Energy and Thermal Performance Management Through Utilisation of Building Information Models

Transcription

1 Energy and Thermal Performance Management Through Utilisation of Building Information Models Tuomas Laine Vice President for Innovation and Technology Olof Granlund Oy Helsinki Finland Antti Karola, Olof Granlund Oy, Helsinki, Finland, Prof. Gerhard Zweifel, Lucerne University of Applied Sciences and Arts, Technology & Architecture, Switzerland, Summary The use of building information modelling (BIM) during the design and construction process has grown quickly. Benefiting of BIM allows also possibilities to include more energy and thermal analysis by dynamic simulation methods in the building process to support design of sustainable and energy efficient buildings with healthy and comfortable indoor conditions. The main barrier for wider usage of dynamic analysis methods has been the required big manual input work, where BIM utilisation has the potential to cut down required input work to a minimum. Especially important is to introduce energy and thermal performance analysis to the early phases of design, where the most important decisions are made. To raise the level of BIM utilisation in energy and thermal performance management requires also export of the main analysis results to support requirements management process. This paper describes the utilisation of BIM in energy and thermal performance analysis and in thermal requirements management by using open IFC standard. The process and information requirements for energy and thermal analysis are discussed and recent standardisation actions to improve data transfer from architectural BIM into energy analysis by so called space boundaries are presented. Case examples are included to show new software implementations to support thermal requirements management process and energy analysis with models of different maturity levels. Keywords: building information modelling, BIM, IFC, BuildingSMART, energy analysis, thermal analysis, requirements management 1. Introduction As buildings are recognised as an important contributor to the consumption of non renewable energy resources and to the associated environmental impact, especially in terms of greenhouse gas emissions, the requirements to their thermal performance are increasing. Standards and regulations are getting more restrictive and are increasingly aimed at an overall energy demand approach rather than focusing on single aspects. This leads to an increased demand for the thermal analysis of buildings in the design process. Primary energy consumption and/or greenhouse gas emissions due to the operation of buildings can only be quantified by a holistic consideration of the building and its HVAC systems, typically by a dynamic simulation. Of special importance is to integrate at least the first steps of this analysis into an early stage of the design process. At this phase, which represents only a minimal fraction of a building s lifecycle cost, 70% of the total lifecycle cost is determined. Furthermore, this is a phase where decision-making is

2 flexible and where alternative ideas can be visualized and tested at low cost. The main obstacle for a more extensive use of thermal analysis of buildings has for a long time been the high amount of required input data, especially data which are present in other design documents needed for other purposes, leading to an increased amount of manual work and multiplication of input into different tools. The development of building information models (BIM), based on open standards as Industry Foundation Classes (IFC) [1]or gbxml [2] has opened new possibilities in this respect and helps solving this problem to a certain extent. CAD programs as well as simulation tools have IFC interfaces, enabling digital data exchange between them. Olof Granlund Oy has been a competent developer in this area, and its RIUSKA simulation tool [3] has been in operation since 1996, using imported IFC data since This paper describes some of the recent research and development work. 2. BIM in the Early Design Stage 2.1 Problem Analysis In the frame of the European research project InPro [4], the use of BIM in the early design stage is analysed and solutions for its improvement developed. InPro s main output is the InPro Open Information Environment, an advanced system that supports and integrates different aspects of early design: - Open and flexible collaboration between all stakeholders of the building value chain, - Design from a lifecycle perspective, based on 3-dimensional Building Information Models, - Decision support to make informed choices based on knowledge of each decision s consequences on the building lifecycle, - Early planning of build and operation processes based on computer enabled simulation of smart digital prototypes. Several key processes for the early design stage have been identified in the InPro project, building thermal analysis being one of them. The analysis of the current stage of this process showed several gaps to be filled by the projects developments. Fig. 1 shows a simplified description of this process and its information exchange requirements. The gap analysis was made based on the energy analysis process in fig. 1. The dashed line shows identified problems in data exchange and the red box, where BIM based data exchange was completely missing. The main tasks and information exchange needs with other disciplines in energy analysis utilise IFC, proprietary BIM-formats and traditional documents. The main gaps in the energy analysis process are related to the tasks Obtain building and space data and Analyze comfort and energy, where the exporting of the energy Fig. 1 Simplified description of the thermal analysis process and its information exchange requirements consumption results from energy analysis software is missing. Additional to this there are software tool specific gaps. The gaps found can be summarised as follows: - Poor quality import of architectural IFC BIM o Missing or erroneous data from architectural export such as space boundaries o Poor support for very early phase architect models without openings/windows/doors - Missing export of energy results o Incomplete export possibilities to IFC o No partial model interfaces to BIM servers - Incomplete BIM based transfer of spatial requirements o Missing data of utilisation (loads, schedules)

