Environmental performance and sustainable architecture a critical review in the context of singapore public housing 3

Chapter 9: Land Use Efficiency 9.1 Prelude Part III extends the discussion of environmental performance to sustainable housing performance with empirical dimension through: – identifying

Part III From Environmental Performance to

Sustainable Housing Performance –

Empirical Discussions

Chapter 9: Land Use Efficiency 9.1 Prelude

Part III extends the discussion of environmental performance to sustainable housing performance with empirical dimension through:

– identifying the limitations of building environmental assessment method, and

– including socio-economic factors and architectural design in sustainable housing discourse

Both discussions are substantiated by practices found in Singapore public housing For each

of the five sustainable housing performances, i.e land use efficiency, energy efficiency, water conservation, material efficiency, and experience of home, the discussion is generally structured as followed:

(a) Elaborate how each of the corresponding environmental performance criteria is

measured, and empirically analyse their interrelationship with other environmental performance criteria, in order to highlight conflicts (where occur) among case studies’ results of environmental performances and the hierarchical approach in suggesting solutions to the conflicts;

(b) Correlate the results of Singapore public housing case studies’ environmental

performances against pertinent socio-economic data, in order to illustrate the limitations of environmental performance domain and the influential factors of socio-economics domain; and

(c) Discuss the approaches to achieve high sustainable housing performance from the

Integrated Framework for Sustainable Housing Design and Discourse, substantiated through the analysis of Singapore public housing practices The study:

o Identifies case examples of architectural design and socio-economics

strategies that contribute to sustainable housing performances as well as

environmental performances, but not reflected in building environmental assessment method

o Identifies additional factors in socio-economics and architectural design

domains, on top of environmental performance domain, impacting building environmental performances and sustainable housing performances

o Establishes an integrated approach to each sustainable housing performance

issue and give empirical dimension to the theoretical-constructed Integrated Framework for Sustainable Housing Design and Discourse (established in Chapter 5) Subsequently, the assessment criteria and factors that impact each sustainable housing performance issue will be proposed and discussed

The discussion in this chapter focuses on land use efficiency Globally, land use efficiency is one of the main issues in sustainable development (Jenks & Burgess, 2000) to undertake both population growth and prevention the lost of natural environment to the development of built environment Locally, due to land scarcity and population growth, land use efficiency is always

a prime issue, especially in housing development

9.2 Land use performance and Plot Ratio

The environmental performance of land use in GBC is relatively new concept for applying in analysing public housing design The constituting components of land use performance criterion (L) in GBC, as expressed in equation (12), include the total site area (Asite), building footprint area (Af), percentage of hard-paved area of the site (P), and total net usable area of the building (Anet)

In a housing development, Asite is fixed, while the other components are variants In order to achieve good land use performance, the building footprint area (Af) and the percentage of hard-paved area of the site (P) should be kept as low as possible, and the total net usable area

of the building (Anet) should be as large as possible

In Singapore, scarcity of land has always been a dominant issue, and has resulted in the proliferation of high-rise high-density housing development in the country The legislative measurement and control of land use for each development is Plot Ratio (PR), which is also commonly and conventionally found in architectural practice In the Handbook on Gross Floor Area by the Urban Redevelopment Authority, 'Plot Ratio of a site is defined as the ratio

of the gross floor area of a building(s) (Agross) to its site area' (URA, 2003), or:

In a housing development, Asite is fixed, while Agross is the variant In order to achieve good land use in terms of PR, the commonly found strategies are designing higher building height and higher housing density, or narrower spacing among housing blocks (HDB annual report, various issues)

In the comparison between land use performance and PR, the strategies to achieve high PR are found to be more limited and do not recognise the credit of greenery provision on site The relationship between land use performance and PR can be described as that PR does not determine, but only constitute to the score for land use efficiency

In order to gain further insight to the above relationship, empirical investigation into public housing case studies are carried out When juxtaposing indicative trendlines of PR values and land use performance scores (Figure 9-1), the relationship between the two is not obvious The reason is that, in land use efficiency, it is the sum of building footprint and hard-paved area, rather than the gross floor area in PR calculation that constitutes the values Therefore, case studies with larger total greenery area on ground and smaller building footprint yield for higher land use efficiency score

2.7 3.1 3.6

3.3 2.9

1.1 2.8

0.2 0.8 0.2

1.2 0.8 1.5

-0.6

2.4 0.7

Figure 9-1: Juxtaposition the indicative trendlines of Plot Ratio values and land use performance scores, of public

housing case studies

Case study number 08 – 5-room point block – is a good example, where the PR value is 2.1, being the third lowest among the values of all case studies, but the score for land use efficiency

is 3.5, being the highest among the scores of all case studies This is attributed to the large greenery area in the total site of the development and the small footprint of the housing block

Figure 9-3: Large surface parking area around the housing blocks in case study number 09

In juxtaposing the two indicative trendlines of PR and land use performance (Figure 9-1), it is observed that in the early decades, the two types of values are not correlated to each other with the dominant low scores for land use performance This is due to (1) the preference of slab block structure, which has larger building footprint and lower building height, and (2) the often use of open spaces among housing blocks for surface parking – a common practice found in public housing at the time In the period after 1990s, the indicative land use performance trend in public housing design shows improvement This is due to

