Large Office Building Research Articles

A model predictive control optimization environment for real-time commercial building application

A model predictive control (MPC) environment is described. The environment integrates Matlab and EnergyPlus with a modified particle swarm optimizer to predict optimal building control strategies. A supporting framework is described which couples the environment to a building automation system, allowing real-time optimization considering operator overrides and updated weather forecasts. Challenges unique to integration with EnergyPlus for real-time optimization are discussed. Application of the environment is demonstrated in two simulation cases. First, the environment is used to determine hourly cooling set points minimizing daily energy cost for EnergyPlus's Benchmark Large Office building. Results suggest 5% cost savings during the study period. Second, the environment is used to determine hourly supply water temperature and circulator availability that minimize daily energy consumption for a small office building having a thermally activated building system (TABS). Compared to the base case, energy savings up to 54% are reported, with often improved occupant comfort.

Simulation-Assisted Management and Control Over Building Energy Efficiency – A Case Study

The specific aim of this research paper is to demonstrate how much energy use will be reduced if the simulation -assisted building energy management and control system is applied to a representative large office building. The methodology applied includes: (1) choosing an appropriate building simulation software to assess energy savings, (2) selecting a representative building and then creating the building model for simulation, (3) identifying the year with available weather data and actual building energy consumption data for the building selected, and then calibrating the simulation model using the actual building energy consumption, (4) selecting proper energy-saving strategies and applying them to obtain hourly energy use for a day. The optimal temperature schedule that saves the most energy was identified. Cost effectiveness studies were performed to evaluate how much annual energy saving has been achieved by using the management and control optimization strategy and how long it will pay back.

Levels of microbial agents in floor dust during remediation of a water-damaged office building

We examined the effects of remediation on loads of culturable fungi in floor dust collected from a large water-damaged office building during four cross-sectional surveys (2002, 2004, 2005, and 2007, respectively). We created a binary remediation variable for each year for each sampled workstation using information on remediation associated with water damage obtained from building management and used generalized linear mixed-effects models. We found significantly lower levels of culturable total and hydrophilic fungi at remediated workstations than at non-remediated workstations in 2004 and 2005 after completion of major remediation. The remediation effect, however, disappeared in 2007. The fraction of hydrophilic to total fungal concentrations was lowest in 2004, increased in 2005, and was highest in 2007. Our results indicate that the 2003 remediation lowered dust indices of dampness temporarily, but remediation was incomplete, consistent with a building assessment report of water infiltration. This study demonstrates the utility of longitudinal evaluation of microbial indices during remediation of water damage in this building, in which elimination of sources of moisture was not fully addressed. Our findings indicate that the fraction of hydrophilic fungi derived from concentrations of fungal species may be a useful index for assessing the long-term effectiveness of remediation. This study demonstrates the utility of longitudinal evaluation of microbial indices during remediation of water damage in this building, in which elimination of sources of moisture was incomplete. Our findings indicate that the fraction of hydrophilic fungi derived from concentrations of fungal species may be a useful index for assessing the long-term effectiveness of remediation.

Optimal supervisory HVAC control: Experiences in Australia

A number of HVAC system vendors and operators have started to implement demand management systems in commercial buildings, yet this study contends that the impact of such systems on building performance and occupant comfort is poorly understood. This article examines such issues, showing the results from demand response experiments in two large office buildings. For optimal performance, it is believed that the HVAC management system should be dynamic and intelligent, responding to changing events and considering a variety of external factors, such as occupancy, human comfort, electricity price, and weather forecast. An example of such a system is detailed.

Measuring the carbon footprint of existing office space

Methods for assessing the environmental performance of new and existing office space cover a range of criteria that includes energy, water, materials and waste, health and wellbeing, pollution, transport, land use and ecology, but the overwhelming environmental objective is to reduce the amount of carbon dioxide (CO2) emitted from office use. The two main sources of office‐related CO2 emissions are building operation and commuting and, in these respects, existing buildings pose a different set of challenges to new developments; energy is embodied in the existing structure and systems, and the location is fixed in relation to facilities such as public transport nodes and amenities. Using standardised published metrics on CO2 emission from office occupation and commuting, this paper estimates the amount of CO2 emitted by the stock of medium to large office buildings in a large regional city in the UK. The results are put into context of government targets and current environmental performance assessment methods. The paper argues that the existing office stock of a typical UK city performs poorly in terms of CO2 emission and that most current assessment instruments do not reveal the full extent of that poor performance. Depending on the instrument, this is for one or more of three main reasons: actual energy consumed/CO2 emitted is not measured, insufficient weight is placed on CO2 emission relative to other, often more qualitative green credentials, and either insufficient or no regard is paid to CO2 emitted as a result of commuting and business travel.

