COGENl (2000) (See 6.3.1.)

L.2 Emission of ozone-depleting

substances Emission of ozone-depleting substances 0 gm CFC-11 equiv / m2 / yr Criterion is automatically achieved due to Singaporean regulation (Hui, 1995)

L.3 Emission leading to acidification from

energy consumption for building

operations

The annual emissions of gases (SO2

eq.) leading to acidification from annual operating emissions for building operations, in Kg/m2 , normalized for net area

0.096 kg/m2/year Benchmark is calculated from energy used for building operations through formula provided by

EC-ASEAN COGENl (2000) (See 6.3.1.)

L.4 Emissions leading to photo-oxidants

from energy consumption for building

operations

The annual emissions of gases leading to formation of photo-oxidants from annual operating emissions from building operations,

in gm of PCOP equivalent and normalized for net area

480.06 gm/ m2/year Benchmark is calculated from energy used for building operations through formula provided by

EC-ASEAN COGENl (2000) (See 6.3.1.)

L.5 Emissions with eutrophication

L.6 Solid wastes

L.6.1 Avoidance of solid waste from

clearance of existing structures on

the site

Avoidance of solid waste from clearance of existing structures on the site

0% weight of solid wastes resulting from clearance of existing structures on the site that will not be sent to a solid waste facility

L.6.2 Avoidance of solid waste resulting

from construction process Avoidance of solid waste resulting from construction process

0% weight of solid wastes resulting from construction of the new or renovated facility

on the site that will not be sent to a solid waste facility

L.6.3 Avoidance of solid waste resulting

from tenant and occupant operations

Avoidance of solid waste resulting from tenant and occupant

operations

Measure of the criterion is changed to description of solid waste disposed system and recycle waste collection and methods

GBC measures this criterion based on the area devoted for waste classification both centralised and every floor system This is not suitable to public housing context as refuse chute are used and recycling waste are door to door collected

L.7 Liquid effluents

L.7.1 Storm water flows disposed of on site Storm water flows disposed of on site 0.23 m

3/m2/yr (volume of storm water, per unit area, that will not require disposal by a municipal storm waste water system)

Benchmarks are derived from calculation of the baseline housing block The calculation is based

on estimates of average annual local rainfall, absorption capacity of site through permeable paving and landscaping (See 6.3.3.) L.7.2 Sanitary waste water flows disposed

of on site or on-site grey water re-use

Sanitary waste water flows disposed of on site or on-site grey water re-use

The annual volume of sanitary water flows that will not require the use of a municipal sanitary sewer system: 0 m3/m2/yr

All waste water in the housing block is discharged

to municipal drainage system Central grey water treatment facility, rather than discrete on-site facility, is applied in Singapore

L.8 Hazardous wastes resulting from

renovation or demolition wastes Not applicable

There has been no record of hazardous wastes resulting from renovation or demolition wastes (Source: informal interview with senior HDB staffs)

L.9 Environmental impacts on site and

adjacent properties

L.9.1 Thermal emissions to lake water or

sub-surface aquifers due to the use of

Ground source heat pump system Not applicable Not applicable

Ground source heat pump system is not used in Singaporean public housing

L.9.2 Reflectance of horizontal building

surfaces and hard-surfaced site areas Reflectance of horizontal building surfaces and hard-surfaced site areas Average of 45% reflectance of roof surfaces and paved site surfaces Benchmarks are derived from calculation of the baseline housing block (See 6.3.4.) L.9.3 Impact of construction process or

landscaping on soil erosion within or

Q INDOOR ENVIRONMENTAL

QUALITY

Q.1 Air Quality and Ventilation Air Quality and Natural Ventilation

Q.1.1 Moisture control

Q.1.1.1 Moisture promoting mould growth

inside the building: To be assessed

relative to text description of

detailing of exterior building

envelope, where exterior winter

design temperatures are below 00C

The weight is set to zero where

winter design temperature is above

00C

Not applicable Not applicable Singapore has a hot tropical climate Temperature is above 00C all year round

