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Building and Environment ] (]]]]) ]]]–]]]
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Application of the analytic hierarchy process (AHP) in multi-criteriaanalysis of the selection of intelligent building systems
Johnny K.W. Wong�, Heng Li
Department of Building and Real Estate, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong
Received 23 February 2006; received in revised form 14 June 2006; accepted 5 November 2006
Abstract
The availability of innumerable intelligent building (IB) products, and the current dearth of inclusive building component selection
methods suggest that decision makers might be confronted with the quandary of forming a particular combination of components to suit
the needs of a specific IB project. Despite this problem, few empirical studies have so far been undertaken to analyse the selection of the
IB systems, and to identify key selection criteria for major IB systems. This study is designed to fill these research gaps. Two surveys: a
general survey and the analytic hierarchy process (AHP) survey are proposed to achieve these objectives. The first general survey aims to
collect general views from IB experts and practitioners to identify the perceived critical selection criteria, while the AHP survey was
conducted to prioritize and assign the important weightings for the perceived criteria in the general survey. Results generally suggest that
each IB system was determined by a disparate set of selection criteria with different weightings. ‘Work efficiency’ is perceived to be most
important core selection criterion for various IB systems, while ‘user comfort’, ‘safety’ and ‘cost effectiveness’ are also considered to be
significant. Two sub-criteria, ‘reliability’ and ‘operating and maintenance costs’, are regarded as prime factors to be considered in
selecting IB systems. The current study contributes to the industry and IB research in at least two aspects. First, it widens the
understanding of the selection criteria, as well as their degree of importance, of the IB systems. It also adopts a multi-criteria AHP
approach which is a new method to analyse and select the building systems in IB. Further research would investigate the inter-
relationship amongst the selection criteria.
r 2007 Elsevier Ltd. All rights reserved.
Keywords: Intelligent building; Building systems; Selection criteria; AHP
1. Introduction
For many years, buildings that offer comfortable,flexible and energy efficient living environment at aminimal cost has been the expectation of building ownersand occupiers. To attain this aspiration, a variety ofadvanced building technologies have been developed in thepast two decades, aiming to improve the buildingperformance to satisfy a variety of human needs andenvironmental sustainability. While a plethora of advancedbuilding products have been accessible, it has becomeincreasingly evident that developers are confronted withthe quandary of choosing the apposite components orproducts to suit the needs and to accomplish the unique
e front matter r 2007 Elsevier Ltd. All rights reserved.
ildenv.2006.11.019
ing author. Tel.: +852 2766 5882; fax: +852 2764 3374.
ess: [email protected] (J.K.W. Wong).
s article as: Wong JK, Li H Application of the analytic hierarc
ms. Building and Environment (2007), doi:10.1016/j.buildenv.2
configuration of a particular intelligent building (IB)project. The problems inherent in justifying the optionsof IB systems and components can be attributed to twofactors.First, there is a dearth of systematic and rigorous
methods in existence for selecting new building technolo-gies. Many of the current approaches were criticized foroveremphasizing the quantitative and financial aspects [1].Models focused only on the cost performance (i.e. purchaseor maintenance costs), which was easily quantifiable, butoverlooked other benefits such as improved humancomfort, environmental sustainability, and building flex-ibility. Consequently, option of building systems with thepre-eminent cost saving are generally chosen by using thisevaluation approach. This probably led to selectionmyopia and a biased decision. As such, a model ormethodology which can incorporate qualitative factors
hy process (AHP) in multi-criteria analysis of the selection of intelligent
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(i.e. human judgments) in quantitative approach is helpfulin selecting the IB systems.
Second, many performance criteria that were not easilyexpressed or quantified failed to be captured in manyevaluation approaches. The negligible considerations of theperformance factors have serious long-term consequences.In an IB, each building system is designed to enable allindividual systems to interrelate with one another in anatured way, allowing for interaction between systems andthe control of that system, so that the systems wouldcollaborate to respond flexibly to changing conditions anduser requirement throughout the whole life of the building[2]. An IB that fails to recognize the significance ofperformance and systems interface may lead to systemincompatibility, malfunctioning, and risk of obsolescence.If the building systems malfunction, it affects the businessoperations of occupants. The maintenance cost and thecost associated with a potential plunge in revenue arisingfrom loss of tenants have an adverse effect on the financialviability of the building [2]. The failure to match occupants’and clients’ expectations may eventually lead to disen-chantment and a serious decline in interest and confidencein IB. Based on these problems, the analysis of IB optionsduring the design stage is considered important.
In pursuit of excellent performance of IB, the last decadehas seen an explosion of interest in the assessment andevaluation in IB literature and research. A rich body ofknowledge has been developed [3–8]. Studies haveattempted to identify the performance criteria and toestablish the appraisal methods for IB. These performancecriteria provide a guideline and enabled feed-forward intoimproved planning, design and construction of futurebuildings [9]. Although these studies provide effectivefoundation for the evaluation of IBs, many current IBappraisal methods lack the power of comparabilityregarding the features of IBs [10]. The existing literaturein justification and selection of IB systems consists ofarticles or case studies only either in the internal report orin practitioner-focused journals [5,11]. There is a lack of apractical guide helping to compare two options of buildingsystem for one IB project, and researchers [1,12,13] alsorepeatedly emphasize the need for a model which assists theevaluation of IB options during design stage. Based on thecurrent research deficiencies, this paper proposes a multi-criteria decision-making model using the analytic hierarchyprocess (AHP) approach to evaluate the selection of IBsystems. This paper aims to identify the crucial selectioncriteria for IB systems; to test the criticality and compar-ability of the selection criteria; and to develop a model tohighlight the selection of the appropriate IB components orsystems.
