Indoor Temperature In Winter Research Articles

Inequalities in exposure to indoor environmental hazards across England and Wales – can more energy efficient homes help?

Housing is an important modifier of outdoor environmental hazards due to features such as the amount of passive and active ventilation a dwelling receives, the proportion of the façade that is glazed and the building’s thermal insulation levels. Using Artificial Neural Networks based on an indoor building physics model, we simulate indoor temperature and air pollution concentrations in ~15 million English and Welsh dwellings and assess how exposure to indoor hazards varies for different population groups. The model is derived using simulations from the dynamic thermal modelling tool EnergyPlus, taking a spatially-distributed housing stock as input. Results are linked to the latest 2021 Census data on area-measures of population demographics to assess if vulnerable subgroups bear a disproportionate risk from indoor environmental hazards. We find neighbourhoods in England and Wales with a higher proportion of infants, ethnic minorities and income-deprived populations experience higher two-day maximum indoor temperatures in summertime; whilst more ethnically diverse areas have elevated annual average indoor concentrations of outdoor-sourced PM2.5. Areas with a higher proportion of those aged 65+ had a lower standardised indoor temperature (SIT) in winter, increasing the risk of fuel poverty. We then implement a stock-wide, home energy retrofit, in line with national decarbonisation targets. Results suggest energy-efficient building interventions may exacerbate heat inequalities without the provision of external shading, but improve population exposure to winter indoor temperatures and indoor concentrations of ambient-sourced PM2.5.

Cold homes in Australia: Questioning our assumptions about prevalence

Australia is considered by many to be a warm climate country and hence winter cold and its health effects are often overlooked. The majority of the Australian population live in temperate climate regions, which are heating-dominated and experience cold wintertime conditions. The prevalence of cold in Australian homes has to date been rarely measured or estimated, and the few studies that do are based on proxy data that estimate a low prevalence (around 5 %). This paper tests these proxy measures, using high resolution temperature data on indoor temperature from 100 homes across temperate Australia. The data were assessed using the World Health Organization's Housing and Health guideline for minimum indoor temperature (18 °C), which provides an internationally recognised benchmark for defining cold in homes. Across the sampled homes, 81 % were below 18 °C on average across the whole of winter (June–August 2022). Average winter indoor temperatures were 16.5 ± 2.7 °C across all homes, with no significant difference between locations. These early findings suggest that the problem of unhealthily cold homes in Australia is likely to be significantly more prevalent than previously estimated. Far from affecting 5 % of Australian households, the affected population may be 10 times this value. These initial findings have important implications for how we model health impacts and develop policy. This early release data from a recently commenced large environmental monitoring project is of timely importance. It challenges our understanding of the prevalence of cold housing in Australia context, flagging the pressing need to increase policy attention in advance of winter.

Association between Indoor Temperature in Winter and Serum Cholesterol: A Cross-Sectional Analysis of the Smart Wellness Housing Survey in Japan.

Issuance of the WHO Housing and health guidelines has paralleled growing interest in the housing environment. Despite accumulating evidence of an association between outdoor temperature and serum cholesterol, indoor temperature has not been well investigated. This study examined the association between indoor temperature and serum cholesterol. We collected valid health checkup data of 2004 participants (1333 households), measured the indoor temperature for 2 weeks in winter, and divided participants according to whether they lived in a warm (average bedroom temperature ≥ 18℃), slightly cold (12-18℃) or cold house (＜12˚C). The relationship between bedroom temperature and serum cholesterol was analyzed using multivariate logistic regression models, adjusting for demographics, lifestyle habits and the season in which the health checkup was conducted, with a random effect of climate areas in Japan. The sample sizes for warm, slightly cold, and cold houses were 206, 940, and 858, respectively. Compared to those in warm houses, the odds ratio of total cholesterol exceeding 220 mg/dL was 1.83 (95%CI: 1.23-2.71, p=0.003) for participants in slightly cold houses and 1.87 (95%CI: 1.25-2.80, p=0.002) in cold houses. Similarly, the odds ratio of LDL/non-HDL cholesterol exceeding the standard range was 1.49 (p=0.056)/1.67 (p=0.035) for those in slightly cold houses and 1.64 (p=0.020)/1.77 (p=0.021) in cold houses. HDL cholesterol and triglycerides were not significantly associated with bedroom temperature. Besides lifestyle modification, improving indoor thermal environment through strategies such as installing high thermal insulation and appropriate use of heating devices may contribute to better serum cholesterol condition.

