Computer-based performance simulation for building design and ...

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Computer-Based Performance Simulation for Building Design and Evaluation: The Singapore Perspective Wong Nyuk Hien, Lam Khee Poh and Henry Feriadi Simulation Gaming 2003; 34; 457 DOI: 10.1177/1046878103255917 The online version of this article can be found at: http://sag.sagepub.com/cgi/content/abstract/34/3/457

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SIMULATION Hien et al. / THE &SINGAPORE GAMING / September PERSPECTIVE 2003

ARTICLE 10.1177/1046878103255917

Computer-based performance simulation for building design and evaluation: The Singapore perspective Wong Nyuk Hien Lam Khee Poh Henry Feriadi National University of Singapore

This article provides an overview of the usage of performance-based simulation tools for building design and evaluation in Singapore based on an extensive industry survey. It highlights the status and difficulties encountered in the usage and the needs of the industry for such tools. Recommendations are also given to promote the pervasive use of such simulation tools. KEYWORDS:

performance-based simulation; building design process; coevolution; integrative design support

The design of buildings is a complex process. To ensure that a building can satisfy the needs of occupants, it is essential that during the design stage, all environmental factors that affect the performance of the building are carefully considered. Such environmental factors include various weathering elements such as wind, sun, noise, rain, and so forth. To provide a better understanding of the impact of such environmental factors, various methods have been developed to simulate the effects of such weathering elements. The most fundamental approach involves the building of physical scale models and studies their behavior under the various weathering elements. Various tools have also been developed to simulate such effects. For example, a wind tunnel for the simulation of wind effects, and an environmental chamber for the simulation of the effects of solar radiation, moisture, relative humidity, and so forth. However, with the increased usage of computers and the rapid advances in the development of computer technology and modeling techniques, there has been an increasing emergence of computer-based performance simulation tools that could simulate the effects of various weathering elements and serve to provide valuable assistance to building designers. Many simulation tools also have the capability to simulate the behavior of various building systems such as air conditioning systems, artificial lighting, sound sources, and so forth. Over the past decade, the design and performance evaluation of buildings has become increasingly complex. Such complexity arises from the rapid advances in technology; changing perceptions and demands of building owners, operators, and SIMULATION & GAMING, Vol. 34 No. 3, September 2003 457-477 DOI: 10.1177/1046878103255917 © 2003 Sage Publications

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SIMULATION & GAMING / September 2003

tenants; as well as the increasingly importance of the building as a facilitator of human control, productivity, and information interchange (Tham, 1992). One of the challenges is to understand the interaction between various aspects of building performance and also their implications on complex control. The overreliance of mechanical systems to achieve the required comfort and health has also obscured the inherent performance implications of other critical building design decisions. As a result, the decision on mechanical systems and controls was frequently decoupled from the building design. The dynamics of the organizational workplace as well as the flexibility of the building infrastructure also have important effects on the environmental and technical quality of the offices (Tu & Loftness, 1998). Over the past few years, the pressure for competitive differentiation is also leading property developers and designers to include novel and innovative design features in the core design work. Unfortunately, there is considerable uncertainty in assessing the performance of such designs if the dynamic and integrated response of the building and its environmental systems is not taken into account. The aspiration of designers to create a sustainable built environment for the future by consciously taking into consideration issues such as energy efficiency, passive building, and ecologically friendly design has further added to the complexity of the design process. With such increasing complexity involved in building design and performance evaluation of buildings, the need for the use of computational building performance evaluation and design support tools throughout the process is recognized. Such tools allow the building designers to evaluate the impact of design on the various performance mandates such as thermal, air, acoustic, and visual quality (Hartkopf, Loftness, & Mill, 1986). To some extent, they are able to replace expensive and time-consuming field tests and provide a comprehensive range of test conditions. They can also lead to an improved understanding of the behavior of various climatic agents and provide confidence in design. They are also especially important for making preliminary evaluation of complex design strategies (Mahdavi & Lam, 1991). This article, through an extensive industry survey, provides an overview of the usage of performance-based simulation tools for building design and evaluation in Singapore, highlighting particularly the status and difficulties encountered in the usage and the needs of the industry for such tools.

