Learning from Parametric Manipulation of Architectural
Volume
3D modeling revealing thermal performance of buildings in architectural
curriculum and design
Jan Janusz
University of Technology and Life Sciences in Bydgoszcz, Poland jjanusz88@wp.pl
Abstract. This study is concerned with the building thermal performance education in the context of computer application. The project contains the original script coded in Maxscript for use in Autodesk 3ds Max. The tool workflow and functionality focus on the thermal calculations connected with sculpturing manipulation of architectural volume in pre-conception project stages, when detailed project solutions are undefined. The algorithm is based on the manual methods included in the curriculum. The paper also presents a study of software analyzing thermal performance as a justification for the script vision and educational implementation. The script is rather an addition than alternative for existing software, so it does not assume any resignation from more sophisticated products.
Keywords. Parametric design; thermal optimization; sustainable design education; Maxscript; energy estimation.
INTRODUCTION – GENERAL INFORMATION
The problem of sustainable development manifest-ed within objects of architecture requires, among other issues, constant awareness of building ther-mal performance. The one of the most basic topics concerns thermal insulation of the building compo-nents (Krygiel and Nies, 2008). The contemporary requirements create the necessity for adaptation of architectural education model to contemporary requirements. Universities ought to put much em-phasis on development of their students’ creativ-ity and therefore the application of new tools and software is expected, in order to show that aesthetic and technical decisions are constantly connected
with economical and ecological topics. Despite the wide development of various software, it is still dif-ficult to find the one which fulfills the need for get-ting experience on heat transfer through building components. The application which could present a connection between volumetric changes or ma-terial decisions and the object’s energy status in a comprehensible way. This article presents the origi-nal script aimed at dynamic estimation of thermal losses, based on 3D model. It is programed in Max-script and works with Autodesk 3ds Max. It was cre-ated for educational purposes and implemented at University of Technology and Life Sciences in
Bydgo-szcz [UTP] thus its application comes down to fast verification of thermal parameter changes being the result of manipulation of geometry and material in buildings. It can also be used to create a record of energy requirement changes connected with some defined parameters changes (e.g. correlation between windows area and interior temperature, reasonableness of winter gardens etc.). The article shows general profits connected with computer ap-plications which automatize measurements and di-agnoses in 3D environment.
GENERAL ISSUES
The development of the final application form re-quired solving many problematic issues and taking decisions related both to the functionality, workflow and the vision of educational implementation. It is reflected in the paper structure, which starts from the analysis of the key issues in a broad context, des-ignation of certain problem and then description of the final project decisions. The article includes also the description of the script functionality, didactic implementation and the developmental perspec-tives. The study of software analyzing thermal per-formance occupies a prominent place, among the elaborated topics. These analyses give the substan-tiation for a choice of a particular development en-vironment for the application. Another point is the selection of the calculation algorithm. Many meth-ods and approaches were considered. The basic as-sumption implied that the choice of the methods of computation shall be closely linked with the cur-riculum of classes conducted at University of Tech-nology and Life Sciences in Bydgoszcz. Therefore the main concern was focused on estimation methods described in standard Energy performance of build-ings – Calculation of energy use for space heating and cooling PN-EN ISO 13970:2008. The main guideline was the transparent representation of the methods of calculation of heat loss along with leaving an overall picture for others programs used during the classes. Finally, the article shows the mechanism of the script application in the design and education processes. Besides the elementary description of the
script, the paper also contains the future perspec-tives of the application’s development.
