Summer Indoor Temperatures Research Articles

Indoor Climate Monitoring in Office Buildings—Comparative Analysis of Two Office Buildings without Air Conditioning

Against the background of climate protection and the rising costs of a fossil-fuel-based energy supply, the interest in the energy performance and indoor climate of buildings in real operation is rising. This paper, therefore, deals with the indoor climate investigation of two medium-sized office buildings in Germany by taking measurements over a whole year. These relate to one new building and one refurbished building. Sensors of various types were installed and operated in a large number of office rooms, so that in total results are available for over 100 rooms, typically occupied by one or two persons. The analysis focuses on the indoor temperature in summer and the air quality in winter based on the CO2 concentration. The comfort classes according to DIN EN 16798 including the adaptive comfort approach are used as a basis to cluster the results. Both buildings have movable sun protection and openable windows but no facilities for active cooling. They, thus, represent a large number of existing ‘low tech’ office buildings in Germany and central Europe. The results reflect the respective building concepts but also show a wide range between the rooms due to the user preferences and behaviour. The refurbished building shows better results, especially in terms of air quality but also in terms of summer room temperatures. This underlines the benefit of the targeted measures as a result of an analysis of the deficits in the existing building before the refurbishment. The additional measures for decentralised mechanical ventilation and passive cooling are having positive effects. As part of the projects, further measures to improve the indoor climate were investigated in both buildings. In one case, this involved CO2 traffic lights to stimulate personal window ventilation in winter, and in the other, the use of newly developed individual ceiling fans supports convective heat dissipation on the human body during hot spells in summer. The positive effect could be demonstrated for both measures.

Thermal and Humidity Performance Test of Rammed-Earth Dwellings in Northwest Sichuan during Summer and Winter.

Rammed-earth dwellings have a long history in the construction field. It is a natural material that is both green and environmentally friendly. In recent years, the advantages of rammed earth, such as environmental protection, low cost, and recyclability, have attracted considerable attention. In this study, the thermal and humidity physical properties of rammed-earth materials in the northwest Sichuan region, the variation laws of thermal physical parameters, such as the thermal conductivity of rammed-earth under different moisture content conditions, and isothermal moisture absorption and desorption curves were investigated. The results indicated that the thermal physical parameters of the rammed earth measured in the experiment increased with an increase in moisture content, and its moisture absorption performance was better than the moisture release performance in the range of 11.31-97.3% relative humidity. The experimental site, Mianyang City, Sichuan Province, is a subtropical monsoon humid climate zone characterized by warm winters and hot summers with four distinct seasons. In this study, we investigated the hygrothermal coupling transfer of walls, as well as the indoor temperature and humidity changes in new rammed-earth buildings during summer and winter climates. During the test period, the maximum indoor temperature in summer was 35.08 °C, the minimum temperature was 33.76 °C, and the average daily temperature fluctuation was 3.62 °C. In winter, the maximum indoor temperature was 8.59 °C, the minimum temperature was 6.18 °C, and the average daily temperature fluctuation was 1.21 °C. An analysis was performed on the thermal insulation performance of rammed-earth buildings in an extremely high-temperature climate during summer, thermal insulation performance, the thermal-buffering capacity of walls in a low-temperature and high-humidity climate during winter, and thermal and humidity regulation of indoor environments provided by walls during summer and winter. The results showed that the rammed-earth buildings exhibited warmth in winter, coolness in summer, and a more stable and comfortable indoor environment.

Assessing the Potential of Integrated Shading Devices to Mitigate Overheating Risk in University Buildings in Severe Cold Regions of China: A Case Study in Harbin

Creating a comfortable indoor environment in education buildings is an important design objective. Climate change has resulted in rising summer indoor temperatures in the severe cold regions of China, and evidence of summer overheating risk in these regions has not yet been fully investigated. This study presents evidence of overheating in a university building in a severe cold region of China, discusses the potential of integrated shading devices for mitigating overheating, and proposes design ideas for the application of shading devices. Temperature monitoring and simulation were performed in a university building with natural ventilation located in Harbin, and various configurations of integrated shading devices were simulated using IES Virtual Environment software. The results demonstrate that 69% of classrooms were overheated; furthermore, south-facing classrooms could be overheated for up to 152 h during summer occupancy hours. This study finds that integrated shading devices reduce overheating hours by up to 59.2%. The design of appropriate parameters for shading devices can effectively improve indoor thermal comfort while maintaining daylight levels and controlling the increase in energy consumption. The methodology and results presented in this study offer a reference point and practical guidance for mitigating regional overheating, aiming to promote the improvement of regional standards and optimisation of thermal environments in the severe cold regions of China.