– the requirement of minimum greenery shaded area was established under design

guidelines of public housing (HDB, 1995),

– multi-storey carparks with smaller land area usage for parking purpose were

introduced giving more area for greenery landscape, and

– housing blocks are designed with various building shapes and higher building height

leading to smaller building footprints in its percentage to the total building net area

Despite of the differences between the two concepts, there still exists, in general, a correlation between PR and land use performance Nevertheless, a high PR value, although does not promise, is a constituting components leading to, high land use performance score

In summary, the primary difference between the two is the area of greenery on the site While greenery area is a component in measuring land use performance, it is not considered in PR calculation From environmental perspective, this difference provides more flexibility in architectural design to achieve high land use performance This is illustrated by: case studies with higher PR do not promise to have high land use performance; and conversely, case studies with lower PR are still able to gain high land use performance (Figure 9-1) The second case is of particularly encouraging for buildings in area with limited PR allowed by planning control This is because the design of the building still can overcome the obstacle

9.3 Land use performance and its interconnectedness

9.3.1 Land use performance and change in ecological value of the site

The relationship between the land use performance, and change in ecological value of the site performance demonstrate a supportive reciprocation While the prior criterion encourages minimising the use of land and to maximise greenery area, part of the later criterion takes a step further in encouraging the providence of greenery area that contains high ecological value The measurement of the second criterion bases on 'the presence or absence of design features that demonstrate that the site ecology has been disturbed, retained or improved' (GBTool User Manual, 2002) The rationale is that to be high land use performance by maximise the area of greenery alone is not enough because the environmental quality and ecological values of the greenery have not been defined and are not controlled

The above discussion can be better comprehended through a comparison between case study number 8 and case study number 19 (Figure 9-4) In case study number 8, there are ample areas of greenery and small building footprint, whereas case study number 19 has smaller percentage area of greenery and larger building footprint However, the ecological value of case study number 8 is lower than the one of case study number 19 As illustrated in Figure 9-4, the large greenery areas of case study number 8 comprises of, however, mostly sparely-grown grassland and barely a number of small tree This setting yields minor room for biodiversity development and does not contain high ecological value In reverse, although case study number 19 has smaller percentage of greenery area, the design and replanting of mangrove trees along the river banks have not only restored the ecological value of the site after construction, but also act as a green connector and promote biodiversity As described by the landscape architect, the riverbanks have been designed as green connectors linking Pasir Ris Park in the north to the neighbourhood centre The replanted mangrove plants and natural vegetation have intermixed with each other along the riversides, restoring the natural state of

the river Mangrove shells, fishes, birds including kingfisher, are among other species can be found in the area (rewritten from interviewing with the senior landscape architect, June, 2004) The comparison of the two case studies has illustrated the necessity of, and positive interaction between, the two criteria of land use performance and of change in ecological value of the site performance, for a meaningful and comprehensive environmental and ecological consideration in terms of land resource usage

Figure 9-4: Comparison of land use performance and change in ecological value of the site performance between

case study number 8 (above) and case study number 19 (below)

9.3.2 Land use performance and daylighting performance

Plot Ratio and visible angle of sky at window

The increase of PR, thus constituting to higher land use performance, is perceived as overwhelming and suppressing opportunities for daylighting performance of the building

In calculating daylight factor, one of the constituting factors to enhance the performance is the visible angle of sky at window (degree) This visible angle of sky is 900 minus reduction for overhangs and nearby buildings (GBTool User Manual, 2002) The implication for design strategies to obtain high daylight factor is to have larger distance between housing blocks and lower building heights in the housing estate in order to achieve a larger visual angle of sky at window This is obviously in contrast to the design strategies to achieve the objective of high land use performance

By juxtaposing the two indicative trendlines of PR and of the visual angle of sky at window

of public housing designs, the opposite trends of the two indicators are clearly addressed While the PR of public housing has been increasing decade after decade, the indicative trend

of visual angle of sky at window has been decreased, impacting the trend of daylight factor performance In the first two decades of public housing development, housing estates are designed with the dominant PR ranged from 1.9 to 2.7, and the dominant visual sky angles at window are ranged from 240 to 450 Conversely, in the case studies built in year 2000 and beyond, the PR values are higher (ranging from 2.9 to 3.7); whereas the visual angles of sky

at window are relatively lower (dominantly ranging from 220 to 380)

30 60

30 25 15 30 60

20 45 60

38 60

Figure 9-5: Juxtaposition the indicative trendline of Plot Ratio and the one of visual angle of sky at window

The two trends are not obvious in the 1980s and 1990s, as the case studies have mixed PR values, and mixed visual sky angles at windows Nonetheless, case studies with high PR values (ranging from 3.6 to 4.2 for case studies numbers 9, 13, 16, and 19) yield low visual sky angles at windows

of 300 Similarly, case studies with high visual sky angles at windows (600 as found in case studies numbers 10, 12, 17, and 22) do not have high PR values (2.7, 2, 2.7, and 2.9 respectively)

