ANALYSIS OF THE IMPACT OF SUSTAINABILITY RELATED DESIGN PARAMETERS IN THE ARCHITECTURAL DESIGN PROCESS. A CASE STUDY RESEARCH.

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1 AALYSIS OF THE IMPACT OF SUSTAIABILITY RELATED DESIG PARAMETERS I THE ARCHITECTURAL DESIG PROCESS. A CASE STUDY RESEARCH. Lieve WEYTJES 1 Griet VERBEECK Dr.EngArch. 2 1 Department of Architecture, University College Limburg/ UHasselt, Diepenbeek, Belgium, Lieve.weytjens@phl.be 2 Department of Architecture, University College Limburg, Belgium, GVerbeeck2@mail.phl.be Keywords: architectural design process, case studies, design parameters, energy use, indoor climate Abstract Literature review shows that early decisions in the architectural design process have the largest impact on the sustainability of the final design. However, in practice, many early decisions on sustainability are solely based on the experience and intuition of the designer. Especially in small projects, which lack engineering support due to limited budgets, designers often only use their own experience to incorporate sustainability in their design. Therefore, a research project has been established to develop a design support tool that provides designers with sustainability related feedback at every stage of the design process, based on the available information. In a first step of the research project, the design process is analyzed to identify the presence of sustainability related design parameters during each stage. The focus lies on residential buildings and on parameters related to indoor climate and energy use. The paper presents the results of several case studies in which architectural design projects in Flanders, Belgium, were investigated through an analysis of all design documents and an interview with the designer, based on an EPBD coupled framework of sustainability related design parameters. The data reveals that architects can be divided in two subgroups, according to the designing method. Another distinction was made, according to the way architects handle energy related design issues. Results show that parameters such as surface, orientation, volume, and organization are available very early in the design process, followed by glazing area, whereas for instance system components are only vaguely defined, even late in the process. These results are important information for the development of the design support tool, since these initial design decisions might already be sufficient for a first evaluation on e.g. the impact of glazing area on energy consumption or summer comfort. 1. Introduction Although the term sustainability is omnipresent, sustainable construction is not common practice yet. Both in practice and in architectural education, the attention paid to sustainable design issues during the design process, is still limited. At the same time, a number of studies have demonstrated that early decisions in the design process have the largest impact on the sustainability of the final design (Ellis et al. 2001, Holm 1993, euckermans 1992, Zhu et al. 2007). However, at that moment little information on sustainable design aspects is available to designers. Many decisions are therefore solely based on experience, rules of thumb, reference projects, or intuition, without considering the substantial consequences of these decisions (De Wilde et al. 1999, Geebelen 2003, Maassen et al. 2003, Pedrini et al. 2005). Especially in small projects, which lack engineering support due to limited budgets, designers are forced to use their own knowledge and experience to incorporate sustainability in their design (Mahdavi et al. 2003).

2 To counter this, a research project has been established to develop a design support tool that provides designers with sustainability related feedback at every stage of the design process, based on the available information. Consequently, it is important to have a clear understanding of the architectural design process and the designerly way of knowing (Cross 2006). The literature shows that the decision is the elementary building stone of the design process (Geebelen 2003, Van Bakel, 1995). Accordingly, the design process was analyzed to identify the presence of sustainability related design parameters during each stage of the process and to identify at what point designers take decisions about which design aspects. Since sustainability is a very broad concept, the current research project has been limited to energy use and indoor climate of buildings. This paper reports on the results of several case studies involving design projects by architectural practices in Flanders, Belgium. After presenting the methodology of the case studies, this paper describes the results, obtained from the crosscase analysis, followed by the suggested parameter ordering and a discussion. 2. Methodology 2.1 Motivation. The literature provides no clarity about when exactly designers take decisions about design parameters affecting the energy use and indoor climate of buildings. Morbitzer et al. (2003) discussed these parameters according to their occurrence in the design process. This work serves as a basis for the current research, but the resulting scheme is strictly divided in three blocks, each corresponding with a design phase, and only contains a limited number of parameters. Hence, the presence of these parameters in the architectural design process was studied in detail. Various research methods are available for the study of design processes. Overviews are given in Cross (2006) and Lawson (2004). The current research opted for the case study method, since this method allowed to study the design process in its real context and during its entire course, unlike the widely used protocol studies. The aim of the case studies was to map the different design parameters that have an impact on the energy use and indoor climate of buildings, according to their presence in each stage of the architectural design process, and to gain insight into the way architects design. 