Abstract: We present unprecedented datasets of current and future projected weather files for building simulations in 15 major cities distributed across 10 climate zones worldwide. The datasets include ambient air temperature, relative humidity, atmospheric pressure, direct and diffuse solar irradiance, and wind speed at hourly resolution, which are essential climate elements needed to undertake building simulations. The datasets contain typical and extreme weather years in the EnergyPlus weather file (EPW) format and multiyear projections in comma-separated value (CSV) format for three periods: historical (2001–2020), future mid-term (2041–2060), and future long-term (2081–2100). The datasets were generated from projections of one regional climate model, which were bias-corrected using multiyear observational data for each city. The methodology used makes the datasets among the first to incorporate complex changes in the future climate for the frequency, duration, and magnitude of extreme temperatures. These datasets, created within the IEA EBC Annex 80 “Resilient Cooling for Buildings”, are ready to be used for different types of building adaptation and resilience studies to climate change and heatwaves.

Abstract: The world is facing a rapid increase of air conditioning of buildings. It is the motivation of Annex 80 to develop, assess and communicate solutions of resilient cooling and overheating protection. Resilient Cooling is used to denote low energy and low carbon cooling solutions that strengthen the ability of individuals and our community to withstand, and prevent, thermal and other impacts of changes in global and local climates. Within Annex 80, there is a manifold need to use key performance indicators (KPI, i.e. performance metrics). This study employs a structured approach to evaluate Key Performance Indicators for assessing the resilience of buildings across various technologies. All suggested KPIs pertinent to assessing building resilience were collected and listed comprehensively. This involved an extensive review of existing literature, standards, and expert opinions. The aim was to compile a comprehensive inventory of KPIs that encompass diverse aspects of building resilience. Each identified KPI is systematically described to ensure clarity and understanding. This description includes a definition, a list of commonly used synonyms, units of measurement, and sources for the information.

Abstract: The world is facing a rapid increase of air conditioning of buildings. It is the motivation of Annex 80 to develop, assess and communicate solutions of resilient cooling and overheating protection. Resilient Cooling is used to denote low energy and low carbon cooling solutions that strengthen the ability of individuals and our community to withstand, and prevent, thermal and other impacts of changes in global and local climates. This report summarizes the structure and the outcomes of Annex 80 – Resilient Cooling of Buildings, which was conducted as a five-year international research project within the IEA Technical Collaboration Programme EBC – Energy in Buildings and Communities. Annex 80 covered the spectrum of the following four technology groups: (1) Reducing heat gains to the indoor environment and people environments (2) Removing sensible heat from the indoor environment (3) Increasing personal comfort apart from space cooling (4) Removing latent heat from indoor environment Its outcomes are published in seven official Annex Deliverables. In addition, partial results of Annex 80 have been published in numerous scientific journals. This document provides a comprehensive overview of all deliverables and directs readers to the locations where all related publications can be accessed.

Abstract: International Energy Agency Energy in Buildings and Communities (IEA EBC) Annex 80: Resilient Cooling of Buildings promotes a rapid transition to the mainstream and preferred use of resilient low-energy and low-carbon cooling systems in buildings. Annex 80 Subtask D (Policy Actions) advances policy-related endeavors that support energy efficiency and resilience in cooling. The Subtask team analyzed product labelling programs; air conditioning minimum energy performance standards (MEPS) and voluntary measures; and building regulations, standards, and compliance requirements, identifying policy gaps and opportunities. It then generated a set of 37 policy recommendations that boost resilience to heat waves and/or power grid failure by reducing heat gain, removing sensible heat, enhancing thermal comfort without mechanical cooling, or removing latent heat. Strategies addressed include advanced solar shading/advanced glazing, cool envelope materials, evaporative envelope surfaces, ventilated envelope surfaces, heat storage and release, ventilative cooling, adiabatic/evaporative cooling, compression refrigeration, high-temperature cooling systems using low-grade thermal energy, comfort ventilation, micro-cooling and personal comfort control, and whole-building solutions. Each recommendation identifies the mechanism(s) through which the policy would be applied and the disruption(s) mitigated; details the what, why, how, who, where, timeline, cost, and potential undesirable side effects of implementation; and suggests a policy model to follow.

Abstract: The world is facing a rapid increase of air conditioning of buildings. It is the motivation of Annex 80 to develop, assess and communicate solutions of resilient cooling and overheating protection. Resilient Cooling is used to denote low energy and low carbon cooling solutions that strengthen the ability of individuals and our community to withstand, and prevent, thermal and other impacts of changes in global and local climates. This report offers a collection of 16 technologies, well suited to form a part of Resilient Cooling solutions of Buildings. It is meant as a package of information for those who are in the position to draw decisions upon building-design, both retrofit and new constructions. The 16 technologies are structured in four main sections, which represent the four general approaches to making a building resilient against heat: - Reducing heat loads to people and indoor environments - Removing heat from indoor environments (production, emission and combined) - Increasing personal comfort apart from space cooling - Removing latent heat from indoor environments Each technology is described in a concise manner, sub structured in the chapters: Description, Key Technical Properties, Performance and Application and Further Reading.

Abstract: This IEA Annex 80 Subtask C report and the associated brochures provide examples of well-documented field studies. These field studies apply resilient cooling technologies to reduce energy demand and carbon emissions for cooling and reduce the overheating risk in different types of buildings, including newly constructed and existing buildings. Examples and details on building information, energy systems, resilient cooling technologies, key performance indicators (KPIs), and performance evaluation amd lessons learned are included in the report and the brochures. The present report summarizes all 13 field study buildings collected in Subtask C of IEA-EBC Annex 80. This summary presents information on the field studies, the resilient cooling technologies applied in the field studies, the KPIs, and the performance evaluation and lessons learned. The values of KPIs for building similar functions, i.e., residential buildings, under different climate conditions were discussed. In the field study brochures, detailed information is inlcuded for each building. The field studies are presented in brochure format. Each brochure contains information in a standardized format. This includes the introduction & climate, building information, resilient cooling, KPI evaluation, design simulation, performance evaluation, discussion, lessons learned, references & key contacts.

Abstract: The world is facing a rapid increase of air conditioning of buildings. It is the motivation of Annex 80 to develop, assess and communicate solutions of resilient cooling and overheating protection. Resilient Cooling is used to denote low energy and low carbon cooling solutions that strengthen the ability of individuals and our community to withstand, and prevent, thermal and other impacts of changes in global and local climates. This midterm report sums up the developments of the Annex 80 since its first Expert Meeting in October 2019 in Vienna, Austria until July 2021. During this period several conference calls as well as the second, third and fourth Expert Meeting have been held by the Operating Agent (OA) and its team. The formation of a common understanding of concepts and definitions of resilience had been the focus of the group during the first period of the annex. Members with different scientific background discussed various approaches and developed an understanding of resilience in relation to cooling of buildings. The group identified two major threats for the cooling of buildings: extreme heat events and power outages. Others such as extreme rain events, flooding, landslides, or storms influence the built environment too but are not as strongly connected to cooling of buildings. Therefore, the group of scientists decided not to address these disruptions. Different task groups were set up to define thermal boundary conditions, generate future weather files and compile key performance indicators for the assessment of cooling technologies through dynamic simulations. The groups summarized their results and published short technical reports. The weather data task group planned to publish their methodology and results as scientific paper.