CASE STUDY - SOFTWARE ANALYZING
THERMAL PERFORMANCE
The structure and systematics of the programs are described by Maile et al. (2007). They maintain that programs consist of a computational engine and in-terface for data input and results output. There are many computational engines including BLAST and DOE-2, but their results are not always identical with the estimation methods included in standard (PN-EN ISO 13970:2008). Although the software market is very developed, the majority of products is cre-ated for commercial purposes. U.S. Department of energy provides the online directory of 396 building software tools for evaluating energy efficiency, renew-able energy, and sustainability in buildings [1]. The information and a review of the market show the division between two different kinds of software. The first group consists of independent analyzing programs. They work on imported or native 3D or 2D vector graphics and many of them allow to cre-ate full documentation. They allow to conduct the physical simulation of the process of heat propaga-tion. A wide range of products includes programs dedicated for a physical model testing and applica-tion destined for architectural design purposes. The examples of these two software groups exploited at UTP are AnTherm and Trisco for laboratory use by the expert thermal researcher and Audytor OZC 3D for building status analysis. Strzeszewski (2008) describes that Audytor OZC 3D is based on the lo-cal standard (PN-EN ISO 13970:2008) and allows for comparison of different computation methods. The main disadvantages of these programs are: the ne-cessity for adaptation to a new interface and work primarily in the final stage of the design (Moon et al., 2011). The second group includes a wide variety of applications connected with Building Information Model technology. The majority of them considers Archicad and Revit Architecture as source BIM ap-plications. The mechanism of this connection was described by Moon et al. (2011). By its very structure,
this technology possesses the advantage over the classical methods based on CAD drawings, because it is based on components of the building which cre-ate the parametric digital structure of information about the architectural object (Azhar et al., 2010). The huge number of research dedicated to these programs proves that their impact on design proce-dure is significant. A comparative analysis presented in paper made by Azhar et al. (2008) shows that the implementation of these tools can improve the op-timization of buildings, but it focuses also on their weak points. The disadvantages highlighted in their article are: difficult interface and lack of insight into the process of calculation among listed programs such as Autodesk Ecotect, Autodesk Green Building Studio and Integrated Environmental Solutions. The automation of the calculation process and the input of the default parameter values have the advantage in terms of commercial use, so the BIM applica-tions collect indirectly information about building components and automatically interpret them as mathematical data with default parameters (Pau-wels et al., 2008). Nevertheless, such automation for educational purposes is inadvisable. For didactic practice much better solution is to go through the
process step by step (Hensen and Radošević, 2004). It is also worth noting that many professionals treat BIM-based program with mistrust and antipathy. Ibrahim (2006) claims that it is connected with false stereotypes and long process of adaptation, how-ever he admires that many architects and architec-tural teachers still choose other software. The work of Attia et al. (2009) describes the statistical survey on thermal analyzing software conducted among 249 architects from the United States. Its goal was to identify the most demanded features and to evalu-ate 10 selected programs in the context of these fea-tures. More than a half of the respondents were LEED accredited professionals. Among the most popular programs were the following ECOTECT, eQUEST, En-ergy PLUS as a SketchUp plugin. The significant in-terest in the plugin connected with Google Sketch-Up shows the large interest in diagnostic program cooperating with open 3D modeling environment like Autodesk 3ds Max, Maya or Blender. The major-ity of the surveyed declared that the most impor-tant criterion for support of the design process is providing a quick energy analyses that support the decision making process. This overview gives a jus-tification for the project and provides a guideline for decisions connected with the script idea.
SCRIPT IDEA – EDUCATIONAL PURPOSE
The curriculum of sustained design for architects at UTP is based on the standard mentioned in the introduction (PN-EN ISO 13970:2008). Providing an application founded on exact copies of the meth-ods included in the standard would be an invalu-able assistance in education process. The benefits would include: good assimilation of local standards and requirements and transparent illustration of procedure in the open script. The simplicity and im-mediacy of usage would allow to gain experience on heat transfer mechanism quickly. In contrast to commercial software the script shall calculate at first interim results and then lead the user step by step to the overall result (Figure 1). It would show relation-ships and build an awareness of the building’s phys-ics. Moreover, the excessive automation, default pa-Figure 1
The comparison of commer-cial and educational software model.
rameters and internal libraries are not advisable for aware participation in the procedure. At this stage, it should be stressed that the educational usage of the script does not assume abandonment of the ap-plication of other programs such as Ecotect, eQUEST and Energy PLUS in the curriculum. These programs allow to conduct a holistic analysis. In contradiction to them, the presented script focuses only on the heat loss aspect. Naturally, the other estimations can be added to open script, but even so, they would be put separately. The intense concentration on a sin-gle feature allows to obtain a clear illustration of the individual basic relationships for educational and statistical purpose.
This solution illustrates the fundamental chang-es associated with the manipulation of the body of the building, at the stage of pre-conception and conceptualization. The adaptation for early project stages induces to choose an open modeling en-vironment. The software which allows fast global changes of form and materials. The approach prac-ticed at UTP leaves the decision on the selection of software in the hands of the student. The experi-ence with students leads me to a conclusion that the majority of them works on 3D studio which is quite typical for the environment of Polish architects. A quick survey has shown that more than 90 percent of students regarded it to be the best 3D modeling tool. All things considered, the aim was therefore to create an application that could dynamically explore the thermal insulation of the building, simultane-ously allowing the sculptural approach to undefined object and leading through the overall procedure step by step.