Investigation on Thermal Comfort and Thermal Adaptive Behaviors of Rural Residents in Suibin Town, China, in Summer

With global warming, the climate is becoming hotter, even at higher latitudes. In order to clarify the thermal environment and thermal comfort level of rural residents at higher latitudes in summer, a field survey on thermal comfort was conducted in Suibin Town, China. The results show the following: (1) The correlation between the operative temperature and the mean thermal sensation score is stronger than that between the operative temperature and the thermal sensation score. Moreover, the applicability of the thermal comfort evaluation index of the operative temperature in severely cold areas was verified. The linear regression method showed that the neutral temperature is 25.1 °C and the thermal acceptable range is 22.5–27.6 °C. (2) There is a strong correlation between thermal sensation and thermal acceptability. (3) The preferred temperature in summer is 25.3 °C. Moreover, rural residents prefer cooler indoor temperatures in summer. (4) The clothing insulation of rural residents decreases with an increase in the indoor operative temperature. (5) Rural residents’ acceptance of the indoor temperature in summer is influenced by the economy, psychology, adaptive behaviors, etc. Moreover, rural residents expect cooler indoor temperatures in summer and will adapt to the thermal environment via low-cost adaptive behaviors.

Energy consumption performance using natural ventilation in dwelling design and CFD simulation in a hot dry climate: A case study in Sudan

Introduction: Sudan is taking proactive steps towards environmental sustainability, including initiatives to improve energy efficiency and reduce costs in a hot, dry climate. This article assesses the contribution of natural ventilation to heat transfer and temperature conditioning in urban areas in Khartoum, Sudan.Methods: The research methodology used a combination of building modeling with computational fluid dynamics (CFD) integrated with IESV Autodesk software to model natural ventilation and simulate energy consumption by incorporating natural ventilation into home design.Results: The best-case scenario for natural ventilation resulted in a 71.1% yearly energy savings. The design point of internal air speed was approximately 0.7 m/s, the point at which 95% of the indoor areas had an average air speed between 0.43 m/s and 0.9 m/s. The worst-case scenario occurred in the east/west direction, when 80% of the interior had an airflow between 0.05 m/s and 0.01 m/s; near open windows, the airflow was approximately 0.1 m/s.Discussion: This study was the first research in Khartoum on the design of clean and energy-saving sustainable architecture. The architectural design process for energy-efficient living in the urban region of Al-Azhari City was implemented and defined in a city quarter in Khartoum. The results showed that natural ventilation can maintain a comfortable indoor temperature in summer and significantly reduce energy costs. The findings may have implications for the design of sustainable buildings in other hot, dry climates.

A holistic assessment of indoor environmental quality perception in Australian high-rise social housing

The indoor environmental quality (IEQ) in social housing is commonly aggravated due to poor design and construction characteristics. Within Melbourne, a considerable proportion of social housing are high-rise buildings, for which no integrated IEQ studies have been conducted. This paper examines residents’ IEQ perception in high-rise social housing in Melbourne. Data from 94 apartment units were collected through a survey. Residents were least satisfied (33%) with the indoor temperature in summer, while they were most satisfied with daylight (72%). The most influential parameter over the overall IEQ satisfaction was “noise”, despite being rated the second least important. Sleep disturbances (61.8%) and not being able to open the windows for ventilation (43.4%) were identified as the most unfavourable effects of outdoor noise. Correlations were found between IEQ parameters and the frequency of building-related health issues. No clear relationship was found between perceived satisfaction and importance of IEQ parameters. There is an evident problem associated with overheating in summer, though winter underheating was not problematic. Differences in the share of IEQ parameters on the overall IEQ satisfaction question their equal weightage. The significance of this study is the integrated assessment of IEQ parameters and health impact in the Melbourne social housing context.