Abstract: The world is facing a rapid increase of air conditioning of buildings. It is the motivation of Annex 80 to develop, assess and communicate solutions of resilient cooling and overheating protection. Resilient Cooling is used to denote low energy and low carbon cooling solutions that strengthen the ability of individuals and our community to withstand, and prevent, thermal and other impacts of changes in global and local climates. It encompasses the assessment and Research & Development of both active and passive cooling technologies of the following four groups: a) Reduce heat loads to people and indoor environments. b) Remove sensible heat from indoor environments. c) Enhance personal comfort apart from space cooling. c) Remove latent heat from indoor environments. The present review sums up the state of the art in cooling solutions which may be regarded as resilient. Its main objective is to systematically describe the available cooling solutions, their physical basis, their benefits and limitations, their technology readiness level, their practical availability, and applicability. Doing so, the State-of-the-Art Review forms the basis for the work of EBC Annex 80.

Abstract: Resilient cooling is used to denote low energy and low carbon cooling solutions that strengthen the ability of individuals, and our community as a whole to withstand, and also prevent, the thermal and other impacts of changes in global and local climates, particularly with respect to increasing ambient temperatures and the increasing frequency and severity of heat waves.

Abstract: Cool (solar reflective) roofs and walls can reduce solar heat gain and decrease unwanted heat flowing into indoor spaces. To explore the potential of these strategies to mitigate energy and thermal comfort challenges in Los Angeles, we conducted a study that used EnergyPlus building energy simulations. Our analysis focused on single-family homes in Los Angeles under various historical and future weather conditions, including both typical meteorological year (TMY) and heatwave weather year (HWY) scenarios, based on the COordinated Regional Downscaling EXperiment (CORDEX) framework under the Representative Concentration Pathway (RCP) 8.5. Our study evaluated the impact of cool envelope strategies on heating, ventilation, and air conditioning (HVAC) primary energy intensity savings and thermal comfort improvements. We employed three thermal comfort models: predicted mean vote (PMV), adaptive, and heat stress. Our findings indicate that in Los Angeles, a package of cool roof + walls (reflective roof and reflective walls) can reduce annual HVAC energy consumption by at least 11% for buildings equipped with mechanical cooling systems. They can reduce occupants’ warm thermal discomfort (thermal-sensation-scale-unit-weighted warm exceedance hours) by at least 28% in air-conditioned buildings and by at least 16% in buildings without mechanical cooling systems. Cool envelopes can also lower daily heatwave heat stress by at least 9%.

Abstract: With climate change leading to more frequent, more intense, and longer durations of extreme weather events such as heat waves and cold snaps, it is essential to maintain safe indoor environmental conditions for occupants during such events, which may coincide with, or even cause, power outages that expose residents to health risks. Analyzing the impacts of extreme weather events on the thermal resilience of buildings can help stakeholders (including occupants) understand the risk and inform them about mitigation and adaptation actions. Moreover, analyzing the technological, social and policy dimensions of thermal resilience is critical for climate-proofing buildings. This paper presents 10 questions that highlight the most important issues regarding the thermal resilience of buildings for occupants in the face of climate change. The proposed questions and answers aim to provide insights into current and future building thermal resilience research and applications, and more importantly to inspire new significant questions in the field.

Abstract: This study explores the spatial variability of the thermal responses of older occupants’ in indoor environments at various locations in Montreal, Canada. Urban climate in and around the city over an extreme heat event in 2018 is simulated at 1 km spatial resolution using Weather Research and Forecasting (WRF) model, and data for 29 long-term care building locations in the city is extracted. A long-term care building was modelled using EnergyPlus and calibrated with measured hourly indoor air temperatures; it was then used to evaluate how local weather conditions affect indoor thermal conditions. The building simulation results were then applied to a physiological model for older (65y+) people that permitted evaluating individual's thermal responses. Further analysis was conducted by comparing the difference between responses of older and young occupants and between people’s responses in original and retrofitted buildings. More than 4 ? variations in the standard effective temperature (SET) of older occupants are observed in the studied buildings. The conclusions highlight the importance of applying strict indoor temperature limiting thresholds or retrofit requirements for long-term care buildings.

Abstract: Climate heat waves occurring in urban centers are a serious threat to public health and wellbeing. Historically, most heat-related mortalities have arisen from excessive overheating of building interiors housing older occupants. This paper developed an approach that combines the results from building simulation and bioheat models to generate health-based limit criteria for overheating in long-term care homes (LTCHs) by which the body dehydration and core temperature of older residents are capped during overheating events. The models of the LTCHs were created for buildings representative of old and current construction practices for selected Canadian locations. The models were calibrated using measurements of indoor temperature and humidity acquired from monitoring the building interiors and the use of published building energy use intensity data. A general procedure to identify overheating events and quantify their attributes in terms of duration, intensity, and severity was developed and applied to LTCHs to generate the limit criteria. Comparing the limit criteria from the proposed and comfort-based methods showed evident differences. The proposed method predicted the overheating risk consistent with the overall thermal comfort during overheating events in contrast to the comfort-based methods. The new limit criteria are intended to be used in any study to evaluate overheating risk in similar buildings.

Abstract: The objective of Annex 80 is to develop, assess and communicate solutions for resilient cooling. The systematic assessment of resilient cooling strategies is one of the main activities of Annex 80. The previous approach for assessing the resilience of cooling strategies is mainly based on qualitative comparison and based on results from individual research, which lacks common boundary conditions and universal indicators for resilience evaluation. This study aims to provide a consistent approach for assessing the resilience of different cooling strategies by dynamic simulation. Various cooling strategies will be tested on the reference buildings under present and future weather conditions in different climate zones, and proposed key performance indicators will be applied to evaluate summertime overheating risk and climate resistance of cooling strategies.

Abstract: In this study, the synergistic interactions of the urban heat island effect and the heatwaves occurring in the summer of 2018 in the cities of Montreal and Ottawa, Canada, are discussed through a comparison between days with and without a heatwave event. Three (3) time frames were prepared as part of this comparison: a pre-heatwave period from June 24 to June 29, 2018 (6 days); a heatwave period from June 30 to July 05, 2018 (6 days); and a post-heatwave period from July 06 to July 11, 2018 (6 days). The urban climates of these two cities were simulated using a Weather Research and Forecast (WRF) model at a grid resolution of 1 km; the urban heat island intensity was calculated using two methods: (i) calculating the temperature difference between urban and rural grid cells at a distance ranging between 3 to 10 km to the boundary of the urban area; (ii) using the “urban increment” method by which the temperature of urban grid cells are compared to the results of another simulation having all the urban land cover replaced by cropland. The diurnal evolution of several near-surface variables was compared throughout these three periods, including the ground surface temperature, the 2-m air temperature, relative humidity, and the 10-m wind speed.

