Improvement Of Thermal Comfort Research Articles

The Effect of Geometry Parameters on Energy and Thermal Performance of School Buildings in Cold Climates of China

This paper discusses the role of geometry parameters including building shape, window to wall ratio, room depth, and orientation on the energy use and thermal comfort of school buildings in cold climates of China. The annual total energy demand and summer thermal discomfort time were compared through computer simulations with DesignBuilder. Furthermore, a questionnaire was conducted that related to the students’ subjective preference for various building geometry parameters. Results showed that a maximum of 13.6% of energy savings and 3.8% of thermal comfort improvement when compared to the reference case could be achieved through variations in geometry parameters. The H shape performed the best when the building thermal performance and students’ preferences were considered, as well as the various design options for architects. Window to wall ratio, room depth, and orientation should also be carefully addressed in terms of different building types. The results of this study can serve as a reference for architects and school managers in the early design stages of schools in cold climates of China.

Experimental study on using PCMs of different melting temperatures in one cooling vest to reduce its weight and improve comfort

This study aims at evaluating experimentally phase change material (PCM) cooling vest performance when incorporating two types of PCM with different melting temperatures with varied PCM placement on the lower, upper, front and back of the torso. Experiments on a thermal manikin were conducted to assess cooling rate observed with the various PCM arrangements while experiments on six male subjects were conducted to assess associated physiological and comfort votes after exercising for 45min.The main findings of manikin testing were that an improved cooling effect can be achieved by covering the upper torso with PCM packets at 28°C melting temperature while covering the lower torso with the 18°C packets. Human subject testing established that similar improvements in thermal comfort and sensation levels could be attained when covering the back or lower torso segments with 18°C instead of covering all the torso. In addition, a maximum reduction in local skin temperatures of 5.45±1°C was achieved accompanied with a reduction of 64W in body heat storage. Covering the chest and upper back segments with the 18°C packets suppressed sweat production and improved wetness sensation. Finally, 16% lower vest weight might be possible with prolonged working periods of two hours at 35°C.

The impact of air conditioning system upgrade on energy use and comfort in low income housing

Abstract: The ‘Beat The Heat!’ project was a project of the Australian Federal Governments ‘Low Income Energy Efficiency Program’ (LIEEP). This project aimed to enhance the resilience and improve the comfort and wellbeing of Adelaide households during South Australias long, hot summers. The installation of ceiling insulation and new air-conditioners in the main living areas of low-income households were two of the key interventions made through this project. Total electrical energy consumption of each household and the air-conditioner were monitored following these interventions and compared with electricity bills before the installation, during matched summer periods. Indoor temperatures of the main living area were also monitored, following the intervention, to assess the improvement in thermal comfort. Significant differences between the energy use before and after household interventions, along with associated household perceptions, are discussed in this paper. Specifically, the impact on energy consumption of factors such as household income, the source of cooling energy prior to the intervention and differences in climate and thermal comfort are explored. For houses where an old, inefficient and ineffective air-conditioner was replaced by a new, efficient split system (3.23

Social housing retrofit: Improving energy efficiency and thermal comfort for the housing stock recovery in Mexico

Abstract: Social housing in Mexico has been built without considering internal thermal comfort. This situation has forced people to live in adverse conditions, increase the use of air-conditioning systems for those who can afford it, or to abandon the houses looking for a better place. Currently Mexico has nearly five million abandoned dwellings and 40% of built housing deficit requires expansion and/or improvement. Retrofit of existing buildings has been carried out in the world to improve energy efficiency or to reduce green housing emissions; however, in Mexico retrofit is not widely applied and less in social housing. This paper proposes and applies in two case studies with hot, semi-humid climate a method to evaluate the improvement of indoor thermal comfort through enhancing envelopes U value. Finally, an economic analysis is conducted to assess retrofitting social housing with Mexican government programs funds.

Thermal comfort improvement of naturally ventilated patient wards in Singapore

Located near the equator, Singapore has a tropical rainforest climate with high temperature and high humidity. In hospitals of Singapore, the subsidized patient wards are designed to be naturally ventilated, considering the affordability for patients. However, due to the high occupant density of the patient wards and the hot humid climate, occupants may feel discomfort, especially in the older hospital wards which were not well designed for natural ventilation. In this paper, the thermal comfort level of occupants at Singapore's Changi General Hospital (CGH) is evaluated based on both in-situ measurements and modeling analysis. Against this backdrop, several low energy solution concepts that potentially improve the thermal comfort level of occupants in patient wards are analyzed and simulated using detailed building thermodynamic and airflow simulation. We found that this approach of combining thermodynamics, computational fluid dynamics, and thermal comfort level models was effective for analyzing and comparing the thermal comfort impact of alternative, low-energy building retrofit concepts. We also found that passive solutions to ventilation could be used effectively for a patient hospital ward, even in the tropical warm climate of Singapore.