Understanding the design process The building design process starts from the client who has certain ideas and requirements for a building. The appointment of an architect for a new building project carries with it a high degree of uncertainty in almost all the aspects of the design at this point in time. In selecting the architect, the client begins with a leap of faith in the architect. The client wants to ensure that the building will be built within their expectation, time duration, and budget limit. The design process involves translating the requirements of the client into a physical design which is buildable, fulfilling the needs of the client as well


Hien et al. / THE SINGAPORE PERSPECTIVE

459

T I M E + B U D G E T Communication

Design Need

Communication

Design

SIMULATION

Construction

TRANSITION

Use / Operation

REALITY

Design remains a simulation until construction

FIGURE 1:

Design Simulates Reality

as complying with the building regulations as specified by the government regulatory bodies (see Figure 1). The process undoubtedly involves intensive communication between client and architect, where the client describes the need or the architect asks about the client’s specific requirement. The solution in each problem that arises becomes invaluable experience and good practical knowledge.

Design decision and building performance Throughout the design process, the various aspects of building performance such as comfort, economics, code compliance, energy requirement, environmental impact, esthetics, and so forth must be considered. Therefore, the building design process can be seen as a dynamic process of generating ideas that involve specific strategies and technologies and then estimating and evaluating their performance with respect to the various performance considerations within the specific design context (see Figure 2). To estimate the performance of building designs, designers need to simulate the operation of the building using various types of modeling techniques. As the need for additional and more accurate performance considerations is increasing, new simulation techniques are becoming available. Table 1 shows the evolution of computerbased performance simulation tools (Clarke & Maver, 1991). The performance evaluation process requires the comparison of multiple alternative design schemes as well as the performance of existing buildings. Such evaluation also requires concurrent and integrated consideration of the various performance mandates. Although performance prediction can be facilitated with the use of computerbased performance simulation tools, their usage for performance evaluation is limited. This is because the current simulation tools are mostly developed based on one single aspect of building performance, although such tools can facilitate the evaluation process by the provision of appropriate user interface that generates graphical representation of the output data and allows direct comparison of multiple solutions with respect to multiple performance consideration (Papamichael, Porta, & Chauvet, 1997).


460


Building Design

Available Strategies / Technologies

Performance Prediction

Aesthetics Energy Economics Comfort etc

Performance Evaluation

Simulation process circle

Decision Making

FIGURE 2:

The Importance of Building Performance Simulation in Design Decision Making

TABLE 1: Evolution of the Computer-Based Performance Simulation Tools First generation

Second generation

Third generation

Next generation

Handbook oriented Simplified Piecemeal Dynamics important Less simplified Still piecemeal Field problem approach Numerical methods Integrated energy subsystems Heat and mass transfer considered Better user interface Partial CAD integration CAD integration Advanced numerical methods Intelligent knowledge based Advanced software engineering

Indicative Applications limited Difficult to use

Predictive Generalized Easy to use

Table 2 shows the state-of-the-art performance simulation tools that are currently available.

The use of performance simulation tools in Singapore 1. The problem Despite the proliferation of many performance-based simulation tools and their increasing usage for building design and evaluations, especially in North America,


TABLE 2: List of Performance Simulation Tools Software Type

Brief Description

Example


Energy and HVAC sizing

Analysis of energy consumption Selection and sizing of HVAC equipment

DOE-2 BLAST HVACSIM+

Ventilation and indoor air quality

Analysis of airflow in and around buildings, pollutant emission and migration, natural ventilation, and air conditioning Two common approaches used are Computational Fluid Dynamics (CFD) model and Multizone Network Model Geared toward electrical lighting design and evaluation Some models also provide for daylighting evaluation Common approaches used include Zonal Cavity method, Ray Tracing, or Radiosity Technique Application of building and room acoustics simulation tools extremely limited Approaches used include Finite Element Method (FEM) and Boundary Element Method (BEM)

Natural and electrical lighting

Acoustical

Software Developer

Country

PHOENICS FLOVENT COMIS

Lawrence Berkeley National Laboratory University of Illinois National Institute of Standards and Technology Concentration, Heat and Momentum Limited Flomerics Incorporated Lawrence Berkeley Laboratory

United States United States United States United Kingdom United States United States

RADIANCE LIGHT-SCAPE LUMEN MICRO

Lawrence Berkeley National Laboratory Lightscape Techniques Lighting Technologies