Abstract: Understanding and quantifying the interactions between urban microclimate and urban buildings is essential to improve the urban environment and building performance, especially during heatwaves. Most previous studies used tool or application specific data exchange mechanisms that cannot be generalized for other tools or applications. In this paper, we introduce a new flexible and tool-agnostic data schema to facilitate the exchange of data between urban building energy models and urban microclimate models. The JSON schema was tested using a district of 97 buildings in San Francisco and running simulations with CityBES and CityFFD as the urban building energy and microclimate modeling platforms, respectively. Compared with simulation results using the historical weather data, simulation results considering interactions between two models over a two-day heatwave event showed a 5.3°C higher average peak building facade temperature, an 8.9 °C higher average peak air node temperature, and a 19.5% higher peak cooling energy use.

Abstract: The concept 'Resilience' has gained wide international attention by experts and is now seen as the future target for the design of buildings. However, before using the word 'resilience’, we must understand the semantics of the word. Resilience is not 'resistance' and is not 'robustness and is not 'sustainability', it is a more complex definition. As part of the International Energy Agency Annex 80 on resilient cooling in buildings, this paper focuses on formulating a definition for resilient cooling. Resilient cooling is used to denoting low energy and low carbon cooling solutions that strengthen the ability of individuals, and our community as a whole to withstand, and also prevent, the thermal and other impacts of changes in global and local climates; particularly concerning increasing ambient temperatures and the increasing frequency and severity of heatwaves. This paper focuses on the review of most of the existing resilient cooling definitions and the various approaches towards possible resiliency evaluation methodologies. It presents and discusses possible answers to the abovementioned issues to facilitate the development of a consistent resilient cooling definition and a robust evaluation methodology. The paper seeks to impact national building codes and international standards, through a clear and consistent definition and a commonly agreed evaluation methodology.

Abstract: Bioeffluents emitted from person lying down in bed can be removed by ventilated mattress (VM) before mixing with the room air. VM is designed to suck air through an exhaust opening located near the feet and move the sucked air inside the mattress. The air moves through the whole mattress and is removed to the exhaust or cleaned and discharged back to the room. The VM can change the thermal conditions in the bed micro-environment and provide uncomfortable local cooling of the person in the bed. Therefore, the design of the ventilated mattress is further improved by incorporating local heating. The response of people to the bed thermal environment generated by the mattress was studied at three room air temperatures – 19°C, 23°C and 28°C. 30 human subjects (15 males, 15 females) of age 20 - 29 years old and body mass index in the range 18 - 27 were exposed to the bed thermal environment provided by the VM. The subjects were covered with a thin duvet (2.9 clo) at room temperature 19°C, a double cotton sheet at 23°C and a single cotton sheet was used at 28°C. The subjects were dressed with pajama (short-sleeve shirt, shorts) and underwear. Thermal sensation assessment was collected through standardized questionnaires. The subjects answered questions regarding their whole body thermal sensation and local thermal sensation of separate body parts including face, head, neck, chest, back, arms, hands, thighs, lower legs, and feet. The bed thermal micro-environment was adjusted by the exhaust flow rate through the ventilated mattress and the localized heating depending on the acceptability of the subjects’ thermal sensation collected every 7 minutes. The results show that the applied control of the bed thermal environment increased the acceptability of the whole body thermal sensation votes and the risk of local cold discomfort (especially on the feet and hands) decreased over time. Local heating at the feet will be needed to achieve thermal comfort in room temperatures below 23°C. Local heating incorporated in the VM or separate and the airflow through the mattress can be controlled based on physiological signals of the person’s body.

Abstract: The changes in climate and the expected extreme climate conditions in the future, given the long life span of the buildings have pushed the design limits. In this study, the changes in primary energy use (PEPET), total energy use and CO2 emission were investigated for a prototype residential building. The building fulfils nearly zero energy building (NZEB) characteristics, imposed by the Swedish building regulations. Different cooling technologies and various typical meteorological year (TMY) climate files assembled for different periods, as well as automatic shading were investigated. The assembled TMY files advocated for the present (2001–2020) and mid-future (2041–2060) period using the CORDEX data. Different cooling methods and set-points (24–28 °C) were defined to evaluate the cooling energy demand changes. It was discovered that the freely available typical climate file fails to cover the induced changes in climate and its extreme implications on the building. The required cooling energy use increased from 1.7 to 5.8 times the freely available climate file, when using the projected TMY and the extreme climate files. Addition of automatic shading system reduced cooling energy up to 75% within the studied cooling methods and set-points. Moreover PEPET and CO2 emission also decreased for the studied cooling methods, climate and weather files.

Abstract: The thermal comfort in public buildings is affected by multiple psychological and physical factors. A deep understanding of these factors is necessary for intelligent ventilation control and architectural design. In this study, it was quantified the physiological and psychological parameters of the occupants in a library situated in Changsha using a questionnaire. Then, with the use of Principal Component Analysis (PCA), the dimensionality of the database was reduced. We found that the Zero-mean and unit variance projection is better than the Zero-mean projection, and 43-dimensional data can replace more than 90% of the original 61-dimensional data. Machine learning algorithms were used to analyze the results after PCA, which showed that the effect of thermal comfort on emotions is greater than that of emotions on thermal comfort. In addition, the performance of six machine learning algorithms (Linear Regression (LR), Linear Discriminant Analysis (LDA), K-Nearest Neighbors (KNN), Classification and Regression Trees (CART), Gaussian Naive Bayes (NB), and Support Vector Machine (SVM)) were compared. It is found that the predicted results of LDA were more accurate, and other algorithms showed different performances in different cases. These findings can contribute to the study of the subjective and objective feelings of indoor thermal comfort in public buildings, thereby guiding architectural design, intelligent control of ventilation systems, and realizing human-building interaction interfaces.

Abstract: Physiological modeling is important to evaluate the effects of heat and cold conditions on people’s thermal comfort and health. Experimental studies have found that older people (above 65 year old) undergo age-related weakening changes in their physiology and thermoregulatory activities, which makes them more vulnerable to heat or cold exposure than average aged young adults. However, addressing the age-related changes by modeling has been challenging due to their wide variability among the older population. This study develops a two-node physiological model to predict the thermal response of older people. The model is built on a newly developed two-node model for average-age young adults by accounting for the age-related attenuation of thermoregulation and sensory delays in triggering thermoregulatory actions. A numerical optimization method is developed to compute the model parameter values based on selected benchmark data from the literature. The proposed model is further validated with published measurement data covering large input ranges. The model predictions are in good agreement with the measurements in hot and cold exposure conditions with a discrepancy 0.60 °C for the mean skin temperature and of 0.30 °C for the core temperature. The proposed model can be integrated into building simulation tools to predict heat and cold stress levels and the associated thermal comfort for older people in built environments.