The discrepancy, as illustrated by the above two indicative trends, however, is not applied to all the case studies There are individual cases that demonstrate to achieve both high PR values and large visual angles of sky at windows This can be achieved as a result of design strategies in articulating estate layout that allows windows facing to larger open spaces, rather than to narrow the spaces between housing blocks Taking the extreme example of case study number 24 – block 660C Boon Lay, there are no windows facing East and West to the narrow spacing between housing blocks Instead, extensive windows are designed to face North and South to

the large open spaces Stagger layout of housing blocks in the housing estate also help in achieving this

Figure 9-6: There are no windows facing East and West to the narrow spacing between housing blocks Instead,

extensive windows face North and South to the large open spaces

Nevertheless, there is an inconsistency between the objective of achieving higher PR and the one of achieving larger visible angle of sky at window, as reflecting in the two indicative trends of public housing evolution (Figure 9-5) This leads to the existence of a potential discrepancy between the objective of land use performance and that of daylighting performance

Land use performance and daylight factor

When mapping the indicative performance trends of land use and of daylighting, both trends show positive progression over times, regardless of the potential discrepancy as analysed The reason originates from the measurements of both land use performance and daylight factor, that are not determined by the building height and spacing between buildings alone In land use performance, other considerations include building footprint area and percentage of greenery area in the site In daylight factor, other constituting components in the measurement include the total area and reflectance of interior surfaces, the total area and average visibility transmittance of windows

When correlating the indicative performance trends of daylight factor and of visible angle of sky at window, it is observed that there is a reverse trend between the two While the indicative trend of visible angle of sky at window descends, the one of daylight factor performance ascends over times This is because of the increase in window size (especially in living/dining area) towards the later years of public housing development (Figure 9-8)

Trendline of Land Use Performance (GBC score)

1.1 2.8

0.2 0.8 0.2

1.2 0.8 1.5 0.6 0.3 -0.6

2.4 0.7

60

30 60

30 25 15 30 60

20 45 60

38 60

Figure 9-8: An imagery trendline to illustrate windows in living area of public housing has been getting larger and

larger over times

In brief, although there is a potential conflict in the objectives between land use performance and daylighting performance, the practice of public housing development has demonstrated that this potential discrepancy can be minimised and even diminished through various design strategies

9.3.3 Land use performance and impact on access to daylight of adjacent building

The measurement of impact on access to daylight of adjacent building performance base on the vertical angle measured from the building line on the ground of the nearest adjacent property to the roof line of the case study housing The smaller the angle, the higher score the case study housing achieves for this performance This suggests design strategies of larger spacing between buildings, and of lower building height; both of which, however, contradict

to strategies to obtain high land use performance

In order to find out how the design of public housing over times has embarked upon this discrepancy, the environmental performance of land use is mapped with the one of impact on access to daylight of adjacent building (Figure 9-9) Empirically, the indicative trend of land use performance has been increasing, whereas the other has been decreasing over time Case studies

in the early stage, up to and including the 1980s, are often in slab block structure, 10 to 13 floor heights, and are often placed parallel with other housing blocks in the estate with a minimum distance of approximate 28m These case studies yield for a rather steady and dominant higher scores for impact on access daylighting of adjacent building, in compared to the case studies in the 1990s and the year 2000 and beyond The reasons for the relatively mixed scores among the

performances of case studies in the later decades include (1) more variety of building shapes, forms and heights are applied even in one estate, and (2) housing blocks in an estate are designed less rigorously in terms of spacing among buildings and orientations

Trendline of land use efficiency (GBC score)

1.1 2.8

0.2 0.8 0.2

1.2 0.8 1.5

-0.6

2.4 0.7

-1 -1.5

Figure 9-9: Mapping the indicative performance trend of land use performance and the one of impact on access to

daylight of adjacent property

At more detailed level, case studies with higher land use performance do have low performance

on impact on access to daylighting of adjacent building, and vice versa An example can be found in case study number 07 – a 4-room slab bock in Clementi The case study housing has low land use performance score (-0.6) – the fifth lowest score for this performance among the case studies There is large spacing between the case study and its adjacent housing block, which has windows facing the case study building This large spacing resulted in the highest score (3) for impact on access to daylight of adjacent building among the case studies

Figure 9-10: Large spacing between the case study housing and the adjacent housing block (case study number 7)

In brief, the empirical indicative performance trends of public housing coincide with the earlier theoretical analysis, in which there is a discrepancy between the design objectives of land use performance and impact on the access to daylighting of adjacent building Furthermore, it is observed that land use performance of public housing design has been receiving higher priority in the later decades

9.3.4 Land use performance and visual privacy

The assessment of visual privacy performance bases on the distance of available point that horizontal and downward views are available of the interior of bedroom and living areas of certain percentage of dwelling units of the building Interpreting from the above objective, design strategies include:

(a) Providing large spacing from the case study housing to its surrounding structures so

that the long distance from this external viewing points can limit viewing ability to the case study housing;