United States Canada United States

COMET/acoustic

Automated Analysis Incorporation

United States

MODELER TAP

Bose Corporation Trane Company

United States United States

461

462


their usage by architectural and engineering consulting firms in Singapore has not been very encouraging. The traditional approach of relying on accumulated experience of the building designers is still prevalent. Rule-of-thumb solutions developed over time were motivated by the need for compliance with codes of practice and very often were applied rigidly without considering the overall design context. Such decision tends to be unidisciplinary because most of the codes of practice were developed to fulfill one particular aspect of the building performance. For example, the Overall Thermal Transfer Value (OTTV) requirement was developed taking into consideration only the heat transfer process through the building façade for air-conditioned buildings. The implication of such requirement on other building performance, such as the potential for the utilization of daylight, was not considered. To provide a better understanding of the extent in which performance-based simulation tools are used in building design and evaluation, a survey was conducted among the architectural and engineering consulting firms in Singapore. The survey also serves to identify the problems and difficulty encountered by them and the needs of the industry for such tools. 2. Methodology A self-administered questionnaire was sent to the architectural and engineering consulting firms in Singapore. The questionnaires were structured in such a manner that would provide information regarding the following: • performance-based simulation tools commonly utilized in building design and evaluation, • educational background of the software users, • the stage of design process where the software were utilized, • reasons for the usage of such tools and the problems encountered, • reasons for not utilizing such tools, • perception of integrative design support environment, and • suggestions toward the enhancement of such software utilization.

The survey was conducted for a period of 1 month from early December 1998 to early January 1999. A total of 584 firms were surveyed, comprising 440 architectural firms, 134 engineering consulting firms, and 10 government statutory bodies. Approximately 28% of the questionnaires sent were completed and returned (see Figure 3). 3. Status of usage of performance-based simulation tools Table 3 shows the usage of various performance-based simulation tools by the firms surveyed. The results revealed that the usage of energy and HVAC sizing software by architecture firms was extremely low. Most architecture firms indicated that they were not aware of the existence of such software tools and that the usage was beyond the scope of their work. Although 46.4% of the engineering consulting firms surveyed were using the software, the majority of the software were supplied by the HVAC



463

Statutory Bodies Engineering Architecture 0

100

200

Number Surveyed FIGURE 3:

300

400

500

600

Number Responses

Response Rates From the Various Groups

TABLE 3: Percentage of the Firms Surveyed Using Various Performance-Based Simulation Tools Percentage of Firms Surveyed Response Group

Energy and HVAC Sizing

Architecture Engineering Statutory bodies Combine

1.6 46.4 16.7 15.6

Daylighting and Electric Lighting 11.3 25.0 0.0 14.6

manufacturers, which served to assist them in the design and selection of HVAC systems and components. The usage of generic energy and HVAC sizing software such as DOE-2 was very limited. Of the architecture firms, 11.3% were using the lighting software. However, the software were used mainly for rendering to enhance the visual impression of the design. They were not used specifically for the design of artificial lighting or daylighting. About 25% of the engineering consulting firms were using the lighting software supplied by the lighting manufacturers for the design of artificial lighting. In most cases, daylighting was not considered in their design. Again, the usage of generic lighting software such as Radiance or Lightscape was very limited. The survey also revealed that software for the analysis of acoustics, ventilation, and indoor air quality were not used at all by the firms surveyed. Most firms surveyed expressed that they had not come across any of such software and felt that such software should only be used by the specialists. Table 4 reveals the educational background of the software users. The majority of the energy and HVAC sizing software users were mechanical engineers and building services engineers. For the daylighting and electric lighting software, 71.4% of the users were electrical engineers and about 28.6% were building services engineers. The usage by architects was about 14.3%. Table 5 reveals the frequency of usage of the various simulations tools. Of the energy and HVAC sizing software users, 46.2% utilized the software frequently, with 30.8% indicating that they seldom used it. For daylighting and electric lighting software, 66.6% of the software users utilized the software occasionally.