Abstract: When assessing a buildings' performance under overheating conditions there is a need to identify extreme hot years (EHYs) for a given climate location. Different types of EHYs can be selected depending on the criteria used for their selection, such as long, intense, or severe heatwaves defined based on dry-bulb temperature and other thermal comfort indices. However, the effect of the EHY type on the extent of indoor overheating has not been quantitively evaluated. The selection of multi EHYs also complicates the overheating assessment process. Therefore, an investigation was undertaken to explore the suitability of different EHY when assessing the extent of indoor overheating in buildings. In this study, the “Percentage of Synchronization” (POS) of outdoor and indoor-based extreme years was proposed as an approach to the selection of EHYs. A higher value of POS for a given EHY implied that there was a more significant risk for indoor overheating to occur. Thus when evaluating different EHYs, the most suitable choice in EHY would then be selected as the one with the highest POS value. The proposed method was demonstrated for residential archetype building models for five different climate zones. In the selection of EHYs for building overheating analysis, the thermal-based index was confirmed to be more suitable than the temperature-based index in the selection process; in the same context, the heatwave intensity and severity are more important than the duration of the event. Representative EHYs for each of the cities studied were identified; these include: 2010 (Ottawa and Montreal), 2013 (Toronto), 2006 (Baltimore), 1992 (Phoenix), and 2005 (Houston).

Abstract: As a consequence of global warming and rapid urbanization around the globe, the magnitudes and frequencies of extreme heat events (EHEs) are increasing and this trend is expected to continue into the future. In this study, the added benefit of modelling climate at convection-permitting spatial resolutions (grid spacing <4 km) is considered for a set of exterior climate and interior building simulations during EHEs in the urban areas of Ottawa and Montreal, Canada over the summer of 2018. The climate is modelled at two spatial resolutions: i) 25 km – typically considered for regional-scale climate modelling; and ii) 1 km. The results derived from modelling at each of these resolutions is compared in respect to their adequacy in predicting different measures of overheating outdoors as well as those within a typical single-detached home. The results clearly demonstrate that simulations undertaken at a 1 km resolution permit more accurately calculate the magnitude of overheating, whereas simulations completed at a 25 km resolution lead to an underestimation of overheating in about 95% of the urban grids within either of these two cities. These results suggest the necessity of using convection-permitting climate simulations for overheating assessments over the urban scale.

Abstract: Over the last decades overheating in buildings has become a major concern. The situation is expected to worsen due to the current rate of climate change. Many efforts have been made to evaluate the future thermal performance of buildings and cooling technologies. In this paper, the term “climate change overheating resistivity” of cooling strategies is defined, and the calculation method is provided. A comprehensive simulation-based framework is then introduced, enabling the evaluation of a wide range of active and passive cooling strategies. The framework is based on the Indoor Overheating Degree (IOD), Ambient Warmness Degree (AWD), and Climate Change Overheating Resistivity (CCOR) as principal indicators allowing a multi-zonal approach in the quantification of indoor overheating risk and resistivity to climate change. To test the proposed framework, two air-based cooling strategies including a Variable Refrigerant Flow (VRF) unit coupled with a Dedicated Outdoor Air System (DOAS) (C01) and a Variable Air Volume (VAV) system (C02) are compared in six different locations/climates. The case study is a shoe box model representing a double-zone office building. In general, the C01 shows higher CCOR values between 2.04 and 19.16 than the C02 in different locations. Therefore, the C01 shows superior resistivity to the overheating impact of climate change compared to C02. The maximum CCOR value of 37.46 is resulted for the C01 in Brussels, representing the most resistant case, whereas the minimum CCOR value of 9.24 is achieved for the C02 in Toronto, representing the least resistant case.

Abstract: The urban canyon albedo (UCA) quantifies the ability of street canyons to reflect solar radiation back to the sky. The UCA is controlled by the solar reflectance of road and façades and the street geometry. This study investigates the variability of UCA in a typical residential area of London and its impact on outdoor and indoor microclimates. The results are based on radiation measurements in real urban canyons and on a 1:10 physical model and simulations using ENVImet v 4.4.6 and EnergyPlus. Different scenarios with increased solar reflectance of roads and façades were simulated to investigate the impact on UCA and street level microclimate. The results showed that increasing the road reflectance has high absolute and relative impact on UCA in wide canyons. In deeper canyons, the absolute impact of the road reflectance is reduced while the relative impact of the walls' reflectance is increased. Results also showed that increasing surface reflectance in urban canyons has a detrimental impact on outdoor thermal comfort, due to increased interreflections between surfaces leading to higher mean radiant temperatures. Increasing the road reflectance also increases the incident diffuse radiation on adjacent buildings, producing a small increase in indoor operative temperatures. The findings were used to discuss the best design strategies to improve the urban thermal environment by using reflective materials in urban canyons without compromising outdoor thermal comfort or indoor thermal environments.

Abstract: Urban microclimate analysis is often associated with computational fluid dynamics simulations of urban aerodynamics and thermal conditions, air quality, heat island, humidity, and rain at a building level. Conventional microclimate analyses are often limited by the size of the simulation domain, turbulence models, and sparse digital urban data available. This study introduces CityFFD with its supporting web portal of digital cities for large-scale urban simulation problems. A few novel algorithms, including backward and forward sweep interpolation schemes, time-adaptive technique, and the 2nd-order temporal scheme, were implemented to enhance the computing speed and accuracy of the model. Parallel computing on graphics processing units (GPU) speeds up the simulation. CityFFD is equipped with a large eddy simulation method to capture the turbulence behavior in the urban roughness sublayer. This paper reports the structure of CityFFD, and a group of benchmark cases, including airflow around buildings, natural ventilation, and thermal stratifications around building blocks in an actual urban area, and CityFFD is shown to predict acceptable results of the urban scale wind speeds, temperatures, and flow patterns. This study demonstrates a new approach to modeling urban microclimate by CFD simulations on GPUs.

Abstract: Wind power is known as a major renewable and eco-friendly power generation source. As a clean and cost-effective energy source, wind power utilization has grown rapidly worldwide. A roof-mounted wind turbine is a wind power system that lowers energy transmission costs and benefits from wind power potential in urban areas. However, predicting wind power potential is a complex problem because of unpredictable wind patterns, particularly in urban areas. In this study, by using computational fluid dynamics (CFD) and the concept of nondimensionality, with the help of machine learning techniques, we demonstrate a new method for predicting the wind power potential of a cluster of roof-mounted wind turbines over an actual urban area in Montreal, Canada. CFD simulations are achieved using city fast fluid dynamics (CityFFD), developed for urban microclimate simulations. The random forest model trains data generated by CityFFD for wind prediction. The accuracy of CityFFD is investigated by modeling an actual urban area and comparing the numerical data with measured data from a local weather station. The proposed technique is demonstrated by estimating the wind power potential in the downtown area with more than 250 buildings for a long-term period (2020–2049).