3 2.2 Spatial Requirement Data Exchange To start with the last point of the above list: spatial requirements are an important part of the building thermal analysis input. For a calculation in time steps of an hour or below, the values for the following data are needed with their time dependent resolution, i.e. in form of schedules and/or maybe control schemes: - Required indoor climate and environment parameters like temperatures, humidities, air velocities, indoor air contamination concentrations, illumination level etc. - For heating and cooling operation, maxima/minima values not to be exceeded, control setpoints etc. - Assumed utilisation of the different space types, including occupation density and presence, use and electrical power or heat release of the lighting, ditto for the equipment This information is not only of importance for the thermal analysis. In fact, it is together with the required areas of the different space types for the intended use essential information for any building project in the beginning. It forms, in a document like the space program, the starting point of a project. Therefore it is a piece of information which should be agreed on and documented in a design process. Many expensive lawsuits and expertise contracts could have been avoided if this had been done properly. As an example, among the authors there are experiences with bank office buildings with overheating problems, not having enough cooling power to extract the internal heat gains from office equipment. In the frame of the expertise work it was detected that the design had been made under certain assumptions (made by the HVAC designer) in respect of occurring loads, which were neither officially agreed upon, nor were they communicated to the later user of the building. The real later use of the building exceeded the assumptions and caused the problem. This should illustrate that the utilisation information consists of more than just the space type and is an essential part of the contract. However, many customers are usually not aware of the required level of detail of the information, nor do they have the knowledge of the respective values. Even specialists like the HVAC designers often do not have the respective knowledge of the entire information. Space type libraries are therefore a valuable resource for this. A recent publication of standardised data in Switzerland [5], was a big success and is widely used in the building design. In fact, its use is planned to be extended in areas which it was not intended in the beginning. However, this may depend on the culture and in other countries treated as company knowledge. Exceptionally professional customers like Senate Properties in Finland may have their own libraries. Some of the information may be derived data rather than the basic requirements. E.g. minimum ventilation flow rates per floor area may be used, providing the necessary indoor air quality, rather than the contamination concentration values. The provenances of many of the data are standards and/or regulations. The integration of this information in the BIM based design process, as found as a gap in the InPro project, has been resolved in Granlund s software suite according to fig. 2. Fig. 2 Spatial requirements management in Granlund s software suite

4 Fig. 3 Space type library in ROOMEX The process is controlled by the project management program. The architectural BIM in IFC format is read, maybe cleaned (see below) and then opened by the space type allocation tool ROOMEX. This software shows a floor by floor space layout from the IFC file and allows the user to access space type libraries (internal or external, e.g. from customer specified libraries, see fig. 3) and to allocate the appropriate space types to the selected spaces. This process can principally occur automatically, provided the space names in the IFC files comply with those in the libraries agreed to be used in the project. The same software also allows the generation of HVAC groups and the allocation of the spaces to these. Fig. 4 IFC import and data completion in RIUSKA The information is then read by the thermal analysis software RIUSKA, and the data missing for the thermal analysis are added (see fig. 4). These are: - Definition of thermal properties of all building structures and mapping that to the imported structural type definitions - External shading devices or structures - Occupant schedules and schedules for lighting and equipment loads - Infiltration rate - Air conditioning systems and operating schedules

5 In respect of the first point it can be argued that construction information, with layers and their allocated materials (and maybe even the thermo-physical properties of the materials) can be contained in the IFC format and could be imported to the thermal analysis software. From the point of view of the energy analyst and the simulation software vendor this may be desired as a further resource of automation and rationalisation. Accordingly, some programs allow for the import of this information from IFC. Also, the information can be seen as a valuable resource for other design tasks like cost calculation and ecological balancing for life cycle analysis, based on the quantity take off process. However, an approach based on construction types, characterized by their name, with links to separate libraries can be considered the better choice for the following reasons: - The respective information is subject of the optimisation process and therefore not clearly defined at the stage of the data import. - Constructions are supplier company dependent and different libraries can be allocated, which can be online sources and updated by the supplier. - Constructions involve more information than layers of materials to be taken into account for both cost and eco balance calculations. As stated above, the occupancy, lighting and equipment information in libraries could in future be enriched by Fig. 5 Visualisation of comparison between simulated and target values in ROOMEX 2.3 Energy Analysis Result Mapping their schedules, which is not the case at the current stage. The results from the thermal analysis can be exported again to the IFC file and read by the ROOMEX program, which allows for a visual comparison with target values (fig. 5). Also, the required HVAC room based equipment power demand and air flow rates can further be read by the system design software and used for the design of the system. However, this is only true for design values, but not for energy results at the current stage. This refers to the second gap reported by InPro. Future extensions were defined to include the results according to table 1 in the IFC-file. Table 1 Energy result data required to be exported to IFC according to InPro Attribute Name Time period Heating energy Cooling energy Lighting energy Equipment energy Other energy Total energy Explanation The unit period of time in which energy consumption is measured (per month, per year, etc.) The amount of energy consumed for heating purposes during the time period specified The amount of energy consumed for cooling purposes during the time period specified The amount of energy consumed for lighting purposes during the time period specified The amount of energy consumed for equipment (plug load) purposes during the time period specified The amount of energy consumed for other (other than heating, cooling, lighting and equipment) purposes during the time period specified The total amount of energy consumed for all purposes during the time period specified