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TABLE 4: Educational Background of the Software Users Percentage of Firms Surveyed Educational Background Architecture Mechanical engineering Electrical engineering Building services engineering


Daylighting and Electric Lighting

0.0 69.2 7.7 38.5

14.3 0.0 71.4 28.6

TABLE 5: Frequency of Usage of the Various Software Tools Percentage of Firms Surveyed Frequency of Usage Seldom Occasionally Frequently Always



30.8 15.3 46.2 7.7

16.7 66.6 0.0 16.7

TABLE 6: Design Stages Where the Various Software Tools Were Utilized Percentage of Firms Surveyed Design Stage


From beginning of schematic design During design development After the design is completed

15.4 53.8 7.7


40.0 40.0 20.0

Table 6 shows 53.8% of the energy and HVAC sizing software users utilized the software during the design development stage. For daylighting and electric lighting software, 80% of the users utilized the software from beginning of the schematic design as well as during the design development stage. 4. Reasons for using simulation tools Figure 4 shows the major reasons for the usage of performance-based simulation tools. Of the firms surveyed, 69% utilize the tools to enhance the design in terms of providing better understanding of impact of design on building performance, and 58.6% felt that the tools speed up the design process as well as provide confidence in the design. Only about 35% expressed that the usage is to fulfill the client’s requirements. Some firms also expressed that the adoption of such simulation tools will



Increase competitiveness of company

13.8%

44.8%

Enhance evaluation of complex design strategies

48.3%

Fulfill company's strategy to maximize use of IT in design

48.3%

Provide confidence in design

17.2%

13.8%

10.3%

58.6%

Replace expensive and time consuming field test

34.5%

24.1%

Enhance design in terms of providing better understanding of impact of design on building performance

6.9%

69.0%

Speed up design process

6.9%

58.6%

Fulfill Client's requirements

17.2%

34.5%

0.0%

10.0%

465

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

Percentage (%) Agree

FIGURE 4:

Disagree

Reasons for Using Simulation Tools

Staffs lack the skills and training in the usage

55.0%

Does not enhance deisign

18.3%

10.0%

35.0%

Very steep learning curves and not user friendly

50.0%

Not aware of existence of such simulation tools

50.0%

8.3%

23.3%

Expensive and not cost effective to consultants

55.0%

Does not speed up design process

55.0%

Client not willing to pay for simulation study

6.7%

21.7%

50.0%

11.7%

Not the requirements for most Clients

70.0%

0.0%

10.0%

20.0%

30.0%

8.3%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%


FIGURE 5:

Disagree

Reasons for Not Using Simulation Tools

enhance the image of their companies and thus increase their competitiveness in securing projects. 5. Reasons for not using simulation tools Figure 5 reveals the major reasons for not using the simulation tools. Of the firms surveyed, 70% felt that most clients do not stipulate the employment of such tools as an essential requirement. Most firms viewed the use of simulation tools as involving extra cost and effort but with little recognition and appreciation from the clients. Very tight


466


Staff do not see usefulness of such tools

33.9%

41.1%

Expensive in maintaining and upgrading the software

Lack of training facilities

19.6%

51.8%

Resistance from staff

46.4%

17.9%

0.0%

10.0%

20.0% Agree

FIGURE 6:

1.8%

64.3%

30.0%

40.0% 50.0% Percentage (%)

60.0%

70.0%

80.0%

Disagree

Obstructions in Usage of Simulation Tools

project schedule and budget further aggravate this problem. Other major reasons include staff lacking the skills and training in the usage, the high cost of simulation tools, and the belief that the use of such tools would incur more design time in the process. In addition, 50% also expressed that most of the tools have very steep learning curves and are not user-friendly. Most firms surveyed also felt that the usage of such simulation tools was beyond their scope of work. The opinion is that such tools should be utilized only by the specialist consultants or the suppliers. The lack of “suitable projects” further hampered the regular utilization. The lack of support from the local software developer is another obstruction because such software was not easily available and those developed in United States or Europe may not be suitable for local use. The output generated from the simulation tools could be extremely difficult to interpret and utilize for design decisions. It could also be difficult to justify cost savings in the design to the clients. Their basic objective of the design was to fulfill the requirement as specified by the codes of practice; thus, the usage of complicated simulation tools was not essential. Of greater concern is perhaps the apparent lack of awareness of the existence of such tools. Figure 6 shows the barriers encountered in the usage of simulation tools. About 64% felt that the main barriers were the high cost of maintaining and upgrading the software. The lack of training facilities and that staff did not see the usefulness of such tools are other major factors. Figure 7 shows the perception of the limitations of current simulation tools by firms surveyed. Of the firms surveyed, 69% felt that the main limitation is the very extensive data input required. This can indeed impose a very serious problem, especially during the initial design stage where design information is very limited. Another hindrance is that simulation tools are largely platform-dependent, requiring firms to possess specific computer systems. The tools do not match the existing design process, and there