Characteristics of the thermal environment, air quality, and passenger comfort in the underground transfer space of metro stations in Beijing

With the increase in Beijing's metro mileage and passenger numbers, it is becoming especially necessary to investigate the indoor environment and passenger comfort of metro stations. In this study, the transfer spaces in the top seven transfer stations with the largest passenger flow within the Beijing metro system were selected for conducting indoor environment (thermal environment and air quality) measurements and a subjective comfort survey of over 600 passengers. The results showed that the thermal environment and air quality experienced by passengers changed dynamically with the passenger transfer process. Indoor temperature and relative humidity (RH) were affected by not only aboveground weather changes but also station depth, and the indoor temperature in winter was more comfortable than that in summer. The trend in subjective feelings of passengers' thermal comfort was similar to that of the relative warmth index (RWI) evaluation of seven transfer stations during the measurement periods, and passengers' thermal comfort during the summer morning rush hours was not ideal but was slightly hot overall. Although the concentrations of carbon dioxide (CO2) and particulate matter (PM: including PM2.5 and PM10) met the indoor air quality maintenance standards, the percentage of passengers uncomfortable with the air quality exceeded 80% during both seasons, and the centralized tendency in winter was very uncomfortable. Passengers are very concerned about air quality, and their subjective feelings are relatively susceptible to psychological factors. Regarding the overall comfort trend, passengers' subjective feelings of comfort during the morning rush hours in summer and winter were both “slightly uncomfortable”. This paper provides a valuable reference for further research on environmental, health, and energy saving issues in metro stations and presents reliable primary research data for the design and operation management of ventilation and air conditioning systems in metro stations.

Research on Passive Reconstruction and Energy Supply System of Existing Buildings in Cold Areas

Faced with the problems of existing buildings in cold areas, such as poor insulation performance of envelope, high heating cost and substandard indoor temperature in winter, based on DeST-h energy consumption simulation software, taking typical single buildings in Zhangjiakou as an example, several factors affecting building energy consumption were analyzed. The building energy consumption values in heating season under 9 envelope reconstruction conditions were obtained by orthogonal experiments, and 4 different energy supply systems were designed for buildings under 9 envelope reconstruction conditions. The “with or without comparison method” is used to evaluate the building energy efficiency of 40 working conditions after the superposition of the initial state and passive transformation of existing buildings in the whole life cycle. The evaluation results show that the external wall insulation and extrusion plate thickness is 80 mm, the roof insulation and extrusion plate thickness is 100 mm, and the glass type is ordinary hollow glass ( 6 + 9 + 6 ). The air source heat pump assisted energy supply effect is the best, but the overall economy will change with the initial investment, local electricity price policy and building scale.

Interaction Effect of Room Size and Opening on Trombe Wall Performance in Sichuan–Tibet Alpine Valley Areas

The Trombe wall (T-wall) system is one of the most effective systems for passive solar energy utilization technology, which is of great significance for the alleviation of the energy crisis and the protection of the environment. Taking as an example Tibetan dwellings in the Sichuan–Tibet alpine valley which have installed T-walls for heating, the effects of the length of the room (Factor A), the width of the room (Factor B), the width of the opening on the north wall of the room (Factor C), and the distance from the lower edge of the opening to the floor (Factor D) on the indoor air temperature and room energy consumption are studied by orthogonal experiment and numerical simulation. Results show that the four factors all have a significant effect on the two analysis indicators. The rankings of the factors are consistent for their impact on the two analysis indicators, as, in both cases, Factor A > Factor B > Factor C > Factor D. Therefore, the influence of room configuration cannot be ignored in the optimization of T-wall design. Additionally, the optimal parameter combination for the highest indoor temperature and low energy consumption in winter is also proposed. This research can further improve the study of T-walls, and provide a reference for the thermal environment design of buildings.