Potential use of recycled materials on rooftops to improve thermal comfort in sustainable building construction projects

The study has two objectives. First, it experimentally measures the indoor and outdoor temperatures of a building in Peshawar and conducts validation with CFD modeling. Second, it simulates the building with the addition of locally available, natural, and recycled insulator materials on the rooftop to keep the indoor environment within a comfortable temperature range, especially in the winter and summer seasons. To achieve these objectives, experimental temperature data for January and June were recorded and validated, followed by a simulation, using ANSYS-Fluent 16 CFD, of the residential building with the application of waste thermal insulators such as straw bale, sheep wool, and recycled glass materials on the rooftop to reduce the indoor temperature. Experimental temperature measurement showed that the lowest recorded indoor temperature was 15°C on 2 January 2022 and that the highest recorded indoor temperature was 41°C on 11 June. The predicted and validated temperature results were similar, with a slight difference of less than 15%. Recycled glass positively and significantly reduced the indoor temperature in summer by 10.2% and thermal amplitude by 48.3%, with a time lag increase of 100% and an increase in the period of comfort hours of 380%. In winter, the daily average temperature increased by 7.4%, thermal amplitude was reduced by 59.3%, and the time lag increased by 100% in comparison with the baseline case results. The study concludes that recycled glass distribution gives the best improvement compared to straw bale and sheep wool.

The Use of Horizontal Shading Devices to Alleviate Overheating in Residential Buildings in the Severe Cold Region and Cold Region of China

Global warming is resulting in higher summer indoor temperatures in the severe cold region and cold region of China, and this is affecting thermal comfort. Local building design codes consider these regions as cool in summer, and do not consider the phenomenon of overheating or propose countermeasures. This paper studied the possibility of overheating in residential buildings in these areas. It suggested alleviating this phenomenon using external horizontal shading, and discussed how to integrate thermal comfort into the building design and save energy consumption. The IESVE software was used to simulate 18-storey residential buildings with natural ventilation in Yichun, Harbin, Shenyang, Dalian, and Beijing, and to calculate the change in indoor operative temperature. Horizontal shading was designed for case study building to attempt to alleviate the overheating phenomenon in summer. The results showed that the case study building in the five cities experienced different degrees of overheating. External horizontal shading was successful in reducing indoor overheating, especially in the severe cold B and C zones and the cold A and B zones. The relevant building codes should be modified to take this into account. Reasonable design of horizontal shading can effectively reduce energy consumption, particularly when compared with air-conditioned buildings.

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.

Post-Occupancy Evaluation of Indoor Air Quality and Thermal Performance in a Zero Carbon Building

Maintaining a comfortable indoor environment throughout the year makes up the main part of energy consumption caused by people’s use of buildings. In recent years, China has started to integrate sustainable technologies into green building design and construction. However, some post-occupancy reports on certified buildings revealed that such integration has been perceived to prioritize energy savings over comfort. This paper aims to investigate the ability of the first Chinese zero carbon building to maintain comfortable and healthy indoor conditions in the summer season. The research implements a combination of occupant survey and on-site measurements to evaluate the occupants’ perception of the indoor environment quality (IEQ) and benchmark the measurements against relevant standards. The results from this study show that the mean summer indoor temperature was 0.9 °C above the standard limit, while on average, occupants gave a positive score to the indoor thermal environment. High contentment with the building acoustics was reported by users and supported by sensors measurements meeting the standard values. The illuminance levels were mainly maintained high with the exception of the light in one of the studied zones. Analyzing the data on occupants experiencing sick building syndromes revealed that 45.8% of respondents experienced at least one of the symptoms.

Evaluation of the Summer Overheating Phenomenon in Reinforced Concrete and Cross Laminated Timber Residential Buildings in the Cold and Severe Cold Regions of China

As the climate changed in recent years, an increase in summer indoor temperatures in severe cold and cold regions of China has started to affect thermal comfort. However, the local design standard for energy efficiency does not recognize this phenomenon. This paper reports the potential overheating phenomenon in residential buildings and examines the rationale for the current thermal designs adopted in severe cold and cold regions of China. In this study, the two most commonly used building materials, reinforced concrete (RC) and cross laminated timber (CLT), are used separately in the design of an 18-story residential building envelope located in six different cities in the severe cold and cold regions. The energy consumption and indoor operative temperatures during the operation of these buildings are simulated using Integrated Environmental Solutions Virtual Environment (IES VE). The results demonstrate that both the RC and the CLT buildings experience varying degrees of overheating in any climate subregion. The CLT buildings have longer overheating hours compared to the RC buildings, especially in the cold regions. The results also indicate that for apartments on higher stories, the cooling energy consumption and indoor temperature also increase gradually. The research results suggest that the local design standard for energy efficiency needs to be adjusted by adding thermal design methods for summer to reduce the periods of overheating.

