Sara Khair Abbas
M.Sc.Thesis, 2024
ABSTRACT:
The growing discourse on environmental concerns to reduce pollution and energy consumption, led to the development of a wide variety of methods for rating buildings and standards for Green Building, which attempt to determine a set of values by which the degree of impact of a planned project on the environment can be assessed. Also in Israel, standards have been developed in recent years for green building and rating of buildings according to their predicted energy consumption. These standards aim to equip architects with practical planning tools for achieving superior architectural outcomes and solutions, while offering consumers discernible criteria for identifying and comprehending product quality, thereby fostering demand and implementation for green building. Through the adoption of such tools, entities ranging from organizations to individuals can transition their existing or proposed dwellings into environmentally conscious spaces, thereby enhancing their image, reducing costs, and minimize the environmental damage.
The Israeli standard, SI 5281 “Sustainable buildings (green buildings)” (2005, 2011), establishes a multidisciplinary framework for evaluating buildings of various types. This standard comprises a system of criteria and requisites across various domains, wherein new constructions and renovated buildings accrue points and fulfill threshold conditions. Beyond facilitating environmentally construction goals, SI 5281 serves as a comparative tool akin to similar global standards worldwide, enabling the analysis and ranking of buildings’ environmental performance.
Checking compliance with the requirements of the energy section of the above standard is done by examining the energy performance of the building according to SI 5282 “Energy Rating of Buildings ” (SI, 2011), using either a prescriptive method offering pre-tested alternatives or a performance method utilizing energy simulation models of buildings that compare the function of the planned building to a reference building as defined in the Standard. Typically, consultants and energy simulation models are employed at various planning stages to ensure compliance with the Standard. The advent of digital tools in architecture has significantly impacted building design, construction, and functionality, transitioning from mere drafting tools to sophisticated application of complex geometries and problem-solving platforms by using a model that includes all building data to serve a variety of consultants, such as Building Information Modeling (BIM).
The role of computer aided design tools in architecture can be noted in two different main areas (Gross, 1994):
– Computer-aided modeling and visualization.
– Computer-aided problem solving.
Advanced digital tools and software for performing simulations for analysis and problem solving enhance building performance across all planning stages. It can influence the way buildings are designed and constructed in complex projects in the field of high-performance green buildings. Despite this, the use of these tools is usually carried out after the building’s design, when at this stage there are restrictions on making substantial changes. While simulation tools enhance the efficiency of the design process and building performance, there often exists a disparity between predicted and actual performance due to variances in real-world conditions. Despite the widespread adoption of green building standards in Israel, electricity consumption continues to rise globally and locally, underscoring concerns regarding the efficacy of green building methods in achieving energy efficiency goals.
The reviewed literature highlights the development of computer tools, ranging from energy modeling software and machine learning techniques to optimization methodologies, used to predict and manage energy use in green construction. However, a significant challenge that has arisen is the “performance gap”. Indications of the performance gap began to appear from the mid-nineties and with continuous coverage until today. The performance gap, spanning various aspects such as energy efficiency, thermal comfort, and indoor air quality, has garnered attention within the sustainable construction domain since the mid-nineties. The recurring theme across various studies highlights the challenges associated with accurately predicting energy consumption, which require continuous efforts and the refinement of existing methodologies for more accurate results.
This research aims to examine and investigate this performance gap within Israel’s green building standard, assess the magnitude and origins of the performance gap formation, explore avenues for its mitigation in future projects, and evaluate its correlation with the utilization of evaluation tools in architectural planning processes . This is done by examining the buildings’ compliance with the performance calculated during the design phase and the certification phase, the performance after occupancy and discern contributing factors, and propose strategies for improvement. The study focuses on four buildings with diverse programs and ratings, comprising two public buildings – the Porter Building School of Environmental Studies at Tel Aviv University, and Rakafot School in Kiryat Bialik – along with two residential buildings: the Lev Alonim project in Yokneam, certified under SI GB, and a residential building in the Hasavyon neighborhood in Nesher constructed in the 1990s without SI GB certification. A comparison was made between the calculated energy consumption versus the actual energy consumption, for the purpose of checking the existence of gaps. A comparison was made between the value of the expected annual energy consumption EPdes, and the value of the actual annual energy consumption Epact (the definition formulated for the research needs). The values are derived using different calculation methodologies, the EPdes value is achieved through calculations based on the ENERGYui simulation results conducted in the planning process for SI certification, and the EPact values is determined based on information gathered from reports that were available and allow to estimate the actual consumption of the building. To compare calculated and actual energy consumption (EPdes and Epact), the study employed two methodologies. Firstly, a numerical comparison method assessed the average expected and actual annual energy consumption per square meter (measured in kWh/m2.year). Secondly, a rating-based evaluation compared the initial energy consumption rating determined during planning stages with a rating based on actual electricity consumption, as per the criteria of Israeli energy rating standard SI 5282 . Following the comparison between the actual electricity consumption, which reflects the operational dynamics of the building after occupancy, and the simulation results conducted at various planning stages, the gaps were identified. Steps were then taken to identify reasons leading to these disparities. Following the comparison between the EPdes and EPact values, identifying disparities between actual consumption and simulation results involved examining various planning processes and their alignment with SI 5282 criteria for green building certification. This entailed analyzing simulation results at different planning stages to discern their impact on compliance with green standards. Subsequently, the study identified reasons for these gaps and proposed recommendations for improvement.
The study concluded with an analysis and conclusions for each case study, followed by a horizontal comparison of all projects and recommendations for narrowing the identified gaps in future construction endeavors . The initial case study, the Porter Building, underwent extensive simulations during various planning stages, reflecting a commitment to enhancing energy efficiency. However, significant disparities between predicted and actual consumption emerged. Conversely, Rakafot School and Lev Alonim residential building in Yokneam primarily relied on basic simulations for certification, while Hasavyon Nesher residential building underwent no computerized planning, only an assessment. Despite employing both basic and advanced simulation methods, a substantial energy consumption gap persisted across the cases. The results reveal gaps with actual consumption 2.2, 1.1, and 1.7 times the simulation results in educational and public buildings, compared to small gaps of consumption 0.55 times (reduced consumption) from the simulation results in residential buildings. This study reveals that the gap is not specific to building types; both educational and residential buildings encounter challenges in predicting accurately energy usage. Public buildings often underestimate consumption, while residential buildings tend to overestimate it. Discrepancies stem from unrealistic EPref values, particularly severe in residential settings. Moreover, simulation assumptions do not always align with real-world conditions, necessitating a comprehensive understanding of user behavior and building operation to bridge the gap. The analysis identifies discrepancies attributable to inconsistencies between planning decisions and simulation outcomes. Others highlight varied usage that diverge from simulated scenarios. Additionally, discrepancies arise from disparities in apartment occupancy hours and climatic conditions compared to simulation assumptions. Furthermore, limitations in simulation programming, particularly in modeling complex buildings, warrant consideration. It should also be noted that the different versions of the standard that referred to different uses affected the results. Discrepancies also stem from mismatches between simulated and actual usage conditions, necessitating a nuanced understanding of user behaviors. To promote sustainable construction, advanced simulation tools must be integrated into the planning process. However, achieving accurate energy consumption predictions requires not only advanced simulation tools but also a deep understanding of user behaviors. Discrepancies are attributed to user behavior patterns and planning phases, highlighting the importance of aligning preparatory efforts with simulation outcomes. Moreover, to advance green construction practices, public access to building consumption data is imperative.