Abstract: With the increased severity, intensity, and frequency of “heatwaves” due to climate change, it has become imperative to study the overheating risks in existing buildings. To do so, a building simulation model needs to be calibrated based on measured indoor temperatures under the current weather conditions. This paper presents a robust automated methodology that can calibrate a building simulation model based on the indoor hourly temperature in multiple rooms simultaneously with high accuracy. This methodology includes a variance-based sensitivity analysis to determine building parameters that significantly influence indoor air temperatures, the Multi-Objective Genetic Algorithm to calibrate different rooms simultaneously based on the significant parameters identified by the sensitivity analysis, and new evaluation criteria to achieve a high-accuracy calibrated model. Maximum Absolute Difference (MAD), a new metric, that calculates the maximum absolute difference between simulated and measured hourly indoor temperatures, Root Mean Square Error (RMSE), Normalized Mean Bias Error (NMBE) were used as the evaluation criteria. Another new metric is introduced, 1 °C Percentage Error criterion that calculates the percentage of the number of hours with an error over 1 °C during the calibration period, to select the best solutions from the Pareto Front solutions. 0.5 °C Percentage Error criterion is also used for the level of accuracy the model can achieve. It was found that the calibrated model achieved these metrics with RMSE of 0.3 °C, and MAD of 0.8 °C, and 85% of data points with an error less than 0.5 °C for a school building case.

Abstract: The objective of Annex 80 is to develop, assess and communicate solutions for resilient cooling. The systematic assessment of resilient cooling strategies is one of the main activities of Annex 80.The previous approach for assessing the resilience of cooling strategies is mainly based on qualitative comparison and based on results from individual research, which lacks common boundary conditions and universal indicators for resilience evaluation. This study aims to provide a consistent approach for assessing the resilience of different cooling strategies by dynamic simulation. Various cooling strategies will be tested on the reference buildings under present and future weather conditions in different climate zones, and proposed key performance indicators will be applied to evaluate summertime overheating risk and climate resistance of cooling strategies.

Abstract: Overheating exposure over time can lead to discomfort, productivity reduction, and health issues for the occupants in buildings. The time-integrated overheating evaluation methods are introduced to describe, in a synthetic way, the extent of overheating over a span of time and predict the uncomfortable phenomena. This paper reviews the time-integrated overheating evaluation methods that are applicable to residential buildings in temperate climates of Europe. We critically analyze the methods found in (i) 11 international standards, namely, EN 15251 (2006), EN 16798 (2019), ISO 7730 (2004), ISO 17772 (2017–2018), ASHRAE 55 (2017), ASHRAE 55 (2020), CIBSE Guide A (2006), CIBSE TM52 (2013), CIBSE Guide A (2015), CIBSE TM59 (2017), and Passive House (2015), (ii) five national building codes based on the Energy Performance of Building Directive (EPBD) in Belgium, France, Germany, the UK, and the Netherlands, and (iii) two studies in the scientific literature. For each method, we present the thermal comfort models along with the time-integrated overheating indices and criteria. The methods are analyzed according to some key measures in order to identify their scope, strength, and limitations. We found that most standards recommend the static comfort models for air-conditioned buildings and the adaptive comfort models for non-air-conditioned ones. We also found a promising method based on three indices, namely, Indoor Overheating Degree (IOD), Ambient Warmness Degree (AWD), and overheating escalation factor (αIOD/AWD) that allows for a multi-zonal and climate change-sensitive overheating assessment. Finally, some guidance is provided for practice and future developments.

Abstract: As suggested by many guidelines, a high ventilation rate is required to dilute the indoor virus particles and reduce the airborne transmission risk, i.e., dilution ventilation (DV). However, high ventilation rates may result in high energy costs. Ventilative cooling (VC), which requires high ventilation rates like DV, is an option to reduce the cooling energy consumption. By combining DV and VC, this paper investigated the operation of the mechanical ventilation system in high-rise buildings during the COVID-19 pandemic, aiming to minimizing the cooling related energy consumption and reducing COVID-19 transmission. First, a modified Wells-Riley model was proposed to calculate DV rates. The ventilation rate required to achieve VC was also introduced. Then, a new ventilation control strategy was proposed for achieving DV and VC. Finally, a case study was conducted on a real high-rise building, where the required DV rate and the impact of the settings of the mechanical ventilation on the energy savings were evaluated. The results indicate that the required ventilation rates vary from 36 m3/s to 3306 m3/s depending on the protective measures. When the occupants follow the protective measures, the proper settings of the mechanical ventilation system can reduce energy consumption by around 40%.

Abstract: The global effects of climate change will increase the frequency and intensity of extreme events such as heatwaves and power outages, which have consequences for buildings and their cooling systems. Buildings and their cooling systems should be designed and operated to be resilient under such events to protect occupants from potentially dangerous indoor thermal conditions. This study performed a critical review on the state-of-the-art of cooling strategies, with special attention to their performance under heatwaves and power outages. We proposed a definition of resilient cooling and described four criteria for resilience—absorptive capacity, adaptive capacity, restorative capacity, and recovery speed —and used them to qualitatively evaluate the resilience of each strategy. The literature review and qualitative analyses show that to attain resilient cooling, the four resilience criteria should be considered in the design phase of a building or during the planning of retrofits. The building and relevant cooling system characteristics should be considered simultaneously to withstand extreme events. A combination of strategies with different resilience capacities, such as a passive envelope strategy coupled with a low-energy space-cooling solution, may be needed to obtain resilient cooling. Finally, a further direction for a quantitative assessment approach has been pointed out.

Abstract: The two-node bioheat model is widely used in thermal comfort standards and design tools. In recent years, there have been many new experimental studies and thermoregulatory models developed under stressful heat or cold conditions, but those have not been tested under the two-node model structure. Furthermore, limited validation studies of the two-node model revealed significant discrepancies in the prediction of skin temperature. This study collects relevant thermoregulatory models (six for sweating, three for skin blood flow and shivering, and four for sweat evaporation efficiency) and devises a methodology to compare the accuracy of various model combinations against experimental data. An improved model is developed and validated under heat and cold exposure conditions. The RMSE method is used to compare the accuracy of various model combinations and to optimize the proposed thermoregulatory model constants. The results reveal that only several model combinations can be considered as accurate for the core and skin temperature predictions, amongst which are the proposed models at the first rank.

Abstract:  Mechanical ventilation systems have great potential to provide cooling in high-rise buildings and reduces cooling energy consumption, i.e. mechanical ventilative cooling (MVC). However, the energy performance of MVC highly depends on weather conditions. In the previous studies, the energy performance of MVC usually was investigated under the typical or historical weather conditions. Considering that weather conditions will change due to global warming, it is necessary to assess the influences of climate change on the energy performance of MVC. This study uses the morphing method to predict the future weather conditions and a hybrid model to simulate the energy performance of MVC. The hybrid model combines the machine learning model built by multilayer perceptron and energy models. With a case study building in Montreal, the results show that the amount of energy saving of MVC will increase slightly due to climate change. This study contributes to the application of MVC systems in high-rise buildings.

Abstract: This paper entails the computational assessment of a number of occupant-centric radiant cooling elements. These radiant elements are positioned close to users and can accommodate potential surface condensation. As such, they can be operated with panel surface temperatures below the dew point. The computational assessment focuses on their effects on occupants' thermal comfort. To this end, four different climatic regions are considered. The results point to both the potential of the proposed radiant cooling approach and the limitations, especially with regard to extremely hot and humid conditions.