Q.1.1.2 Spray in wet cooling towers and

standing water in HVAC distribution

systems Not applicable Not applicable Public housing does not have HVAC system

Q.1.2 Pollutant control

Q.1.2.1 Mineral fibre control Not applicable To be assessed relative to text description of HVAC distribution system Public housing does not have HVAC system

Q.1.2.2 VOC emissions in interior spaces Applicable but not assessable

Measure is based on the percentage by weight

of interior finish materials specified that conform to VOC emissions standards of a recognized certification agency

Code of practice on air pollution control has the allowable emission standard only for industry There is

a lack of standard for residential building (Kafil, 2000) Q.1.2.3 Airborne pollution migration between

occupancies through HVAC distribution

system Not applicable Not applicable Public housing does not have HVAC system Q.1.2.4 Radon control Not applicable To be assessed relative to text description of under-grade detail in area with radon problem Radon is present in Singapore but its concentrations is below the action levels of the

WHO (Chong, Tan, Soo & Ng, 1996)

Q.1.2.5 Location of outdoor air supply for

HVAC systems to sources of

polluted air Not applicable

The score is a combination of two factors - the height of air intakes above ground level, and the distance between intakes and exhausts or sources of polluted air – 11.5

Public housing does not have HVAC system

Q.1.2.6 Filtration performance in HVAC

systems Not applicable Not applicable Public housing does not have HVAC system Q.1.3 Ventilation and outdoor air delivery Natural Ventilation

Q.1.3.1 Total outdoor air rate ventilation in

mechanically conditioned areas of

Multi-unit residential occupancy Not applicable Not applicable

The case-studied housing is assessed under natural ventilation condition

Q.1.3.2 Ventilation performance in

naturally ventilated areas of the building

with single-sided ventilation

Ventilation performance in naturally ventilated areas of the building with single-sided ventilation

In naturally single-sided ventilated areas, the index of the distance from the window line and ratio of openable window area or other controllable openings to net primary area:

0.18

The number in benchmark is calculated from GBC’s algorithm and assigned to facilitate assessment Input data is calculated from the design of the baseline housing block (See 6.4.1.)

Q.1.3.3 Ventilation performance in

naturally ventilated areas of the

building with cross-ventilation

Ventilation performance in naturally ventilated areas of the building with cross-ventilation

In naturally cross-ventilated areas, the index

of the distance from the window line and ratio of openable window area or other controllable openings to net primary area:

0.13

The number in benchmark is calculated from GBC’s algorithm and assigned to facilitate assessment Input data is calculated from the design of the baseline housing block (See 6.4.1.) Q.1.4 Ventilation effectiveness in occupant

zone of primary occupancies Ventilation effectiveness in dwelling unit 45 % of the area of dwelling unit are provided with cross-ventilation Benchmark is based on the design of baseline housing block

Q.2 Thermal Comfort

Q.2.1 Air temperature in primary

occupancies Air temperature in living area

The percentage of operating hours that indoor air temperature within living area are likely to

be within accepted comfort ranges

In accordance to GBC's manual, for natural ventilated area, the indoor operative temperature must be maintained between 31.50C and 17.50C during periods when the mean monthly outdoor temperature ranges from 100C to 33.50C to be considered in the acceptable comfort range No humidity or air speed limits are required

Research findings in thermal measurement in HDB flats indicates that indoor air temperature in living area whole day round are within the above ranges (Chowdhury, 2000)

In assessing the case studies in this research, an indoor temperature measure will be taken when the outdoor air temperature is higher than 320C to confirm the above statement

Q.2.2 Mean radiant temperature (Not

assessed in GBC2000) Solar radiation index Index of 1.125

Although Mean radiant temperature has not been assessed in GBC 2000, solar radiation index as recommended by HDB, Public Housing Design Handbook (HDB, 1995) is applied (See 6.4.2.) Q.2.3 Relative humidity created by HVAC

system in primary occupancies

during heating and cooling season Not applicable Not applicable

The case-studied housing is assessed under natural ventilation condition

Q.2.4 Air movement in primary

occupancies (Not assessed in GBC

2000) Applicable but not assessable Not applicable

Air movement in primary occupancies is under developing in GBC 2000

Q.3 Daylighting and Illumination Daylighting

Q.3.1 Provision of daylighting in primary

areas of all occupancies Provision of daylighting in living and kitchen area 1.5% daylight factor Benchmark is calculated from the baseline housing block, based on GBC’s algorithm