Use of sponge iron dosing in baffled subsurface-flow constructed wetlands for treatment of wastewater treatment plant effluents during autumn and winter

Sponge iron (SI) is widely used in water treatment. As effluents from wastewater treatment plant (WWTP) require advanced treatment methodology, three forms of constructed wetlands (CWs): wetlands with sponge iron (SI), copper sulfate modified sponge iron (Cu/SI), and sponge iron coupled with solid carbon sources (C/SI), have been investigated in this paper for the removal effects of organic matter and nutrients in WWTP effluents, and the corresponding mechanisms have been analyzed. The results showed the effect of baffled subsurface-flow constructed wetland (BSFCW) with SI dosing to purify the WWTP effluents after the stable operation. The water flow of this BSFCW is the repeated combination of upward flow and downward flow, which can provide a longer treatment pathway and microbial exposure time. The average removal rates of total inorganic nitrogen (TIN) were 27.80%, 30.17%, and 44.83%, and the average removal rates of chemical oxygen demand (COD) were 19.96%, 23.73%, and 18.38%. The average removal rates of total phosphorus (TP) were 85.94%, 82.14%, and 83.95%. Cu/SI improved the dissolution of iron, C/SI improved denitrification, and a winter indoor temperature retention measure was adopted to increase the effectiveness of wetland treatment during the winter months. After comprehensively analyzing X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and two-dimensional numerical simulation diagrams, a plausible conjecture that microbes use electrons from SI for autotrophic denitrification is presented. Moreover, the stress effect of wetlands dosed with SI on plants decreased stepwise along the course since C/SI used on wetlands had less impact on plant stress.

Descriptive epidemiology of winter indoor and outdoor temperatures and their relationships based on SWH survey

Objectives The purpose of this study was to make clear the descriptive epidemiology and the relationship between the room temperature of living room, bedroom, dressing room, and outdoor during winter, based on the climate areas in Japan.Methods This study targeted 3,781 people, survey for 5 years from 2014, based on the Smart Wellness Housing (SWH) project, which was carried out nationwide with the support of the Ministry of Land, Infrastructure, Transport and Tourism. During winter, we recorded the outdoor temperature and living room, bedroom, and dressing room temperatures at 1 m above the floor and near the floor for two weeks. Covariance structure analyses were used to clarify the relationship between room temperature and outdoor temperature based on six climate areas in Japan. The analyses were performed using SPSS22.0 and AMOS22.0 for Windows.Results The temperature near the floor inside the house was lower than the room temperature at 1 m above the floor, and both the room and near the floor temperature in the morning tended to be the lowest. The temperature disparity between the dressing room and living room was the largest. Based on climate areas, the room temperature in the Area 2 was the highest, while the room temperature in the Area 4 was the lowest. The outdoor temperature was more closely associated with the room temperature near the floor than the room temperature at 1 m above the floor, especially in the southern Areas, except Area 7.Conclusion The temperature near the floor inside the house was lower than room temperature at 1 m above the floor. The temperature disparity between dressing room and living room was the largest. The room temperature and near the floor temperature were lowest in the energy-saving Area 4. The outdoor temperature was more closely associated with the room temperature near the floor than the room temperature at 1 m above the floor, especially in the southern Areas, except Area 7.