2. Review of research in IB appraisal and evaluation
As an exploratory study, a particular set of selectionattributes must be derived in this study prior to the testing.The search for criteria was conducted first by reviewing the
Please cite this article as: Wong JK, Li H Application of the analytic hierarc
building systems. Building and Environment (2007), doi:10.1016/j.buildenv.2
literature. Despite the dearth of studies on evaluating theselection criteria of IB components, there has been asubstantial amount of research into the method ofappraising the performance of IBs. Since the 1980s,scholars [3,14,15] and professional bodies [16–20] haveconducted a considerable amount of research effort inunderstanding and measuring the performance of IBs. Forexample, Arkin and Paciuk [3] devised a unified index,‘intelligent building score (IBS)’, to assess the systemintegration in IBs and enable a building performance to bequantified in terms of the building systems installed and thelevel of integrated that exists between them. Smith [14]developed the ‘reframing’ and ‘quality facilities strategicdesign (QFSD)’, the former method aims to evaluate the IBenabling ability of the building to meet organizationalobjectives through the examination of four different frames(i.e., organizational structure, politics, human resourcesand culture), while the latter analyses the design character-istics and aims at establishing an order of priorities for thestakeholder requirements. Smith [15] further developed a‘building intelligent assessment index (BIAI)’ which aims toassess building intelligent level through seven buildingcharacteristics (i.e., site specification, operational cost,intelligent architecture, identity, intelligent technology,system responsiveness, and access and security). However,most of the assessment approaches were criticized for theirrestricted scope on either tangible (i.e., IBS and IBIA) orintangible (i.e., reframing and QFSD) aspects of buildings,and failed to provide a complete performance assessmentof IBs [15].In addition to the research conducted by scholars, there
have been various rating methods initiated by IB institutesfrom North America, Europe, and Asia in recent years[16–20]. These rating methods rely on a series of factors orindicators related to the performance issues together withtheir defined scales to rate an IB [10]. For example, theAsian Institute of Intelligent Buildings (AIIB) developedan ‘intelligent building index (IBI)’[19,20] to assess theperformance and categorize the IB. The BRE [16] devised amatrix tool for assessing the performance of IBs. Cur-rently, the CABA [21] is developing a new assessment toolnamed ‘intelligent building ranking tool (IBRT)’ whichaims to assess the level of integrated systems within an IB.Chen et al. [10] reviewed various latest IB assessmentsystems and found that the IBI method [19,20] has thebroader coverage of assessment clusters of indictorscompared with other IB assessment methods. Other ratingmethods, for example, the IB rating by SCC, onlyconcentrates on the Engineering cluster, while bothMATOOL and ASCIB assessment approaches cover fewerclusters (i.e., management, engineering and environment)than IBI. Although the identified factors established byAIIB [19,20] were designated for post-occupancy evalua-tion of IB, it was argued that these factors could beexploited as feedforward into improved planning anddesign of future building [22]. Table 1 summarizes theproposed selection criteria with respect to each of the IB
hy process (AHP) in multi-criteria analysis of the selection of intelligent
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Table 1
Summary of proposed selection criteria suggested by literature
Proposed selection
criteria
Intelligent building systems
Integrated
building
management
system
Telecom
and data
system
Addressable
fire detection
and alarm
system
Security
monitoring
and access
control system
HVAC
system
Vertical
transportation
system
Digital
addressable
lighting
control system
Energy
mgt.
system
Hydraulic and
drainage
system
Internal
layout
system
Building
fac-ade
system
Work efficiency
Further upgrade � � � � � � � � � � �Grade of system �Reliability (i.e.
frequency of
breakdown)
� � � � �
Capability for
integrating systems
�
Protocol standard
compliance
�
Efficiency (i.e. rate
of transmission)
� � � �
Service life � � � � � � � � � � �Electromagnetic
compatibility
�
Intranet
management system
�
Provision of
broadband Internet
�
Provision of fibre
digital data interface
(FDDI)
�
Superhighway
satellite conferencing
�
Leakage detection �Access for erection
and maintenance
�
Compatibility (i.e.
with other building
systems)
� � � � � � � � �
Connection to BAS � � � � � � � � �Fire detection and
fighting code
compliance
�
Fire resistance code
compliance
�
Automatic and
remote control/
monitoring
� � � � � � �
Time for public
announcement
�
Time for informing
building management
�
Time for total
egress
�
Waiting time �Journey time �Maximum interval
time
�
Permanent artificial
lighting average
power density
�
Preventive
maintenance scheme
� � � � � �
Area under power
supply
�
Uniformity of lux
level
�
Area under
supervision and
monitoring
�
Earthquake
monitoring
�
Wind load
monitoring
�
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]] 3
Please cite this article as: Wong JK, Li H Application of the analytic hierarchy process (AHP) in multi-criteria analysis of the selection of intelligent
building systems. Building and Environment (2007), doi:10.1016/j.buildenv.2006.11.019
ARTICLE IN PRESS
Table 1 (continued )
Proposed selection
criteria
Intelligent building systems
Integrated
building
management
system
Telecom
and data
system
Addressable
fire detection
and alarm
system
Security
monitoring
and access
control system
HVAC
system
Vertical
transportation
system
Digital
addressable
lighting
control system
Energy
mgt.
system
Hydraulic and
drainage
system
Internal
layout
system
Building
fac-ade
system
Structural
monitoring
�
Handling capacity �
Technological Issues
Use of high-tech
design
� � � � � � � � �
Use of advanced
artificial intelligence
(AI)
� � � � � � � � �
Cost effectiveness
Initial costs � � � � � � � � � � �Operating and
maintenance costs
� � � � � � � � � � �
Proposed selection
criteria
Intelligent building systems
Building
automation
and energy
mgt. system
Information
and
communication
network system
Fire
protection
system
Safety and
security
system
HVAC
system
Vertical
transportation
system
Lighting
system
Electrical
installation
system
Hydraulic
and
drainage
system
Internal
layout
system
Building
fac-ade
system
Environmental Issues
Average efficacy �Total energy
consumption
� �
Energy conservation
and regeneration
� �
Noise pollution � � � �Method of cooling �Pollution related to fuel
consumption
�
Sunlight pollution (by
curtain wall)
�
Total harmonics
distortion (THD)
�
Allow for natural
ventilation
�
Electrical power quality �Permanent artificial
lighting average glare
index
�
Permanent artificial
lighting average lux level
�
Pollution-free product � �
Safety Issues
Safety regulations
compliance
� �
User comfort
Predict mean vote
(PMV)
�
Indoor air quality
(IAQ)
�
Spatial flexibility �Acoustic comfort � � �Overall thermal
transfer value (OTTO)
�
Special ventilation in
particular area
�
Appearance �Odour level �Daylight factors �Ventilation for
excessive heat
�
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]]4
Please cite this article as: Wong JK, Li H Application of the analytic hierarchy process (AHP) in multi-criteria analysis of the selection of intelligent
building systems. Building and Environment (2007), doi:10.1016/j.buildenv.2006.11.019
ARTICLE IN PRESS
Table 1 (continued )
Proposed selection
criteria
Intelligent building systems
Building
automation
and energy
mgt. system
Information
and
communication
network system
Fire
protection
system
Safety and
security
system
HVAC
system
Vertical
transportation
system
Lighting
system
Electrical
installation
system
Hydraulic
and
drainage
system
Internal
layout
system
Building
fac-ade
system
Cleanliness � � �Average colour
temperature
�
Colour rendering �Glare � �Amount of fresh air
(i.e. change of air)
� �
Ease of control �Response to change in
temperature
�
Response to change in
sunlight
�
Vibration level �Acceleration and
deceleration
�
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]] 5
systems. These proposed criteria were identified based onthe work of AIIB [19,20] as well as other empirical studiesand literature [2,15,23–25], as shown in Table 2.