69.0%

Requires very extensive data input

13.8%

34.5%

Computationally very expensive

31.0%

48.3%

Computer platform dependent

13.8%

44.8%

No integration with CAD tool

0.0%

17.2%

48.3%

Does not simulate design process

10.0%

467

20.0%

20.7%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


FIGURE 7:

Disagree

Limitations of Current Simulation Tools

is no integration with CAD tool. Only about 35% felt that investment in this technology is expensive. This is because of the tremendous improvement in the computer technology and the drastic reduction in the price of computer memory. 6. Comparison with other countries To a have better understanding of the reasons for not using the performance simulation tools in Singapore, it is essential to compare the situation in other countries to identify whether such reasons are specific in Singapore. A literature review was carried out to identify similar surveys that were conducted in other countries. 6.1. United States. Donn (1997), in a survey of 421 firms in the United States that were mainly HVAC engineers, simulationists, and utility support groups, found that 68% of the responses referred to bottom-line costs as the aspect of simulation that interests clients. The survey also revealed the following perceptions of the practitioners: • • • •

simulation is costly and slow; simulation requires special and expensive equipment; simulation is a specialist’s tool, useful only for high-value commissions; and there is a poor match between measurements and prediction.

Johnson and Clayton (1998), in the survey of 273 Fortune 500 firms that were involved in facility management, revealed that only 12% of the responses indicated that the building simulation and analysis was very useful. However, when the firms were asked whether such tools can become more useful in the next 5 years, 47% indicated that it was very likely. The survey also found that the major challenges faced by the firms in the usage of the tools include the following:


468


• customizing proprietary software to meet their needs, • measuring the results of implemented solutions based on the simulation, and • evaluation of the implemented solution using economic analysis.

6.2. United Kingdom. In the survey of 69 simulation tool users by the Building Performance Research Unit of Anglia Polytechnic University (Robinson, 1996), improvements that were required for existing simulation tools were identified. They include the following: • • • • •

links to CAD, better reporting facilities, better application documentation, more comprehensive databases, and the need for more comprehensive training.

A separate survey (Hand, 1998) revealed the main barriers to the use of building energy and environment simulation software. They include the following: • • • • • • • •

perceived steep learning curve, ease of use and user interface, fear of effect of user errors, time required for preparation and calculation, lack of CAD integration, lack of suitable default values, lack of good data set, and credibility of prediction.

6.3. Czech Republic. This survey (Dunorska, Drkal, & Hensen, 1999), conducted in Czech Republic classified the barriers to the use of building simulation under three main headings: cultural, economical, and technical. The cultural barriers result mainly from the fact that various parties involved in building design are not aware or convinced of the advantages offered by the simulation. Traditional design tools enforced by Czech national standards are still prevalent. The language barrier also handicaps the use of building simulation. Most of the software is available only in English, and this discourages many potential users. The economical barriers are related to the remuneration of the professionals and the fees in their services. The market is highly competitive and the building developers and investors expect quick results for low fees. Examples of technical barriers are the lack of detailed input data (e.g., climate data and building material reference databases) and the lack of hardware. 6.4. The Netherlands. Pieter (Wilde, Augenbroe, & Voorden, 1999), in his two case studies, revealed the status of the usage of simulation tools in the Netherlands. The role of computational tools has been mostly limited to confirming expectations concerning energy consumptions. The only noticeable impact of computational result on the design appear to be limited to fine tuning of systems.



469

The existing tools do not comply with the requirements of the design phase in which support is most needed. The use of simulation tools in the design process is solely at the discretion of the consultant who uses these tools.

What can be done to enhance the usage The above survey results confirmed the general feeling that the usage of performancebased simulation tools for building design and evaluation in Singapore was very limited. The comparison with other countries also revealed that the main problems and barriers to the usage of simulation tools for building design and evaluation are fairly universal. The main reasons for the limited usage of such simulation tools can be summarized as follows: • inherent system limitations of current simulation tools, • structure of existing building delivery process, and • prescriptive nature of the building legislation.

