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Among environmental controls, solar shading and ventilative cooling are widely considered as key passive strategies for limiting the overheating risks in buildings. While their application is encouraged through Energy Performance of Buildings Directive regulations, several studies have shown that summer thermal comfort in heating-dominate temperate climates still requires deeper investigation, particularly in low-energy residential buildings. Based on qualitative and quantitative data collected through surveys and monitoring in 147 highly insulated houses in Wallonia (Belgium), this paper gives an overview of the implemented passive strategies and discusses their effectiveness. Statistical tests are conducted to evaluate their impact on both perceived and measured indoor conditions. In general, the results highlight a limited impact of the implemented strategies, questioning their proper operation. Operational modes for environmental controls thus appear crucial, and should better respond to occupants' needs, preferences and control opportunities. At a more general level, the study calls for a better understanding of the barriers inhibiting successful integration and operation of environmental controls, in order to effectively reduce overheating risks in residential buildings and limit future diffusion of active cooling systems with their induced environmental impacts. [ABSTRACT FROM AUTHOR]

While the potential impact of climate change mitigation measures is well documented in building sciences literature, there are only relatively sparse studies focusing on the efficiency of adaptation strategies. This paper aims to contribute to this topic by evaluating the extent to which the design of a typical nearly Zero Energy Buildling (nZEB) house in Wallonia (Belgium), and its current operation, could provide summer thermal comfort in a changing climate. Based on calibrated whole building energy simulations, and on the integration of future climate data directly derived from a high-resolution climate model, this study evaluates the potential evolution of overheating risks in the living room and in the main bedroom of the house. Discussing the compliance with existing overheating criteria, the study shows that the passive strategies currently deployed in the house might not be sufficient to guarantee summer thermal comfort especially in the bedroom, and that other strategies might be necessary in the future to limit the use of active cooling systems and curb their environmental impacts. This study concludes that considering the potential of these strategies to guarantee summer thermal comfort in a changing climate should be a priority for the design of nZEB houses (and their related policies) also in temperate oceanic climates. [ABSTRACT FROM AUTHOR]

The number of studies on green spaces' cooling effects has significantly increased in recent years, driven by the rising occurrence and severity of heat waves. Nevertheless, our current understanding of optimal green space designs for mitigating heat stress remains limited. This study delves into the historic Japanese dry gardens to examine the design strategies employed by ancient Japanese people in addressing hot and humid climates while crafting a thermally comfortable environment for garden visitors. We selectively investigated the thermal condition and spatial design of four compact dry gardens (<1500 m2) in Kyoto, Japan as we aimed to propose design strategies for small urban green spaces which are the major urban green spaces in Japan. The results indicated that the thermal condition in all the resting areas of the gardens was dramatically ameliorated to a "warm" condition when nearby open areas were "extremely hot." This enhancement was achieved through the provision of extensive shade, primarily in the form of roofs, covering approximately 80% and 70% of the areas within 5 and 10 m radii around the resting areas, respectively. Nonetheless, we observed spatial heterogeneity in thermal conditions among the resting areas, which were influenced by the varying degrees of greenery cover within a 20 m radius. This study demonstrates that Japanese dry gardens were designed climate accordingly and can effectively reduce summer heat stress. It highlights the value of historic gardens as urban green spaces providing regulating ecosystem services and as a strategic design reference for guiding climate-adaptive green space designs. [ABSTRACT FROM AUTHOR]

While the potential impact of climate change mitigation measures is well documented in building sciences literature, there are only relatively sparse studies focusing on the efficiency of adaptation strategies. This paper aims to contribute to this topic by evaluating the extent to which the design of a typical nearly Zero Energy Buildling (nZEB) house in Wallonia (Belgium), and its current operation, could provide summer thermal comfort in a changing climate. Based on calibrated whole building energy simulations, and on the integration of future climate data directly derived from a high-resolution climate model, this study evaluates the potential evolution of overheating risks in the living room and in the main bedroom of the house. Discussing the compliance with existing overheating criteria, the study shows that the passive strategies currently deployed in the house might not be sufficient to guarantee summer thermal comfort especially in the bedroom, and that other strategies might be necessary in the future to limit the use of active cooling systems and curb their environmental impacts. This study concludes that considering the potential of these strategies to guarantee summer thermal comfort in a changing climate should be a priority for the design of nZEB houses (and their related policies) also in temperate oceanic climates.