6 2.4 Space Boundaries In respect of the first mentioned gap, the main problem that had been identified in IFC-based data exchange was missing or differently implemented space boundaries. Space boundaries (SB) are a concept for providing a logical connection between spaces and the building elements (e.g.walls and slabs) that enclose a space (see fig. 6, left side). SB also provide the geometry associated with the boundary independent from the geometry of the bounding element. They are a property of the space. SB are needed to support different tasks, such as energy calculation, lighting calculation, indoor navigation, quantity take off, facility management. These different tasks require different kinds of space boundaries, but all should be derived from the same principles. More granular kinds are derived from more general kinds. A kind of space boundary is also referred to as level. In the frame of the InPro project and in cooperation with the buildingsmart groups concerned, guidelines for space boundaries were created to Fig. 6 Visualisation of 1 st and 2 nd ensure that space boundaries are level SB (left) and of differences between 2 nd defined in a way as simple, clear and level SB depending on connected redundant free as possible. The following principles were defined: element - There should be only two levels of space boundary implementations: o Space surfaces boundaries, also referred to by 1 st level o Thermal space boundaries, also referred to by 2 nd level - Each IFC exchange file can only contain boundaries of one single level, either 1 st or 2 nd. A combination of the two is not allowed, and the level used is indicated in the IFC file header. The differences between SB levels are influenced by their reaction on what is on the other side: for 1 st level SB there is no influence from this, whereas for 2 nd level SB there is (fig. 6, left side). Within the 2 nd level there is a differentiation depending on the kind of element which is on the other side: in case 2a) there is a space behind, in case 2b) there is no space behind, but a physical element (fig. 6 right side). Openings (including doors and windows) have SB. They do not generate holes or inner loops in the SB of the walls or slabs in which they are contained. This is equally valid for 1 st and 2 nd level SB. SB shall completely border any space, leading always to an air tight, completely enclosed space. The surface orientation shall always be correct, its normal pointing outward of the space (into the material). A prototype implementation of the new guideline was done in the BSProLib tool, which is used as a middleware tool for IFC interfacing for different tools in the building industry, including energy analysis software RIUSKA. To produce a real project scale test model, MagiCAD Room software by Progman Oy with the prototype BSProLib client interface was used. The demonstration and testing proved that a prototype implementation based on the rules in the developed implementation guidelines for the 1 st level SB is working as required. The real advantage of the 1 st level space boundaries is reached when architectural CAD software vendors make the implementation according to the developed guidelines. 3. Testing and Certification 3.1 BuildingSMART Several years ago, IAI/buildingSMART introduced a certification procedure which had the goal to check and certify, whether a specific software developer is able to implement the support of IFC in