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.

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.

Identification of overheating in the top floors of energy-efficient multilevel dwellings

This study investigates summer indoor temperatures in energy-efficient multilevel houses built since 2010 in Adelaide to identify and define overheating during summer months. The method includes three steps: 1) calculating the number of days with top-floor maximum daily air temperature above 32 °C during four summers (December-February of 2011–2015); 2) calculating the frequency, integral and average of outdoor air temperature above 35 °C and the same parameters for top-floor temperature exceeded ground floor temperature for the naturally ventilated (NV) mode during eight summers (December-February of 2011–2018); and 3) correlation between ground floor temperature and outdoor sunshine hours as well as running mean outdoor temperature for NV mode during the same eight summers.Results showed the top-floor maximum daily air temperature was above 32 °C for 21% of the summer days for a mix of air-conditioned (AC) and NV modes. Overheating occurred in the top floors. Overheating occurs in low-performance energy-efficient houses about twice more often than high-performance energy-efficient houses. While the ground floors of high-performance houses matched the adaptive thermal comfort standard, the top floors exceeded the adaptive thermal comfort by overheating for 243 h, with 250 integral and intensity of 3.5 °C. Overheating in top floors lasts significantly longer than the outdoor high summer temperature. The paper also proposes novel parameters for evaluating the occurrence of overheating based on analysis of the data.

The summer indoor temperatures of the English housing stock: Exploring the influence of dwelling and household characteristics.

As the high temperatures experienced during the summer of 2018 may become commonplace by 2050, adaptation to higher indoor temperatures while minimising the need for mechanical cooling is required. A thorough understanding of the factors that influence indoor temperatures can enable the design of healthier and safer dwellings under a warming climate. The aim of this paper is to provide further insight into the topic of indoor overheating through the analysis of the largest recent sample of English dwellings, the 2011 Energy Follow-Up Survey, comprised of 823 dwellings. Following the pre-processing stage, the indoor overheating risk of 795 living rooms and 799 bedrooms was quantified using the criteria defined within CIBSE's Technical Memorandum 59. Approximately 2.5% of the dwellings were found to exceed Criterion 1, with this figure approaching 26% when Criterion 2 was considered. Subsequently, the indoor temperatures were standardised against external weather conditions and the correlation of 11 dwelling and 9 household characteristics was examined. Factors such as the main heating system, tenure and occupant vulnerability were all found to have a statistically significant association with the indoor temperatures. Further analysis revealed multiple correlations between household and dwelling characteristics, highlighting the complexity of the indoor overheating problem.Practical application: By applying the criteria in CIBSE's TM59, 26% of the dwellings monitored during the 2011 Energy Follow-Up Survey were found to overheat. Since 2011 was a cool summer and future temperatures are expected to be warmer, even more dwellings are expected to fail these criteria in the future. Multiple dwelling and household characteristics were associated with higher indoor temperatures, including: dwellings with a SAP rating > 70, more recently built and with communal heating. Thus, it is crucial to consider indoor overheating risk at the building design or refurbishment stage to prevent the possible consequences of uncomfortably high indoor temperatures.

Research on Passive Energy - saving Renovation of the Roof of Traditional Residences

With the rapid development of social economy and people’s living standards continue to improve, summer air-conditioning energy consumption has gradually become the focus of modern society energy consumption. At the same time, the traditional residences are an important part of the ancient Chinese architecture culture and heritage, which contain rich experience in ecological construction, but limited to the economic level and construction technology at that time, and the traditional residences have their flaws. As one of the largest energy consumption of the envelope, the roof is the need for renovation. In this paper, energy-saving renovation of the demonstration building on the town of Chongqing was taken as an example. It puts forward the practice of using the controllable ceiling and uses DesignBuilder software to compare the energy consumption before and after the transformation and the indoor temperature in summer. The results show that the building energy efficiency rate is 54.35%, and the cumulative percentage of the length of the temperature of bedroom1 over 30 ℃, while over 28 ℃ is reduced by 7%. The cumulative percentage of the intermediate bedroom temperature over 30 ℃ is reduced by 16 %, and over 28 ℃ by 12%. By taking the control of the ceiling to reduce the cumulative time of the indoor high temperature, which can be delayed air conditioning opening time by the next day, to achieve energy-saving effect.