Abstract: The consequences of global warming and urban heat islands have led, amongst other things, to a rapid increase in cooling-related energy use and environmental emissions. Given the serious implications of this development, concerted efforts are needed in view of required new strategies. In this context, the present contribution focuses on an alternative user-centric radiant cooling solution. Conventional radiant cooling systems have been promoted in view of their energy efficiency potential, as well as enhanced thermal comfort provision, due to a draft-free cooling process. However, condensation risk can limit the application scope of these conventional systems. The alternative user-centric strategy is intended to address this limitation by positioning vertical radiant panels closer to occupants and incorporating drainage systems for potential surface condensation. A preliminary laboratory study was conducted to gain a first impression of the performance of user-centric vertical radiant panels. To this end, radiant panels were installed and operated in two test rooms. A small group of participants subjectively evaluated thermal comfort under different ambient air and panel surface temperatures. The results point to both the potential and the limitations of the proposed user-centric radiant cooling solution.

Abstract: Due to the current rate of global warming, overheating in buildings is expected to be more frequent and intense in future climates. High indoor temperature affects occupant productivity, comfort, and health. Thus, it is necessary to predict the thermal performance of buildings concerning climate change. This paper applies a climate change sensitive overheating assessment method to a lightweight timber house in Eupen, Belgium. Three metrics are used, namely Indoor Overheating Degree (), Ambient Warmness Degree (), and Building Climate Vulnerability Factor (). The overheating risk is assessed under four climate scenarios representing historical and future scenarios using dynamic simulation tool EnergyPlus v9.0. This method accounts for overheating severity and frequency, considering zonal occupancy profiles and thermal comfort models. The results indicate BCVF<1 for the Passive House case study showing its high potential in suppressing the outdoor thermal stress in the long-term. Finally, the increase in ventilation rate proves to be an adequate measure by decreasing the zonal peak temperatures up to 10? and indoor overheating risk by ~60%. Key Innovations • Warm discomfort during the heating period is contained within the overheating analysis • Lower base temperature for calculation of AWD is considered • Climate change-sensitive overheating assessment is applied on a high-performance building in the Belgian context Practical Implications This paper provides a basis for the field experts in climate-resilient building design. It makes them aware of expected overheating risks in future climates and consider adaptation strategies in early-design stages.

Abstract: Under heat-stressful conditions, occupants can adapt to the environment by regulating sweating or blood flow to the surface of the skin. However, the ability of the human body thermoregulation declines with age due to agerelated physiological and thermoregulatory changes such as the delay in vasodilation and sweating and lower metabolism. Therefore, elderly people (>60 years old) are more vulnerable during indoor overheating events than younger people. This study addressed the development of a general two-node bioheat model for the elderly to predict their thermal response under hot exposure. The elderly model is built on an improved two-node model for young adults but considers the delayed threshold temperatures for vasodilation and sweating suitable for the average elderly. Both models for the young (by turning off age-related physiological changes) and elderly people were validated using third-party experimental data. The discrepancy between the model predictions and measurement data for the core and mean skin temperatures are within 0.15 °C and 0.5 °C, respectively.

Abstract: This study aims to inform building designers about overheating risks in nearly zero-energy dwelling and the importance of calculation methods. Three overheating risk indicators are selected and compared, comprising 1) the EPBD overheating indicator, 2) the Passive House overheating indicator, and 3) the ambient warmness degree and indoor overheating degree indicators developed by Hamdy et al. (2017) (Hamdy et al., 2017a). The third overheating calculation method represents the latest state-of-the-art method for overheating assessment. With the help of the EnergyPlus energy modeling program, a calibrated building energy model was created. Annual simulations took place for a typical meteorological year comparing overheating risk according to three calculation approaches. Results confirm a 216% difference in the overheated hours between the Energy Performance of Buildings Directive (EPBD) method and the used method of Hamdy et al. 2017. Results emphasize the need to improve the Belgian EPBD calculation method and integrate long-term thermal discomfort indicators to represent climate change and overheating risks in dwellings. Key Innovations ? Overheating risk estimation is calculated based on three different calculation methods, and results are compared ? One of the overheating calculation method takes into account future climate change scenarios and applies long-term thermal comfort evaluation indicators ? The findings urge the call for a new standardised wat to calculate overheating within the EU Energy Performance of Buildings Directive (EPBD) Practical Implications This paper provides a basis to integrate a new overheating calculation method in the EPBD tools in Belgium and other EU member states.

Abstract: The resilient building design has become necessary within the increasing frequency and intensity of extreme disruptive events associated with climate change. Since thermal comfort is one of the main requirements of occupants, evaluating building resilience from a thermal perspective during and after disruptive events is necessary. Most of the existing thermal resilience metrics focus on thermal performance only during disruptive events. Building designers are still seeking metrics that can capture thermal resilience in both phases (i.e. during and after the disruptive events). This paper introduces a novel benchmarking framework and a multi-phase metric for thermal resilience quantification. The metric evaluates thermal resilience concerning building characteristics (i.e. building envelope and systems) and occupancy. It penalises for thermal performance deviations from the targets based on the phase, the hazard level , and the exposure time of the event. The introduced methodology is validated by quantifying the thermal resilient performance of six building designs against a four-day power failure as a disruptive event. The six designs represent minimum and passive building requirements with and without batteries or photovoltaics as resilience enhancement strategies. For the considered case study, upgrading the building from the minimum to the passive design has a huge impact (71%) on resilience improvement against power failure in winter. The application of the battery and PVs can improve the thermal resilience of the two designs in the range of 19%–27% and 44%–60%, respectively. Findings can provide a useful reference for building designers to benchmark the building’s thermal resilience and constitute resilience enhancement measures

Abstract: Prolonged and/or extreme heat has become a natural hazard that presents a significant risk to humans and the buildings, technologies, and infrastructure on which they have previously relied on to provide cooling. This paper presents a conceptual model of a resilient cooling system centred on people, the socio-cultural-technical contexts they inhabit, and the risks posed by the temperature hazard. An integrative literature review process was used to undertake a critical and comprehensive evaluation of published research and grey literature with the objective of adding clarity and detail to the model. Two databases were used to identify risk management and natural hazard literature in multiple disciplines that represent subcomponents of community resilience (social, economic, institutional, infrastructure and environment systems). This review enabled us to characterise in more detail the nature of the temperature hazard, the functionality characteristics of a resilient cooling system, and key elements of the four subsystems: people, buildings, cooling technologies and energy infrastructure. Six key messages can be surmised from this review, providing a guide for future work in policy and practice.

Abstract: Ventilation has proved to be an effective solution for reducing building cooling load in high-rise buildings, i.e. ventilative cooling (VC), especially in cold climates. Mechanical ventilation system can achieve VC (i.e. mechanical VC) in high-rise buildings, but it needs appropriate control to reduce cooling related energy consumption and to consider the impact of climate change. This study aims to develop an optimal control method for mechanical VC and evaluate its energy performance, based on an advanced model. In this advanced model, a machine learning model was applied to predict building cooling load and energy models were developed to predict energy consumption. A case study was conducted on a real high-rise building located in Montreal (Canada). Using the measured data from the Building Automation System (BAS), the machine learning model, generated by an algorithm called Gradient tree boosting (GTB), was found to be the most accurate and was used in the optimal control method. The energy models that couple mechanical ventilation and chiller cooling were validated with the BAS measured data. Then, the optimal control method was applied to study the energy performance of mechanical VC under long-term climate conditions. The results indicate that the energy savings of mechanical VC will decrease around 16% during the summer but increase around 105% during the shoulder season due to climate change. The optimal nominal ventilation rate for mechanical VC in the typical meteorological year is twice of that in the 2080 s A1FI weather scenario.