Multi-objective optimization design for rural houses in western zones of China

Limited by the climate, economic level and energy-saving awareness of rural residents in the western China, rural houses are still in a stage of high energy consumption (EC) and low comfort. The passive design strategies should be given priority to provide an optimal design mode. The challenge is to find the best combination of design parameters. In this paper, rural single-storey detached houses are taken as the research objects. Three conflicted indicators are set as the objective function, namely building EC, thermal comfort and economy. The investigated design variables include building orientation, insulating layer thickness, window width & type, and indoor design temperature. A methodology of combining EnergyPlus and MOBO is used for multi-objective optimization, thus getting the Pareto solutions and using the weighted sum method to obtain the optimum parameter combinations. The proposed methodology for simulation-based multi-objective optimization is a useful tool to facilitate decision-making in building design. Highlights An automated optimization method of combining EnergyPlus simulation software and MOBO optimization engine is proposed. The multi-objective method optimizes the building orientation, envelope and winter indoor temperature. Pareto non-dominated solutions for three conflict objective functions are obtained. The final optimum combination is determined by a weighted sum method.

Thermal and humid environment of rammed-earth dwellings in Northwest Sichuan

As a traditional building material, rammed earth has gained popularity for its environmental friendliness and reusability. In this study, the hygrothermal performance of the wall material of traditional rammed-earth dwellings was experimentally measured, and the indoor and outdoor temperature and humidity variations of rammed-earth dwellings were experimentally measured for five days. Considering temperature and relative humidity as the driving potential for heat and humidity transfer and air penetration, an unsteady model of heat and humidity transfer of the rammed-earth wall and indoor and outdoor air was established. The accuracy of the model was verified using the measured data. The model was used to determine the rationality of the wall thickness in local rammed-earth dwellings. Based on data from typical local meteorological years, the indoor temperature and humidity changes in rammed-earth dwellings were numerically predicted. The average indoor temperature and humidity in summer were 26.56°C and 69.74%, and the variances were 3.26 and 43.17, respectively. The average indoor temperature and humidity in winter were 7.25°C and 83.62%, and the variances were 1.14 and 14.83, respectively. The research results demonstrate that a rammed-earth wall significantly reduces the influence of outdoor temperature fluctuation on the indoor thermal environment, with good humidity regulating performance.

Analysis on influencing factors and energy saving potential of photovoltaic curtain wall preheating fresh air system in severe cold area

In the general building air conditioning load, the fresh air load accounts for more than 30%, especially in the severe cold areas in the north, with long winter and large indoor and outdoor temperature difference, the fresh air heat load will account for a larger proportion in the air conditioning system load. Making full use of renewable energy can effectively reduce building energy consumption. In this paper, the air flow field distribution in the ventilation duct of photovoltaic curtain wall is numerically simulated by fluent simulation software, and the air distribution form and temperature field distribution in the system cavity under different ambient temperature, cavity thickness and tuyere position are analyzed and compared, so as to obtain the influence of different influencing factors on the performance of the fresh air preheating system, and combine the photovoltaic curtain wall preheating fresh air system and electric heating system to explore its energy-saving potential. The results show that when the cavity thickness is greater than 400mm, the reduction range of photovoltaic curtain wall temperature becomes smaller, and the overall temperature distribution of the cavity tends to be uniform. When the ambient temperature is different, with the increase of ambient temperature, after the fresh air passes through the photovoltaic curtain wall preheating system, the temperature difference at the inlet and outlet of the air flow channel decreases, and the maximum temperature difference decreases from 4.6k to 3.4K.The combination of photovoltaic curtain wall and electric heating is used to preheat the fresh air. Compared with the traditional method, the same fresh air load is treated, and the energy-saving rate is 60% ∼ 70%. It shows that using photovoltaic curtain wall to preheat the fresh air can achieve better results, which provides guidance for putting forward more appropriate, economic and energy-saving design schemes in the project.