Due to the increasing energy use and greenhouse gas emissions related to HVAC applications in the residential sector, thermal energy storage with phase change materials has caught considerable attention in the last years. Their attractive storage capacity can be adapted to meet the energy needs of buildings. In this work, the design process of a prototype of an air-PCM unit is described, and the corresponding experimental tests are detailed. These experiments were carried out on a plus energy house prototype located in the Southwestern France, during the summertime of 2017. The thermal performance of this unit was assessed through indicators such as indoor air temperature, the operating time, and the Discomfort Degree Hours (DDH) within the house. The results suggest that the unit limits the indoor air temperature rise during its operation, keeping the temperature within the thermal comfort and therefore contributing to decreasing the thermal discomfort. [ABSTRACT FROM AUTHOR]

We developed and studied key performance indexes and representations of energy simulation heat fluxes to evaluate the performance of the evaporative cooling process as a passive cooling technique for a commercial building typology. These performance indexes, related to indoor thermal comfort, energy consumption and their interactions with their surrounding environments, contribute to understanding the interactions between the urban climate and building for passive cooling integration. We compare the performance indexes for current and future climates (2080), according to the highest emission scenario A2 of the Special Report on Emission Scenario (SRES). Specific building models were adapted with both green roof and wetted roof techniques. The results show that summer thermal discomfort will increase due to climate change and could become as problematic as winter thermal discomfort in a temperate climate. Thanks to evapotranspiration phenomena, the sensible heat contribution of the building to the urban heat island (UHI) is reduced for both current and future climates with a green roof. The performance of the vegetative roof is related to the water content of the substrate. For wetted roofs, the impacts on heat transferred to the surrounding environment are higher for a Mediterranean climate (Marseille), which is warmer and drier than the Paris climate studied (current and future climates). The impact on indoor thermal comfort depends on building insulation, as demonstrated by parametric studies, with higher effects for wetted roofs.

Abstract A brief analysis on radiant barriers applied in building roofs, included in a wider study, is presented. A case study which involves experimental measurements carried out in a single-family house, located in a mild climate, specifically in the North of Portugal, where radiant barriers were applied and monitored is described. A computer program (CAPSOL) was also used to carry out a sensitivity analysis and to verify if the results pointed to conclusions similar to those of the experimental measurements. In the experimental part of this work, which took place in the summer periods of two consecutive years, two different roofs were monitored in the same house. Values of temperature, relative humidity, solar irradiance, heat fluxes among other parameters were measured. This article presents some of the collected data. In the numerical simulation, the comparison between the situation of the inclusion of a radiant barrier underneath the roof tiles and over the attic floor slab is presented and compared with another situation without this barrier. In general, it was concluded from this brief analysis that the application of a radiant barrier in the roof of a building proves to be advantageous, especially in what regards the attenuation of the maximum temperatures reached at the roof attic, thus mitigating the risk of overheating. [ABSTRACT FROM AUTHOR]

