Influence of the ventilation system on thermal comfort of the chilled panel system in heating mode

In heating mode, fresh air is still essential for a chilled panel system in order to ensure the indoor air quality. In this paper, a chilled ceiling panel system was designed and built in a typical office room. The thermal environment and thermal comfort in the room were fully measured and evaluated by using the Fanger's PMV-PPD model and the standard of ISO 7730 respectively, when room was heated in two modes, one of which is the chilled panel heating mode and the other of which is the combined heating mode of chilled panel and supply air. The research results indicate that in the combined mode, ceiling ventilation improves the general thermal comfort and reduces the risk of local discomfort. Under the condition of same general thermal comfort, the heating supply upper limit of chilled panel can be increased by 12.3% because of air mixing effect caused by introduction of air ventilation.     

HVAC system strategies for energy conservation in commercial buildings in Saudi Arabia

In recent years, there has been a dramatic increase in energy consumption in Saudi Arabia. The building sector being the largest consumer of electric energy represents a major potential contributor for reducing energy consumption. Due to their functional and operational characteristics, commercial buildings relatively consume more energy (per unit area) than other types of buildings. The heating, ventilating and air-conditioning system (HVAC) is one of the largest end-users of energy in these buildings, particularly in harsh climates. Energy efficient design and operation of HVAC systems in commercial buildings can offer major opportunities for reduced energy consumption and contribute to sustainable development. However, improper utilization of energy conservation measures can result in reduced environmental quality. This in turn exposes the occupants to thermal discomfort and health risks, and consequently diminishes the economic value of the facility. Therefore, a well assessed and balanced energy conservation strategy is required to achieve energy efficiency while maintaining desired level of thermal comfort. In this study, major design and operational parameters for different types of HVAC systems influencing energy consumption are investigated utilizing the Visual-DOE program. Results indicate that energy savings of up to 30% can be obtained while maintaining acceptable level of thermal comfort when HVAC systems are properly selected and operated.     

Evaluation and comparison of thermal comfort of convective and radiant heating terminals in office buildings

Radiant heating systems are increasingly widely utilized in buildings for its energy conservation potential and enhanced thermal comfort. This paper presented an experiment to compare the thermal comfort performance of radiant heating system with convective heating system through objective measurement and subjective survey. Six physical parameters which might influence occupants' thermal satisfaction, including the Mean Radiant Temperature(MRT), humidity, air movement, A-weighted sound level,temperature fluctuation and vertical temperature difference, were measured. In addition, 97 subjects participated in the subjective survey part of this experiment, experiencing all the three environments heated by air source heat pump, radiator and floor heating.And they were asked to vote in six thermal comfort related aspects, i.e. thermal sensation, humidity, draught, local discomfort,overall thermal satisfaction and overall preferences, plus the acoustic environment, since the operation noise of heating system might lead to complains of the occupants. It was found that in continuous heating, no significant difference between radiant and convective heating system was observed in the Mean Radiant Temperature(MRT), indoor humidity and noise issue. Though radiant heating systems resulted in lower draught risk and less local discomfort complains in the feet region due to the less significant temperature fluctuations and vertical temperature gradients, radiant heating did not have significantly higher overall thermal satisfaction votes and was not significantly more preferred by occupants.     

Personal heating: effectiveness and energy use

Buildings use approximately 40% of primary energy with most energy expended on the provision of a comfortable indoor climate. An extended range of indoor temperatures can significantly reduce the energy load. However, lower temperature set points for heating can cause thermal discomfort. Giving building occupants the option to warm themselves (e.g. a local source at their desk or workstation) can mitigate this discomfort by the provision of a personalized conditioning system. A model is presented to assess the performance of personalized heating and its impact on the whole building energy load. Researchers, designers and facility managers can use this model to compare performance and analyse energy savings. The total energy use of personalized heating is estimated by scaling its settings to the actual level of discomfort resulting from a lowered heating set point. This model is used to assess seven different personalized heating systems. Assessments reveal that personalized heating brings a remarkable energy-saving potential, while maintaining or even improving individually perceived thermal comfort. Assessments are based on an assumed linear relation between the power and level of increased thermal sensation. Future research in personalized conditioning systems should be directed towards the development of the full characteristics and specific settings.     