Study on the Performance of Trombe Wall in Hot Summer and Cold Winter Climate under Non-air Conditioning Condition

Trombe walls with phase change materials (PCMs) are well known as passive energy saving technologies, but the interaction between PCMs and Trombe walls was unclear. To explore the effect on indoor thermal environment of various operating strategies, eight cases were simulated under hot summer and cold winter climate. Integrated indoor discomfort duration (ID), integrated discomfort degree-hour (IDH), PCM liquid fraction, wall interior surface temperature and heat flux were used to assess the thermal performance throughout the year, compared with a traditional building. The results show that the effects of various operating strategies to indoors was closely related to ventilation, PCM type and position and massive wall. Ventilation was the most effective way to supply heating in winter and lower indoor temperature in summer; while its efficiency might be weakened if PCMs was installed, even though the overall indoor environment was improved. Without ventilation, massive wall with double PCM layers got better thermal performance than single layer, but the result would be contrary with ventilation. The optimal case for thermal performance is the Trombe wall with ventilation and single PCM layer, whose IDH were 2653.8°C·h in summer and 10204.3°C·h in winter.

Study on the Roof Solar Heating Storage System of Traditional Residences in Southern Shaanxi, China.

Solar energy is a renewable, green, clean, and universal resource that has great potential in rural areas. Combining solar heating technology with building design to increase indoor thermal comfort in winter is an effective energy-saving and environmentally friendly approach. The factors affecting solar building heating mainly include two aspects; one is the lighting area of the building, and the other is the storage of building materials. By increasing the lighting area and using materials with good heat preservation and storage performance, the indoor temperature in winter can be effectively increased, and the heating time can be prolonged, thus decreasing the energy requirements of the building. In this paper, traditional houses in cold winter areas are selected as the research object, and a roof solar heating storage system is proposed. The method is to transform the opaque roof of the traditional houses into a transparent glass roof, and the thermal insulation and heat storage material HDPE is installed in the attic floorboards. The working principle of this system is to increase the amount of indoor solar radiation to raise the indoor temperature and make use of the thermal insulation performance of heat storage materials to prolong the indoor heating time. Through ANSYS software simulation, the heat transfer process, heat transfer mode, and temperature change of the system are analyzed, and the energy saving of the system is analyzed. The system can effectively raise the indoor temperature and has good energy-saving performance. The indoor temperature is raised by 5.8 °C, and the annual heat load of the building is reduced by 1361.92 kW·h, with a reduction rate of 25.02%.

Post occupancy evaluation of 12 retrofit nZEB dwellings: The impact of occupants and high in-use interior temperatures on the predictive accuracy of the nZEB energy standard

The Europe Union needs to reduce its carbon emissions. To achieve the proposed 55% emission reduction target by 2030 it has embarked on a Renovation Wave which aims for more, and deeper, building renovation. Considering this ambition and the scale of the challenge, there remains a surprising paucity of documented post occupancy evaluation studies of deep retrofit projects, particularly those related to the new nZEB standards and of group housing schemes. This paper reports on the post-retrofit performance of a community of 12 single story, one bedroom social houses located in the southeast of Ireland, occupied by retired and elderly tenants. The deep retrofit works included the upgrade of the building fabric, ventilation and heating, all with a view to transforming the living standards of the occupants. They in turn responded, when surveyed, with near unanimous satisfaction. The upgrade and the addition of onsite microgeneration ensured these houses were transformed from lowly F and G national building energy ratings (BER) to A rated homes as calculated by the national energy rating software, DEAP. However, a performance gap is reported between the expected A performance (<75 kWh/m2/yr) and the actual performance, with some homes consuming more than twice the predicted energy, while in one extreme case the mean winter indoor temperatures are more than 7 °C above the operating temperatures assumed by the DEAP software. The higher than expected indoor temperatures are directly correlated with the higher than expected energy consumption, consumed by a heat pump which in itself exhibited inefficiencies in operation.This post occupancy evaluation, post retrofit, provides evidence therefore of high occupant satisfaction, but a satisfaction based on significant energy ‘underperformance’. This case study provides evidence and insights that can help guide future retrofit practices as Ireland progresses towards the transformation of its building stock to near Zero Energy Buildings (nZEB).It also opens up serious questions around the aims and expectations of our national nZEB standard and generates some key insights into the energy consumption of nZEB dwellings and the assessment methods necessary to measure them accurately.