In this paper, we propose a practical approach for decision-making regarding passive cooling design for buildings in dense urban contexts. For non-cooled buildings under temperate climates, assessment of summer thermal discomfort determines the usual passive cooling design together with fossil energy and GHG savings at earth scale. However, passive cooling techniques for indoor climate can be also valuable for local environment impacts, especially urban heat islands’ mitigation. Lack of simple representative criteria and complexity of simulation outputs constitute a barrier for the development of passive cooling. Based on a study of a generic commercial building, we analyzed several designs with Sankey diagram and we developed two performance indexes. This chart synthesis of complex output data allows a direct comparison of design solutions. This analysis gives hints for better designer understanding of urban climate and building interactions for the studied passive cooling solutions: cool roofing, nocturnal natural ventilation and rooftop PV system as shading device. Our results show that nocturnal natural ventilation is efficient to moderate indoor overheating compared to the "cool roof". In addition, cool roofs reduce anthropogenic heat transferred to urban environment. PV panels as shading device mitigate summer discomfort and produce energy that increase building energy efficiency through the year. We defined two Key Performance Indexes (KPIs) to define cooling potential of both indoor and urban environment. These KPIs obtained for different temperate climates highlight new prospects for the design of efficient urban designs with controlled environmental impacts and decision process of stakeholders. [ABSTRACT FROM AUTHOR]

This paper investigates the potential of using form-stable phase change material (FS-PCM) integrated cement mortars in building envelopes to prevent overheating and to improve summer thermal comfort. The FS-PCM integrated cement mortar was applied as the interior surface plastering mortar of a full-scale test hut and compared with identical test huts built on cement plasterboard (OCB) and gypsum plasterboard (GPB). The test huts were exposed to outdoor climatic conditions, and indoor thermal behaviours were continuously monitored throughout the summer period. The effects of PCM in reducing the overheating was analysed by the intensity of thermal discomfort (ITDover) and frequency of thermal discomfort (FTDover) for overheating during the summer days. The comparison between different test huts showed that the application of PCM integrated cement mortars reduced the peak indoor temperature by up to 2.4 °C, compared to GPB and OCB test rooms. More importantly, the analysis of overheating effects revealed that at lower intensive thermal discomfort levels, FS-PCM largely reduces FTDover. As the intensity of thermal discomfort increases, the reduction in ITDover becomes dominant. At highly intensive thermal discomfort levels, the reduction was neither apparent in the intensity of thermal discomfort nor the period of discomfort.

This study analyses which building parameters contribute the most to overheating in dwellings and which properties will make a room ‘critical’, to be chosen for compliance assessment procedure through temperature simulation, as required in Estonia for new residential buildings. Indoor temperature measurements, conducted in 18 apartments from 16 apartment buildings, show clear evidence of overheating. Compliance assessment of 25 new buildings were conducted using IDA-ICE software. The analysed sample consisted of typical multi-storeyed buildings with mainly massive concrete structures. From the simulated buildings, 68% did not meet the requirements, showing that this relatively new building code requirement was not fully established in practice. Results of the analysis indicate that the requirement in apartment buildings is achievable without cooling, if passive measures are properly applied. Recommendations are given to designers, as well as policy-makers, to improve the situation in the residential building sector. [ABSTRACT FROM AUTHOR]

This work analyses the measured indoor environmental data collected during long-term monitoring of a social housing project built to the Passive House (PH) standard. The indoor temperature, CO2concentration and relative humidity levels were continuously logged in 18 of the 354 apartments. The volatile organic compound concentrations were also measured before the tenants moved in. Furthermore, a survey using questionnaires and interviews was performed to evaluate the occupants' satisfaction levels. For comparison, the indoor environment of six dwellings of a similarly constructed low-energy building, but without mechanical ventilation was also measured within this project. Within the Passive Housing, the average indoor temperature distribution during winter showed a surprisingly large difference compared to the low-energy housing and to other documented PH projects in Germany. Overheating during summer seemed to be an issue especially in the top-floor apartments. This re-emphasizes the need for proper shading solutions. The evaluation of the indoor air quality shows the need for controlled domestic ventilation for non-owner-occupied buildings. The combined assessment of measured data and survey results shows the importance of factoring in air humidity when defining ventilation rates. If no humidity-raising measures are applied, air exchange rates well below 0.5 h−1can be recommended for locations with cold and dry climates. In general, the satisfaction level within the presented social housing complex built to the PH standard was very high. [ABSTRACT FROM PUBLISHER]