Abstract: The concept of climate resilience has gained extensive international attention during the last few years and is now seen as the future target for building cooling design. However, before being fully implemented in building design, the concept requires a clear and consistent definition and a commonly agreed framework of key concepts. The most critical issues that should be given special attention before developing a new definition for resilient cooling of buildings are (1) the disruptions or the associated climatic shocks to protect against, (2) the scale of the built domain, (3) the timeline of resilience, (4) the events of disruption, (5) the stages of resilience, (6) the indoor climate limits and critical comfort conditions, and (7) the influencing factors of resilient cooling of buildings. This paper focuses on a scoping review of the most of the existing resilience definitions and the various approaches, found in 90 documents, towards possible resilient buildings. In conclusion, the paper suggests a definition and a set of criteria —vulnerability, resistance, robustness, and recoverability— that can help to develop intrinsic performance-driven indicators and functions of passive and active cooling solutions in buildings against two disruptors of indoor thermal environmental quality—heat waves and power outages.

Abstract: Urban atmospheric flow is characterized by meteorological processes and street-scale perturbations of microclimate wind velocity and air temperature distributions. The Weather Research and Forecasting model (WRF) is applied to investigate the effects of meteorological processes on temperature distribution over the Greater Montreal Area during the 2017 heatwave. The single-layer Urban Canopy Model is coupled with the WRF to estimate the heat fluxes from the canopy to the atmosphere. The mesoscale simulation results provide the boundary conditions for a new city-scale microclimate LES model, CityFFD. This study first validated the WRF model through multiple weather station measurements and the CityFFD model through the literature data, then investigated the impacts of three canyon aspect ratios and three anthropogenic heat regimes, i.e., surface temperature differences, on the boundary conditions setups. The strong anthropogenic heat assumption was applied to modeling the 2017 heatwave for three consecutive days using the integrated model. The transient results show that a difference of ∼4?m/s wind speed could result in a spatial temperature variation of up to 4?°C for the area under consideration. This study shows the importance of microclimate simulations for regional climate models when studying urban heatwaves.

Abstract: As part of the EBC Annex 80 - Resilient cooling of buildings activities, the Thermal Condition Taskforce was created, in April 2020. In coordination with all other groups and the Weather Data Taskforce, two objectives were set by the Annex leader Dr. Peter Holzer. Firstly, to define common thermal conditions to assess different cooling technologies. Secondly, define a standard benchmark that can allow comparing the different cooling technologies worldwide. Several meetings and discussions took place between May and November 2020 to identify a systematic methodology for assessing the overheating risk in buildings and enable the comparative evaluation of resilient cooling technologies. The taskforce succeeded to identify common comfort criteria based on an existing overheating calculation method. Also, reference simulation models for benchmarking were identified. This report presents the outcome of the Thermal Condition Taskforce in the form of a methodological framework that can allow performing a comparative evaluation of cooling technologies. The framework is meant to provide a consistent and structured approach to evaluate and relatively compare different cooling technologies on the building scale, taking into account comfort and not only energy efficiency. Therefore, the framework was designed and tested in line with the Weather Data taskforce choice of sixteen cities worldwide and involving IPCC climate change scenarios. The framework is flexible and open, allowing building simulation modellers to run comparative simulations in different climates and evaluating the Technologies investigated by the Annex.

Abstract: This contribution explores the performance of a usercentric radiant cooling approach. In comparison to conventional radiant cooling solutions, this approach i) positions radiant panels in close proximity to occupants, and ii) allows for panel surfaces temperatures below dew point and thus for potential surface condensation, which is dealt with via integrated water collection devices. The user-centric radiant panels were tested in a laboratory setting. Prototypical panels were installed in two mock-up office rooms. Twenty-eight participants evaluated thermal comfort (including radiant asymmetry and local thermal discomfort) for eight scenarios, including multiple panel surface temperatures as well as different ambient air temperatures. The results provide insights into the potential and limits of the proposed approach. Specifically, the findings pertain to panel surface temperatures, which are necessary to provide thermally comfortable conditions, as well as to surface condensation and radiant asymmetry.

Abstract: Cooling-related energy consumption is growing rapidly in buildings. High-rise buildings usually have high cooling loads and cooling-related energy consumptions. Reducing the cooling load of high-rise buildings is critical for decreasing cooling-related energy consumption and peak electricity demand. Due to their cold climates, ventilative cooling (VC) is available for a long time throughout the year in Canada and Northern Europe, not only during shoulder seasons, but also in summer periods. Mechanical ventilation is an option for providing VC and reducing high-rise cooling load. However, the mechanical ventilation system in high-rise buildings is typically designed and used for maintaining indoor air quality, rather than for removing indoor heat. This study aims to use the mechanical ventilation system for VC in high-rise buildings and explore the associated energy saving approaches. Energy models of components in the cooling system were developed. Based on the models developed, different energy saving approaches were proposed, including applying the optimal control method, using energy efficient fans, and increasing nominal fan flow rates. A case study was conducted on an institutional high-rise building to validate the models developed and evaluate the proposed energy saving approaches. It was found that with energy efficient fans, applying the optimal control method and increasing the nominal ventilation flow rate can achieve energy savings for cooling. Increasing the optimal nominal ventilation rate further does not significantly increase energy savings. The conclusions of this study provide vital information regarding high-rise VC for new building design and HVAC system retrofit in existing buildings.

Abstract: Overheating in buildings has been a major health concern for vulnerable occupants during extreme heatwaves. Even though indoor overheating is highly dependent on outdoor climate, it may also be affected by other factors including building envelope characteristics, HVAC operation and internal heat gains. This study is to investigate the synchronisation of indoor overheating with outdoor heatwave. Archetype residential buildings were created and used to conduct EnergyPlus simulations of 31 years climate data of three major Canadian cities. A heatwave evaluation method developed by National Research Council of Canada was used to define heat events and extreme summer weather years. The method uses the transient standard effective temperature (t-SET) to rank heat events in terms of duration, intensity and severity. The results show that in most building configurations, outdoor extreme heatwaves are synchronised with indoor extreme overheating events. Outdoor-based extreme summer weather years are therefore suitable to study indoor overheating risks.

Abstract: Overheating in residential building is a challenging problem that causes thermal discomfort, productivity reduction, and health problems. This paper aims to assess the climate change impact on thermal comfort in a Belgian reference case. The case study represents a nearly zero energy building that operates without active cooling during summer. The study quantifies the impact of climate change on overheating risks using three representative concentration pathway (RCP) trajectories for greenhouse gas concentration adopted by the Intergovernmental Panel on Climate Change (IPCC). Building performance analysis is carried out using a multizone dynamic simulation program EnergyPlus. The results show that bioclimatic and thermal adaptation strategies, including adaptive thermal comfort models, cannot suppress the effect of global warming. By 2050, zero energy buildings will be vulnerable to overheating.

