Effectiveness of daylighting design and occupant visual satisfaction in a LEED Gold laboratory building

Using daylight as primary light source has been widely recognized as an important strategy to reduce building energy demand and enhance indoor environment quality. However, to design and operate a building to make full use of daylight, which is a dynamic light source, to meet diverse occupant needs remains a challenge. This paper reports a post-occupancy study of the visual environment in a laboratory building on a university campus, and puts a spotlight on the building occupants as it examines the effectiveness of the daylighting design and systems integration in creating a visual environment to support occupant comfort and satisfaction while reducing artificial lighting demand. Results show generally high satisfaction with daylit work environment and positive effect of the horizontal shading strategy. Issues about the integration between daylighting and electric lighting systems and level of occupant control are identified and discussed for improving the effectiveness of daylighting and enhancing the quality of the visual environment in the building of study. A multiple-tool methodology is developed and tested, which included occupant surveys, interviews, illuminance measurements, continuous data loggers, fisheye-lens camera and glare-identifying software, and documentation of spatial settings, systems features, and user behavior.     

Central automatic control or distributed occupant control for better indoor environment quality in the future

Based on a database accumulated from several recent surveys of office buildings located in a temperate climate (Denmark), the effect on occupant perceptions and symptom prevalence was compared in buildings with natural and with mechanical ventilation in which earlier studies have shown a discrepancy in the degree of perceived control. The database was composed of 1272 responses obtained in 24 buildings of which 15 had mechanical ventilation (997 responses) and nine had natural ventilation (275 responses). The number of occupant-reported control opportunities was higher in buildings with natural ventilation. Analysis of occupant responses, after grouping according to categories determined by the degree of satisfaction with the perceived control, showed that it was more likely the degree of control satisfaction that affected the prevalence of adverse perceptions and symptoms. Thus, the degree of control, as perceived by occupants, seemed more important for the prevalence of adverse symptoms and building-related symptoms than the ventilation mode per se. This result indicates that even though the development and application of new indoor environment sensors and HVAC control systems may allow for fully automated IEQ control, such systems should not compromise occupants’ perception of having some degree of control of their indoor environment.     

Evaluation of visualization techniques for use by facility operators during monitoring tasks

Facility operators interact with building automation systems (BASs) on a regular basis for various purposes such as facility maintenance, occupant comfort, equipment monitoring, safety and security. Evaluation of various BAS interfaces showed that there are challenges faced by facility operators that impede their efficiency and accuracy of their responses to reported situations. These challenges revolve mainly around the lack of spatial context for the monitored sensor readings and equipment statuses, and operators' information overloading. Various visualization techniques have been used in commercially available BASs, however, their impact on the situation awareness of facility operators is not clearly known. This study focuses on this need and evaluates various visualization techniques that best suit to the needs of facility operators. This study identifies visualization techniques that are applicable to encode sematic information in spatial context, and details the design and implementation of user studies that were performed with seventeen expert and six novice facility operators to understand the impact of visualization techniques on operators' accuracy and timeliness to reported situations in relation to building system monitoring. The findings suggested that visualization-based interfaces generally improve the accuracy and efficiency of facility operators' decisions in monitoring tasks as compared to interfaces designed mainly with tabular displays. The results can be used by practitioners in the industry, not only for greenhouse facility monitoring, but also for facility monitoring in general, and by vendors to consider for their BAS interfaces.     

Energy analysis of the personalized ventilation system in hot and humid climates

Personalized ventilation (PV) is an individually controlled air distribution system aimed at improving the quality of inhaled air and the thermal comfort of each occupant. Numerous studies have shown that PV in comparison with traditional mechanical ventilation systems may improve occupants’ health, inhaled air quality, thermal comfort, and self-estimated productivity. Little is known about its energy performance.In this study, the energy consumption of a personalized ventilation system introduced in an office building located in a hot and humid climate (Singapore) has been investigated by means of simulations with the empirically tested IDA-ICE software. The results reveal that the use of PV may reduce the energy consumption substantially (up to 51%) compared to mixing ventilation when the following control strategies are applied: (a) reducing the airflow rate due to the higher ventilation effectiveness of PV; (b) increasing the maximum allowed room air temperature due to PV capacity to control the microclimate; (c) supplying the outdoor air only when the occupant is at the desk. The strategy to control the supply air temperature does not affect the energy consumption in a hot and humid climate.     