Localization of performance simulation tools Table 2 shows that the performance simulation tools are imported predominantly from the United States. Performance simulation tools that are developed locally are literally nonexistent. This is mainly due to the current lack of demand of such tools in the building industry. Furthermore, there is also a shortage of skilled programmers/software developers who are well versed with computer programming and building simulation principles and technology. For the imported tools, although the majority of them are developed based on the fundamental laws of physics that could be applied universally, some forms of customization to suit the local usage are usually required. They include the following: • incorporation of local weather data, • provision of local building material databases, and • provision of local building components’ performance characteristics.

In most cases, such data are not easily available. The incorporation of such databases in the performance simulation tools in some cases could be difficult. Thus, it is essential that the local academic institutions should play a vital role in compiling such data and making them available to the industry. The survey also shows that academic institutions should play active roles in providing the training and learning environment for the usage of such simulation tools (see Table 7). Only about 6% felt that it is not important or least important. Table 8 shows that the provision of such training should be most appropriate in the form of short courses for existing working designers and also should start at the undergraduate level.


470


Table 7:

Level of Importance in the Provision of Training and Learning Environment by Academic Institutions

Level of Importance

Percentage

Most important Important Somehow important Not important Least important

33.8 46.2 18.5 4.6 1.5

TABLE 8: Level of Training Provided by Academic Institutions Level of Training Undergraduate Graduate Short courses Executive programs

Percentage 48.5 22.1 55.9 25.0

Development of integrative design support environment To ameliorate the inherent system limitations of the current simulation tools, concerted efforts have been made by researchers to effectively incorporate performance simulation within computer-aided design environments. Some of these research efforts include STEP (ISO, 1992), COMBINE (Augenbroe, 1992), ICADS (Pohl & Reps, 1988), and SEMPER (Mahdavi et al., 1996). Such tools are characterized by the use of computer-aided building design tools fully integrated with advanced numerical methods that allow integrated performance assessments. The CAD system can be dynamically linked to different performance simulation tools, which allows the concurrent and integrated consideration of the various performance mandates (Mahdavi, A., Mathew, P., Lee, S., Rohini, B., Chang, S., Kumar, S., et al., 1996). Research development is also in progress to develop Webbased simulation environment with the use of a high-speed network to allow collaborative design activities to be carried out among the geographically distributed building designers. Figure 8 shows the perception of the firms surveyed on the enhancement of the design process offered by an integrative computational design support environment. Of the firms surveyed, 82.3% felt that such an environment will certainly enhance the design process, particularly in achieving Total Building Performance and Systems Integration (Hartkopf et al., 1986). It will also provide a better understanding of the impact of the design decisions on multiple performance mandates, as well as enhancing the evaluation of the complex design strategies. Such an environment will ultimately improve the total design coordination resulting in eco-friendly energy efficient



Shared database for multiple simulation domains

48.4%

1.6%

64.5%

Ease of interpretation of output

Ease of data input

62.9%

More user friendly

62.9%

Platform independent since it is internet based

8.1%

9.7%

12.9%

53.2%

Better integration of CAD tool with performance based simulation tools

11.3%

74.2%

0.0%

10.0%

20.0%

471

30.0%

4.8%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%


FIGURE 8:

Disagree

Enhancement of Design Process Using Integrative Design Support Environment

Design towards achievement of Total Building Performance and Systems Integration

6.5%

82.3%

Enhance evaluation of complex design strategies

9.7%

79.0%

Better undestanding of impact of design on multiple performance mandates

8.1%

80.6%

51.6%

Speed up design process

0.0%

10.0%

20.0%

30.0%

33.9%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


FIGURE 9:

Disagree

Elimination of Limitations of Current Simulation Tools

buildings. It will also enhance contact between design consultants in various disciplines and will improve the cost-effectiveness of the design solution. Figure 9 shows the perception of the firms surveyed on the elimination of the limitations of current simulation tools with the use of an integrative computational design support environment. Most firms felt that such an environment will certainly provide a better integration of CAD tools with performance-based simulation tools. It would also facilitate the data input and interpretation of the output and is more user-friendly. It also has the advantage of having a shared database for multiple simulation domains.