2.2 Approach to the Case Studies. To carry out the case studies, a framework was set up, based on literature review on the design process and on the Flemish version of the EPBD, i.e. the EPB (EPB Besluit Bijlage I 2005). According to the RIBA plan of work (Lawson 1983), the design process was divided in three design stages, namely the conceptual design phase, the preliminary design phase and the detailed design phase, to structure the cases, or rather to facilitate the comparison between the cases. The definition and detail of the various design stages may vary for different designers, but the basic idea remains the same, as Ellis et al. (2001) pointed out. The different design parameters, needed to determine the energy use and indoor climate of buildings were identified according to the EPB, which is based on the European norm: E ISO13790 (2004). The case study method is described in detail in Yin (2003 a, 2003b). In the context of the multiple case studies, several architects in Flanders were contacted. Out of these, nine architects and twelve projects in the residential sector were selected, among which both sustainable and conventional projects. Different information sources were used to clarify the way designers work and when designers take decisions regarding energy use and indoor climate. Each case study consisted of an analysis of all design documents, such as drawings, reports, photos, 3D images, s, etc. and a semistructured interview with the designer, to complement these documents. The present study consisted of retrospective analyses, in order that the designers were able to look back on the complete design process. Besides, since architectural projects are usually spread over relatively long periods of time, it is not possible to follow up projects in a realtime setting. The selection of the projects was based on the completeness of the design documents, which reflect the architectural design process. After collecting data, the analysis of the design documents was executed using the framework previously mentioned. Results of each case were summarized in a graphic scheme, giving an overview of the successive design parameters according to their presence in the different design stages. Subsequently, the designer of the project was interviewed and the scheme was checked by the designer. In the semistructured interviews, open questions were asked about the design process in general and the design process of the particular project. Based on the results of the interview, the scheme of the project was adapted, if necessary. Finally, in a crosscase analysis, the cases were compared for similarities and differences. Results of the crosscase analysis are presented in the next section. Finally, a decision, made by designers, can be divided into four issues: 1. what is the subject of the decision? (what), 2. when is the decision taken? (when), 3. on which basis is the decision taken? (why), and finally, 4. how is the decision taken? (how). As shown in figure 1, the former two were primarily derived from the document analysis, whereas the latter two were mainly determined by the interviews. While the separate design parameters, which influence energy use and indoor climate of buildings, could also be derived from the documents, the interviews only disclosed groups of parameters. Further, the documents revealed the way of drawing in the different design stages, whereas the interviews primarily focused on the way architects design.

3 Figure 1 Analysis of design decisions according to four issues. 3. Results 3.1 General Overview of the Projects An overview of the analyzed projects is given in table 1. Twelve residential projects of nine architects were analyzed. Two projects consisted of renovations, the other projects involved new buildings. Five projects were concerned with minimizing energy use, and thus with improving the energy performance of the project beyond the legal requirements. From these, the performances of two were imposed by local authorities and two by the project s client. Only one architectural practice, i.e. respondent number 6, is concerned with low energy architecture within its daily practice. From 2006 on, the Flemish government has translated the EPBD into regional legislation, i.e. the EPB. In this context, a maximum Elevel and a maximum Klevel are enforced by regional authorities. The Elevel stands for the level of primary energy use, calculated for standard climate conditions and standard occupants behaviour and takes into account the energy use for heating and cooling of spaces, domestic hot water, ventilation, auxiliary energy, and energy gains from solar energy systems. This primary energy use is compared to a reference use. The current legal requirement sets the maximum Elevel at E100, meaning that the calculated energy use may not exceed the reference value. The Klevel takes into account the mean Uvalue of the building envelope, and the compactness of the building (i.e. the ratio of heated volume and overall heat loss area). The maximum is set at K45, representing a U mean = 0,45 W/m²K, for a compactness of 1m. As an example, a passive house represents a K10 to K15 level and a E30 to E40 level, whereas a low energy house has an insulation level of around K35 and an energy performance level of E60 to E70. Research has pointed out that the economic optimum corresponds with E60 and K2535 (Verbeeck 2007). As a consequence, the current regulation is generally not strict. Table 1 Overview of the projects Respondent Project Type Energy Performance Imposed by Result 1 Max. E75 local authorities E56 K ot specified client E76 K31 E98 K43 4 Max. E75 local authorities E67 K31 Max. E60 client 5 K R R Max. E60 designer E100 K45 9 = new building R= renovation Since the final report of the E and Klevel has to be submitted six months after the commissioning of the building and some projects are still in construction, the resulting E and Klevel has not yet been determined for each project. 