3. Research methodology
This study consisted of two surveys: a general survey andthe AHP survey. The general survey is first undertaken inorder to identify the perceived critical selection criteria andto select those professionals with relevant qualification andexperience to enter into the AHP survey. A pilot study wasfirst conducted prior to the general survey to test thesuitability of proposed criteria summarized from theliterature, and to examine the comprehensibility of thequestionnaire prior to sending it out. In order to sharpenand refine the results of the general survey, the AHP surveywas conducted to prioritize and assign the importantweightings for the perceived criteria. The research metho-dology and layout of this study are depicted in Fig. 1.
4. General survey: Identification of critical selection criteria
4.1. Data collection
A pilot study was initially conducted with a number ofIB experts including E&M design consultants, architects,and property developers with extensive knowledge andexperience of IB projects. The experts were presented withthe proposed selection criteria of IB systems. They wereinvited to review the relevance, coherence and the clarity ofthe questionnaire. At the end of the pilot study, a numberof amendments were made. Due to the assortment of IBsystems, this study is limited to 11 key IB systems asrecommended by the experts. These building systemsinclude: (1) integrated building management system(IBMS) for overall monitoring and building management
Please cite this article as: Wong JK, Li H Application of the analytic hierarc
building systems. Building and Environment (2007), doi:10.1016/j.buildenv.2
function; (2) energy management system for electrical andpower quality monitoring and analysis; (3) HVAC systemfor heating, ventilation and air-conditioning system forcomfort control and IAQ; (4) addressable fire detectionand alarm system for fire prevention and annunciation; (5)telecom and data system for communication networkbackbone; (6) security monitoring and access system forsurveillance and access control; (7) smart/energy efficientvertical transportation system for multi-floors service; (8)digital addressable lighting control system for light designand control; (9) hydraulic and drainage system; (10)building fac-ade systems; and (11) building layout systems.A total of 136 local construction experts (i.e., academics,
developers, design consultants, quantity surveyors, andconstruction practitioners) were invited to complete thequestionnaire. With their varied background and knowl-edge in the field, their views provided an accurate reflectionof the selection attributes and their relative importance.Finally, a total of 71 valid usable replies were received. Inorder to elicit the crucial criteria, the respondent percep-tions were measured on the interval basis using a five-pointLikert scale (where 1 represented ‘not important at all’, and5 represented ‘extremely important’). Only those criteriawith mean ratings above or equal to ‘4’ (‘important’) wereincluded for consideration. In the questionnaire, they werealso invited to add new attributes or criteria if necessary.Furthermore, in order to check the mean for each proposedcriterion that whether the population would consider thecriterion to be significant or otherwise, a t-test analysis wasemployed to examine the proposed criterion. If the t-valueof the statistical test of the mean ratings was larger thancritical t-value (t (70, 0.05) ¼ 1.6669 at 95% confidenceinterval), it suggested that the proposed criterion wassignificant. In addition, the non-parametric Kruskal–Wal-lis one-way ANOVA test was undertaken in orderto ascertain whether there were statistically significant
hy process (AHP) in multi-criteria analysis of the selection of intelligent
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Table 2
References of proposed selection criteria for IB systems
Selection attributes References
Integrated building management system (IBMS)
Work efficiency
Further upgrade, reliability [23,26,27]
Grade of BAS [19]
Capability of integrating systems [8,19,23,28]
Protocol standard compliance, preventive
maintenance scheme
[23,27]
Efficiency [8,23]
Service life [23,27,29]
Automatic and remote control/monitoring [8,23,26,28,30]
Cost effectiveness
Initial costs, operating and maintenance costs [2,19,27,31]
Telecom and data system
Work efficiency
Further upgrade [15,26]
Efficiency (i.e. rate of transmission) [19,26]
Service life [29]
Intranet management system, provision of
broadband Internet
[15,19,26]
Reliability (i.e. frequency of breakdown), provision
of fibre digital data interface (FDDI), superhighway
satellite conferencing
[19]
Electromagnetic compatibility [19,23]
Technological issues
Use of high-tech system [15,19]
Use of advanced artificial intelligence (AI) [19]
Cost effectiveness
Initial costs, operating and maintenance costs [2,31,19]
Addressable fire detection and alarm system
Work efficiency
Further upgrade [26]
Service life [29]
Compatibility (i.e. with other building systems) [31]
Connection to BAS [19,31]
Preventive maintenance scheme, efficiency (i.e. rate
of transmission)
[19]
Fire detection and fighting code compliance, fire
resistance code compliance
[19,24,32]
Automatic and remote control/monitoring [15,33,34]
Technological issues
Use of high-tech system, use of advanced artificial
intelligence (AI)
[19]
Cost effectiveness
Initial costs, operating and maintenance costs [2,19,31]
HVAC system
Work efficiency
Further upgrade [25,26]
Reliability (i.e. frequency of breakdown) [26]
Service life [29]
Leakage detection, access for erection and
maintenance
[19]
Compatibility (i.e. with other building systems) [31]
Connection to BAS [19,23,31,33]
Technological issues
Use of high-tech design, use of advanced artificial
intelligence (AI)
[19,35]
Table 2 (continued )
Selection attributes References
Cost effectiveness
Initial costs, operating and maintenance costs [2,19,31]
Environmental issues
Total energy consumption [19,31,36]
Energy conservation and regeneration [4,19]
Pollution related to fuel consumption, noise
pollution, method of cooling
[19]
User comfort
Predict mean vote (PMV), Indoor air quality (IAQ) [19,37]]
Acoustic comfort [19,26]
Overall thermal transfer value (OTTO), special
ventilation in particular area, appearance, cleanliness
[19]
Odour level [19,38]
Amount of fresh air [19,26,38]
Security monitoring and access control system
Work efficiency
Further upgrade [26,31]
Service life [29]
Compatibility (i.e. with other building systems) [31,39]
Connection to BAS [19,23,40]
Automatic and remote control/monitoring, time for
public announcement, time for informing building
management, time for total egress, preventive
maintenance scheme, earthquake monitoring,
structural monitoring, wind load monitoring
[19]
Area under supervision and monitoring [19,26]
Technological Issues
Use of high-tech design, use of advanced artificial
intelligence (AI)
[19]
Cost effectiveness
Initial costs, operating and maintenance costs [2,19]
Vertical transportation system
Work efficiency
Reliability (i.e. frequency of breakdown) [19,26]
Service life [29,23]
Compatibility (i.e. with other building systems) [23,31]
Further upgrade, connection to BAS [19,31]
Efficiency, automatic and remote control/
monitoring, maintenance
[19]
Waiting time, journey time, maximum interval time [19,23]
Handling capacity [19]
Technological issues
Use of high-tech design [19]
Use of advanced artificial intelligence (AI) [19,23]
Cost effectiveness
Initial costs, operating and maintenance costs [2,19,23,31]
Environmental issues
Total energy consumption, energy conservation