(b) Manoeuvring the orientations of the case study housing windows so that they will not

face to the proximal potential viewing points for privacy intrusion; and

(c) Providing design elements as obstacles, e.g external screen, to limit visual intrusion

to the internal of dwelling units

Among the numbers of design strategies to achieve the objective of visual privacy, the distances to the case study housing from the adjacent structures is of particular concern The longer this distance is, the better the case study housing performs in this aspect This is, however, the potential conflict to land use performance objective, which is in favour for more compact form of development

Trendline of Land Use Performance (GBC score)

1.1 2.8

1.2 0.8 1.5

-0.6

2.4 0.7

1.5

-0.1 -0.8

1 3.5

Figure 9-11: Juxtaposing the environmental performance of land use with the one of visual privacy

To gain insights on how public housing designs over times have addressed this potential discrepancy, the indicative trend of land use performance is mapped with the one of visual privacy performance (Figure 9-11) Unpredictably, the two performance trends appear in general being correlated to each other In the early three decades, majority of case studies receive lower scores for visual privacy performance (except for the individual case studies number 7, 8, 10, 13 and 14) This is because of the dominant estate layout of parallel slab

also allows for large percentage of dwelling units in a housing block, the interiors of which can be seen from the opposite structure The exceptional case studies numbers 8, 10, and 14 are point block structures, in which the numbers of dwelling units are distributed evenly on the 4 facades The most vulnerably visual privacy façade can only affect a percentage of 1/4

of the total dwelling units of the housing, and thus the buildings has better visual privacy performance due to their small percentage of affected dwelling units Furthermore, the point block housings are often arranged staggering with other surrounding blocks (as in case studies numbers 8 and 10), which further enhance their visual privacy performance (Figure 9-13)

Figure 9-12: Parallel layout of slab block housing that reduces visual privacy performance in case study number

04 (photo is taken after the estate underwent the main upgrading programme)

Figure 9-13: Staggering layout of point block housing that enhances visual privacy performance in case study number 10

Majority of case studies, in the period between 1990 to the present day, receive higher scores for visual privacy performance (except for case studies numbers 21, 22, 28 and 29), whereas land use performance has also improved The potential discrepancy between the two performances has been diminished as a result of the application of design strategies to manoeuvre the orientations of the case study housing windows (so that they will not face directly to the proximal potential privacy intrusion viewing points) and providing design elements as obstacles, e.g external screen,

to limit visual intrusion to the internal of dwelling units As for the exceptional case studies, particularly case studies number 21 and 22, which underwent a major main upgrading programme, the visual privacy performance trends has further declined from the already low performance scores This is inevitable due to the 'Space Adding Item' (SAI) of the upgrading programme that narrows the open space sandwiched between the housing blocks (Figure 9-14)

Figure 9-14: Reduce in visual privacy due to narrower spacing between housings after upgraded with SAI (case

In brief, there exists a potential discrepancy between the objective of land use performance and that of visual privacy performance In the early decades, the design of public housing often traded off visual privacy performance owing to the rigorous layout of parallel slab blocks However, in later decades, visual privacy in public housing design has been improved along side with higher land use performance, as a result of being more flexible in building forms, window orientations and estate layouts

In brief, the discussions in this section have indicated that there are potential discrepancies in the interconnectedness between land use performance and environmental performance of daylighting performance, access to daylight of adjacent building, and visual privacy When discrepancies occurred, the implied suggestion from the practice of building environmental assessment is trading-off less important environmental performance for a higher total environmental performance This practice can be seen in how public housing development in the later decades takes on land use performance with higher priority to the performance of access to daylight of adjacent building (see section 9.3.3) With the exception of this case, the other two potential discrepancies, i.e between land use performance and daylighting performance, and between land use performance and visual privacy, can be overcome through architectural design techniques and strategies (see section 9.3.2 and 9.3.4)

9.4 Land use performance and the trend of smaller household size

Globally, land use efficiency is one of the long-discussed issues in sustainable development (Jenks & Burgess, 2000) to undertake both population growth and prevention of the lost of natural environment to the development of built environment Discarding strategies and attempts to be land-use efficiency, e.g building higher and denser, changes in household structure and the trend towards smaller household size (especially in the developed countries), have complicated this issue through the resulted rapidly increase of household numbers Rudlin and Falk state:

At the end of the twentieth century, the debate is […] about housing numbers, as a

result not of population growth but household growth (Rudlin & Falk, 1998)

Due to the small size of the country, population growth and land-use have always been a major issue in Singapore Over the years, the population has continuously increased from about 1.6 million in 1960 to nearly 3.4 million people in 2002 Density, as a result, has simultaneously increased more than two folds from about 2810 persons/km2 in 1960 to 6075 persons/km2 in 2002 (Department of Statistic, Yearbook of Statistics Singapore (various issues)) Strategies to undertake land-use issue include reclaiming land from the sea and increasing building Plot Ratio Nonetheless, the social trend of reducing household size (Figure 9-15) has complicated the efforts