Exceedance Degree-Hours: A new method for assessing long-term thermal conditions

Several “discomfort indices” have been proposed and codified into building standards, with several needs usually reported for such indices. They should: express the severity of discomfort in time steps while incorporating all environmental and personal factors; be usable with any comfort model (and thus, a variety of interests, for example, traditional thermal comfort, sleep comfort), among other requirements. The existing indices, however, fall short of meeting all these goals, limiting their usefulness in many situations, such as assessing conditions in mixed-mode buildings, especially when used for building performance simulation and design optimization purposes. Here, a new discomfort index called “Exceedance Degree-Hours” is developed, which accounts for all six main environmental and personal factors. By using an equivalent temperature index, “Exceedance Degree-Hours” can capture variations in discomfort severity between different thermal conditions that other indices cannot. In contrast with other indices, “Exceedance Degree-Hours” can be paired with various comfort definitions from literature, and, importantly, it can be used to assess thermal comfort in mixed-mode buildings, providing a single value as a result. Here, the results of the proposed method are compared to those of existing discomfort indices suggested in standards, and the advantages and limitations of the proposed approach are discussed.     

被动式降温策略在华南地区旧建筑改造中的设计应用及模拟

该文采用一系列被动武降温策略对华南地区某旧建筑进行改造设计,旨在优化室内热环境并降低建筑能耗,同时也综合考虑如何将建筑技术与空间设计相结合,对我国华南湿热地区的现有建筑改造设计提供参考.为了证明所采用可持续建筑技术的效果,文中使用CFD和Ecotect软件分别对改造前后的建筑所需加热和降温荷载以及不舒适时间进行模拟和测...     

Behavioural responses to cold thermal discomfort

Heating energy demand in buildings depends in part on occupants' behavioural responses to thermal discomfort during the heating season. The understanding of this has become one of the priorities in the quest to reduce energy demand. Thermal comfort models have long been associated with occupants' behaviour by predicting their state of thermal comfort or rather discomfort. These assumed that occupants would act upon their level of discomfort through three types of response: mechanisms of thermoregulation, psychological adaptation and behavioural responses. Little research has focused on the behavioural aspect. One of the key challenges is to gather accurate measurements while using discreet, sensor-based, observation methods in order to have minimum impact on occupants' behaviour. To address these issues, a mixed-methods approach is introduced that enables the establishment of a three-part framework for mapping behaviour responses to cold sensations: (1) increasing clothing insulation level; (2) increasing operative temperature by turning the heating system on/up; and (3) increasing the frequency, duration and/or amplitude of localized behaviour responses such as warm drink intake or changing rooms. Drawing on this framework, an extended model of thermal discomfort response is introduced that incorporates a wider range of observed behaviours.     

The need for temperature zoning in high-performance residential buildings

The development from poorly insulated and leaky buildings to modern high-performance buildings, such as passive houses, has led to considerable improvements regarding thermal comfort. However, user evaluations of passive houses that solely employ air heating indicate that bathrooms are often perceived as too cold and bedrooms as too warm. Based on these experiences, the functional requirement of providing thermal comfort using only air heating has not been adopted in the Norwegian standard for passive houses. Instead, usually local heat sources are installed in living rooms and bathrooms to facilitate temperature zoning within the dwelling. The questions asked in this study are how well this heating and ventilation concept functions in practice from the occupants’ point of view and whether it provides thermal comfort in the various rooms. Therefore, a questionnaire was distributed to the occupants of a typical multifamily passive house project in Norway. Despite the small sample size, the findings give important insight into the residents’ perception of the thermal conditions and clearly demonstrate the limitations of the heating and ventilation solution. Based on the results, the need for further development and further studies to provide temperature zoning is outlined.     

Effectiveness of passive measures against climate change: Case studies in Central Italy

This paper focuses on the effectiveness of passive adaptation measures against climate change, in the medium (2036–2065) and long term (2066–2095), for three case studies located in Florence (central Italy). In order to identify and highlight the passive measures which can provide comfort conditions with the lowest net heating and cooling energy demand, the input assumptions consider a constant thermal comfort level and don’t take into account either the effect of HVAC system’s performance and the degradation of the materials by ageing. The study results show that, in case of poorly insulated buildings, on the medium term, the reduction of energy needed for heating could be bigger than the increase for cooling, resulting in a total annual net energy need decrease, while in the long term the opposite happens. Conversely, considering a high level of thermal insulation, due to the large increase in cooling demand, the total annual energy need rises in both periods. Furthermore, attention should be paid to internal loads and solar gains that, due to the projected climate change, could become main contributors to the energy balance. In general, since the magnitude of energy need increase for cooling and decrease for heating is very significant on the long term, and varies in function of the type of building, the passive measure adopted and the level of thermal insulation, the research results lead to pay close attention to different types of energy refurbishment interventions, that should be selected in function of their effectiveness over time.     