and regeneration
[19,23]
Noise pollution, total harmonics distortion (THD) [19]
Safety issues
Safety regulation compliance [19,23]
User comfort
Acoustic comfort, amount of fresh air (i.e. change
of air)
[19,23,26]
Average illumination [19]
Vibration level , acceleration and deceleration [19,23]
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]]6
Please cite this article as: Wong JK, Li H Application of the analytic hierarchy process (AHP) in multi-criteria analysis of the selection of intelligent
building systems. Building and Environment (2007), doi:10.1016/j.buildenv.2006.11.019
ARTICLE IN PRESS
Table 2 (continued )
Selection attributes References
Digital addressable lighting control system
Environmental issues
Permanent artificial lighting average glare index [19]
Permanent artificial lighting average lux level [15,19]
Average efficacy of all lamps [19,38]
User comfort
Daylight factors [15,19,25,38],
Ventilation for excessive heat, cleanliness [19]
Average colour temperature, colour rendering,
glare
[19,38]
Acoustic comfort [19,26]
Ease of control [15,19,25,26]
Work efficiency
Further upgrade [25,26]
Service life [29]
Compatibility (i.e. with other building systems),
automatic and remote control/monitoring
[25]
Connection to BAS [19,23,25]
Permanent artificial lighting average power density,
preventive maintenance scheme, uniformity of lux
level
[19]
Technological issues
Use of high-tech design, use of advanced artificial
intelligence (AI)
[19]
Cost effectiveness
Initial costs, operating and maintenance costs [2,19,31]
Energy management system
Work efficiency
Further upgrade, reliability (Frequency of
breakdown)
[26]
Service life [29]
Connection to BAS, compatibility (i.e. with other
building systems)
[19,23,25]
Preventive maintenance scheme [31]
Area under power supply [19]
Technological related
Use of advanced artificial intelligence (AI) [19]
Cost effectiveness
Initial costs, operating and maintenance costs [2,19,31]
Safety issues
Safety regulation compliance [19]
Environmental issues
Electrical power quality and demand provision [4,19]
Hydraulic and drainage system
User comfort
Cleanliness [19,20]
Work efficiency
Further upgrade [26]
Service life [19,29]
Compatibility, connection to BAS, automatic
control/monitoring
[19]
Technological issues
Use of high-tech design, use of advanced artificial
intelligence (AI)
[19]
Cost effectiveness
Initial costs, operating and maintenance costs [2,19,31]
Table 2 (continued )
Selection attributes References
Building facade system
Environmental issues
Noise pollution, sunlight pollution (by curtain
wall), pollution free product
[19]
Allow for natural ventilation [4,19]
User comfort
Response to change in temperature, response to
change in sunlight
[2,41]
Work efficiency
Further upgrade [26]
Service life [29]
Compatibility, connection to BAS [19,41]
Automatic and remote control/monitoring [41]
Technological issues
Use of high-tech design, use of advanced artificial
intelligence (AI)
[41]
Cost effectiveness
Initial costs, operating and maintenance costs [2,19,31]
Building interior layout system
Environmental Issues
Pollution-free product, [19]
noise pollution (reverberation time/indoor ambient
noise level)
[19,38]
User comfort
Spatial flexibility [26]
Work efficiency
Further upgrade [26]
Service life [29]
Compatibility, connection to BAS [19]
Technological issues
Use of high-tech design [19]
Cost effectiveness
Initial costs, operating and maintenance costs [2,19,31]
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]] 7
Please cite this article as: Wong JK, Li H Application of the analytic hierarc
building systems. Building and Environment (2007), doi:10.1016/j.buildenv.2
differences or divergences between each group of profes-sionals regarding the relative importance of the criteria.The matched parametric testing method was not employedin this study since the parametric assumptions were notfulfilled and the variables were measured by ordinal scaleof measurement [22,32]. The results of the Kruskal–Wallis test were interpreted by the w2 and degree offreedom (df), and if the p-value was less than 0.05 whichmeant there was a significant difference between thegroups. The analysis indicated that there was no significantbias found among various groups of respondents. Themean scores of the selection criteria were computed andranked in Table 3.
4.2. Findings and discussion
As can be seen in Table 3, ranks of selectioncriteria revealed that each building system containeddifferent sets of criteria with varied degrees ofinfluence. A summary of the survey findings are presented
hy process (AHP) in multi-criteria analysis of the selection of intelligent
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SURVEY ONE
General
Study
To develop a set ofintelligent buildingsystems, proposed
selection criteria, andsub-criteria from the
literature
To design the firstquestionnaire
Identification of agroup of important
selection criteria andsub-criteria
To determine theimportance
weightings for thebuilding systems,
selection criteria andsub-criteria
A refinedconceptual
model
Establishmentof
conceptualmodel
To confirm the firstquestionnaire
To refine theconceptual model
using the AHPmethod
To review relevanceand coherence of
proposed criteria, andto check clarity of
questionnaire
SURVEY TWO
AHP
Survey
Fig. 1. Proposed research methodologies and layout.
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]]8
as follows. The detailed findings of this survey are reportedin Wong and Li [12].
�
P
b
‘Work efficiency’ was perceived as the most importantcore criterion for the selection of IB systems.
� ‘Service life’ and ‘operating and maintenance costs’ wereregarded as the two most crucial sub-criteria in variousIB systems. The high rank of ‘operating and main-tenance costs’ supports that the view of Sobchak [42]that long-term expenses are the major concern of manyowners and decision makers.
� Four building systems (including HVAC system; secur-ity monitoring and access control system; verticaltransportation system; and digital addressable lightingcontrol system) comprised a number of crucial sub-criteria, which indicated that these IB systems could notbe merely justified by a few sub-criteria due to theircomplexity.
� The high rank of ‘user comfort’ sub-criteria (i.e., predictmean vote, indoor air quality, acoustic comfort, andamount of fresh air) in HVAC system implied a strongneed for the provision of a comfortable and productiveworking environment to satisfy the physiological needsof the occupants in IB [37].
� Surprisingly, technological advancement was not con-sidered as a key criterion in the system selection. Thisfinding reinforced the argument of Clements-Croome [2]and DEGW [5] that a true IB is not a building withpurely advanced technologies; instead it should be theone that can ensure efficiency, enhance user comfort andcost effectiveness. This may explain why technologicalissues have a low score.
� Unexpectedly, a number of selection sub-criteria thatquoted as important in the literature were not rated
lease cite this article as: Wong JK, Li H Application of the analytic hierarc
uilding systems. Building and Environment (2007), doi:10.1016/j.buildenv.2
highly in this survey. For example: ‘compliance ofprotocol standard’ for BAS systems [19,30,43,44];‘OTTV and odour level requirement’ for HVAC system[19,39]; ‘noise pollution’ for vertical transportationsystem [19], and building fac-ade systems [41]; and‘spatial flexibility’ for interior layout system [19,39].These sub-criteria were statistically considered as lessimportant, and therefore their importance were de-clined.