Design optimization for ventilation shafts of naturally-ventilated underground shelters for improvement of ventilation rate and thermal comfort

A good ventilation system is essential for an underground shelter to provide a comfortable environment with better indoor air quality. Ventilation shafts are widely used for ventilation purpose in an underground shelter. In the current work, the position of the ventilation shaft is optimized by employing the Response Surface Methodology (RSM). Two RSMs are constructed. The first RSM is constructed by 32 CFD models via Fractional Factorial Design (FFD) and the second model is constructed by 53 CFD models via Central Composite Rotatable Design (CCRD). The first and the second models are subsequently analysed by using the linear and quadratic models, respectively. The result indicates that both models lead to similar predictions on the inputs (factors) that strongly affect the response. Moreover, the response surface values agree well with the CFD values. Based on desirability functions, the optimized design improves the ventilation system by 24.5% as compared to the actual design. Also, the optimized design meets the comfort temperature and design criteria recommended for a naturally-ventilated underground shelter. Overall, this study finds that statistical analysis is a useful tool for the improvements of ventilation rate and thermal comfort.

Improving Thermal Comfort of Low-Income Housing in Thailand through Passive Design Strategies

In Thailand, the delivery of adequate low-income housing has historically been overshadowed by politics with cost and quantity being prioritised over quality, comfort and resilience. In a country that experiences hot and humid temperatures throughout the year, buildings need to be adaptable to the climate to improve the thermal comfort of inhabitants. This research is focused on identifying areas for improving the thermal performance of these housing designs. Firstly, dynamic thermal simulations were run on a baseline model using the adaptive thermal comfort model CIBSE TM52 for assessment. The three criteria defined in CIBSE TM52 were used to assess the frequency and severity of overheating in the buildings. The internal temperature of the apartments was shown to exceed the thermal comfort threshold for these criteria throughout the year. The internal operating daily temperatures of the apartment remain high, ranging from a maximum of 38.5 °C to a minimum of 27.3 °C. Based on these findings, five criteria were selected to be analysed for sensitivity to obtain the key parameters that influence the thermal performance and to suggest possible areas for improvement. The computer software package Integrated Environmental Solutions—Virtual Environment (IES-VE) was used to perform building energy simulations. Once the baseline conditions were identified, the software packages SimLab2.2 and RStudio were used to carry out the sensitivity analysis. These results indicated that roof material and the presence of a balcony have the greatest influence on the system. Incorporating insulation into the roof reduced the mean number of days of overheating by 21.43%. Removing the balcony increased the number of days of overheating by 19.94% due to significant reductions in internal ventilation.

Improvement of thermal comfort and energy efficiency in historical and monumental buildings by means of localized heating based on non-invasive electric radiant panels

Energy efficiency and thermal comfort in historic buildings are very often hampered by preservation needs. This issue is particularly relevant for historical and monumental buildings, which currently represent a large part of the historic buildings stock in Europe. For such protected buildings most of the available retrofitting solutions are not feasible and alternatives have to be investigated to guarantee their usability potential. The purpose of this study is therefore to present a methodology to evaluate the potential of electric radiant panels as retrofitting solutions for historical and monumental buildings, focusing on thermal comfort and energy saving potential when compared with conventional fossil-fuel-based heating systems. In fact, the non-invasiveness and flexibility of electrical panels make them one of the few feasible solutions for protected buildings.An original methodology is developed to evaluate the performance of such localized heating systems; the methodology is based on a dynamic simulation model, calibrated with temperature measurements, which takes into account the geometry and technical characteristics of electrical radiant panels and allows different control strategies to be compared. The methodology is applied to a relevant Italian historical building. The results show that the panels, despite their well-known low-exergy efficiency, may become a viable and attractive solution for historical buildings without undermining their preservation requirements. Apart from significantly increasing thermal comfort, electric radiant panels may also allow annual heating energy savings up to 70% for the selected building.