Evaluating positivist theories of occupant satisfaction: a statistical analysis

An explorative statistical analysis of consistent non-domestic building performance studies is conducted non-domestic buildings (n?=?47) to validate the universal positions of comfort widely cited in industry guidance and standards. The Building Use Studies (BUS) methodology for evaluating occupant satisfaction employed by these studies was tested for reliability and the factor structure explored. The reliability of this method was found to be ‘excellent’ and eight latent variables that characterize a hierarchical factor structure induced. Increased visual display unit use and open-plan arrangements were found to be associated with negative occupant perceptions. This suggests that privacy and personal communication may be defining issues for occupant satisfaction, with implications for space planning. Significantly different perceptions towards air quality and conditions in winter were observed between gender and those familiar with their environments were found to have a tendency to hold more negative perceptions more broadly. It has also been found that perceptions towards seasonal conditions may be improved by providing local control to mechanical services. Such insights highlight the limitations of reliance on positivist theory. Hence, it is recommended that high-performance buildings be provided control and management systems that learn from those occupying the building over time, cautiously adapting service provision accordingly.     

Does thermal control improve visual satisfaction? Interactions between occupants’ self-perceived control,visual, thermal,and overall satisfaction

Occupants’ satisfaction had been researched independently related to thermal and visual stimuli for many decades showing among others the influence of self-perceived control. Few studies revealed interactions between thermal and visual stimuli affecting occupant satisfaction. In addition, studies including interactions between thermal and visual stimuli are lacking different control scenarios. This study focused on the effects of thermal and visual factors, their interaction, seasonal influences, and the degree of self-perceived control on overall, thermal, and visual satisfaction. A repeated-measures laboratory study with 61 participants running over two years and a total of 986 participant sessions was conducted. Mixed model analyses with overall satisfaction as outcome variable revealed that thermal satisfaction and visual satisfaction are the most important predictors for overall satisfaction with the indoor environment. Self-perceived thermal control served as moderator between thermal satisfaction and overall satisfaction. Season had slight influence on overall satisfaction. Random effects explained the highest amount of variance, indicating that intra- and interindividual differences in the ratings of satisfaction are more prevalent than study condition. Future building design and operation plans aiming at a high level of occupant satisfaction should consider personal control opportunities and take into account the moderating effect of control opportunities in multimodal interactions.     

Application of the Building Environmental Performance Model (BEPM) in Hong Kong

Since the energy crisis of 1973, engineers have endeavoured to implement energy conservation in buildings. Unfortunately, their efforts have often resulted in energy saving which ignores the fundamental delivery of indoor satisfaction. Hence, either energy is conserved sacrificing indoor environmental quality (IEQ), or additional energy is consumed for the cooling of occupancy space. These misconceptions have prompted the development of an integrated design and operation protocol based on a so-called Building Environmental Performance Model (BEPM).The Building Environmental Performance Model links the IEQ and the building energy consumption together. It treats a building as a system. Energy consumption in the building services systems is the input to this system with the IEQ as the output. The BEP model incorporates two main modules: an adaptive comfort temperature control module (ACT) and a new CO₂ demand control module (nDCV). These two modules (ACT and nDCV) take an innovative approach and help maintain satisfaction levels as well as optimum energy consumption.The BEP model was built into an algorithm for implementation in a Direct Digital Control system. It was used in a longitudinal monitoring study in a typical Hong Kong office, so that the usefulness of the model could be verified. It was found that the BEPM was able to save up to 15% of total energy used, and maintain the occupant dissatisfaction rate of thermal comfort and indoor air quality at around 20%.The incentive of the BEPM can be deduced from a simple life cycle costing analysis. It assumes an inflation rate and bank interest rate of 8 and 10%, respectively, the total net present value (NPV) for the original airside system is higher than that employing the BEPM by HK$ 19,700,000 for 20 years of operation.     

Artificial intelligence and networking in integrated building management systems

In recent years the emphasis has moved towards integrating all a building's systems via centralised building management systems (BMS). To provide a more intelligent approach to the facility management, safety and energy control in building management systems (IBMS), this paper proposes a methodology for integrating the data within a BMS via a single multi-media networking technology and providing the BMS with artificial intelligence (AI) through the use of knowledge-based systems (KBS) technology. By means of artificial intelligence, the system is capable of assessing, diagnosing and suggesting the best solution. This paper outlines how AI techniques can enhance the control of HVAC systems for occupant comfort and efficient running costs based on occupancy prediction. Also load control and load balancing are investigated. Instead of just using pre-programmed load priorities, this work has investigated the use of a dynamic system of priorities which are based on many factors such as area usage, occupancy, time of day and real time environmental conditions. This control strategy which is based on a set of rules running on the central control system, makes use of information gathered from outstations throughout the building and communicated via the building's data-bus.     