3.2 Subgroups According to Designing Method From the crosscase analysis, it appeared that according to the way of designing, the group of nine respondents can be divided into two subgroups. One group of respondents generally starts from a 2D plan organization, ordering the functions relative to each other, whereas, the other group usually starts from a 3D design of the building volume. Depending on the group designers belong to, they stress different aspects, as shown in figure 2. The first group, usually starting from a 2D organization, is primarily concerned about functional aspects, i.e. the program, whereas the first focus of the second group is the image of the building

4 in its surrounding context. However, this does not imply that architects from one group are not concerned with priorities found in the other group. In his study on strategic working styles of architects, Van Bakel (1995) also recognized that architects integrate different features in their decisionmaking process, but the relative importance of these features depends on personal preferences of the individual designer. Figure 2 Subdivision of respondents according to the way of designing From the five designers of the first group, two designers start from a 2D organization, but immediately check this organization in a 3D configuration. 3.3 Subgroups According to the Implementation of Energy Related Design Issues Apart from the designing method, the respondents can also be distinguished by the way they handle energy and sustainable related design issues. Two extreme situations were found, as shown in figure 3. On the one hand, some architects or architectural practices are primarily engaged in sustainable design in their daily practice, but are not concerned about the configuration or the image of the building (respondent 8). On the other hand, some architects or architectural practices are only concerned about the character of the building, but do not engage in sustainable design (respondent 6). Most of the architects cannot be strictly assigned to either group, but the results tend to reveal that still most designers emphasize the general outline of the building above energy related issues (i.e. the right part of the figure). Only one architect managed to fully integrate energy related issues and the architecture of the design (respondent 2). Figure 3 Subgroups according to the integration of energy related design issues The architects operating from energy efficiency take into account energy related measures, such as compactness, ventilation, thermal mass, orientation, materials, insulation etc. already at the beginning of the design process. They usually decide on experience and are able to estimate roughly the energy performance of the design. Whereas the others, who are not primarily concerned about energy, take into account mainly the orientation and the compactness of the building at the beginning of the design process, but less explicitly. The initiative to construct an energy efficient building is often taken by the client or a local authority. As a consequence, the architect takes the structural related decisions, i.e. about orientation, plan organization, glazing area, etc, whereas the client may ask for the extras, such as solar energy, or ventilation with heat recovery. They usually do not evaluate the insulation and energy performance level of the building, until after the final design, since the required input is too detailed and the calculation too timeconsuming. As a result, energy related issues are often more seen as addon components, which can be fixed in a later stage of the design. This means that components, such as insulation type and thickness, system components, etc. still may be changed in a later stage, even during the construction phase, to fulfill regulations or to improve the performance of the design. However, the architectural design, i.e. the plan organization and the general outline of the building, like volume, façades, etc. is fixed and does not change at that time. Or as one respondent mentioned the design is sacred. 3.4 The Presence of Sustainability Related Design Parameters in the Design Process The crosscase analysis shows that all nine architects use a topdown procedure when designing, or in other words, they start with a general concept of the building and work towards the details. Accordingly, the level of detail increases as the design proceeds. This is also reflected in the way of drawing and modeling, as shown in figure 4, and evolves from sketches and simple line drawings to detailed construction drawings on the one hand, and from elementary to elaborated 3D models on the other hand. The way of drawing in each design stage coincides with the different design parameters being relevant in each stage and with the decisions being taken.