Water-to-air-heat exchanger and indirect evaporative cooling in buildings with green roofs

Green roofs have been proposed for energy saving purposes in many countries with different climatic conditions. However, the energy saving potential of green roofs depends on several aspects, such as the climate characteristics or the building loads. For this reason, the authors have been working on ways to modify the thermodynamic behavior of green roofs through passive low energy systems operating according to rules based on the relationships between the indoor and outdoor temperatures. This paper discusses the improvements in indoor thermal comfort which can be obtained by adopting water-to-air heat exchangers and indirect evaporative and radiant cooling strategies in buildings with green roofs. The study specifically looks at the effect of combining a simple evaporative/radiant system that cools the water pond where the water-to-air heat exchange occurs. Ad-hoc built test cells were investigated in southern California for over a year. Overall, the water-to-air heat exchangers proved to cool the indoor air in the test cells by almost 10°C when the exterior temperatures were above 35°C. In this system, the heat from the interior of the cells that could not be absorbed by the green roof, was transferred to the coupled water sink, and then dissipated into the atmosphere. This study shows that the benefits of the water-to-air heat exchange and of the evaporative cooling system are promising, while the water consumption is limited. Finally, the experimental investigation summarizes the benefits of combining green roofs and evaporative and radiant cooling of a water-to-air heat exchanger as a solution for building cooling and proposes simple equations to anticipate their temperature cooling effects.

Development of bio-based insulation materials for the improvement of thermal comfort of housing in Burkina Faso

Burkina Faso is located in the heart of Africa, where the average temperature during the dry season is about 40 °C. The 75% of the population is located in rural areas but, in the last years, there is a big migratory flow to the cities, in an irregular process of urban expansion where most of the houses are made with walls of concrete blocks and metal sheet roofs, generating a big lack of thermal comfort and habitability conditions. The main objective of this project is to develop a thermal insulation material, with low environmental impact, which could contribute to improve the living conditions in this new urban area of Burkina Faso. To this end, biomaterials locally available, in particular wastes or byproducts of agricultural industry have been used. Several formulations, based on peanut shells and sorghum canes and agglutinated with different kind of binders, have been investigated by evaluating properties as thermal conductivity, mechanical strength and fire reaction. The obtained insulation composites exhibited low thermal conductivity values and acceptable mechanical and fire reaction properties. Thus, according to the results, the material seems to be a promising renewable and locally manufactured product suitable for application in developing countries.

Effects of architectural shapes on surface wind pressure distribution: Case studies of oval-shaped tall buildings

Natural ventilation has been an important strategy for the improvement of indoor air quality and human thermal comfort, and the reduction of energy consumption of buildings. Many investigations have been conducted to examine the natural ventilation of low, multi-rise buildings rather than tall buildings. Starting from enlarging the wind pressure difference to create wind-driven natural ventilation, this paper aims to analyze characteristics of surface pressure coefficients over tall buildings and to identify the influence of building shapes on coefficient distribution. Taking oval-shaped high-rise buildings as examples, this paper numerically investigated the effects of height-width ratio (HWR) and height-thickness ratio (HTR) on mean wind pressure coefficients (Cm) of building surfaces. Results indicated that windward side of oval-shaped buildings suffered from positive wind pressure, while side, top and back surfaces were basically in negative pressure areas. The absolute values of Cm on building surfaces increased as the decrease of HWR. On the contrary, Cm near central axis of side surfaces showed opponent trend due to fluid separation. In HTR scenario, Cm on windward and top surfaces were greatly affected, increasing along the HTR values. However, with the decrease of HTR, properties of wind field on leeward surface changed. Through this work, the architects and HVAC engineers can get a master plan of in which place they can set possible openings for the creation of possible ventilation paths.

Optimal parameters of green roofs in representative cities of four climate zones in China: A simulation study

The energy performance of green roofs is influenced by many factors and the regulation differs significantly to each other in different climate zones. Previous research on green roofs confined to a single climate zone with a single set of properties, lacking comparative studies. In this study, a simulation was used for determination of the optimal parameter settings for green roofs in different climate zones. Firstly, a simulation model was established, and a field experiment examined the bias of the model. Leaf area index, plant height, and soil thickness were used as variables. Harbin, Beijing, Chongqing, and Guangzhou were selected as representative cities of four climate zones in China. For quantification of energy savings and indoor thermal comfort improvements, both cool and conventional roofs were simulated alongside green roofs for comparison. Optimal parameters of green roofs were found to be closely related to meteorological conditions in each city. In terms of energy savings, the recommended soil thickness and leaf area index in the four cities are 0.3m and 0.5, respectively. The optimal plant height is 0.3m, except in Beijing, where it is 0.1m. Optimized green roofs are recommended for heating-dominated cities, while cool and green roofs perform similarly in cooling-dominated areas.