A comparison of the occupant comfort in a conventional high-rise office block and a contemporary environmentally-concerned building

A comparative study of the occupant comfort (neutral) in a conventional high-rise office block and a contemporary environmentally-concerned building for Sheffield UK climate conditions was carried out. A questionnaire was designed for occupants to rate their workplace environment in terms of the thermal, visual, acoustic and overall perception and satisfaction level. The basic physical parameters were measured at the same time, e.g. air temperature, humidity, illuminance and sound level. It is inferred that (1) There is a noticeable difference between the conventional building and environmentally-concerned building in terms of their thermal and visual environment. (2) A clear distinction of the occupant sensation and satisfaction level towards their thermal and visual environment is presented between these two buildings. (3) The effect of basic physical variables on the occupants’ perception and satisfaction level becomes less significant when minimal standards are attained. (4) The acoustic satisfaction level however, was not perceived differently by the occupants of the two building types.     

A window of one’s own: a public office post-occupancy evaluation

ABSTRACT

The prevalence of mechanical climatization in office buildings, alongside the dictate to conserve energy, has misguidedly promoted the construction of buildings with non-operable windows. Research shows that such buildings are detrimental to their occupants’ wellbeing and productivity, sometimes causing them to feel overcooled or overheated. This post-occupancy evaluation illustrates such problems through the case study of a courthouse building in a hot arid environment. A strong association is shown between occupant satisfaction, building ventilation and sense of wellbeing at work. A positive correlation was found between satisfaction with personal control, and overall satisfaction survey results show that workers express a willingness to compromise future salary rises in order to receive operable windows. Key lessons for architects are discussed.     

A fault-tolerant and energy efficient control strategy for primary-secondary chilled water systems in buildings

Primary-secondary chilled water systems with decoupled bypass in building air-conditioning often cannot work in healthy condition as desired in practical operation, due to excess secondary flow demand resulting in deficit flow in the bypass line. This paper presents a fault-tolerant and energy efficient control strategy for secondary chilled water pump systems to solve this operation and control problem providing enhanced operation performance and energy efficiency of chilled water systems. The strategy employs the flow-limiting technique that ensures the water flow of secondary loop not exceed that of the primary loop while still maintaining highest possible delivery capacity of cooling to terminals. The strategy is also integrated with a differential pressure set-point optimizer to determine the optimal set-point. The performance of this strategy is evaluated in a simulated real-life environment representing the chilled water system in a super high-rise building by comparing it with two conventional control strategies. Results show that the proposed strategy can effectively eliminate the deficit flow at both starting and normal operation periods. The energy saving in the secondary chilled water pumps can be up to over 70% and 50% at system starting and normal operation periods respectively compared with the other strategies.     

Investigation on the impacts of different genders and ages on satisfaction with thermal environments in office buildings

This paper investigates the effects of occupant gender and age on thermal satisfaction in office environments. The data used for the analyses was collected from 40-sampled occupants and their workstations on 38 floors in 20 office buildings in the U.S. with support from the U.S. General Services Administration. The field measurements include data collection for air temperature, radiant temperature, temperature stratification, relative humidity and air velocity of the sampled workstations. Occupant satisfaction surveys were distributed to each occupant in the workstations measured, and the thermal attributes of building systems were recorded. The objective and subjective data sets support statistical correlation analysis between environmental qualities and user satisfactions.     

Energy and comfort performance of thermally activated building systems including occupant behavior

In building simulations it is common practice to use standardized occupant behavior and internal gains. Although this is a valid approach for designing systems, the probabilistic nature of these boundary conditions influences the energy demand and achieved thermal comfort of real systems. This paper analyzes the influence of occupant behavior on the energy performance and thermal comfort of a typical office floor equipped with a thermally activated building system (TABS). A multi-zone TRNSYS model with 10 adjacent zones per orientation for a typical moderate Belgian climate is set up. First, the energy performance and thermal comfort of thermally activated building systems (TABS) are compared with the performance of idealized cooling with standardized user behavior. TABS are able to deliver good thermal comfort but show to have a higher energy demand. Secondly, probabilistic occupant behavior was implemented in the TABS simulations. The influence of the occupancy rate, the shading device use and switching of the lights are analyzed by defining user profiles. It is shown that occupant behavior may have an important influence on the cooling demand and thermal comfort. However, as long as good solar protection is foreseen and operated in a correct way, TABS are able to cope with different user behavior modeled in this paper. In this case, normal daily stochastic processes do not considerably affect the cooling demand and thermal comfort during summer.     

Energy efficient design and occupant well-being: Case studies in the UK and India

The purpose of this paper is to demonstrate the relationships between sustainable building design and occupant well-being. It starts with a definition of sustainable design and well-being, and focuses on the relationships between energy performance and occupant feedback. Methodologically it draws on detailed monitoring and surveys of 12 case study office buildings in the UK and India, and the paper uses the data to explore whether energy use and associated CO₂ emissions are correlated to occupant satisfaction and comfort. The results demonstrate that increased energy use in the case study buildings is associated with increased mechanisation (e.g. centralised air conditioning) and reduced occupant control. This reduced control in turn is shown to relate to reduced occupant comfort and satisfaction. Finally, the paper reveals that the reported health conditions of occupants correlates strongly with their levels of satisfaction. The overall conclusion is that energy use in typical office buildings is inversely correlated with the well-being of the occupants: more energy use does not improve well-being.     