In order to compensate for the small storage capacity of lightweight buildings, that usually suffer from pronounced overheating in summer, the incorporation of Phase Change Materials (PCMs) into the opaque envelope can be an effective way to enhance thermal inertia and to improve the thermal comfort. In particular, PCM wallboards are recommended during refurbishment, as they have a small thickness and can be easily applied on the inner surface of both the walls and the ceiling. In this paper, a comprehensive study is presented about the effectiveness of PCM wallboards for improving summer thermal comfort in existing lightweight buildings. The study is based on dynamic simulations carried out with the software EnergyPlus on a sample office building. The analysis is repeated in four different locations, ranging from Southern Europe (Catania, Italy) to Northern Europe (Paris, France). The results of the simulations may help designers to make the correct choices in terms of position of the PCM wallboards, scheduled rate of nighttime ventilation and value of the peak melting temperature for the specific PCM. [ABSTRACT FROM AUTHOR]

In this paper, the authors first clarify the definition of building microclimate in free-running buildings and the relationship with summer thermal comfort. Next, field measurements were conducted to investigate the microclimate in a Chinese traditional vernacular house. Subsequently, the results of measurements were compared with a dynamic thermal and a CFD simulation in order to determine the building microclimate and thermal comfort of the present vernacular house over the period of an entire summer. The field measurements show the present Chinese vernacular house has its own independent building microclimate in summer, which is in accordance with the main character of microclimate in terms of different distributions of solar gain, air temperature and wind velocity in different spaces. The simulation results of the vernacular house could be matched well with the field measurements. According to the simulations, at night, a comfortable temperature could be obtained throughout most of the summer period whereas in the daytime the operative temperature was higher than the comfortable temperature for one-third of the summer period. Wind velocity in the semi-outdoor and outdoor spaces however, improves the thermal comfort significantly. The thermal comfort environment can thus not only change in time but also in space. This example of the vernacular building shows that it is possible to create comfortable conditions for the inhabitants when not only the indoor climate is taken into account but the whole building microclimate as defined in this paper. This paper also shows that the simulations can predict the building microclimate. [ABSTRACT FROM AUTHOR]

In urban planning, sustainability is often synonymous to urban livability. Urban livability seeks to improve living conditions of current and future outdoor users and hence it has become a key priority for cities authorities. Melbourne, as the world second most livable city, sets out to improve its urban life quality through various policies and initiatives. One area of improvement is the creation of sustainable outdoor spaces that provides comfortable thermal conditions for its residents. The relevant strategies to create such spaces are supported by the knowledge of human thermal comfort requirements, particularly during the summer thermal conditions. Hence, this study aims to develop comprehensive thermal comfort benchmarks for Melbourne during the summer. This study builds on 4717 subjective survey responses collected in seven urban environments with different settings. Data collection was performed in Melbourne's summer from 2012 to 2015. Physiological Equivalent Temperature (PET) was used to predict thermal comfort conditions. The results were based on four thermal comfort measures (neutral temperature, preferred temperature, acceptable thermal range and thermal comfort range). The analysis' outcomes suggested that Melbourne's summer acceptable thermal range is between 11.3 °C and 20.3 °C, the preferred temperature value is 21.5 °C, the neutral temperature value is 16.1 °C. Furthermore, PET index was calibrated against thermal responses collected from the surveys. The results would help to inform policies aiming to create sustainable outdoor spaces that are pleasant to outdoor users in Melbourne. • Analytical techniques affect the values obtained for outdoor thermal benchmarking. • The thermal comfort benchmarks inform design strategies to create comfortable outdoor spaces within cities. • Summer preferred PET (21.5 °C) is higher than neutral PET (16.1 °C). • Summer acceptable thermal range is between 11.3 °C and 20.3 °C (PET) in Melbourne. • Further studies should cover other comfort requirements such as visual and acoustics. [ABSTRACT FROM AUTHOR]