7 his application on a relatively high level of quality. A deeper investigation of this procedure [6] showed that its focus is rather on checking the ability, than on checking the achieved level of quality in detail. Based on this, a proposal for a new certification procedure was developed, which is now in the process of implementation and will be in place in the course of the year 2010 [7]. 3.2 AECOO-1 Testbed The AECOO-1 Testbed was jointly led by the buildingsmart alliance (bsa) and The Open Geospatial Consortium, Inc. (OGC ). The Testbed was conducted using the OGC Interoperability Program Policy and Procedures for a Testbed initiative. Two demonstrations were completed which comprised a number of different energy and building performance components of the test building, the results of energy analysis using EnergyPlus and the effect those changes had on quantity of building materials and cost. The demonstrations used a number of different software vendor products that interchanged IFC information using existing commercial off-the-shelf software to perform the necessary calculations and results. The first demonstration was held in Washington at the National Building Museum in March of The second demonstration was via a webinar in May of Nordic Energy Public building owners Finnish Senate Properties and Norwegian Statsbygg have started a common project IFC implementation and testing project for energy analysis applications used in the Nordic countries for implementation and testing of IFC import to energy analysis tools [9]. The purpose of importing IFC data into energy analysis applications is reaching a higher level of automation, which will result in less manual work and a lower risk of human mistakes. Therefore, the factors having the biggest influence on automation are the focus of the project. Testing will be based on one or several Nordic test models. The purpose of the testing is to verify the ability to use IFC data as one input data for the analysis; the analysis results are not tested. The procedure is open to all energy analysis application vendors selling in the Nordic countries. The test results will be published by Senate Properties and Statsbygg, and the participating vendors are free to use them in their marketing. The schedule envisages implementation and testing to occur in Applications used for the test phase are RIUSKA [3] and IDA-ICE [10]. 4. Future Developments Towards Support of Sustainable Building The future Finnish building regulation will have overall primary energy requirements [11]. This will naturally include the quality of the HVAC systems with their seasonal efficiencies as well as the national primary energy factors. As a consequence, more detail will have to be added to the calculations of the HVAC systems, especially the heat and cold generation and distribution part. Consultants may want to show the trade-offs between measures at the building and those in the HVAC domain, and alternatives in heat and cold generation. Recent investigations in Switzerland [12] have shown, that with contemporary insulation and heat and cold generation efficiencies in combination with the application of primary energy factors, the electric energy use for lighting will be the dominant part for office buildings. An example calculation MONTHLY PRIMARY ENERGY CONSUMPTION MWh Lighting electricity Equipment electricity HVAC, cooling electr HVAC, other electr Heating Fig. 7 Primary energy consumption results for the example was done with RIUSKA on a part of an office building, for the climate of Helsinki. Building components were defined according to the current Finnish regulations, and the space usage data were taken from the software s default values. Even the unweighted energy consumption results for this example show that the lighting energy is the biggest part over the whole year. The picture gets much more evident when primary energy factors (2.5 for electricity, 0.5 for heat) are applied, like in fig. 7.

8 In the current version of RIUSKA, the capabilities for daylight dependent control of lighting of the underlying DOE-2 simulation program are not used. This control could be considered by hand corrected lighting schedules. The possible reduction due to such a control was shown in a simple way by on/off switching of all light above an illumination target value of 500 lux, which was applied by expert user intervention directly in the DOE-2 program. The previously dominant lighting energy consumption is reduced by about 2/3, which shows the necessity of the consideration of such controls in future program versions. 5. Conclusions Advanced design methods like dynamic energy analysis are becoming more and more important to support the design of sustainable buildings. The use of BIM integration in the design process supports this by providing more automation, avoiding big manual input work and the related source of mistakes. Recent R&D activities have lead to solutions filling the gaps identified for the use of BIM in the early design phase. The spatial requirements information management, the use of space boundaries and the energy analysis report mapping are areas where improvements are made. Testing and certification schemes have been applied and further developed and will be extended to Nordic countries. Future developments will have to consider new aspects in HVAC systems and lighting control in order to enable overall energy optimisations. 6. Acknowledgements This research relates partly to InPro, an integrated project within the 6 th EU Framework Program for Research and Development ( Co-author Gerhard Zweifel would like to thank Olof Granlund Oy for hosting him during his sabbatical, for giving him insight in the BIM activities and the opportunity to provide his contribution to this paper. 7. References [1] [2] [3] RIUSKA: [4] BERGLUND Brigitta: InPro A brief overview, August 2009, [5] SIA Merkblatt 2024: Standard-Nutzungsbedingungen für die Energie- und Gebäudetechnik, Swiss association of engineers and architects (SIA), Zürich, 2006 [6] KIVINIEMI, A.: IFC Certification Process and Data Exchange Problems in ECPPM 2008 Conference "ebusiness and ework in AEC" (Sophia Antipolis September 2008). Published in the conference proceedings ISBN , pp [7] buildingsmart: Standard Process for a Future Certification, 2009, [8] HECHT Louis, Jr., SIN Raj (ed.): Summary of the Architecture, Engineering, Construction, Owner Operator Phase 1 (AECOO-1) Joint Testbed, buildingsmart alliance - Open Geospatial Consortium, Inc., [9] HIETANEN J., Nordic Energy - IFC implementation and testing project for energy analysis application used in the Nordic countries, vendor s information, 2010 [10] IDA-ICE 4.0: [11] HAAKANA Maarit: Implementation of the EPBD in Finland: Status and planning August 2008, EPBD Buildings Platform, 2008, [12] GADOLA R. et al.: Gesamtenergieeffizienz von Büro-Bauten - Optimierung des Heizwärmebedarfs vs. Optimierung der Gesamtenergieeffizienz ; Lucerne University of Applied Sciences and Arts / Swiss Federal Office of Energy, 2010