Q.3.2 Potential glare in primary areas of all

occupancies Potential glare in living area

To be assessed relative to general text description

The is no potential glare in living area

Q.4 Noise and Acoustics

Q.4.1 Noise attenuation through the

building envelope Noise attenuation through the building envelope Sound transmission class of windows (or its equivalent)

In accordance to GBC manual, this criterion applies only to buildings where ambient noise is considered

to be a problem for occupants For residential building, night-time ambient noise sources are considered

Q.4.2 Transmission of building equipment

noise (HVAC system) to primary

occupancies Not applicable

To be assessed relative to text description of HVAC system and measures taken to reduce noise Public housing does not have HVAC system Q.4.3 Noise attenuation between

occupancies in office or mixed-use

office buildings Not applicable Not applicable

Q.5 Electro-Magnetic Pollution Not applicable Strategies adopted to reduce EMP for building in high level electro-magnetic field The case-studied housing blocks do not often locate in high level EMF (Source: informal

interview with senior HDB staffs)

S SERVICE QUALITY

S.1 Flexibility and Adaptability

S.1.1 Ease of adapting technical building

systems for changing occupant

requirements in non-residential

occupancy

Not applicable Not applicable This GBC criterion is applicable in non-residential building

S.1.2 Suitability of layout for structure and

core for major changes in future uses

Suitability of layout for structure and core for major changes in future uses

To be assessed relative to text description:

Adaptation to another building use requires extensive renovation, and rebuilding of the internal walls and fenestration require only minor modification

S.1.3 Suitability of floor height for major

changes in future uses Suitability of floor height for major changes in future uses 2.8m HDB design guideline (Source: HDB, 1995)

S.1.4 Floor loading capacity for other uses Floor loading capacity for other uses To be assessed relative to general description of structural systems and

approaches to adaptability

S.1.5 Adaptability to future changes in type

of energy supply Adaptability to future changes in type of energy supply

To be assessed relative to general description: Adapting the building to a new fuel source will be possible with a moderate level of renovations, but installing

photovoltaics will require major renovations

of electrical system

S.2 Controllability of Systems

S.2.1 Capability for partial operation of

building technical systems (HVAC

and lighting), applying to

non-residential use

Not applicable Not applicable This GBC criterion is applicable in non-residential building

S.2.2 Capability for control over heating

and cooling systems in primary

occupancies

Capability for control over ventilation and illumination in dwelling unit

To be assessed relative to general description:

opening and lighting switches are controllable by occupants

S.2.3 Level of building automation

appropriate to system complexity

Capability for control over ventilation in principal rooms of dwelling units or, in other occupancies, capability for personal control over indoor environment in primary areas To be assessed relative to description of control systems window, and lighting

Personal control over temperature, ventilation rates, local illumination levels, and acoustics at different occupied rooms is possible

This criterion is more significant in other building type, e.g office or commercial buildings, where high level of automation is often applied

S.3 Maintenance of Performance

S.3.1 Protection of materials from

destructive elements (rain penetration

and moisture-laden air when outdoor

temperature is under 00C)

Not applicable Not applicable Outdoor temperature in Singapore context is always above 00C

S.3.2 Potential to maintain performance of

building systems

S.3.2.1 Access to central technical systems

(HVAC) for maintenance and

replacement Not applicable Not applicable

The case-studied housing is assessed under natural ventilation condition

S.3.2.2 Access to distributed technical

systems (HVAC) for maintenance

and replacement Not applicable Not applicable

The case-studied housing is assessed under natural ventilation condition

S.3.2.3 Access to building elements and

materials for maintenance and

replacement

Access to building elements and materials for maintenance and replacement

To be assessed relative to general description:

Most components are accessible, and regular maintenance and replacement is feasible

S.3.3 Ability to maintain critical

performance parameters under

abnormal conditions

Ability to maintain critical performance parameters under abnormal conditions

To be assessed relative to general description:

The building can function continuously under conditions outside of anticipated design conditions for temperature, rainfall, power and fuel supply; but in a significantly reduced capacity

S.3.4 Metering and monitoring of

performance

S.3.4.1 Monitoring of key system

performance parameters Monitoring of key system performance parameters

To be assessed relative to general description: In residential occupancies, sub-metering of energy use is provided for all individual dwelling units and a central reporting system is provided

S.3.4.2 Provision of leak detection system

covering all main water and gas

supplies

Provision of leak detection system covering all main water and gas supplies

To be assessed relative to general description: A leak detection system is provided for gas supply systems, and an alarm system is provided

S.3.4.3 Provision of measures to reduce

refrigerant leakage in HVAC

system Not applicable Not applicable Public housing does not have HVAC system

S.4 Privacy and access to sunlight and

S.4.1 Visual access to the exterior from

primary occupancies Visual access to the exterior from living area

The unobstructed distance from windows of principal living areas of typical dwelling units is 30 m

S.4.2 Visual privacy from the exterior in

principal areas of dwelling units

Visual privacy from the exterior in living and sleeping areas of dwelling units

From a point 20 m from the exterior windows, horizontal or downward views are available of the interior of bedroom and living areas of no more than 25% of the dwelling units in the building; or a system of exterior movable privacy screens is provided

S.4.3 Access to direct sunlight from

principal day-time living areas of

dwelling units Not applicable Not applicable

Access to direct sunlight is unfavourable in Singaporean climatic context

S.5 Quality of Amenities and Site

Development

S.5.1 Site amenities for shade, relaxation

and play for residents Site amenities for shade, relaxation and play for residents

To be assessed relative to general description:

There is some provision on the site for shade and relaxation for adults or children A multi-functional communal hall is provided

S.5.2 Quality of parking area development

(to minimise the adverse affects of on-grade

a building entrance

S.6 Impact on quality of service of site and adjacent properties

S.6.1 Adverse wind conditions at grade

around high buildings Adverse wind conditions at grade around high buildings

To be assessed relative to general description:

The same height or lower than surrounding buildings and other obstacles and the site is not wind exposed Void-deck provided at grade level

S.6.2 Impact on access to daylight of

adjacent property Impact on access to daylight of adjacent housing block

The vertical angle measured from the building line on the ground of the nearest adjacent property to the roof line of the case-study building is: 600

Benchmark is calculated from the design of the baseline housing block

S.6.3 Impact on solar energy potential of

adjacent property Impact on solar energy potential of adjacent housing block

The percentage of the southerly facing building façade of an adjacent property north of the case-study building, that is shaded by the case-study building at 12 noon on Winter Solstice is: 0%

Although exposing to sunlight is unfavourable in Singapore hot climate, the criterion is considered applicable in the credit of potential solar energy S.6.4 Noise from the case-studied building’s

equipments (HVAC) affecting adjacent

properties Not applicable Not applicable

This criterion is applicable to non-residential building types, e.g industrial or commercial

E ECONOMICS Not applicable For crude assessment Economics issue will not be taken in the final score of performance

M MANAGEMENT Not applicable For crude assessment Management issue will not be taken in the final score of performance

Table 7-2: Localisation and customisation of environmental criteria and benchmarks

7.4 Prioritisation among environmental performances

7.4.1 Prioritisation in building environmental assessment method

In building environmental assessment method, the term 'assessment' seems to refer to what has been done and does not explicitly relate to the attempt of 'knowing the future' However, building environmental assessment method sets a framework for remedial actions in improving the environmental performances of a building during designing stage, or of our collective knowledge of built environment Its ultimate objective is about the future and sustainability

The early version of building environmental assessment methods, e.g BREEAM, does not explicitly prioritise its environmental criteria However, later methods explicitly encompass weighting among environmental issues and criteria This is to reflect another level of understanding to the complexity of environmental sustainability through the acknowledgement

of the systematic structure rather than just the sum of individual issues In Green Building Challenge, environmental criteria are arranged under a nesting system of 4 hierarchies – environmental issues, environmental categories, environmental criteria, and environmental sub-criteria Each hierarchy has its own weighting system and the higher level of hierarchy has higher weight as it is a combination of all components of the lower hierarchy