COMPUTATIONAL METHOD AND THE
PROGRAM CODE
The main document for thermal estimation is PN-EN ISO 13970:2008. It contains various calculation methods describing overall thermal performance. While simpler methods are predestined for manual calculation, the more detailed simulation methods are used in computer programs. Also complex algo-rithms such as DOE-2, SUNCODE, BLAST were
deve-loped for software analyzing thermal performance. The results of various calculation methods differ, to some extent, from each other in terms of accuracy. Their application is defined by building purpose and local requirements. Various methods require different data input, so it is important to define the balance between accuracy and data input time de-pending on purpose and project stage. In the sim-plest terms, the thermal performance consists of heat gains and losses in the context of the building exploitation. The thermal losses are transmission through building components and ventilation heat transfer. The structure of heat gains is far more com-plicated. One of the most important ingredients are internal gains including people temperature, appli-ances, lightning, hot water etc. There are also solar gains and heating systems. The full picture requires also information about storage of heat in the mass of the building and other features like energy con-sumed by heating systems. Each section of listed above, has a separate calculation procedure de-scribed in standards. These factors can be divided due to the sources of data needed for their calcu-lation. Figure 2 describes the correlation between sources of input particulars, the input method and the basic division of thermal gains and losses calcu-lation procedure.
This correlation indicates that manipulation of 3D model affects directly on thermal losses, storage of heat in the mass of the building and solar gains. Other factors are connected with the building use, equipment and technology. While the estimation of thermal losses is based on easy to defined factors like U-value, solar gains requires definition of neigh-borhood and local environment. The educational function of the script assumes implementation of the script on the early project stages with unde-fined design solutions. With undeunde-fined function and building system, the comparison goal is reduced to a query about choosing which architectural form has lesser heat losses and more solar gains. At this moment the script is focused on these two factors, although solar radiation influence is estimated with low precision. It requires more information and has
lesser impact, so the paper gives it less attention. The interface allows a switch between two methods included in the international standard (PN-EN ISO 13970:2008) simple hourly method and seasonal or monthly method (Figure 3 and 4).
Both methods have the similar pattern for trans-mission and ventilation heat transfer estimation, but they differ in calculation of total heat transfer. In Po-land transmission heat transfer bases on mathemati-cal model specified in Thermal performance of build-ings – Transmission heat loss coefficient – Calculation method (PN-EN-ISO 13789:2008).
The transmission heat transfer coefficient (be-tween the internal space and the external air) (PN-EN-ISO 13789:2008) is calculated as:
HD = ∑i AiUi + ∑k lk ψk + ∑jχj (1) where
• Ai is the area of element i of the building enve-lope, in m2
• Ui is the thermal transmittance of element i of the building envelope (W/m2K)
• lk is the length of linear thermal bridge k in me-ters
• ψk is the linear thermal transmittance of ther-mal bridge k, (…)
• χj is the point thermal transmittance j
The script uses object quantitative parameters and information about thermal transmittance (U-value) for calculation. At this moment this param-eter must be set manually by the user. The meas-urements taken automatically from the model are: materials area, length of thermal bridges and heated volume. The last factor could be measured only if mesh was created without any gaps. Furthermore, Figure 2
Data requirements for basic calculation procedures.
it is not required for the thermal transmittance of building components calculation. It is only statistical parameter, used for calculation of ventilation trans-mittance calculated due to PN-EN-ISO 13789:2008. It also allows to calculate complicated mesh, which is almost impossible with manual method. Thermal bridges shall be defined according to the instruction described in the standard. Dylla and Pawloski (2007) subjected this method to critical analysis and
pro-posed an alternative. The Script is based on open code, so it can be adapted to the method described by Dylla and Pawloski (2007). The computational algorithm calculates transmission heat transfer co-efficient through the unheated area and through the ground according to ISO 13379 (PN-EN-ISO 13789:2008). The script is written in Maxscript. While many diverse three-dimensional modeling software platforms could be used, for example Blender or
Figure 3
The comparison of simple hourly method and seasonal or monthly method.
Figure 4
Input panel for simple hourly method and seasonal or monthly method.
Autodesk Maya, herein the selected software envi-ronment for the script is Autodesk 3ds Max. If suc-cessful, the code would be translated to MEL and PYTHON. The interface and computation method can be easily adapted to a specific educational task. The open character of the code allows constant de-velopment.
USE AND WORKFLOW OF APPLICATION
The elementary knowledge of the 3ds Max is re-quired for effective use of the script. The designation of certain material can be made by selection of ap-propriate area and assigning a particular ID number to it (Figure 5).