5. The AHP survey: Prioritizing and assigning important
weightings for the criteria
5.1. The AHP method
In order to prioritize the selection criteria, and todistinguish in general the more important criteria fromthe less important ones, further investigation was con-ducted by employing the AHP approach. The AHPmethod helped to specify numerical weights representingthe relative importance of each individual building systemas well as their associated selection criteria with respect tothe goal (‘to select the most appropriate IB systems’). AHPallows both qualitative and quantitative approaches tosolve complex decision problems [45]. In the qualitativeaspect, AHP structures the problems through decomposingthem into a hierarchy of elements influencing a system byincorporating levels: objectives, criteria, sub-criteria [46]. Inquantitative aspects, AHP can prioritize (or ‘pair-wise’compare) a set of attributes and distinguish in general themore important factors from the less important factors[45–49]. The pair-wise comparison judgments were madewith respect to the attributes of one level of hierarchy giventhe attribute of the next higher level of hierarchy (from the
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Table 3
Ranks of perceived selection criteria for IB systems
Selection criteria Mean t-valuea
Sub-criteria Main criteria group
(a) Integrated building management system (IBMS)
Reliability Work efficiency 4.32 3.384
Operating and maintenance costs Cost effectiveness 4.30 3.535
Capability for integrating systems Work efficiency 4.23 2.633
Efficiency Work efficiency 4.20 2.488
(b) Telecom and data system (TCP/IP)
Reliability Work efficiency 4.35 4.016
Further upgrade Work efficiency 4.28 3.206
Operating and maintenance costs Cost effectiveness 4.24 2.778
Service life Work efficiency 4.23 2.791
Efficiency Work efficiency 4.20 2.411
(c) Addressable fire detection and alarm system
Fire detection and fighting code compliance Work efficiency 4.25 2.846
Fire resistance code compliance Work efficiency 4.24 2.576
Operating and maintenance costs Cost effectiveness 4.24 2.576
Efficiency Work efficiency 4.23 2.709
Further upgrade Work efficiency 4.23 2.440
Automatic and remote control/monitoring Work efficiency 4.21 2.561
Service life Work efficiency 4.17 1.797
(d) HVAC system
Service life Work efficiency 4.24 2.856
Predict mean vote (PMV) User comfort 4.24 2.856
Operating and maintenance costs Cost effectiveness 4.23 2.440
Indoor air quality User comfort 4.21 2.422
Total energy consumption Environmental 4.21 2.303
Connection to BAS Work efficiency 4.21 2.250
Reliability Work efficiency 4.21 2.154
Acoustic comfort User comfort 4.20 2.219
Compatibility Work efficiency 4.20 2.114
Initial costs Cost effectiveness 4.18 2.260
Amount of fresh air changes User comfort 4.17 1.885
(e) Security monitoring and access control system
Time for public announcement Work efficiency 4.42 5.919
Operating and maintenance costs Cost effectiveness 4.41 4.857
Time for informing building management Work efficiency 4.27 2.986
Compatibility Work efficiency 4.25 2.846
Connection to BAS Work efficiency 4.24 2.638
Service life Work efficiency 4.20 2.165
Further upgrade Work efficiency 4.20 2.165
Initial costs Cost effectiveness 4.18 2.077
Time for total egress Work efficiency 4.18 1.932
(f) Vertical transportation system
Safety regulations compliance Safety 4.42 4.750
Service life Work efficiency 4.34 3.872
Waiting time Work efficiency 4.34 3.872
Maximum interval time Work efficiency 4.30 3.188
Total energy consumption Environmental 4.28 3.293
Acceleration and deceleration User comfort 4.27 3.064
Journey time Work efficiency 4.25 2.846
Connection to BAS Work efficiency 4.24 2.576
Compatibility Work efficiency 4.24 2.518
Operating and maintenance costs Cost effectiveness 4.24 2.518
Acoustic comfort User comfort 4.23 2.791
Air change User comfort 4.23 2.440
Vibration level User comfort 4.23 2.440
Automatic and remote control/monitoring Work efficiency 4.17 1.839
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]] 9
Please cite this article as: Wong JK, Li H Application of the analytic hierarchy process (AHP) in multi-criteria analysis of the selection of intelligent
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ARTICLE IN PRESS
Table 3 (continued )
Selection criteria Mean t-valuea
Sub-criteria Main criteria group
(g) Energy management system
Operating and maintenance costs Cost effectiveness 4.25 3.002
Connection to BAS Work efficiency 4.24 2.778
Safety regulation compliance Work efficiency 4.24 2.638
Compatibility Work efficiency 4.20 2.571
(h) Digital addressable lighting control system
Operating and maintenance costs Cost effectiveness 4.32 3.943
Compatibility Work efficiency 4.25 2.712
Connection to BAS Work efficiency 4.24 2.638
Permanent artificial lighting average power density Work efficiency 4.20 2.342
Further upgrade Work efficiency 4.18 2.077
Service life Work efficiency 4.18 2.025
Ease of control User comfort 4.17 2.044
Average efficacy of all lamps User comfort 4.17 1.987
Automatic control/adjustment of lux level Environmental 4.17 1.839
(i) Hydraulics and drainage system
Service life Work efficiency 4.28 3.491
Operating and maintenance costs Cost effectiveness 4.28 3.126
(j) Internal layout system
Operating and maintenance costs Cost effectiveness 4.31 3.683
Service life Work efficiency 4.18 2.194
Initial costs Cost effectiveness 4.14 1.688
(k) Building fac-ade system
Operating and maintenance costs Cost effectiveness 4.52 8.273
Connection to BAS Work efficiency 4.42 4.876
Response to change in temperature User comfort 4.39 4.702
Service life Work efficiency 4.38 4.308
Response to change in sunlight User comfort 4.37 4.058
Compatibility Work efficiency 4.35 3.652
Automatic and remote control/monitoring Work efficiency 4.30 3.048
aRepresents the t-value that is larger than critical t-value (1.6669).
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]]10
main criteria to the sub-criteria). AHP is also able to solicitconsistent subjective expert judgment via the consistencytest. The topic of AHP has attracted wide attention in theconstruction field. Earlier studies applied AHP in evaluat-ing the new construction technologies [50], other applica-tions reported include studies by Cheung et al. [47], Chengand Li [45], Cheung and Suen [51], Al-Harbi [52], and Fongand Choi [53]. Due to the complicated nature of IB systemselection, the AHP approach is applied in this paper toprioritize the crucial selection criteria of the IB systems.The five-stage AHP set out by Saaty [49] is summarized asfollows:
�
P
b
define the problem, and determine the objective;
� development of the hierarchy from the top (the objectivefrom a general viewpoint) through the intermediatelevels (attributes and sub-attributes on which subse-quent levels depends) to the lowest level (the list ofalternatives);
� employ a simple pair-wise comparison matrices for eachof the lower levels;
lease cite this article as: Wong JK, Li H Application of the analytic hierarc
uilding systems. Building and Environment (2007), doi:10.1016/j.buildenv.2
�
hy
006
undertake a consistency test; and
� estimate relative weights of the components of eachlevel.