Numerical investigation of local thermal discomfort in offices with displacement ventilation

Local thermal discomfort in offices with displacement ventilation is investigated using computational fluid dynamics. The standard κ-ϵ turbulence model is used for the prediction of indoor air flow patterns, temperature and moisture distributions, taking account of heat transfer by conduction, convection and radiation. The thermal comfort level and draught risk are predicted by incorporating Fanger's comfort equations in the airflow model. It has been found that for sedentary occupants with summer clothing common complaints of discomfort in offices ventilated with displacement systems result more often from an unsatisfactory thermal sensation level than from draught alone. It is shown that thermal discomfort in the displacement-ventilated offices can be avoided by optimizing the supply air velocity and temperature. It is also shown that optimal supply air conditions of a displacement system depend on the distance between the occupant and air diffuser.     

寒冷地区被动式太阳能系统集热部件玻璃热性能研究——以陕西西安农村为例

目前节能玻璃种类繁多,不同气候区建筑外围护结构透光部分选用的玻璃也有所不同.对于采用被动式太阳能系统的建筑,不可盲目使用节能玻璃作为集热部件.被动式太阳能系统集热部件的关键部件(玻璃及框材)应根据气候条件因地制宜的选用.分析了西安农村地区常用的各种节能玻璃的传热系数、太阳能得热系数等性能指标,得出适宜应用在寒冷地区被动式太阳能建筑集热部件的节能玻璃类型.此种材料可有效地提高太阳能得热和室内热环境的舒适度,减少采暖能耗.     

中国被动房外围护系统研究——以寒冷、严寒气候区被动房项目为例

德国的被动房是目前世界公认的具有超低能耗、超低碳排放量、超高室内舒适度等特点的建筑技术体系。德国的气候特征与中国华北地区的气候特征具有相似性,因此,研究并建造被动房对于我国建筑节能工作的发展具有重大的意义。外围护系统作为被动房设计的重点要素,对建筑的节能效率有重大的影响。以寒冷、严寒气候区的被动房项目为例,对被动房外围护系统进行分析与阐述,并以秦皇岛"在水一方"被动式住宅示范项目为例,进行能耗模拟与对比分析。提出适合我国寒冷、严寒气候区气候特点的被动式超低能耗建筑外围护系统的设计策略。     

Predictions of thermal comfort in stratified room environment

Studies of thermal comfort of occupants started in the early part of the 20th century to describe the comfort level in terms of environmental variables. Field studies have indicated that many of the complaints about unsatisfactory indoor environment can be attributed to the thermal environment. Hence, heating, ventilation, and air conditioning (HVAC) systems are used in buildings to create thermal environments that are capable of providing comfort to the occupants. Among different ventilation systems, displacement ventilation (DV) systems have become popular as more energy efficient room air distribution systems compared with the other more common forms of air distribution systems, such as mixing ventilation. However, local cold discomfort at the lower extremities due to vertical temperature gradient is often reported with DV systems. Although many studies are reported in the literature that compare the performance of the DV systems with the other more conventional types of ventilation systems, the performance of different displacement ventilation types in providing thermal comfort need further investigation. The aim of the current work is to compare the ventilation performance, as predicted by an advanced thermal comfort model, of three commonly used DV air terminal devices (ATDs) for room ventilation: a flat wall diffuser (ATD1), semi-cylindrical wall diffuser (ATD2) and floor swirl diffusers (ATD3). The CBE (Center for the Built Environment at Berkeley) comfort model has been implemented in this study to compare the thermal comfort provided by the three ATDs due to its good performance in non-uniform thermal environments. Based on the test conditions and the results obtained from the comfort model, the predicted occupant’s local sensations for the case of ATD2 were better than those for ATD1 and ATD3 and it showed better overall thermal sensation. Since the local comfort of the CBE model is a function of both local and overall thermal sensations, the predicted occupant’s local comfort values for ATD2 were better than those for ATD1 and ATD3 and consequently it provided better overall thermal comfort.     

Thermal zoning and interzonal airflow in the design and simulation of solar houses: a sensitivity analysis

Many assumptions must be made about thermal zoning and interzonal airflow for modelling the performance of buildings. This is particularly important for solar homes, which are subjected to high levels of periodic solar heat gains in certain zones. The way in which these passive solar heat gains are distributed to other zones of a building has a significant effect on predicted energy performance, thermal comfort and optimal design selection. This article presents a comprehensive sensitivity analysis that quantifies the effect of thermal zoning and interzonal airflow on building performance, optimal south-facing glazing area, and thermal comfort. The effect of controlled shades to control unwanted solar gains is also explored. Results show that passive solar buildings, in particular, can benefit from increased air circulation with a forced air system because it allows solar gains to be redistributed and thus reduces direct gain zone overheating and total energy consumption.     