A Time-Dependent Model for Predicting Thermal Environment of Mono-Slope Solar Greenhouses in Cold Regions

Most greenhouses in the Canadian Prairies shut down during the coldest months (November to February) because of the hefty heating cost. Chinese mono-slope solar greenhouses do not primarily rely on supplemental heating; instead, they mostly rely on solar energy to maintain the required indoor temperature in winter. This study focuses on improving an existing thermal model, entitled RGWSRHJ, for Chinese-style solar greenhouses (CSGs) to increase the robustness of the model for simulating the thermal environment of the CSGs located outside of China. The modified model, entitled SOGREEN, was validated using the field data collected from a CSG in Manitoba, Canada. The results indicate that the average prediction error for indoor and relative humidity is 1.9 °C and 7.0%, and the rRMSE value is 3.3% and 11.5%, respectively. The average error for predicting the north wall and ground surface temperature is 4.2 °C and 2.3 °C, respectively. The study also conducted a case study to analyze the thermal performance of a conceptual CSG in Saskatoon, Canada. The energy analysis indicates the heating requirement of the greenhouse highly depends on the availability of solar radiation. Besides winter, the heating requirement is relatively low in March to maintain 18 °C indoor temperature when the average outdoor temperature was below –4 °C, and negligible during May–August. The results indicate that vegetable production in CSGs could save about 55% on annual heating than traditional greenhouses. Hence, CSGs could be an energy-efficient solution for ensuring food security for northern communities in Canada and other cold regions.

Drivers of winter indoor temperatures in Swedish dwellings: Investigating the tails of the distribution

Residential indoor climate is a key factor for occupant comfort, health and wellbeing, while also affecting the buildings' energy demand. A strong focus has been traditionally placed on low winter indoor temperatures in dwellings due to their considerable health impacts. However, there is a trend towards high and stable indoor temperatures, which also have significant implications. This paper investigates the drivers of winter indoor temperatures by analysing the following three metrics of measured temperatures in a sample of 1039 Swedish dwellings: a) level, through the sample dwellings’ standardised indoor temperatures at 5 °C outdoor temperature, b) daily variation, through the standard deviation of the indoor temperature and c) shape, using daily indoor temperature profiles derived from cluster analysis. The study explores the association of these metrics to building-, dwelling- and occupant-related parameters. The analysis shows that 80% of the standardised indoor temperatures were above 21 °C, with one third of the latter being above 23 °C, while 82% of dwellings had constant temperatures throughout the day. High winter indoor temperatures were more evident in middle-placed apartments in multi-family buildings connected to district heating and in better insulated single-family houses. High temperatures were also associated with experiencing draft from windows, too warm conditions in winter and difficulty to control the indoor temperature, but not with the overall thermal comfort assessment which was very positive in both the high and low temperature tails. Long-term adaptation effects, established norms and comfort expectations are discussed as important confounding factors in the development of residential indoor temperatures.

Auto-Tuning Parameters of Fractional PID Controller Design for Air-Conditioning Fan Coil Unit

The traditional integer order PID controller manipulates the air-conditioning fan coil unit (FCU) that offers cooling and heating loads to each air-conditioning room in summer and winter, respectively. In order to maintain a steady indoor temperature in summer and winter, the control quality cannot meet the related requirements of air-conditioning automation, such as large overshoot, large steady state error, long regulating time, etc. In view of these factors, this paper develops a fractional order PID controller to deal with such problem associated with FCU. Then, by varying mutation factor and crossover rate of basic differential evolution algorithm adaptively, a modified differential evolution algorithm (MDEA) is designed to tune the satisfactory values of five parameters of indoor temperature fractional order PID controller. This fractional order PID control system is configured and the corresponding numerical simulation is conducted by means of MATLAB software. The results indicate that the proposed fractional order PID control system and MDEA are reliable and the related control performance indexes meet with the related requirements of comfortable air-conditioning design and control criteria.

Disparities of indoor temperature in winter: A cross-sectional analysis of the Nationwide Smart Wellness Housing Survey in Japan.