For designing the paired comparison matrices, thedecision hierarchies were formed (Fig. 2). The hierarchiesreaffirmed the results of the general survey and depicted theattributes for selecting IB systems. The top level was theselection goal, and following this was the building systemsof IB. The third and fourth level comprised the selectioncriteria and sub-criteria expanding from the buildingsystems. The relative importance of the criteria and sub-criteria was rated by the nine-point scale proposed by Saaty[49], as shown in Table 4, which indicated that the level ofrelative importance from equal, moderate, strong, verystrong, to extreme level by 1, 3, 5, 7, and 9, respectively.The intermediate values between two adjacent argumentsare represented by 2, 4, 6, and 8.The consistency test is one of the essential features of the
AHP method which aims to eliminate the possibleinconsistency revealed in the criteria weights through the
process (AHP) in multi-criteria analysis of the selection of intelligent
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Fig.2.ThedecisionhierarchyforselectingIB
system
s.
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]] 11
Please cite this article as: Wong JK, Li H Application of the analytic hierarchy process (AHP) in multi-criteria analysis of the selection of intelligent
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ARTICLE IN PRESS
Table 4
The AHP pairwise comparison scale (Source: Saaty [49, p. 54])
Intensity of weight Definition Explanation
1 Equal importance Two activities contribute equally to the objectives
3 Weak/moderate importance of one
over another
Experience and judgment slightly favoured one activity over another
5 Essential or strong importance Experience and judgment strongly favour one activity over another
7 Very strong or demonstrated
importance
An activity is favoured very strongly over another; its dominance
demonstrated in practice
9 Absolute importance The evidence favouring one activity over another is of the highest possible
order of affirmation
2, 4, 6, 8 Intermediate values between the two
adjacent scale values
Used to represent compromise between the priorities listed above
Reciprocals of above
non-zero numbers
If activity i has one of the above non-zero numbers assigned to it when
compared to activity j, then j has the reciprocal value when compared with I
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]]12
computation of consistency level of each matrix [45]. Theconsistency ratio (CR) was used to determine and justifythe inconsistency in the pair-wise comparison made by therespondents. Saaty [54], and Cheng and Li [45] have set theacceptable CR values for different matrix’s sizes: (1) theCR value is 0.05 for 3� 3 matrix; (2) 0.08 for a 4� 4matrix; and (3) 0.10 for larger matrices. If the CR value islower than the acceptable value, the weight results are validand consistent. In contrast, if the CR value is larger thanthe acceptable value, the matrix results are inconsistent andwere exempted for the further analysis.
5.2. Questionnaire design and data collection
The AHP survey aimed at evaluating the comparabilityof the perceived selection criteria. To help accomplish theseaims, a questionnaire was designed for data collection, andthe format was synthesized with reference to AHP matrixproposed by Saaty [49]. Since the assignment of the weightrequires logical and analytical thinking, only the relevantexperts or professionals providing penetrating insights werehighly valuable to an empirical inquiry. In order to selectthe suitable respondents, a question on the preceding(general) survey asked the respondents if they wereexperienced in IB design and development. A total of 16experienced respondents in the general survey replied andexpressed their interest in conducting the AHP question-naire. On the other hand, AHP is a subjective method thatis not necessary to involve a large sample, and it is usefulfor research focusing on a specific issue where a largesample is not mandatory [45,55]. Cheng and Li [45] pointedout that AHP method may be impractical for a survey witha large sample size as ‘cold-called’ respondents may have agreat tendency to provide arbitrary answers, resulting in avery high degree of inconsistency. AHP survey with a smallsample size has been conducted in previous research. Forexample, Cheng and Li [45] invited 9 construction expertsto undertake a survey to test comparability of criticalsuccess factors for construction partnering. Lam and Zhao[55] also invited 8 experts for a quality-of-teaching survey.
Please cite this article as: Wong JK, Li H Application of the analytic hierarc
building systems. Building and Environment (2007), doi:10.1016/j.buildenv.2
In our study, 10 returned questionnaires were received forthe AHP survey. By evaluating the consistency level of thecollected questionnaires, 9 questionnaires appeared to haveacceptable consistency (Table 5) and would enter intoanalysis. Demographic information revealed that allrespondents were highly experienced and in differentconstruction positions, such as E&M engineers and designconsultants, architects, property developers, and construc-tion managers. Eight of them have participated in not lessthan three IB projects, and all replied with more than 10years experience in construction field.
5.3. Findings and discussions
To analyse the survey findings, the judgment matriceswere pair-wise compared and computed via the use ofcommercial software packages (i.e., ExpertChoiceTM). Thelocal priority weights of all main criteria and sub-criteriawere first calculated, and then combined with all successivehierarchical levels in each matrix to obtain a global priorityvector. The higher the mean weight of global priorityvector, the greater the relative importance is. This helps todistinguish the more important elements from the lessimportant ones.The distributive summary in Table 6 suggests that each
group of building systems and criteria have differentprioritization according to the mean weight of therespondent in the final selection of the IB systems. Themean global priority weight differs for the building systems(from the lowest of 0.057 to the highest of 0.119); the maincriteria (from the lowest of 0.010 to the highest of 0.091);and the sub-criteria (from the lowest 0.002 to the highest of0.051). The findings suggested that the criteria are allcomparable, and none of them can be sacrificed. As can beseen in Table 6, some interesting findings on theimportance of IB systems were identified:
�
hy
006
Respondents reported that both IBMS (0.119) andaddressable fire detection and alarm system (0.119) wereprime building systems in their consideration during the
process (AHP) in multi-criteria analysis of the selection of intelligent
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Table 5
Consistency ratio (CR) values for the judgment matrices
Matrix set Respondent
1 2 3 4 5 6 7 8 9 10
A1 (11� 11) 0.030 0 0.063 0.068 0 0.020 0.011 0.010 0.082 0.060
B1 (2� 2) 0 0 0 0 0 0 0 0 0 0
B2 (3� 3) 0 0.010 0.010 0.028 0 0 0 0 0 0
C1 (2� 2) 0 0 0 0 0 0 0 0 0 0
C2 (4� 4) 0.247 0 0 0 0 0 0.023 0 0 0
D1 (2� 2) 0 0 0 0 0 0 0 0 0 0
D2 (6� 6) 0.316 0 0.031 0.024 0 0 0 0 0.022 0.020
E1 (4� 4) 0.128 0.023 0.019 0.058 0 0 0 0 0.070 0
E2 (4� 4) 0.099 0.000 0 0.010 0 0 0 0 0 0.020
E3 (4� 4) 0.099 0.017 0.012 0.023 0 0 0 0 0.023 0
E4 (2� 2) 0 0 0 0 0 0 0 0 0 0
F1 (2� 2) 0 0 0 0 0 0 0 0 0 0
F2 (7� 7) 0.057 0.021 0.068 0.053 0 0.020 0.010 0 0.066 0.020
F3 (2� 2) 0 0 0 0 0 0 0 0 0 0
G1 (5� 5) 0.044 0 0.074 0.012 0 0 0 0 0.016 0.040
G2 (7� 7) 0.168 0.084 0.054 0.020 0 0 0 0.084 0.034 0.010
G3 (4� 4) 0.058 0.070 0 0 0 0 0 0.023 0.023 0
H1 (3� 3) 0 0 0 0.028 0 0 0 0 0 0
H2 (2� 2) 0 0 0 0 0 0 0 0 0 0
I1 (4� 4) 0 0.070 0.058 0.017 0 0 0 0 0.023 0
I2 (6� 6) 0.091 0.034 0.049 0.039 0 0 0 0 0.080 0.060
J1 (2� 2) 0 0 0 0 0 0 0 0 0 0
K1(2� 2) 0 0 0 0 0 0 0 0 0 0
K2 (2� 2) 0 0 0 0 0 0 0 0 0 0
L1(3� 3) 0 0 0 0 0 0 0 0 0 0
L2 (4� 4) 0.044 0.074 0.058 0 0 0 0 0 0 0
L3 (2� 2) 0 0 0 0 0 0 0 0 0 0
Note: (1) The 10 respondents are assigned with no. 1–10; (2) Acceptable CR values (Saaty [49]): 0.05 or below for a 3� 3 matrix, 0.08 or below for a 4� 4
matrix; 0.1 or below for matrices larger than 5� 5; (3) Bolded when a value is larger than the acceptable CR value. Respondent No. 1 has six CR values
above the marginal, and therefore it is not considered in this analysis.