Faced with the above land use issues, this session aims to investigate how the indicative land use performance trend in public housing interacts with population increase, indicative public housing density trend, and social trends of smaller household size The above trends are juxtaposed as illustrated in Figure 9-15 to facilitate the correlation analysis

P opulation and P ublic Housing P opulation

Public housing population (people)

Trendline of Land Use Performance (GBC score)

1.1 2.8

1.2 0.8 1.5

-0.6

2.4 0.7

Ex ec HUDC Mean hous ehold

s iz e

Figure 9-15: Juxtaposing the trend of population and public housing population growth (Source: Department of

Statistic, Yearbook of Statistics Singapore (various issues)); the indicative trendline of land use performance; the indicative trend of public housing density (constructed from the case studies); and the trend of mean household size by flat type (Source: HDB (2000) Profile of Residents Living in HDB Flats, HDB)

It is observed from Figure 9-15 that in the context of continuous increasing trend of population and public housing occupants over the years, there have been responses from public housing design – the strategies of increasing building Plot Ratio, and of building denser and higher housing estates However, despite the efforts, the indicative public housing density trend appears to show an opposite tendency, particularly the sharp fall in the period from the 1960s to the 1980s This inconsistency raises question on the effectiveness of being high land use performance in tackling growing population and land scarcity issues, in other words, question on whether there exists a correlation between them

On the other hand, when juxtaposing the indicative public housing density trend with the trend of mean household size, there appears to be a correlation between the two Both trends show a sharp fall tendency in the period from the 1960s to the 1980s, and continuously and gradually decrease towards the end 1990s

The phenomenon from the above correlation analysis led to the conclusion that there is a strong influence of public housing density from the social trend towards smaller household size Although there may exist a connection between being higher land use performance and higher density in public housing design, this connection is feeble The rationale lies in that land use performance emphasises only on the building physical performance of the effectiveness of site area usage in providing total net usable area of a building, rather than in the numbers of residents accommodated (in other words, the actual social and economic context)

In short, the results of these empirical analyses have substantiated the theoretical discussion in Part I of the thesis

9.5 Approach from the Integrated Framework

It has been understood that the increasing pressure on scarce land resource in Singapore derives from both population growth and social trend of smaller household size The strategies, extracted from environmental performance domain, are not effective enough due to their criteria and weighting system that by-pass the inclusion of current social trend and innovative solution from architectural design By including socio-economics and architectural design domains, the discussion of land use performance in environmental performance can be shifted to that of land use efficiency in sustainable housing performance Before looking into how the Integrated Framework for Sustainable Housing Design and Discourse contributes a systematic approach to land use efficiency; section 9.5.1 reviews and reveals case examples, which address land use efficiency from socio-economics and architectural design approaches, found in Singapore public housing development These strategies and approaches occur both intentionally and incidentally

9.5.1 Case examples of socio-economics and architectural design approaches

Approaches from socio-economics

In the evolution of public housing development, there have been examples of engaging land use issue through dialogues with social and cultural milieus Among the attempts to prevent vacant and unwanted housing (which are land-use inefficiency), the evolution of public housing has been flexible with the social trends that may affect housing demands In the 1960s when meeting housing shortage was an urgent task, public housings were speedily developed with dominant 1-room and 2-room flats However, in mid 1970s, the mass development of 1-room and 2-room flat types has given way to the dominant 3-room flat development; which was in turn ceased to develop due to low demand in the late 1980s 4-room and 5-room flats were the main flat types for development in the 1990s and early 2000s (HDB Annual Report, various issues from 1960 to 2003) In the early 2000s, due to the

impact of economic crisis and the high housing price, the demand for smaller flat size reoccurred In respond, HDB has decided to redevelop the 3-room flat types in mid 2004 (The Strait Times, 15th March 2004)

Besides being flexible in flat type design to meet housing demands, public housing has also engaged another strategy, which is reducing the flat size to respond to the social trend of smaller household size In 1993, all 4-room, 5-room, and Executive flats had their sizes reduced about 5m2 (HDB Annual Report, 1993) In 1997, these flat types had their size further reduced about 10 m2 (HDB Annual Report, 1998) Although the solution can not rely

on continuously reducing flat size that affects the residents’ quality of life (The Strait Times, 25th June 2003); the strategy, again, illustrates the approach to land use efficiency as a social response

A prolonged objective of public housing is to promote the traditional value of extended family

in the region In line with this objective, HDB, after the housing crisis in the 1960s, built multi-bedroom flats in larger number compared to 1- and 2-room flat types However, as the society became more affluence, residents had higher demands pertaining to their living environment Nuclear families started to form, and younger couples began to afford a flat for their own (HDB Annual Report 1970) These leads to the trend of smaller household size till the present day An attempt made in housing design was the introduction of multi-generation flat type, ‘which allow[s] families with grandparents or in-laws the benefits of living together under one roof whilst at the same time retaining privacy for both the younger and older generations’ (HDB Annual Report 1987/1988) Although the flats we re not well received and the construction of these flats was discontinued, this initiative illustrates a potential solution, offered from the socio-economic domain by responding the social setting to engage in environmental issues of land use