Buildings.Occupants: a Modelica package for modelling occupant behaviour in buildings

Energy-related occupant behaviour is crucial to design and operation of energy and control systems in buildings. Occupant behaviours are often oversimplified as static schedules or settings in building performance simulation ignoring their stochastic nature. The continuous and dynamic interaction between occupants and building systems motivates their simultaneous simulation in an efficient manner. In the past, simultaneous simulation has relied on co-simulation approaches or customized source code changes to building simulation programmes. This paper presents Buildings. Occupants, an open-source package implemented in Modelica, for the simulation of occupant behaviours of lighting, windows, blinds, heating and air conditioning systems in office and residential buildings. Examples were presented to illustrate how the models in the Occupants package are capable to simulate stochastic occupant behaviours. The major contribution of this work is to introduce the equation-based modelling approach to simulate occupant behaviours in buildings and to develop an open-source Occupants package in the Modelica language.     

Relationship between quality of building maintenance management services for indoor environmental quality and occupant satisfaction

Two surveys were carried out to investigate the correlation between building maintenance management services for indoor environmental quality (IEQ) and occupant satisfaction. Each maintenance management organization manager was surveyed using the Evaluation Index of Maintenance Management Service Quality, created by Akira Takakusagi. Seven office buildings in Seoul, Korea were investigated in the first survey, and two buildings from the first survey were selected for analysis in the second survey. One is a building with good maintenance management services but low occupant satisfaction, and the other is an office building with low maintenance management services but high occupant satisfaction.     

A tool for integrated hvac,building, energy and control analysis Part 1: overview of QUICKcontrol

This paper describes a tool called QUICKcontrol. The new, simplified, yet extensively verified building model made an efficient integrated tool possible. The system simulation is done using simplified though accurate component models. A unique simulation tool resulted.Any building, any HVAC system, and any control strategy can now quickly be built up using a graphical user interface. The integrated building, HVAC and control problem is then solved iteratively. Energy balances for each component, and for the system as a whole, are obtained. HVAC systems and controls can now be designed, optimised, and commissioned with ease and confidence.The software has already been successfully verified by eight case studies. The results proved to be sufficiently accurate for design, as well as control and energy analyses. For example, energy predictions calculated each minute are generally within 10% of measured values, while zone temperatures are within 1°C for 90% of the time.A new user typically takes a day to master the use of the software. Computing time for a very involved building, HVAC system, and complex energy management controls is approximately 10 min on a 133 MHz Pentium PC with 16 MByte RAM and 40 time steps per h. It is thus easy and practical to investigate a range of alternative control strategies and demonstrate their financial advantages to clients.     

A systematic procedure to study the influence of occupant behavior on building energy consumption

Efforts have been devoted to the identification of the impacts of occupant behavior on building energy consumption. Various factors influence building energy consumption at the same time, leading to the lack of precision when identifying the individual effects of occupant behavior. This paper reports the development of a new methodology for examining the influences of occupant behavior on building energy consumption; the method is based on a basic data mining technique (cluster analysis). To deal with data inconsistencies, min-max normalization is performed as a data preprocessing step before clustering. Grey relational grades, a measure of relevancy between two factors, are used as weighted coefficients of different attributes in cluster analysis. To demonstrate the applicability of the proposed method, the method was applied to a set of residential buildings’ measurement data. The results show that the method facilitates the evaluation of building energy-saving potential by improving the behavior of building occupants, and provides multifaceted insights into building energy end-use patterns associated with the occupant behavior. The results obtained could help prioritize efforts at modification of occupant behavior in order to reduce building energy consumption, and help improve modeling of occupant behavior in numerical simulation.     

A novel personalized thermal comfort control, responding to user sensation feedbacks

This paper presents a novel heating, ventilation, and air conditioning (HVAC) control architecture for office buildings, which uses the predicted mean vote (PMV) index of each occupant as feedback and offers them the opportunity to act on their own comfort level by signalling a possible thermal uncomfortable sensation to a personal user interface. A co-simulation EnergyPlus/Simulink has been used to test this new personalized and adaptive thermal comfort control in an office building for different seasons, up to two employees per office. Simulation results show that such a comfort control algorithm leads to sizeable energy savings as well as comfort improvement for each occupant. Moreover, after processing the order given by the user interface, the control algorithm makes the simulated thermal sensation match the actual thermal sensation of the occupant with a high accuracy, leading to a better consideration of his thermal comfort.