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]] 13
P
b
selection, followed by the telecom and data system(0.103), HVAC system (0.102), and digital addresslighting control system (0.102). The importance ofIBMS was consistent with So and Chan [35], Gann[56], and Carlson and Di Giandomenico [57], whosuggested that the IBMS acts as the ‘heart’ of IB whichprovides more effective and efficient control over allbuilding systems. Similarly, the immediate reaction andthe reliability of fire detection and alarm system are veryimportant to maintain the safety of the occupants in theIB. The importance of the fire protection system in goodtime is critical as it can contribute significantly to thesuccess of rescue operations and to limiting the degree ofdamage [34]. This might support why the fire detectionand alarm system was one of the main considerations inconfiguring IB systems;
� Surprisingly, respondents considered that the buildingfac-ade system (0.057) was the least important in systemselection. The fac-ade system is often regarded as asystem providing protection from the weather as well asclimate modifiers controlling the amount of noise,sunlight and air that enters the buildings and sustaininga healthy environment [2]. The low rank of fac-adesystem may stem from the fact that the respondents
lease cite this article as: Wong JK, Li H Application of the analytic hierarc
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considered the internal building systems were moresignificant and influential in affecting user comfort andperformance of the IB.
Comparing the results of two surveys in this studyrevealed that the importance of selection criteria inAHP survey is slightly different from those of the generalsurvey, but they have a common premise that criteriaare all crucial and comparable. This AHP surveyfurther confirms the significance of all crucial selectioncriteria by the experts who have a high level of exper-ience in IB projects. Findings relating to relative impor-tance of selection criteria and sub-criteria are summarizedbelow:
�
hy
006
‘Work efficiency’ was continuously perceived as themost important main criterion for a number of IBsystems: addressable fire detection and alarm system(0.091), IBMS (0.078), security monitoring and accesscontrol system (0.060), telecom and data system (0.059),hydraulic and drainage system (0.040), and internallayout system (0.030). In addition, ‘‘user comfort’ wasconsidered as slightly more important in HVAC system(0.034) and lighting system (0.032).
process (AHP) in multi-criteria analysis of the selection of intelligent
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Table 6
Relative priorities of the selection criteria of the IB systems
Intelligent building
systems
Local
priority
Global
priority
Main Criterion Local
priority
Global
priority
Sub-Criterion Local
priority
Global
priority
Integrated building
management
system (IBMS)
0.119 0.119 Work efficiency 0.655 0.078 Reliability 0.536 0.042
0.078 Capability of integrating
systems
0.205 0.016
0.078 Efficiency 0.258 0.020
Cost
effectiveness
0.345 0.041 Operating and maintenance
costs
1.000 0.041
Telecom and data
system
0.103 0.103 Work efficiency 0.576 0.059 Reliability 0.362 0.021
0.059 Further upgrade 0.220 0.013
0.059 Service life 0.214 0.013
0.059 Efficiency 0.203 0.012
Cost
effectiveness
0.424 0.044 Operating and maintenance
costs
1.000 0.044
Addressable fire
detection and
alarm system
0.119 0.119 Work efficiency 0.762 0.091 Fire detection and fighting
code compliance
0.253 0.023
0.091 Fire resistance code
compliance
0.199 0.018
0.091 Efficiency 0.139 0.013
0.091 Further upgrade 0.093 0.008
0.091 Automatic and remote
control/monitoring
0.178 0.016
0.091 Service life 0.138 0.013
Cost
effectiveness
0.238 0.028 Operating and maintenance
costs
1.000 0.028
Security
monitoring and
access control
system
0.091 0.091 Work efficiency 0.664 0.060 Time for public
announcement
0.139 0.008
0.060 Time for informing building
management
0.170 0.010
0.060 Compatibility 0.137 0.008
0.060 Connection to BAS 0.146 0.009
0.060 Service life 0.129 0.008
0.060 Further upgrade 0.130 0.008
0.060 Time for total egress 0.149 0.009
Cost
effectiveness
0.336 0.031 Initial costs 0.416 0.013
0.031 Operating and maintenance
costs
0.584 0.018
HVAC system 0.102 0.102 Work efficiency 0.278 0.028 Service life 0.194 0.006
0.028 Reliability 0.442 0.013
0.028 Connection to BAS 0.205 0.006
0.028 Compatibility 0.158 0.004
User comfort 0.337 0.034 Predict mean vote (PMV) 0.226 0.008
0.034 Indoor air quality (IAQ) 0.294 0.010
0.034 Acoustic comfort 0.254 0.009
0.034 Amount of fresh air 0.226 0.008
Environmental 0.198 0.020 Total energy consumption 1.000 0.020
Cost
effectiveness
0.187 0.019 Initial costs 0.399 0.008
0.019 Operating and maintenance
costs
0.601 0.011
Vertical
transportation
system
0.083 0.083 Work efficiency 0.228 0.019 Service life 0.099 0.002
0.019 Waiting time 0.234 0.004
0.019 Maximum interval time 0.200 0.004
0.019 Journey time 0.175 0.003
0.019 Connection to BAS 0.090 0.002
0.019 Compatibility 0.081 0.002
Automatic and remote
control/monitoring
0.122 0.002
User comfort 0.196 0.016 Acoustic comfort 0.248 0.004
0.016 Acceleration and deceleration 0.232 0.004
0.016 Air change 0.264 0.004
0.016 Vibration level 0.257 0.004
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]]14
Please cite this article as: Wong JK, Li H Application of the analytic hierarchy process (AHP) in multi-criteria analysis of the selection of intelligent
building systems. Building and Environment (2007), doi:10.1016/j.buildenv.2006.11.019
ARTICLE IN PRESS
Table 6 (continued )
Intelligent building
systems
Local
priority
Global
priority
Main Criterion Local
priority
Global
priority
Sub-Criterion Local
priority
Global
priority
Safety 0.302 0.025 Safety regulations compliance 1.000 0.025
Environmental 0.149 0.012 Total energy consumption 1.000 0.012
Cost
effectiveness
0.125 0.010 Operating and maintenance
costs
1.000 0.010
Digital addressable