This process is analogical to texturing for visuali-zation. Each ID number is assigned to certain mate-rial with U-value. Thermal bridges can be marked by extrusion of selected edge by the value of 1 and as-signing a created rectangle to specified ID number. It is recommended to give an intense color to ther-mal bridges for better organization. The script cal-culates the surface and adjusts it to the parameter of U-value (Figure 5), which may be obtained from the manufacturer. This procedure is not difficult, but for correct realization it requires the knowledge about
method of constructing a model for calculation in-cluded in standard PN-EN ISO 13789:2008. The data should be entered in accordance with Figure 6.
The reliability of the subsequent calculations depends on the accuracy of this phase. The proce-dure of manual data input teaches exactly how the heat losses through the buildings components are shaped. It builds awareness of the role of particular material. For clarity of the calculation, the individual materials can have textures visible in the preview as in the example (Figure 3). It is also helpful to indicate with a separate color, the part of the building which is not involved in the calculations. The interface has a working character and can be easily adapted for any number of materials and any additional func-tions. The selection of appropriate area and entering all the data takes just a few minutes. The next step is the automatic calculation of the area started by using the proper button. The estimation of the to-tal heat transfer by ventilation requires information about ventilation type, rooms destination and man-ual input of airflow rates. The estimation takes place after selecting the method of calculation and input of all required data like environment type or locali-zation (Figure 5). The calculations are immediate. At Figure 5
The method of data input - the workflow of the script.
this stage, the basic function of the application can be noted. The script allows a dynamic comparison of the thermal losses due to manipulation of the ge-ometry or materials. The panel shows a visual list of the calculations (Figure 7), which allows to compare and track all changes. This tool helps to realize the impact of certain actions on the building thermal performance.
APPLICATION GOAL – EDUCATIONAL
IMPLICATION
The University of Technology and Life Sciences in Bydgoszcz set an objective for developing students’ sensitivity to the environmental and economical as-pects of sustainable architectural design. All projects are developed according to the technical and nor-mative directives. The problem of thermal efficiency was considered as immensely important, therefore separated ”Low-Energy Building Design” classes were carried out. Didactic objectives were focused on learning physical mechanisms, assimilating lo-cal standards and development of awareness on the impact of each factor on the energy balance, in all phases of the project. Within the framework of these tasks, students were encouraged to implement the
relevant applications in their projects. During the classes some relevant applications such as Ecotect and Green Building Studio were described. Students were also encouraged to implement analyzing tools during their projects. However, the procedure of the manual calculation methods is considered to be very important in the educational process. The original script provides with assistance with its de-scription step by step. Its main goal is to automatize the calculation of marked building components. The didactic implementation of the script starts with its introduction, given to students, in the form of pres-entation. An instant calculation shows students in what way the thermal status depends on a certain project modification in materials and geometry. Also the thermal performance of many significant cases is shown during this presentation. In the fol-lowing step, students learn the script with assistance of teachers. They have an opportunity to make some experiments with many building cases. Next, they have two months to prepare their semester project for ”Low-Energy Building Design” classes. During the project, each progress should be verified with soft-ware or manual methods included in the standard. The script can provide with help this procedure.
Figure 6
The method of construct-ing a model for calculation included in standard (PN-EN ISO 13789:2008, p. 7).
CONCLUSION AND DEVELOPMENT
PER-SPECTIVES
At the moment, the script is completed and it is prepared to fulfill its educational function. Its full version was shown and given to students. The re-sults of work and opinions of the users are used for project development. It is a beginning for a bigger project and if current work turns out to be success-ful, it will be improved. The plans for future include: generation of project documentation with required illustrations, the addition of more accurate calcu-lation method, internal libraries of materials and finally, overall thermal performance calculation. Under this assumption the application would serve for both educational and professional purposes. The main idea of the article gives a base also for other software. The same methodology could also be used for quick estimation of other building parameters. For example, it could help with making building cost calculation. It would measure area and volume of certain materials and multiply it by its price. The
plurality of possibilities for subject development show how important and useful computer skills in architecture are. The paper also shows also that development of computer aids for educational pur-pose require transparency and defined functional model. It presents also the 3D modeling tools as a good environment for quick comparison and get-ting experience with thermal performance. Once again the paper emphasizes the demand for using analyzing software, because economical and ecol-ogy requirements force to have control over build-ing thermal performance durbuild-ing every and overall design process.
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Figure 7
The list of the calculations comparison of the thermal losses due to manipulation of the geometry or materials.
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