Long-term perceptions of outdoor thermal environments in an elementary school in a hot-humid climate.

Previous studies on thermal comfort in school environments have focused more on indoor thermal environments than outdoor ones, thus providing a limited understanding of occupants' long-term thermal perceptions. Taiwan is located in a subtropical region, where it can be stiflingly hot outside in summer. This highlights the need to ensure proper thermal comfort on campus. In the present study, thermal environment parameters were measured and collected in several outdoor spaces of an elementary school in southern Taiwan. In addition, a questionnaire was used to explore occupants' long-term thermal perceptions of these spaces. During summer months, the physiological equivalent temperature (PET) of these outdoor spaces in over 60% of the daytime in summer between 10 a.m. and 4 p.m. was higher than 38°C PET, indicating high heat stress. The results of occupants' long-term perceptions of the thermal comfort of these spaces suggested that dissatisfaction with thermal comfort was associated more with solar radiation than with wind speed. Finally, this study simulated a campus environment where more trees are planted and compared the thermal comfort indices before and after the simulation. The results indicated that this solution contributed to a decrease in the PET of these environments, thereby alleviating high heat stress. This study can inform the improvement of microclimates and thermal comfort during campus layout planning. Planting trees judiciously across a campus increases outdoor shades and creates outdoor spaces that are more comfortable and adaptable to hot weather conditions, thereby ensuring frequent use of these spaces.

Computational and Field Test Analysis of Thermal Comfort Performance of User-controlled Thermal Chair in an Open Plan Office

In this study, a thermal chair prototype was developed that allowed personal control over the temperature settings of the back-rest and the seat. Limited research focuses on different methods to provide individual user control over the thermal environment. This is particularly difficult to achieve in an open plan office setting, where changing the temperature in one area directly influences the comfort and satisfaction of other occupants seated nearby. In this study, the application of the thermal chair was analysed using Computational Fluid Dynamics (CFD) and field-test analysis in an open plan office in Leeds, UK during winter. The results of the CFD model indicated an improvement in the local thermal comfort of the user. The CFD analysis provided detailed analysis of the thermal distribution around a siting manikin and was used to design and construct the thermal chair. The results of the field data survey indicated a great improvement in users’ comfort (20%) and satisfaction (35%). This study concludes that local thermal control of the occupant improves their overall thermal comfort. It recommends further work to optimise the design of the thermal chair and to improve the modelling for better predictions.

Effect of a Superabsorbent for the Improvement of Car Seat Thermal Comfort

The use of super absorbent polymers (SAP) for moisture absorption and comfort is still unexplored. The aim of this work was to observe the application of super absorbent fibres in car seats for comfort purposes. In this research the efficiency of different SAP fibrous webs were determined under different moisture percentages to examine the sorption and desorption efficiency. A SAP fibrous web with low thickness and high moisture absorption were tested with a multilayer sandwich structure of a car seat cover to determine moisture absorption through the cover material. The standard Cup method was used to determine the moisture permeability of different car seat covers with a superabsorbent layer closed with impermeable polyurethane foam. It was observed that the SAP fibrous layers are very effective in absorbing and desorbing water vapour under extremely high and low moisture percentages. In extreme humid conditions (95%RH), 20g of the SAP layer absorbs nearly 70% of its weight in water vapour, reaching the maximum absorption capacity in 6 hours.

Design and control optimisation of adaptive insulation systems for office buildings. Part 2: A parametric study for a temperate climate

This paper is the second of a two part study, which aims to evaluate the performance of adaptive insulation. Part 1 proposes a simulation framework for optimising adaptive insulation design and control parameters, it describes its implementation, and validates the simulation strategy qualitatively. This second paper applies the simulation framework, by means of a parametric study on a specific building typology in a particular climatic region, to explore the potential of adaptive insulation in this context. Alternative adaptive insulation configurations and control strategies for opaque wall applications are evaluated, for an office room in a temperate climate of Shanghai, in order to optimise two design objectives: total primary energy saving and thermal comfort. It is found that adaptive insulation, when properly designed and controlled, has significant potential to improve both design objectives simultaneously. For the case study considered in this paper, yearly energy savings and thermal comfort improvements of up to 50% could be achieved by adaptive insulation compared to an equivalent astatic insulation alternative. The performance improvements of the adaptive insulation depend on the design choices (thermal mass, position of the adaptive insulation, switching range of insulation) and control strategy adopted.