lighting control
system
0.102 0.102 Work efficiency 0.23 0.023 Compatibility 0.131 0.003
0.023 Connection to BAS 0.146 0.003
0.023 Permanent artificial lighting
aver. power density
0.180 0.004
0.023 Further upgrade 0.158 0.004
0.023 Service life 0.203 0.005
0.023 Automatic and remote
control/monitoring
0.182 0.004
User comfort 0.312 0.032 Ease of control 1.000 0.032
Environmental 0.191 0.019 Average efficacy of all lamps 1.000 0.019
Cost
effectiveness
0.267 0.027 Operating and maintenance
costs
1.000 0.027
Energy
management
system
0.095 0.095 Work efficiency 0.249 0.024 Connection to BAS 0.566 0.013
0.024 Compatibility 0.434 0.010
Safety 0.539 0.051 Safety regulations compliance 1.000 0.051
Cost
effectiveness
0.212 0.020 Operating and maintenance
costs
1.000 0.020
Hydraulic and
drainage system
0.069 0.069 Work efficiency 0.585 0.040 Service life 1.000 0.040
Cost
effectiveness
0.415 0.029 Operating and maintenance
costs
1.000 0.029
Internal layout
system
0.06 0.06 Work efficiency 0.503 0.030 Service life 1.000 0.030
Cost
effectiveness
0.497 0.030 Initial costs 0.525 0.016
0.030 Operating and maintenance
costs
0.475 0.014
Building fac-ade
system
0.057 0.057 Work efficiency 0.317 0.018 Connection to BAS 0.238 0.004
0.018 Service life 0.341 0.006
0.018 Compatibility 0.148 0.003
0.018 Automatic and remote
control/monitoring
0.273 0.005
User comfort 0.325 0.019 Response change in
temperature
0.538 0.010
0.019 Response change in sunlight 0.462 0.009
Cost
effectiveness
0.358 0.020 Operating and maintenance
costs
1.000 0.020
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]] 15
�
P
b
Consistent with the results of the general survey,reliability (0.042) and operating and maintenance costs(0.041) were further regarded as important sub-criteriain choosing the IBMS in this AHP survey. This isconsistent with the suggestions of So and Chan [33] inwhich the system reliability was reported as a keycriteria of choosing the right IBMS. Achieving expectedIBMS operational performance and reliability requiresattention to the selection and specification of thecomponents [33].
� The sub-criterion, operating and maintenance costs(under main criteria ‘Cost effectiveness’), was perceivedas the most important selection sub-criteria in four IB
lease cite this article as: Wong JK, Li H Application of the analytic hierarchy
uilding systems. Building and Environment (2007), doi:10.1016/j.buildenv.2006
systems: telecom and data system (0.044), fire detectionand alarm system (0.028), building fac-ade system(0.020), and, security monitoring and access controlsystem (0.018).
� The findings further revealed that in various IB systems,none of sub-criteria was dominant. For example, varioussub-criteria under ‘work efficiency’ were equally impor-tant in the vertical transportation system (from 0.002 to0.005); security monitoring and access control system(from 0.008 to 0.010); lighting system (from 0.003 to0.005); building fac-ade system (from 0.003 to 0.006).
� As shown in Table 6, ease of control (0.032) was justifiedas the most important subcriteria for the selection of
process (AHP) in multi-criteria analysis of the selection of intelligent
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Fig.3.A
refined
conceptualmodel
fortheselectionofIB
system
s.
J.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]]16
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ARTICLE IN PRESSJ.K.W. Wong, H. Li / Building and Environment ] (]]]]) ]]]–]]] 17
digital addressable lighting control system. This findingis consistent with the suggestions of Atif and Galasiu[58] that a careful control is an important factor inlighting systems justification as it helps reduce theelectric energy consumption as operation irregularities(i.e., reduced dimming linearity, incorrect adjustment ofthe phases of the dimming control system) can reducethe energy efficiency of the lighting control system.
Fig. 3 depicts a modified conceptual model of IB systemselection which is developed from the findings of thesurveys in this study. This modified conceptual modelillustrates the importance of the selection sub-criteria ofeach IB systems. It also suggests the accomplishment of theIB through the interaction and collaboration among the IBsystems.
6. Conclusions
This exploratory study evaluated and identified thecrucial selection criteria for the IB systems. A model forthe IB systems selection was established. The findings fillthe gaps that exist in the current body of research in thisarea. Our findings suggested that each IB system wasdetermined by a disparate set of selection criteria withdifferent weightings. Amongst all main selection criteria,‘work efficiency’ was perceived as the most important,while ‘user comfort’, ‘safety’ and ‘cost effectiveness’ werealso considered to be significant. Two sub-criteria, ‘relia-bility’ and ‘operating and maintenance costs’, were rankedhighly important by respondents. This implied that long-term expenses were the major concern of many owners anddecision makers. Also, reliability of systems can minimizethe risk of disillusionment as well as decline in interest andconfidence in IB systems by the occupants. It is expectedthe key criteria identified in this study improve theunderstandings of industry practitioners in IB systemsselection.
However, the examination of relationships was limited tothose between the building systems and selection criteriawith the use of the AHP method in this study. The inter-relationships amongst the selection criteria remainedunexplored. Future research would examine the underlyinginter-relationship amongst the criteria, i.e. by using theanalytical network process (ANP). For example, the inter-relationship between the ‘operating and maintenance cost’and ‘service life’ as well as their effects to the selection of IBsystems can be tested. Their interrelationship may affectthe extent to how to create the successful and well-performed IB systems.
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