Approaches from architectural designs

From architectural design perspective, inclusive and innovative approaches can contribute much to the sustainable performance of land use efficiency While inclusive approach contributes to the issue by designing for environmental performance of land use without or with least negative impacts to other environmental performances, innovative approach progressively provides fresh solutions to the issue

Case examples of the above architectural design approaches, found in the evolution of public housing, are based on the exploration of sharing concept, e.g sharing neighbourhood park, precinct garden, etc., among number of housing estates and housing blocks Case study number 17 is an ideal example to illustrate this strategy Within the estate boundary, there are minimum open spaces and site amenities for resident relaxation and recreation At the building immediate South is a driveway and a multi-storey carpark, and to its immediate North is a beautiful neighbourhood park lusted with greenery and recreational facilities The design of the housing block has taken full advantage of the view and openness of the neighbourhood park by orientating as many as possible windows facing it Such a design deliberately locates the long common corridors on the South side of the building facing the driveway and the carpark Therefore, the housing design achieves high land use performance (calculated within the estate boundary) and at the same time is accessible to various public amenities, and achieves good views and openness of the large neighbourhood park

Windows open to the neighbourhood park

Corridors face driveway and multi-storey carpark

Rooftop garden on top of integrated multi-storey carpark has been experimented and has become a popular feature in public housing since the year 2000 This design feature, as found

in case study number 25 and 30, provides parking space to replace conventional surface parking At the same time, it also provides quality greenery communal space for the residents with large spacing between housing blocks and beautiful garden view The design provided good land use performance with minimum negative impacts on other environmental performances, i.e daylighting, access to daylight of adjacent building, visual privacy, and access to view The role of weighting system or prioritising environmental criteria, often found in BEAMs, is much less significant in this case Therefore, the inclusive and innovative approaches of architectural design in answering environmental issues can provide a better solution to land use efficiency with minimum trading-off other environmental values

Figure 9-18: Architectural design for land use efficiency with least trading-off other environmental performances

– rooftop garden on integrated multi-storey carpark, which also provides large spacing for housing blocks (Case

Figure 9-19: Rooftop garden on integrated multi-storey carpark, which also provides large spacing for housing

blocks (Case study number 30)

9.5.2 A systematic approach to land use efficiency

Hitherto, the chapter has empirically analysed and discussed to gain insight to:

– the strengths, weaknesses, opportunities and threats of the environmental performance

of land use,

– the significant impact of socio-economic forces to land use performance and applying

this understand to form strategies to be land use efficiency, and

– the strategies from architectural design to be land use efficiency

Integrating the above understandings and organised them into the Integrated Framework for Sustainable Housing Design and Discourse, a systematic approach to land use efficiency can

be formed (Figure 9-20)

Figure 9-20: A systematic approach to sustainable performance of land use efficiency, based on the Integrated

Framework for Sustainable Housing Design and Discourse

The systematic approach to sustainable performance of land use efficiency in Figure 9-20 are structured under the following main principles:

– The socio-economic settings and resident culture and behaviours need to be analysed

and understood in order to gain insights into the strengths, weaknesses, opportunities and threats to sustainable housing performance These settings include population growth, trend of smaller household size, economic force (e.g rise of housing price), and the cultural value of extended family living

– Through the above understandings, appropriate strategies can be set in architectural

design so that: strengths will be preserved and enhanced (e.g the cultural value of extended family); weaknesses will be minimised (e.g population growth); opportunities will be exploited (promoting vibrancy); and threats will be aware of and prevented (e.g trend of smaller household size)

– The knowledge of environmental performance domain can contribute to architectural

design in terms of knowledge-based inputs and inspiration For instance, the understanding of potential discrepancies between land use performance and other environmental performances (e.g daylighting, visual privacy, etc.) can inform and inspire architectural design for inclusive and innovative approach to overcome The awareness of ecological value of site from environmental performance domain also informs architectural design concerning proper site selection, minimising ecological destruction, and enhancing ecological value in greenery area, e.g making greenery area part of the green connector system of larger urban context

It is acknowledged that all sub-pathways in the systematic approach (Figure 9-20) contribute not only to the sustainable performance of land use efficiency, but also to other sustainable performances of energy efficiency and sustainable lifestyle For example, the inclusive and innovative approaches from architectural domain could resolve the potential conflicts between

the sustainable housing performance of energy efficiency (see Chapter 10) Promoting sharing from socio-economic approaches, e.g viewing into and sharing amenities of neighbourhood parks, will also lead to an opportunity for strengthening community living This

facility-is a constituent of creating the 'experience of home' – the fifth issue of sustainable housing performance (see Chapter 13)

9.6 Assessment criteria and influencing factors

The next question from the established concept of 'sustainable housing performance of land use efficiency' is how to assess its performance The current environmental performance criteria related to land use in GBC – (1) Area of land used for building and related development purposes / total net usable area of building; and (2) Change in ecological value of the site – demonstrate some advances in physical realm and in ecological terms However, section 9.4 has pointed out that these criteria do not reflect any socio-economic trends (e.g changes in household sizes) and thus exclude certain architectural design attempts in addressing these issues The result of correlation analysis in section 9.4 suggests that 'density' can reflect socio-economic factors related to land use, and 'density' can be the indicator to assess how land use efficiency performance responses to the issue of rising population Therefore, it is suggested that the assessment of sustainable housing performance of land use efficiency includes 'density' together with the existing environmental performance criteria of GBC