The effects of higher temperature setpoints during summer on office workers' cognitive load and thermal comfort

Typical commercial lease agreements in Australia stipulate 22.5 ± 1.5 °C in summer as the acceptable thermal condition that buildings have to meet, even though the overcooling incurs excessive and unnecessary energy use, gas emissions and financial expense. An argument that backs up this practice asserts that office workers' productivity and comfort will be jeopardised outside this temperature range. This paper investigated whether the office environments with a practical higher temperature setpoint can still be cognitively efficient and comfortable for office workers. In a controlled climate chamber, 26 office workers experienced the typical summer indoor temperature condition in Australia (22 °C) followed by the condition with a higher temperature setpoint (25 °C). In both conditions, subjects were required to fulfil Cambridge Brain Science (CBS) cognitive performance tests, NASA Task Load Index (NASA-TLX), and thermal comfort and air quality questionnaires. Meanwhile, participants' electroencephalogram (EEG) and heart rate (HR) were recorded under three different difficulty levels of Paced Auditory Serial Addition Tests (PASAT). Results showed that CBS test scores were not significantly affected by temperature; a higher temperature of 25 °C incurred a significantly reduced cognitive load for subjects, as has been observed by NASA-TLX, but probably due to the learning effect; the comparison between EEG and HR features during different temperatures did not show any significant difference. Participants' thermal comfort was not significantly jeopardized by the 3 °C temperature setback either. Results from this study favourably support a practical setback of temperature setpoints in Australian office buildings during summer.

Study of Passive Evaporative Cooling Technique on Water-retaining Roof Brick

This paper introduces a new method water-retaining roof brick to reduce the energy cooling load in meeting people's comfort demands in hot seasons. An experimental model of passive evaporation is designed in order to explore a complete heat transfer process law of water-retaining brick in hot summer and cold winter region. The result of using a flat roof with water-retaining brick shows a drop of 1.9°C in the indoor temperature in summer compared to the base case of the conventional flat roof in residential buildings. In addition, the results indicate the cooling load required for the building will decrease after using water-retaining bricks on roof and also using the radiation shield on roof. The best solution to increase the indoor thermal comfort is water-retaining brick rather than roof with shield, because the evaporation process plays a supporting role to ease the city heat island effect. Thus, it's the most optimal scheme.

Is Sweden ready for climate change? -summer indoor temperatures in Swedish care homes

Is Sweden ready for climate change? -summer indoor temperatures in Swedish care homes

Optimization of health and sustainability goals for low income housing (the Optihouse study)

Introduction: Housing has multiple influences on health and is central to many development and environmental objectives. Optihouse aims to examine how housing may be improved in low income populations to fulfil health protection and environmental sustainability goals in the context of climate change and energy insecurity. Pilot case studies are being developed in Delhi, Cape Town, Mexico and the UK. Methods: Stakeholder meetings are used to elicit the primary occupant needs with regard to housing and health, and the factors that constrain development options. Survey data on dwelling form and indoor environmental monitoring inform building physics models used to investigate alternatives of dwelling design, materials and operation that could improve function for health and sustainability, including CO2 emissions. Results: Preliminary investigations indicate the need and potential to improve factors relating to the indoor environment, including ambient temperature and air quality. For example, monitoring studies in Delhi have indicated mean summer indoor temperatures of 33°C, with peaks up to 47°C, and in winter temperatures were recorded below 10°C with more than 40% of hours deemed uncomfortable. Modelling of indoor concentrations of PM2.5 suggests a highly polluted environment with hourly peaks up to 2000µg/m³ and an indoor/outdoor ratio of 2.30±0.15. Energy consumption was estimated to be low (<5500kWh per year). Modelling suggests that low cost adaptations could improve indoor conditions, but to a limited degree without increasing energy consumption. More substantial improvements could be achieved through fundamental design changes, but may require significant investment costs unlikely to be feasible without subsidies or external funding. Conclusions: Housing of low income populations in many settings seems poorly adapted to provide a healthy sustainable environment, but practicable improvements to the design could aid both occupant health and energy use.