IFC-Based Framework for Evaluating Total Performance of Building Envelopes P. Fazio1, H. S. He1, A. Hammad2, M. Horvat3 Abstract Evaluating the overall performance of buildings has emerged as a trend in building engineering in recent years. Several programs that evaluate building performance have been developed or are being developed in different regions of the world. The Building Envelope Performance Assessment Tool (BEPAT) was initiated at Concordia University based on the feedback received from manufacturers. After briefly introducing the development of the tool, this paper presents an integrated framework which applies Information Technology (IT) and the international standard Industry Foundation Classes (IFC) to ensure that the building envelope satisfies energy requirements as well as other requirements such as moisture and thermal performance, concurrently. The framework is designed to extract geometric and material layers’ data of a house from CAD drawings in IFC data model, link to performance evaluation applications, such as HOT2000 and MOIST3.0, and compare evaluation results with a set of criteria. To demonstrate the functionalities of this framework, a prototype system has been developed including a preprocessor that imports the building model from an IFC-compatible CAD application, an application integrator, and a postprocessor. Finally, a case study, which aims to validate this prototype system, is discussed in detail. CE Database subject headings: framework, building envelope, performance evaluation, Industry Foundation Classes (IFC). 1 Building Envelope Performance Laboratory; Centre for Building Studies; Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, Quebec, Canada 2 Concordia Institute for Information Systems Engineering, Concordia University, Montreal, Quebec, Canada 3 Ryerson University, previously at Building Envelope Performance Laboratory; Centre for Building Studies; Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, Quebec, Canada 1Introduction There is a global trend in understanding and evaluating the overall performance of buildings. In several countries (Sweden, EU, Japan, US, etc.) such programs have been or are being developed in an attempt to assess the issues that influence the performance of the building itself and, in some cases, to assess the impact of the building on its surrounding. Examples of these programs are: P-mark (Sweden) (Anneling,1998), Housing Quality Assurance Law – HQAL (Japan) (Ministry of Construction Japan, 2000), ETAG 007—European Technical Approval Guideline for Timber-frame Building Kits (European Community) (EOTA , 2001), R-2000 Program (Canada) (NRCan, 2005), Novoclimat (Quebec, Canada) (Quebec Agency for Energy Efficiency, 2005), LEEDTM (US) (U. S. Green Building Council, 2003), etc. A comparative review of these existing certification programs that deal with evaluation and assessment of housing presented advantages and shortcomings of such programs and identified issues specific for Canada (Horvat and Fazio, 2005). In addition, the need for developing a similar kind of evaluation program was voiced by Canadian manufacturers and exporters of prefabricated houses. This resulted in two studies done jointly by Concordia University and Forintek Canada Corp.: Assessment of the Prefabricated Building Industry (Fazio at al., 2000; Horvat et al., 2001) and Durability in Housing: A Review of Quality Certification Programs and Recommendations (Horvat et al., 2002). The studies showed that recognition of superior quality would be an asset in marketing the products for domestic as well as export markets (Fazio et al., 2000). Based on these studies, a program for the performance evaluation of building envelopes has been developed at Concordia University, Montreal, entitled: Protocol and assessment tool for overall performance evaluation of light-frame building envelopes used in low-rise buildings (Horvat & Fazio, 2003, Horvat & Fazio, 2004). This protocol defines a strategy to evaluate a building envelope as an integrated sub-system of the entire building at the design stage, laboratory testing stage, execution stage, and finished stage of the building. The overall performance evaluation protocol includes the following functional requirements: air tightness, moisture management performance, thermal performance, energy consumption performance, structural stability of the building envelope, acoustic resistance, and fire 2response of the building envelope. The protocol follows a performance-based concept, where each functional requirement is divided into its performance or operative requirements and their corresponding criteria and verification methods. The protocol has been designed for Montreal conditions; however, it can server as a framework for developing similar programs in other regions. The building envelope is an integral part of the building system and must be well integrated with the structure and the HVAC for the effective performance of the building. The envelope should be treated, therefore, as an integrated part of the building when being designed, and the performance characteristics and construction details of contiguous subsystems should be taken into consideration concurrently (Fazio, 1990). Accordingly, a holistic approach to performance evaluation will ensure that the multiple criteria of the building envelope, such as structural, thermal, integrity, moisture, acoustics, etc., are all satisfied and will ensure that compatibility among the subsystems is established, such as the envelope with the structure, the HVAC, and lighting systems of the building. The performance of building envelopes can be evaluated through tests or computer simulation. Experimental studies can be carried out in laboratories and in the field, but they are usually more expensive and time consuming than computer simulations. Computer simulation, on the other hand, is less expensive and time consuming, but requires validation. A large number of computer-based applications are already available, e.g., HOT2000 (Buildings Group/NRCan, 2005; Buildings Group/NRCan, 1995), Energy Plus (U.S. Department of Energy, 2005), RIUSKA (Granlund, 2005), WUFI-ORNL/IBP (ORNL/IBP, 2005), hygIRC (IRC/NRC, 2005), MOIST3.0 (BFRL/NIST, 2005), CONDENSE (GES, 2005), and Airpak (Fluent Inc., 2005). However, the data input in these applications is complex and time
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