Figure 9-21 summarises the assessment criteria and factors that can influence the sustainable performance of land use efficiency The influential factors were revealed from the analyses of case studies in early sections of this chapter, and are from all three domains of socio-economics, architectural design and environmental performance and their interconnectedness The factors are constituent components contributing to, and thus can be looked up for the improvement of, the overall land use efficiency performances

Land Use Efficiency

Criteria:

1 Area of land used for building and related development purposes / total net usable area of building (as in GBC)

2 Density (new criteria)

3 Change in ecological value

of the site (as in GBC) Factors:

Socio-Economics:

- Population growth

- Trend of smaller household size

- Economic forces, e.g rising housing cost

- Social incentive

- Economic incentive

- Social value: extended family

- Social value of sharing and vibrancy

- Planning policies Architectural Design

- Innovative design

- Inclusive design

- Qualitative design

- Contextual design + Design for higher density + Design for higher building height

+ Design for multi-functions + Mixed-use development + Smaller flat size + New flat types for multi-generation families + Site selection + Minimise destruction and enhance ecological value of greenery

Environmental Performance

- Quantitative information of land scarcity

- Potential conflict with other environmental performances

- Knowledge-based: awareness

of ecological value of site

Figure 9-21: Sustainable housing performance of land use efficiency - assessment criteria and influencing factors

9.7 Conclusion

The discussions related to land use issue in this chapter began with reviewing the practice of environmental performance and concluded with establishing a systematic approach to the sustainable housing performance related to land use, its assessment criteria, and influencing factors The first discussion highlighted the differences between the concept of land use performance and the often-found concept of Plot Ratio It is found that although achieving high

PR value does not promise achieving good land use performance, PR is a constituting components leading to good land use performance The primary difference between the two is the area of greenery on the site, which is a component in measuring land use performance, but is not considered in PR calculation From the environmental perspective, this difference provides more flexibility in architectural design to achieve high land use performance, even in a site with limited PR allowed by planning control, through the providence of more greenery area

The second discussion was the interrelationship between land use performance and other environmental performance criteria The discussion has led to a conclusion that there are potential discrepancies in the interconnectedness between land use performance and the environmental performances of daylighting performance, access to daylight of adjacent building, and visual privacy However, these potential discrepancies can be overcome through architectural design techniques and strategies, i.e innovative and inclusive approaches in architecture design By doing so, the role of weighting system in BEAMs (in implying a suggestion of trading-off when confronting discrepancies) is less necessary

The third discussion investigated how land use performance in the evolution of public housing interacts with the growth of population, public housing density trend, and the social trend towards smaller household size in Singapore The correlation analysis shows that there

is a strong influence of public housing density from the social trend towards smaller

household size Although there may exist a connection between being higher land use performance and higher density in public housing design, this connection is rather weak The reason lies in the fact that land use performance emphasises only on the building physical performance of the effectiveness of site area usage in providing total net usable area of a building, rather than in the number of residents accommodated

Finally, the discussion shifted focus from environmental performance to sustainable performance of land use efficiency Based on the above three discussions, the explorative studies and case examples (of how strategies from socio-economics and architectural design tackle land use efficiency) found in the practice of Singapore public housing, and the Integrated Framework for Sustainable Housing Design and Discourse; a systematic approach towards the sustainable housing performance of land use efficiency, its assessment criteria and influencing factors have been established

Chapter 10: Energy Efficiency 10.1 Prelude

Energy efficiency – the triggering and greatest concerning issue in sustainable development –

is the focus of this chapter The discussion includes:

– An attempt to better understand the wide impacts of 'environmental performance of non-renewable energy consumption' and on its relationship to other environmental performances in GBC;

– Questioning what are the significant factors that can reduce energy consumption performance of housing In order to shed insight on the issue, the discussion includes a triple correlation analysis between:

o the indicative trendline of energy consumption of residents in public housing,

o the constituent environmental performances (thermal comfort, natural ventilation, and daylighting) derived from energy efficiency design, and

o the socio-economic factors of resident affluence and of resident consumption (particularly air conditioning usage)

– Shifting the discussion from environmental performance of energy consumption to sustainable housing performance of energy efficiency The Integrated Framework for Sustainable Housing Design and Discourse is applied in order to derive a systematic approach to energy efficiency This approach will be built upon observations and analyses of architectural design’s case examples and socio-economics strategies that both negatively impact and positively contribute to energy efficiency These however are not reflected in building environmental assessment method Based on the above analyses and case illustrations from the everyday practices found in public housing, the assessment criteria and factors influencing energy efficiency will be proposed and discussed

10.2 Environmental performance of energy consumption

Energy consumption relates to other resource consumptions (e.g fuel) and the worsening of atmospheric pollution through combustion leading to the emission of CO2 and other airborne pollutants In GBC, there are two criteria to assess the environmental performance of energy consumption: embodied energy of building materials, and the operational non-renewable energy