Optimization of building thermal design and control by multi-criterion genetic algorithm

The design of buildings is a multi-criterion optimization problem, there always being a trade-off to be made between capital expenditure, operating cost, and occupant thermal comfort. This paper investigates the application of a multi-objective genetic algorithm (MOGA) search method in the identification of the optimum pay-off characteristic between the energy cost of a building and the the occupant thermal discomfort. Results are presented for the pay-off characteristics between energy cost and zone thermal comfort, for three design days and three building weights. Inspection of the solutions indicates that the MOGA is able to find the optimum pay-off characteristic between the daily energy cost and zone thermal comfort. It can be concluded that multi-criterion genetic algorithm search methods offer great potential for the identification of the pay-off between the elements of building thermal design, and as such can help inform the building design process.     

Wind, sun and temperature—Predicting the thermal comforf of people in outdoor spaces

We describe a procedure to predict the thermal comfort of people in outdoor spaces, and show its application in determining the effects of urban height and bulk regulations around public open space in downtown San Francisco. The procedure is based on a computer model of the human thermoregulatory system, run on a typical year's hourly climate data, to produce the number of hours, by time of day and season of year, that comfort or discomfort are to be expected. The climate data are synthesized to take into account the city's influence on wind and sunlight, and are distinct for each ground-level location. The wind influences are estimated from wind tunnel tests, and the sunlight availability from one of several types of shading analysis.

This procedure was used to evaluate the effect of four different levels of potential development on seven major open spaces in the city. A number of design conclusions could be drawn from the results. For the climate of San Francisco, building-induced solar blockage nearly always influenced comfort more than wind acceleration caused by buildings. This finding will not necessarily hold in other climates. The new procedure allows a more sensitive analysis of building effects on comfort than wind analysis alone.     

On natural ventilation and thermal comfort in compact urban environments – the Old Havana case

The Historical Centre of Old Havana in Cuba is currently undergoing a comprehensive preservation and urban recovering program. Housing units are built in existing vacant plots of the old city. The design of the new buildings should be integrated in the compact urban structure that has developed throughout the past centuries. This compact morphology, however, obstructs the breezes that are an essential component to achieve thermal comfort by passive means in warm and humid climates. New courtyard buildings should be designed in such a way that natural ventilation and thermal comfort are enhanced. Research on natural ventilation and thermal comfort in compact urban environments, however, is scarce. This paper first presents an historical overview of the typological evolution of the residential architecture in this part of the city and its relation to natural ventilation and thermal comfort. Next, it provides a partial study of the morphological characteristics of the Historical Centre. From this study, appropriate locations have been selected for field measurements and a limited comfort survey, from which a tentative summer comfort zone for residential buildings in Old Havana is suggested. Finally, based on the historical overview, the measurements and the survey, some preliminary design recommendations for residential buildings in Old Havana are provided.     

Windows in the workplace: examining issues of environmental sustainability and occupant comfort in the selection of multi-glazed windows

Windows are important in the workplace for both environmental and psychological reasons. Good glazing design can reduce energy outputs by lowering the requirements for heating or cooling; frame design can utilise more sustainable materials and those with lower embodied energy, such as timber and aluminium-clad timber. Windows are also important for the provision of daylight and a view, both of which have known psychological benefits, although glare and passive solar gain can be problematic.Three studies were undertaken to look at sustainability and comfort issues for a number of different types of multi-glazed windows. Focus groups and interviews with professionals were used to examine issues of sustainability and productivity. Four case study buildings were surveyed to examine the level of energy use for different glazing specifications. A post-occupancy survey was then used to examine the level of comfort in these buildings. Results showed that architects consider comfort and productivity in their designs, but consider sustainability less often. Surveys of energy usage showed that building design can influence the efficiency of multi-glazed windows; this result was mirrored in the post-occupancy survey where design factors influenced occupant comfort. The research concludes that comfort and productivity in the workplace is related more to design factors than to sustainability factors.     

电加热相变蓄热地板供暖房间热特性数值模拟与分析

介绍了电加热相变蓄热地板供暖的优点，综合考虑室外气象因素、室内辐射特性和相变材料自身的热物性建立了电加热相变蓄热地板供暖系统的计算模型。比较了相变蓄热地板与传统散热器供暖的热舒适性和能耗，结果表明相变蓄热地板能够改善室内热舒适性和降低能耗。     

Predictive controllers for thermal comfort optimization and energy savings

The present work is focused on the study of indoor thermal comfort control problem in buildings equipped with HVAC (heating, ventilation and air conditioning) systems. The occupants’ thermal comfort sensation is addressed here by the well-known comfort index known as PMV (predicted mean vote) and by a comfort zone defined in a psychrometric chart. In this context, different strategies for the control algorithms are proposed by using an only-one-actuator system that can be associated to a cooling and/or heating system. The first set of strategies is related to the thermal comfort optimization and the second one includes energy consumption minimization, while maintaining the indoor thermal comfort criterion at an adequate level. The methods are based on the model predictive control scheme and simulation results are presented for two case studies. The results validate the proposed methodology in terms of both thermal comfort and energy savings.