Abstract: Buildings globally are subjected to climate change and heatwaves, causing a risk of overheating and increasing energy use for cooling. Low-energy cooling solutions such as night cooling are promising to realize energy reduction and climate goals. Apart from energy performances, resilience is gaining importance in assessing the performance of the building and its systems. Resilience is defined as “an ability to withstand disruptions caused by extreme weather events, man-made disasters, power failure, change in use and atypical conditions; and to maintain capacity to adapt, learn and transform.” However, there is a clear lack of Resilience indicators specific for low energy cooling technologies. In this paper, the resilience of the night cooling in a residential building in Belgium is assessed for two external events: heat wave and shading failure. This paper shows the first attempt of a resilience indicator for night cooling as the effect on the shock of solar shading failure, heat wave or combination of both. It takes 3.4 days to bring down the temperature below 25?, in case of shading failure and heatwaves compared to 9 hours in the reference case. Further research is needed to determine resilience indicators as a performance criteria of low-energy cooling systems.

Abstract: In Montreal, following a heatwave in 2018, up to 53 deaths were reported with most being elderly, and who suffered from mental or chronic illness. Most of them lived in buildings without access to air-conditioning and vulnerable communities of the city center, where it is significantly hotter than rural areas. To ensure the resiliency of Canadian buildings against overheating, and protect Canadians’ health from a changing climate, Concordia University is leading a national research project collaborating with the National Research Council, Environment Canada and Climate Change, and Health Canada on the assessment and mitigation of summertime overheating in vulnerable buildings of urban agglomerations. The research activities include 1). Field monitoring: Indoor thermal conditions of selected buildings and exterior climatic conditions will be monitored to assess risks of summertime overheating. 2). Simulations: Development of urban-scale microclimate model and building-scale overheating model. The urban-scale model will be developed to simulate the surrounding microclimate effects on specific buildings for the detailed whole building simulations to predict indoor thermal conditions under extreme heat events. 3). Mitigations: Development of mitigation strategies at building levels by considering urban-scale microclimate and climate change for different Canadian climatic zones. 4). Guidelines: Development of design guidelines to support the National Building Code of Canada and Canadian construction standards to address climate change. This paper reports the most recent progress of the field monitoring and simulation tasks with the focus on Montreal, Canada.

Abstract: The Reynolds independence has been important for scaled experiments of urban aerodynamics in wind environment engineering. It helps to circumvent the difficulty in conserving the Re number for large scaling ratios. However, the criteria for Re-independence and its working mechanism have not been well investigated quantitatively. In this study, a dimensionless numerical analysis is conducted to provide a microscopic view of the problem both theoretically and numerically. The conditions of the similarity and Re-independence are identified theoretically. A series of simulations of the typical urban canopy layer model with three typical building-street aspect ratios were performed to quantify the similarity levels by some new evaluation metrics, local adapted deviation rate (ADR), the turbulence viscosity ratio (TVR), and the fraction of laminar viscosity (μ’/μeff’). It is found that one explanation for the similarity of Re-independence is that either the convection of the flow dominates the diffusion, and/or the turbulence viscosity dominates the laminar viscosity inside the diffusion term. A regional critical Re number (Recr−r) concept is introduced to describe the case-specific and region-specific Re-independence: it is around 10,000–30,000 for the canyon and building height regions, and 60,000–140,000 for the near-wall regions.

Abstract: Many urban and building microclimate problems are featured with a big computational domain and a large number of computing grids, so a fast and accurate solution by computation fluid dynamics (CFD) remains a challenge. The simulations are often only steady-state and, if there exists a transient model, the solution is often limited for a short period. For these computationally expensive simulations, large timesteps and coarse meshes (LTCM) seem preferable among users with limited computing resources, whereas many existing CFD models may not perform well for LTCM problems. This study developed a new fast fluid dynamics (FFD) model based on the semi-Lagrangian approach with high-order temporal and spatial schemes designed for LTCM problems. For large timesteps, a 2nd-order temporal scheme estimates the characteristic curve of each fluid's particle by accounting for the acceleration of the flow field. For coarse meshes, a 4th-order spatial scheme applies a backward-forward sweep technique for better accuracy in space. The performance of the proposed method is verified and validated by five benchmark cases, including a pure advection problem, forced convection in a single room, transient wind flow around a cylinder, airflow around a group of low-rise buildings, and airflow around a high-rise building. Then, we demonstrated the model for the study of the urban wind flows in a city downtown area with 2500 buildings and 35 million grids. As one of the first studies of applying FFD to urban aerodynamics, this study shows its strong potential for solving big transient problems with large timesteps and coarse meshes.

Abstract: Considering the diverse uncertainties in building operations and external factors (i.e., occupancy and weather scenarios that can impact a building’s energy and comfort), performance robustness has become as important as the building performance itself. Selecting a robust and high performance building design is challenging, particularly when multiple performance criteria should be fulfilled. It requires performance evaluation, robustness assessment, and multi-criteria decision making in three sequential steps. The current study introduces a new robustness-based decision making approach that integrates the robustness assessment and decision making steps and is more transparent than previously used approaches. The proposed approach normalizes each objective function based on its defined target and combines them into one comprehensive indicator. Moreover, it penalizes solutions that do not meet the targeted margins. The new approach is tested on a case study of a single-family house, where eight competitive designs and 16 occupant and climate scenarios are investigated. Exhaustive searches and sophisticated engineering analysis are applied to validate the logic behind the approach’s results. In addition, a test framework is used to validate the reliability of the approach under different combinations of scenarios. The results show that the proposed approach can select a high performance and robust building design simultaneously with less analysis effort (no need for weighting the objectives nor for conducting a robustness analysis for each objective separately) and with much trustworthy rate (selecting solution in comparison to the defined targets and with less dependency on the scenario conditions) compared to one frequently used approach (i.e., the Hurwicz criterion).

Abstract: With rapid economic growth, the number of high-rise buildings increases significantly due to land shortage in highly populated cities. Compared with other types of buildings, high-rise buildings have a higher cooling load and are more energy intensive, leading to huge cooling energy consumption and peak electricity demand. Ventilation has proved to be an effective approach to reduce cooling load and thereby save cooling-related energy and reduce peak electricity demand for high-rise buildings, which is important for achieving sustainable development of cities and society. Building safety is a challenge in high-rise ventilation. Fires and the resultant air pollution in high-rise buildings are often disastrous and cause huge losses if the high-rise ventilation system is not designed and operated well. This paper presents a review of previous studies on energy efficiency and building safety for high-rise ventilation, including natural ventilation, mechanical ventilation and hybrid ventilation. Statistical analysis was conducted on the research methods, number of literature review sources, and topics. The research gap was also discussed. Through the review, it was found that increasing research has been conducted on high-rise ventilation, especially on the topic of building safety. It was also recommended to consider both safety and energy simultaneously, in order to achieve energy efficiency and safety in high-rise ventilation and therefore to promote the application of ventilation in high-rise buildings.