The first assessment criterion is not assessable in Singapore public housing, and is omitted in this research, due to the lack of local information Most building materials in Singapore are imported from different countries, and these importing sources are not static, driven by variant economic forces Therefore, embodied energy of building materials is acknowledged for its important role, but will not be included in the scope of this research

The second criterion assesses energy consumption performance based on the amount of renewable energy consumed for the operation of the case study building At the onset, the criterion emphasises and promotes the use of energy from renewable sources While the technologies to harvest renewable energy have been progressively evolving, the current application and production of such technologies have not been extensive enough to replace completely the reliance on fuel-based energy For many buildings and regions, including public housing in Singapore, fuel-based energy is still the main source to be taped on Under this circumstance, the main concern is the amount of non-renewable energy used for the building operation In the following discussions, the term energy consumption refers to non-renewable energy consumption The computation for the energy consumption performance, as suggested in GBTool Manual, should account for: 'annual HVAC energy consumption, annual site lighting energy consumption, annual plug load (tenant equipment) energy consumption,

non-service hot water energy consumption' (GBTool User Manual, 2002) The energy consumption performance is then addressed by the amount of energy consumed per square metre of net usable area per annual (MJ/m2/year)

Besides this direct measurement criterion to energy consumption performance, there are several other environmental performance criteria in GBC that have their measurements based

on the energy consumption performance They are: Green House Gas emissions from all energy used for building operations, emission leading to acidification from energy consumption for building operations, and emissions leading to photo-oxidants from energy consumption for building operations The performance levels of these criteria of a case study building are in line with the performance levels of energy consumption of the same building (see section 8.4.1) This illustrates the important role of energy consumption performance being acknowledged and highlighted in GBC

With reference to the environmental performances that constitute the energy consumption, GBTool User Manual (Cole & Larsson, 2002) identifies that thermal comfort and daylighting performances are the underlying factors influencing energy consumption performance In hot and humid tropical climatic context, natural ventilation is an additional constituent factor (Fry

& Drew, 1956; Wong et al, 2002) Design strategies to achieve high performances for these three environmental performances – thermal comfort, natural ventilation, and daylighting – are often referred to as energy efficiency design (Zeither, 1996) The underlying assumption

is that when the interior environment of a building is thermally comfortable, well ventilated, and daylighting sufficient, then there is not need to consume electricity for supplementing those performances to the comfort levels of the users The comprehensiveness of this assumption will be empirical investigated in the next section

10.3 Energy-efficiency design, energy consumption, and resident affluence

From environmental performance practice, energy efficiency design to achieve thermal comfort, good natural ventilation, and daylighting provision are the main factors determining energy consumption performance of a building However, from socio-economic perspective,

it is resident behaviours, especially resident affluence, that leads to that 'we are buying more and more appliances for our homes, whilst industry is becoming ever more capital (and machine) intensive This leads to a greater and greater energy demand' (Smith, Whitelegg & Williams, 1998)

In local context, increasing energy consumption in public housing is often thought of as the increase in air-conditioner installation and usage (Rajagopalan, 2001; Soemara, 2002) to condition the indoor environment From environmental performance practice, this phenomenon implies that the designs of public housing in later decades are less energy efficient However, from the socio-economic perspective, the trend of resident affluence over the last few decades can also be the main cause for increasing domestic energy consumption The discussion in this section looks into the triple relationship between energy-efficiency design, energy consumption and resident affluence, through correlating analysis of domestic energy consumption, thermal comfort, natural ventilation, daylight factor, household income, and air-condition usage

10.3.1 Energy-efficiency design, energy consumption, and household income

As a background, it is perceived that two main factors have contributed to the success of Singapore public housing (Wong & Yeh 1985) Firstly, the slum living condition and the severe housing shortage in the 1960s led to the initiation of mass public housing development

economic conditions The coverage of public housing has changed from merely targeting very-low-income households in the 1960s and 1970s to including middle-income households since the 1980s This constitutes to the ascending trend of affluence of households in public housing since the 1960s (Figure 10-1) As society becomes more affluent, resident aspirations change and consumptions increase This happens in two aspects, owning of household appliances and energy consumption

In the correlation of household affluence trend to that of energy consumption (Figure 10-1), there appears to be a concurrence between the two As an indicative analysis without taking inflation into consideration, the trend of household affluence started with very low average monthly household income in the 1960s This is followed by a slight increased till middle of the 1970s, when the increase momentum started to pick up and gradually developed till middle of the 1980s This was also the milestone of the change in public housing policies to include middle-income households into its coverage The average monthly household income since then upturned and has been rapidly and continuously increasing till 1998 Correspondingly, the trend of domestic energy consumption started with very low consumption in the early 1960s.This was also followed by a slight increased till the mid of 1970s, speeded up its ascending trend till the end of 1980s when the trend surged, and has been rapidly and continuously increasing till 2002 In brief, there is a close correlation between two trends, not only about their general ascendance but also about the levels of increase at certain periods