The two important roles of weighting in GBC, as stated by Cole (2001), are:

– Weighting is intimately linked with the manner in which performance results are

summarized and communicated

– Weighting is essential to make practical decisions The weightings assigned to the

various performance criteria are an explicit declaration of their importance As such,

they can provide guidance to a design team on performance areas that will lead to

the greatest environmental benefit (Cole, 2001)

Establishing weighting system in GBC, however, is still an ongoing research issue due to the lack scientific objectivity and framework in any current methodology In the current practice, there are two main methodologies to establish weighting system Firstly, GBC, by default, suggests that the weighting system can be voted by taking the average from opinions of six experts in the field at the national level (Cole, 2002) Secondly, weighting system can also be developed through applying a prioritisation method named Analytic Hierarchy Process (AHP) AHP is an approach to explicate the underlying mental process in multi-criteria prioritisation through employing simpler pairwise comparison procedure to arrive at a more complex scale of preferences among components (Saaty, 1980) An example of the second method can be found

in the weighting system of Swedish Eco-Effect assessment method (Glaumann, Malm, & Larsson, 1999)

Both methodologies aim to derive a weighting system that is less subjective and reflect closely the actual environmental situation related to built environment in a region The default methodology of GBC tries to reduce individual subjectivity through seeking consensus among

reliability Experts, who votes for weighting, make their judgements based on, and thus often being partial to, their own professional experiences and expertises Therefore, the consensus-based weighting system may turn out to be a balancing process of different interests On the other hand, Analytical Hierarchy Process provides a scientific based to reduce the 'subjectivity'

in developing weighting system through mathematical mechanism In this research, the AHP is opted to be the method to derive weighting system for GBC's environmental issues and catalogues

7.4.2 The method: Analytic Hierarchy Process

Background

Prioritisation is one of the fundamental issue in predicting the future and decision making process There are two well-known approaches: 'causal processes' and 'purposive action

and event are identical to be the 'cause' that can be internal or external to a system In 'purposive

action processes', where action event consequence for the actors involve, the 'action' and

above is not sufficient to describe a complex system, which includes both the natural causal factors and human controlling actions

The problem of prioritisation is to find the relative importance or priority among components of a system with respect to an objective Once we have to make prioritisation, especially a complex one,

we often base our judgement on our own gut feeling, preference, understanding, experiences, or all of them While our feeling and preference are purely objective, which may not be convincing

to the others; our understanding and experiences are limited, local, and partial to capture holistic view of the overall situation As described by Saaty & Vargas (1982), 'our minds have a limited capacity to assimilate and retain large amount of information for short periods of time'

The Analytic Hierarchy Process responds to both of above shortfalls by two characteristics, (1)

methodology, and (2) encompassing a mathematical method to minimise subjective partiality in the actors' judgements (Saaty & Vargas, 1982)

The former characteristic allows the actors to assess the factors (or causes) that likely lead to certain types of outcomes, and at the same time, facilitate the actors creativity and flexible to

performance of a building, there are certain causal factors in building design (e.g providing large openings) that leads to certain environmental performance (e.g good natural ventilation and poor indoor privacy) At this point, the actors must make a judgement to sway towards either natural ventilation or privacy The AHP allows the inclusion of both situations

The second characteristic of the AHP is allowing subjective judgements but admitting inconsistency

in these judgements and thus providing a method to minimise subjectivity and to measure inconsistency The AHP derives priority for a multi-criteria system through:

– starting with manageable, familiar and smaller scale pair-wise comparisons with numerical

assignment, and

– combining outcomes of pair-wise comparisons through a mathematic mechanism to derive a

priority system This system describes the relative levels of importance among criteria under

a complex system

Underpinning mathematical theory

The application of the Analytic Hierarchy Process is (1) to establish a matrix of pair-wise

matrix The following is a brief summary of the mathematical theory of the AHP, as reference

can be established as follows:

where ai/aj = aj/ai for all i, j = 1, 2,…, n

of the estimated weight ai of criteria Ai over the estimated weight aj of criteria Aj)

If the judgement of pair-wise comparison were perfectly consistent, which means