Automated code compliance checking for supporting integrated energy-efficient design of building envelope and HVAC systems

Abstract

Heating, ventilation and air conditioning (HVAC) systems are the most energy consuming devices among the building services, which attributes for about 38% and 30% of the total electricity consumption for residential and commercial buildings respectively in Hong Kong. The envelope of a building is decisive for its energy performance and the consequent impact on cooling load by air-conditioning. As a fundamental and essential aspect of energy conversation, the overall thermal transfer value (OTTV) is stipulated as a mandatory control for the building envelope design in Hong Kong. Furthermore, the code of practice for energy efficiency of air conditioning (AC) installations is also released as a part of the comprehensive set of building energy codes. By convention, the compliance of building designs with such regulations is checked to a large extent manually. However, textual regulation documents consist of complicated logic sentences and building design is an iterative process with repeated modifications or changes for a large size of building information. Hence, the manual compliance checking process is laborious, time-consuming, cumbersome and error-prone in practice. The development of building information modelling (BIM) has brought diverse opportunities by serving as a rich digital information hub and a collaborative information sharing platform for automated code compliance checking (ACCC) practices. To automate the checking process, building data requirements are first identified through a nuanced analysis of the OTTV and HVAC codes. Thereafter, code translation mechanism is proposed for code contents in different forms. In particular, an object-oriented code information extraction method using bidirectional long-short term memory (BiLSTM) and conditional random field (CRF) networks is developed to deal with textual code sentences in natural language. Meanwhile, compliant design procedures are translated into business process modeling notation (BPMN) models. Thereafter, the corresponding IFC BIM data are prepared and mapped with those data requirements in the OTTV and HVAC codes. An IFC BIM-based OTTV calculation and checking method is proposed and implemented with the developed prototype application on a typical commercial building and a residential hall for validation purposes. Eventually, a simplified cooling system is created for a building envelope design and simulated for two buildings to examine the building envelope cooling load and the effect of air flow rate on indoor temperature. The implementation in case study indicates that the proposed OTTV calculation and checking method is feasible, and can substantially reduce human intervention and achieve high accuracy compared with the manual calculation and commercial energy simulation tool. The fine-grained OTTV calculation results based on a 3D semantic enriched building envelope surface model can help with troubleshooting and design optimization for building envelope designs. Integrated energy-efficient design of building envelope and HVAC systems is supported with the proposed code checking method and has been considered from an early design stage.