472


Level 1:

Building Design Process Client

Architect

Engineer

Contractor

Government

FIGURE 10: Building Design Process Level 1

Coevolution of building delivery process and simulation tools 1. Overview of current building delivery process The hindrances caused by the existing structure of the building delivery process for the effective usage of simulation tools for design evaluation are well documented (Mahdavi, 1998). The predominant factor is the emphasis on cost, specifically the initial and capital cost. Building projects are generally characterized by tight schedules and budgets. This problem is further compounded by the current project development trend where the completed buildings are not occupied by the building owners but are leased out. As such, the developers may have minimum interest in the ultimate performance of the buildings. However, the unwillingness to invest in preliminary investigative studies using simulation tools may result in remedial or abortive work as well as higher operating and maintenance cost. 2. Current practice in design process Most cases of current practices in traditional building delivery process have shown a poor integration among the professionals, and the process is highly fragmented from design to construction phase. To have a better understanding of the current practices in design process—their advantages and disadvantages—the current practices can be classified into two levels of design relationship, that is, Level 1 and Level 2 design relationship. At the Level 1 design relationship (see Figure 10), the communication among the design professionals is based on the “one direction approach” where the focus is on their respective design responsibilities without any significant input from other design professionals. The simulation tools used are mostly visualization tools with great emphasis on visual perception (drafting software, 3D modeling, material and rendering tools, etc.). Occasionally, building performance tools may be used by engineers to enhance the accuracy in building system design. The government agency usually acts as a building regulator to ensure the compliance of prescriptive standard performance (building structure code, OTTV, fire safety code, etc.).



473

Level 2: Building Design Process Client

Architect

Engineer

Contractor

Government

FIGURE 11: Building Design Process Level 2

The Level 2 design (see Figure 11) is mostly common for projects where the client will occupy and use the building. The client will usually be involved right from the initial stage of the design and give invaluable input to the design team. The client, architect, and engineers work in a dynamic relationship (sharing the idea and concept), and the important decision in the building design process will usually include some aspects of performance. To ensure that the building design and performance are well integrated, building performance simulation tools are employed so that the reciprocal impact of the architectural design decision to some aspects of building performance can be better analyzed and justified. Finally, the contractor will translate the integrative design into the real building. 3. Needs for coevolution process In recent years, the simulation tools have been continuously developed to perform and achieve some targets such as high accuracy, integrative simulation, and userfriendly interfaces. Undoubtedly, all the above objectives can only be accomplished by the parallel development of some external factors such as new computer technology, the advance of theory and researches, and the innovation in building components and systems. On the other hand, the evolution should also occur in the design process such that simulation tools with new capabilities can enhance their usage in the building design process. To maximize the tool usage in design process, there are at least three factors that need to be considered: attitude (motivation) of the tool user; redefinition of the roles in design process, continuous training, and education; and building regulation enforcement (see Figure 12). 4. Evolution of design process Design processes that adopt performance-based simulation tools certainly necessitate a conducive and integrative environment, without which the optimum design performance will be impossible to achieve. The conducive design environment means that all the parties involved in the building design (client, architects, engineers, and


474


Building System

Computer Tech.

Theory and Research

Building Performance Simulation Tools

CO - EVOLUTION

Building Design Process

Tools User

Education and Training

Regulation

FIGURE 12: Coevolution Design Process and Simulation Tools

government) and all necessary infrastructures and regulations provide supportive efforts and motivations on the adoption of simulation tools. The two important concepts in integrative design process are the integration of total building performances in the design and the integration of various parties in the design process. Integrative building performance design cannot be solely dependent on good architectural design without any further consideration on the overall building performance. The usage of simulation tools enables the design team to evaluate the impact on various building performances. Integration in design process emphasizes more distributed responsibility in the design team and dynamic design decision making (see Figure 13). It is different from conventional design, which is based on linear (highly fragmented) approach. The client, architect, and engineers work in a dynamic relationship (sharing the idea and concept). The contractor can also be involved if the client has already appointed him or her for the projects. After the preliminary design is finished, the contractor is asked to give constructive input, especially on the construction method, buildability, and availability of all building services systems and elements. In some cases, the good feedback may come from specialized contractors and manufacturers of building systems and components. With the support from the integrative building performance simulation tools, the architect and engineers evaluate the various aspects of building performance. Simulation will be used not only to evaluate the building performance more accurately but also to analyze critically the economic aspect and life cycle cost of the future building in operation. The performance modeling process can be facilitated by the usage of common CAD system. The tools also support an intensive shared data communication for the geographically distributed users. The drawing and simulation data can be used to support the construction phase and project management. The government agency can adopt and actively encourage the use of a building performance concept for their building code compliance procedure. This can be achieved through the usage of performance-based regulatory systems.