5 Figure 4 The way of drawing/modeling in the architectural design process Figures 5 and 6 show the different sustainability related design parameters according to their presence in the design process. A distinction is made according to the designing method. The figures only show the different parameters being relevant or being decided on at a certain time in the design process, but do not point out when these parameters are fixed, since each design process is unique. Many parameters change during the design process, such as the volume, the floor area, and the plan organization, which are usually decided on early in the process. Most room for changes resides in these early design stages, considering the corresponding design objectives and scopes. In the schemes, the design process is represented as a linear process, running from general to detail. However, this is a considerable simplification of reality, since the design process is generally characterized as a dynamical, cyclical process with continuous feedback loops between the different design stages and between different decisions (Van der Voordt, et al. 2000), and the different design stages may also overlap in practice. evertheless, the chronological ordering of the parameters being relevant in subsequent design steps, remains the same for most design projects. Besides, architects design within a context and a framework of preconditions, such as site conditions, budget, etc. For instance, the client s budget defines in many cases the maximum floor area and building volume of the design. It was also observed that some architects generate a number of variants or alternative designs at the beginning of the process, whereas others usually start with one design and transform this in detail. From the crosscase analysis, it appeared that this does not affect the chronological ordering of the sustainability related design parameters. Figure 5 Design parameters in the architectural design process Group 1: 2D organization The first subgroup of architects, designing from a 2D organization, usually starts with a functional organization chart of the building. The maximum floor area is often defined on the client s budget. The construction type, i.e. heavy or light construction, is also usually decided on in a first step. A plan organization is established, based on the functional organization chart, in a second step. Windows or at least the position of large glazing areas are already drawn in the earliest floorplans. As a result, the building envelope is defined according to opaque and transparent construction elements and the orientation of the different functions or rooms is determined. The position and area of the windows in the façades is often not yet determined in this step. The slope of the roof, namely flat or inclined, is generally addressed early in the process. Further, an indication of the heated volume, the total loss area and the compactness of the building can be defined on the floor area and an average floor height. The next parameters taken into consideration are the area and position of the windows in the façades, the materials, the volume, the loss surface, the heated volume and the compactness. However, it is possible that in some projects the façade s materials are determined in an earlier or even in a later step. Finally, the last parameters taken into account are the wall, floor and roof composition, the materials (in detail) and the building systems.

6 The second subgroup of architects (figure 6) first addresses parameters such as building volume, the shape of the building, the heated volume, the total loss area, and the compactness, unlike the first subgroup. Another difference is that the second subgroup often bears in mind the façade s materials very early in the design process, since these have a significant impact on the configuration of the building. The orientation of the building volume, the roof slope (flat versus inclined) and the construction type are also very early defined. The plan organization is taken into consideration after the building volume. Usually, windows or at least the position of large glazing areas are already drawn in the earliest floorplans. As a consequence, the building envelope is defined according to opaque and transparent construction elements and the orientation of the different functions or rooms is determined. From the plan organization on, the ordering of the parameters follows the same path as the chronological parameter ordering of the first subgroup. Consequently, the next parameters taken into consideration are the area and the position of the windows in the façades. Finally, the last parameters taken into account are the wall, floor and roof composition, the materials (in detail), and the building systems. Figure 6 Design parameters in the architectural design process Group 2: 3D design The interviews revealed that the parameter materials shows up at least twice in the building design process, namely once to determine the façade s materials and once during the detailed design phase, when parameters such as for example wall composition are precisely defined. The orientation of the building is a very important parameter for architects and is mostly part of the initial concepts. The parameter glazing area is usually first addressed in the floorplans. The building façades are often not immediately taken into consideration when designing the plan organization of the building, but are often considered after a first plan organization or even after the final preliminary floorplans design. Only one of nine architects deals with floorplans and façades simultaneously, from the start, as shown in table 2. However, most architects have very soon an image of the building in their mind and thus of the positioning of large glazing areas according to the building s orientation. Table 2 Results for glazing area Façades and floorplans simultaneously Façades after first floorplan design Façades after final preliminary design R. 5 T. 1/9 R. 3 T. 3/9 R. 1 T. 5/9 R. 4 R. 2 R. 6 R. 7 R. 8 R. 9 R= respondent number T= total number of respondents Further, it must be noted that not all parameters that are needed to determine energy use and indoor climate of buildings are documented in the schemes above. It concerns parameters for which no general line could be drawn in the crosscase analysis, such as exact roof slope or presence of shadings. The impact these detailed parameters have on the energy use and indoor climate will be derived from a sensibility analysis in further research, in order to address the importance of these parameters. Finally, sustainability related design parameters that have an impact on the configuration of the design often are considered very early in the design process. For example, measures related to sun protection are addressed very early in case of overhangs, since these have an impact on the configuration of the building, whereas sun screens are usually not considered until detailed design stages when overheating problems come forth.