Influence of changing trees locations on thermal comfort on street parking lot and footways

Locations of trees in street parking lots (SPL) impact outdoor thermal comfort and should be considered during the urban planning process. In this paper we developed a procedure for changing trees locations in order to improve outdoor thermal comfort on SPL and associated footways. Furthermore, a sensitivity test on the effect of different tree crown shapes on outdoor thermal comfort was carried out. We applied theprocedure on real-world SPL design in the City of Novi Sad (Serbia). A temporal analysis is performed for the heat wave period using Universal Thermal Climate Index (UTCI) calculations in the Ladybug software.The results showed improvement of outdoor thermal comfort on 77 % of all body locations in proposed SPL design with predetermined number of trees. The largest outdoor thermal comfort improvement was noticed in the afternoon hours with up to 3.3°C UTCI decrease on single body location. By adding trees to the SPL, heat stress was reduced on 84 % of all body locations with maximal UTCI decrease of 3.7°C on single body location. Furthermore, heat stress reduction by cylinder-shaped tree crowns showed to be more pronounced compared to the sphere-shaped and the cone-shaped tree crowns. Proposed procedure showed that the locations of trees as well as tree crown shapes are very important for the improvement of outdoor thermal comfort and creation of environmentally conscious SPL design.

Thermodynamic and exergoeconomic analysis of a non-domestic Passivhaus retrofit

This paper presents a thermodynamic and exergoeconomic analysis of a recently-retrofitted Passivhaus non-domestic building. The selected case study, a Community Centre located in London, underwent a deep-energy retrofit in 2011, becoming the first ‘non-domestic Passivhaus’ retrofit in the country. As the building was retrofitted per Passivhaus standards, which is based solely on First Law analysis, a thermodynamic investigation can provide a novel means by which to assess its exergy efficiency and cost-effectiveness. As such, the aim of this paper is to conduct a comprehensive exergy and exergoeconomic analysis, presenting novel performance indicators for the pre-retrofit and post-retrofit Passivhaus building. First law outputs show that the improvement presents high levels of energy savings (75.6%), reductions in carbon emissions (64.5%), and occupant thermal comfort improvement (28.8%). Second law outputs present a reduction in primary exergy input reduction of 56.4% and exergy destructions of 60.4%, leading to improve building exergy efficiency from 9.8% to 18.0%. Nevertheless, exergoeconomically the building did not perform as expected due to high capital cost and exergy destructions cost rates. These results give an insight into the thermodynamic impact of the Passivhaus approach, providing a critical assessment of the strengths and limitations of the standard under both thermodynamic laws.

Experimental Study for the Integration of an Innovative Air Distribution System in Operating Rooms

Hospital buildings in general and especially the operating rooms are a challenge for building services engineers which are struggling to ensure indoor environmental conditions satisfying all the occupants. The requirements imposed by standards often lead to the discomfort: while surgeons require low temperatures for sanitary reasons, anesthesiologists and assistants feel uncomfortable and prefer warmer conditions. In past studies the estimated entrainment in the case of the jets issued from the lobed perforated panel was found to be greater than in the case of the standard circular perforated panel. The lobed flow offers a larger induction and a longer throw, a more uniform distribution of the flow, allowing thermal comfort improvement if such perforated panels were used. We integrated this concept of perforated air diffuser in the air distribution system referred to as “laminar flow ceiling” for the operating rooms in hospital environments. We found that the lobed perforated panel is performing better than the circular perforated panel in isothermal conditions for several volumetric flow rates. The special geometry do not generate supplementary noise as the sound pressure levels were determined for both grilles for different discharge flow rates while the pressure losses are less than 30Pa in the velocity range which corresponds to standard application of the air diffusion.

Improving Thermal Comfort and Indoor Air Quality through Minimal Interventions in Office Buildings

High internal heat gain and slow reaction of occupants to overheating have been identified as major contributors to risk of thermal discomfort in offices. This paper reports on the findings of a research programme which investigates the impacts of reducing internal heat gain and introducing automated ventilation strategies into lightweight open plan offices. It is aimed to developed intervention strategies with minimum disruption to occupants in order to improve energy performance thermal comfort and indoor air quality (IAQ). A case study building was selected and dynamic thermal simulation was conducted to test the performance of proposed strategies. The results reveal that tested strategies reduced the risk of overheating and poor IAQ by 64% and 90%, respectively. The energy consumption was also reduced by 2.1% for the best case scenario.