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Dynamic integration in design process

Client

Architect

Engineer

Contractor

Simulation Team Design team

Government

FIGURE 13: Integration in Building Design Process

The use of performance-based regulatory systems To encourage the usage of performance-based simulation tools, it is essential to shift the current regulatory systems from a prescriptive to performance-based approach. This shift is not a recent phenomenon as the evolution of building legislation from the practice of prescriptive requirements to performance-based solutions has taken place over the past 10 years or so in countries such as Australia (Chang, Lim, & Williamson, 1998). Although the traditional prescriptive approach is relatively simple to understand and the requirements are treated as rules to be compiled with, its provisions are often regarded as “cumulative, conservative in nature and in reality only suitable in relation to ‘standard’ building configurations” (Hatton, 1996). On the other hand, the basic concept of a performance-based approach is not to prescribe solutions but rather to demonstrate that the proposed design meets defined objectives. This approach may result in alternative designs that are more flexible, rational, and innovative, as well as cost-effective. This approach can also be multidisciplinary, consciously taking into consideration the implications and synergistic effects of the various performance mandates. A comprehensive performance-based approach necessitates the ability to translate the objectives into quantifiable parameters, to set limits for these parameters, and to have means of estimating performance of proposed design to validate compliance with the required performance parameters (Beck, 1997). In this respect, simulation tools should be able to play vital roles in achieving such objectives.

Conclusion The increasing complexity in the design and performance evaluation of buildings has resulted in the need for the use of computational building performance evaluation


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and design support tools throughout the process. However, the survey results, as shown in this article, reveal that the usage of performance-based simulation tools for building design evaluation in Singapore is still very limited. The limited usage of such simulation tools arises mainly from the inherent system limitations of current simulation tools. Emphasis on initial or capital cost by the clients, coupled with the fragmented building delivery process, has resulted in little progress in the augmentation of simulation tools for design evaluation. The prescriptive nature of the current codes of practice and design guidelines also does not promote its usage. With the move toward the development of an integrative computational design support environment where there is effective integration of CAD system with various performance-based simulation tools, it will enhance the design process as well as eliminate the major limitations of current discrete simulation tools. It is hoped that this development will become an impetus for building designers to utilize the tools for performance evaluation of their design. The shift from the prescriptive nature of the building legislation to performancebased approach will further enhance such usage. It is also essential to provide the necessary conditions for a positive coevolutionary cycle of process evolution and tool development, achieved through a critical review of the status quo and in-depth reflections on the dialectics of process and tools.

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Wong Nyuk Hien received his PhD from Carnegie Mellon University after completing his thesis titled “Computational Airflow Modeling for Integrative Building Design.” His research work has contributed to the development of a simulation-based computer software for the analysis of indoor air quality and ventilation in buildings. While he was at Carnegie Mellon, he was actively involved in the SEMPER project, an integrative design support environment, which effectively integrates the various performance-based simulation tools with CAD systems. Lam Khee Poh holds a joint appointment in the Departments of Architecture and Building in the School of Design and Environment at the National University of Singapore. His fields of research include total building performance studies and the development of computational design support systems. Henry Feriadi is a PhD candidate in the building science program. His current research topic is on the thermal comfort modeling for naturally ventilated buildings in the tropics. Since 1992, he has been working as a lecturer as well as practicing his profession as an architect in Indonesia. ADDRESSES: WNH: Department of Building, School of Design and Environment, National University of Singapore, 4 Architecture Drive, Singapore 117566; telephone: +65 6874-3423; fax: +65 6775-5502; e-mail: [email protected]. LKP: Department of Building, School of Design and Environment, National University of Singapore, 4 Architecture Drive, Singapore 117566; telephone: +65 6874-6445; fax: +65 6775-5502; e-mail: [email protected]. HF: Department of Building, School of Design and Environment, National University of Singapore, 4 Architecture Drive, Singapore 117566; telephone: +65 6874-3450; fax: +65 6775-5502; e-mail: [email protected].