7 4. Discussion This study is based on twelve residential design projects of nine architects in Flanders. Therefore, the results reported here may not extend to populations in other regions and countries, or other types of projects. Besides, a respondent group of nine cannot be regarded as fully representative for the entire population. However, we do believe to be able to draw some conclusions. The data suggest that architects can be divided into two subgroups, according to the designing method. The first subgroup of architects generally starts from a 2D plan organization of the building, whereas the second subgroup generally starts from a 3D design of the building volume. The parameter analysis identified that different parameters are addressed by the subgroups in the earliest stages of the design. Design support tools should take this into consideration, since it implies that not only different input is required for the two subgroups, but the input style should also be different for the two subgroups in the earliest design stages. As a result, a link to an early design CAD tool could be meaningful for the second group, in case they use 3D modeling software in early design stages, while this CAD link would not be very suitable for the first group, since this group generally starts from a 2D organization of the building. On the contrary, this group requires tools with a simple way of manual input in the early design stage. Where is the design in sustainable design? (Hosey, 2007). The data implies that this cliché is still present in the building industry in Flanders. Based on the results of the crosscase analysis, a second division was made in the respondent group of architects, according to the way they handle energy related issues in design projects. Two extreme situations were identified, but most architects cannot be strictly assigned to either side. However, many architects often still think of sustainability as an addon component that only shows up in the specifications. Since the final report of the EPB only has to be submitted six months after the commissioning of the building, the danger exists that architects do not integrate energy related issues in their designs until then. Besides, the EPB performance is often only fulfilled to check compliance with regulations. While some architects claim that they do pay attention to energy related issues during their design process, the resulting EPB values show this is not always accurate. Only one architect, respondent 1, managed to fully integrate energy use and the architecture of the building, although the initiative was taken by the client. Ideally, sustainability related issues and the architecture of the design are simultaneously incorporated in the design. This study tends to reveal that there is still a long way to go and implies that not only the client or the architect should be aware of the importance of sustainable design, but they both should be. The results of the performed crosscase analysis further suggest that most architects use a topdown procedure when designing, meaning they first handle the general concept of the building before elaborating the details. This is in contrast with the current simulation process, since most simulation programs require detailed input parameters from the start. This contrast was already identified by Holm (1993). The present study showed this detailed input is seldom available in the early design stages. This is an important issue that should be addressed to integrate simulation into the building design process. The present paper gives a possible overview of the different parameters in a chronological ordering that should be subsequently taken into consideration by design support tools for sustainable architecture. The orientation functions in many cases as a starting point and is therefore a very important parameter to architects. The schemes show that architects usually first consider parameters that may have an impact on the general outline of the building, such as volume, surface, compactness and glazing area, before shifting their attention to detailed parameters such as system components, wall composition, glazing type, insulation type, etc. Hence, design support tools should first take into account general issues, such as the geometric configuration of the building, the compactness and the opaque and transparent parts of the building envelope, before moving up to detailed parameters. However, since energy conscious architects often may know which systems and which materials to use from experience, design tools must also support the option for them to include these parameters already earlier in the evaluation of the energy performance of the design. evertheless, the case study indicated that even then, the detailed parameters may change in later design stages. Therefore the schemes presented in this paper may well be a good basis to adjust new tools for the design process. It was further observed that glazing area is often not immediately worked out in the façades. Only a rough indication of the glazing area is known at the beginning of a design. This is an important finding, since it should make it possible to reduce the complexity of design support tools for the early design stages. Finally, the crosscase analysis demonstrated that it is not possible to strictly divide the design process in design stages. The stages highly overlap in practice and different issues may be addressed in different stages by different architects. evertheless, the chronological ordering of the parameters remains the same. Hence, design support tools should be capable of handling different design steps in a fluent manner. 5. Conclusion This paper reports on the results of several case studies involving architectural design projects by architects in Flanders. The research identified the different sustainability related design parameters being relevant to evaluate in a chronological ordering. Two different ways of designing can be observed in the architectural practices in Flanders. The parameter analysis identified that different parameters are addressed by these subgroups in the earliest stages of the design. Another subdivision can be made in the respondent group of architects, according to the way they handle energy related issues in design projects.