In a context of global warming, summer thermal comfort is a key issue for the design and operation of nearly zero-energy buildings (nZEBs). Although there are various methods and benchmarks for the long-term evaluation of summer thermal conditions in free-running buildings, their application to the residential sector is still debated. Based on data from post-occupancy measurements and survey campaigns, this paper evaluates the compliance with commonly used overheating criteria defined by existing standards (CIBSE and Passive House Institute) of 23 nZEB houses in Wallonia (Belgium). The quantitative relationship between measured and perceived comfort is statistically analysed, and building characteristics leading to the most critical overheating situations are qualitatively discussed. The results show that summer thermal discomfort is frequent in nZEB houses in Wallonia, despite its temperate climate. In living rooms, the long-term appraisal of thermal conditions appears to be related to the frequency of extreme temperatures, while occupants' thermal perception in bedrooms seems to be more affected by smaller temperature deviations. These results imply a critical review of the capacity of the criteria commonly used for the evaluation of overheating risks in free-running residential buildings to predict the satisfaction of occupants with their summer thermal comfort. More generally, the findings reinforce the importance of a better integration, even in temperate climates, of environmental controls – and their required operation by the occupants – to properly mitigate overheating risks in nZEB houses. • Compliance with common overheating criteria is compared with comfort perception. • Summer thermal discomfort is common in Walloon nZEB houses, especially in bedrooms. • In living areas, summer perception is more influenced by extreme temperature episodes. • In bedrooms, summer thermal comfort is driven by smaller temperatures deviations. • Better understanding of how environmental controls are operated by occupants is needed. [ABSTRACT FROM AUTHOR]

We developed and studied key performance indexes and representations of energy simulation heat fluxes to evaluate the performance of the evaporative cooling process as a passive cooling technique for a commercial building typology. These performance indexes, related to indoor thermal comfort, energy consumption and their interactions with their surrounding environments, contribute to understanding the interactions between the urban climate and building for passive cooling integration. We compare the performance indexes for current and future climates (2080), according to the highest emission scenario A2 of the Special Report on Emission Scenario (SRES). Specific building models were adapted with both green roof and wetted roof techniques. The results show that summer thermal discomfort will increase due to climate change and could become as problematic as winter thermal discomfort in a temperate climate. Thanks to evapotranspiration phenomena, the sensible heat contribution of the building to the urban heat island (UHI) is reduced for both current and future climates with a green roof. The performance of the vegetative roof is related to the water content of the substrate. For wetted roofs, the impacts on heat transferred to the surrounding environment are higher for a Mediterranean climate (Marseille), which is warmer and drier than the Paris climate studied (current and future climates). The impact on indoor thermal comfort depends on building insulation, as demonstrated by parametric studies, with higher effects for wetted roofs. [ABSTRACT FROM AUTHOR]

This paper investigates the potential of using form-stable phase change material (FS-PCM) integrated cement mortars in building envelopes to prevent overheating and to improve summer thermal comfort. The FS-PCM integrated cement mortar was applied as the interior surface plastering mortar of a full-scale test hut and compared with identical test huts built on cement plasterboard (OCB) and gypsum plasterboard (GPB). The test huts were exposed to outdoor climatic conditions, and indoor thermal behaviours were continuously monitored throughout the summer period. The effects of PCM in reducing the overheating was analysed by the intensity of thermal discomfort (ITDover) and frequency of thermal discomfort (FTDover) for overheating during the summer days. The comparison between different test huts showed that the application of PCM integrated cement mortars reduced the peak indoor temperature by up to 2.4 °C, compared to GPB and OCB test rooms. More importantly, the analysis of overheating effects revealed that at lower intensive thermal discomfort levels, FS-PCM largely reduces FTDover. As the intensity of thermal discomfort increases, the reduction in ITDover becomes dominant. At highly intensive thermal discomfort levels, the reduction was neither apparent in the intensity of thermal discomfort nor the period of discomfort. [ABSTRACT FROM AUTHOR]