The WHO Housing and health guidelines recommend a minimum indoor temperature of 18°C to prevent cold‐related diseases. In Japan, indoor temperatures appear lower than in Euro‐American countries because of low insulation standards and use of partial intermittent heating. This study investigated the actual status of indoor temperatures in Japan and the common characteristics of residents who live in cold homes. We conducted a nationwide real‐world survey on indoor temperature for 2 weeks in winter. Cross‐sectional analyses involving 2190 houses showed that average living room, changing room, and bedroom temperatures were 16.8°C, 13.0°C, and 12.8°C, respectively. Comparison of average living room temperature between prefectures revealed a maximum difference of 6.7°C (Hokkaido: 19.8°C, Kagawa: 13.1°C). Compared to the high‐income group, the odds ratio for living room temperature falling below 18°C was 1.38 (95% CI: 1.04‐1.84) and 2.07 (95% CI: 1.28‐3.33) for the middle‐ and low‐income groups. The odds ratio was 1.96 (95% CI: 1.19‐3.22) for single‐person households, compared to households living with housemates. Furthermore, lower room temperature was correlated with local heating device use and a larger amount of clothes. These results will be useful in the development of prevention strategies for residents who live in cold homes.

The Role of the Extensive Green Roofs on Decreasing Building Energy Consumption in the Mediterranean Climate

Buildings portion in global energy consumption is 40%, and in the building envelope, the roof is a crucial point for improving indoor temperature, especially in the last and second last floors. Studies show that green roofs can be applied to moderate roof temperature and affect the indoor temperature in summer and winter. However, the performance of green roofs depends on several parameters such as climate, irrigation, layer materials, and thickness. In this context, the present research deals with a comprehensive experimental analysis of different thermal impacts of green roofs in summer and winter in a Mediterranean climate. Measurements carried out in one year in three different types of green roofs with different thicknesses, layers, and with and without the insulation layer. The analysis determined the possible period that indoor cooling or heating might be required with and without green roofs and demonstrated the positive impact of green roofs in moderating the roof temperature and temperature fluctuations, which in summer was remarkable. In conclusion, since in the Mediterranean climate, the thermal differences between green roofs and conventional roofs in summer are much higher than winter, it seems that the green roof without an insulation layer would show better performance.

Experimental thermal performance of wallboard with hybrid microencapsulated phase change materials for building application

Combining phase-change materials (PCM) into building envelopes can improve indoor environmental comfort and reduce energy consumption. To adapt to seasonal changes (e.g., hot summer and cold winter), a novel type of hybrid PCM-containing wallboard (including three different PCMs) was fabricated. The hybrid PCM wallboard has a wide phase-change temperature range and can work under different climates for indoor thermal comfort and energy saving. Reduce-scale test cells, two hybrid PCM wallboard integrated test boxes (including Mode 1 PCM wallboard and Mode 2 PCM wallboard) and another equipped with gypsum wallboards, were compared to study the thermal performance of the PCM contained wallboard in both passive and active systems. The results indicate that the hybrid PCM system can narrow indoor air temperature fluctuations and maintain indoor thermal comfort at any time of the entire year. Mode 2 PCM wallboards were found to be more suitable for regulating the indoor thermal environment, as they exhibited more heat release to the indoors during the daytime and less heat loss at nighttime during winter. Under stimulations of different temperature fluctuations, three different layers of the PCMs worked to respond to the temperature fluctuations. Two indices (I and E) were put forward to evaluate the thermal performance of the PCM wallboards. The I index showed that Mode 1 PCM wallboard is suitable for reducing fluctuations of indoor temperature in winter and transition season scenarios. According to the E index, throughout one year, Mode 2 PCM wallboard has higher utilization efficiency than that of Mode 1. Finally, a comparative test was performed with the active system to evaluate the energy saving potential of the two hybrid PCM wallboards. The results show that energy consumption in the hybrid PCM wallboard box is nearly 30% less than that of gypsum wallboard.