8 The orientation of the building often functions as a starting point and is therefore a very important parameter to architects. The schemes show that architects usually first consider parameters having an impact on the general outline of the building, such as volume, surface, compactness and glazing area, while design parameters such as system components and glazing type are not addressed until detailed design stages. Many architects often still think of sustainability as an addon component that only shows up in the specifications. Ideally, energy and comfort related design issues are integrally synthesized in the architectural design, at the same way architects deal with the synthesis of other design issues. However, this is not a simple task to perform, since it concerns complex and highly interwoven design aspects. Therefore, architects need information on the energy and indoor climate performance of the design, right from the beginning, because most room for changes resides in the early design stages. Further research is needed to determine whether detailed design parameters, such as climatic boundary conditions, roof slope etc. have a substantial impact on the energy use and indoor climate of buildings, since there is no general line to draw for those parameters. This will be studied using a sensibility analysis. References Cross, Designerly ways of knowing. London: Springer. De Wilde, P., G. Augenbroe, and M. Van Der Voorden. 1999, Invocation of building simulation tools in building design practice. Building Simulation 99.International IBPSA Conference, Kyoto1999. pp Ellis, M.W. and E.H. Mathews. 2001, A new simplified thermal design tool for architects. Building and Environment 36, (9) pp E ISO 13790: Thermal performance of buildings. Calculation of energy use for heating. EPB Besluit Bijlage I. 2005, Bepalingsmethode van het karakteristiek jaarlijks primair energieverbruik van woongebouwen. Geebelen, B. 2003, Daylight availability prediction in the early stages of the building design process. Ph.D. Thesis, K.U.Leuven, Leuven. Holm, D. 1993, Building thermal analyses: What the industry needs: the architect s perspective. Building and Environment 28, (4) pp Hosey, L. 2007, The good, the bad : Where is the design in sustainable design?. Architect Magazine, (Washington D.C.), 96 (4) pp. 43 Lawson, B How designers think. (2 ed.). The Architectural Press, London, UK. Lawson, B What designers know. Elsevier: Architectural Press, Oxford. Maassen, W., E. De Groot, and M. Hoenen. 2003, Early design support tool for building services design. Model development. Building Simulation th International IBPSA conference, Eindhoven, the etherlands. Mahdavi, A., S. Feurer, A. Redlein and G. Suter. 2003, An inquiry into the building performance simulation tools usage by architects in Austria. In Augenbroe and Hensen (eds.) Proceedings of building simulation th International IBPSA Conference, Eindhoven, The etherlands. pp Morbitzer, C., P. Strachan, J. Webster, B. Spires and D. Cafferty. 2001, Integration of building simulation into the design process of an architecture practice. In Proceedings of Building Simulation Seventh International IBPSA Conference. Rio De Janeiro. Brazil euckermans, H. 1992, A conceptual model for CAAD. Automation in Construction, 1. pp. 16 Pedrini, A., and S. Szokolay. 2005, The architects approach to the project of energy efficient office buildings in warm climate and the importance of design methods, In Proceedings of Building Simulation inth International IBPSA Conference. Montréal. Canada. Van Bakel, A.P.M., 1995, Styles of architectural designing: Empirical research on working styles and personality dispositions.ph.d Thesis, T.U.Eindhoven Van der Voordt, T. and H. Van Wegen. 2000, Architectuur en gebruikswaarde. Programmeren, ontwerpen en evalueren van gebouwen. Bussum: uitgeverij THOTH. Verbeeck, G Optimisation of extremely low energy residential buildings. Ph.D. Thesis, K.U.Leuven, Leuven. Yin, R.K. 2003a, Applications of case study research. (second ed.): Thousand Oaks: SAGE Yin, R.K. 2003b, Case study research. Design and methods. (third ed.): Thousand Oaks, CA. Sage. Zhu, Y., C. Xia, and B. Lin. 2007, Discussion on methodology of applying building thermal simulation in conceptual design. Building simulation 07, 10 th international IBPSA Conference, Beijing, China.