Vibration Serviceability of a Building Floor Structure. II: Vibration Evaluation and Assessment

People are generally very sensitive to unexpected vibrations. Very small levels of building floor movements due to activities such as walking can become annoying to occupants. Accurate prediction, evaluation, and assessment of vibrations can greatly assist engineers and architects to design cost-effective building structures without such problems. In an attempt to clarify some of the issues related to this common serviceability problem, this paper presents a study of the various parameters used for the evaluation and assessment of building vibrations. Provisions of several current standards and design guides commonly used in North America and U.K. to evaluate and assess building vibrations as related to human perception and comfort are reviewed. These provisions are then applied using the vibrations measured during a number of walking tests conducted on a large cantilevered office building floor. Based on the results of this study, it is concluded that the vibration dose value (VDV) recommended by some st...

Evaluation of a turbine driven CCHP system for large office buildings under different operating strategies

Combined cooling, heating, and power (CCHP) systems use waste heat from on-site electricity generation to meet the thermal demand of the facility. This paper models a CCHP system for a large office building and examines its primary energy consumption (PEC), operational costs, and carbon dioxide emissions (CDE) with respect to a reference building using conventional technologies. The prime mover used in this investigation is a load share turbine, and the CCHP system is evaluated under three different operation strategies: following the electric demand of the facility, following the thermal demand of the facility, and following a seasonal strategy. For the various strategies, the percentages of total carbon dioxide emissions by source are presented. This paper explores the use of carbon credits to show how the reduction in carbon dioxide emissions that is possible from the CCHP system could translate into economic benefits. In addition, the capital costs available for the CCHP system are determined using the simple payback period. Results indicate that for the evaluated office building located in Chicago the CCHP operation reduces the operational cost, PEC, and CDE from the reference building by an average of 2.6%, 12.1%, and 40.6%, respectively, for all the different operational strategies.

Energy Audit and Potential Energy Saving in an Office Building in Riyadh, Saudi Arabia

Energy audit is used in this paper as an efficient method/tool to assess and study the energy profile of a large office building in Riyadh City. The various components of the building are analyzed, such as specifications of the walls, the roofs, the windows, the lighting fixtures, the office equipments, the chillers, HVAC, the additional air conditioning units known as split types and the other equipments in the building. It has been found that air conditioning system represents 50% of the total installed power. The energy audit study has helped to diagnose and then define certain solutions and modifications for increasing energy efficiency in the building. The potential energy saving and the pay-back period of the proposed modifications are also calculated and analyzed for different solutions. After the implementation of the proposed modifications, the pay-back period is estimated to be 29 months. Recommendations are suggested according to the optimum solution.

In-Place Testing of In-Duct Ultraviolet Germicidal Irradiation

This paper reports results from a field study designed to demonstrate a method for evaluating a building's in-duct ultraviolet germicidal irradiation (UVGI) system using naturally occurring airborne microorganisms and to evaluate its potential effectiveness against selected airborne microorganisms. Forty-eight 64 in. (1.63 m) long ultraviolet germicidal lamps were installed perpendicular to airflow and upstream of the cooling coils in a heating, ventilating, and air-conditioning (HVAC) system for a retail space in a large New York City office building. A portable in-duct UVGI apparatus was used to benchmark ultraviolet susceptibility of naturally occurring airborne microorganisms. Benchmarking was accomplished by measuring the portable apparatus's efficiency for inactivating UVGI-resistant microorganisms in the laboratory at various operating conditions. Inactivation efficiency for both the in-duct UVGI-equipped HVAC system and portable in-duct UVGI apparatus were then measured simultaneously using naturally occurring microorganisms. If the UVGI-equipped HVAC system had higher inactivation efficiency than the portable in-duct UVGI apparatus, then the UVGI-equipped HVAC system's efficiency for inactivating the UVGI-resistant microorganisms used in the laboratory would be expected to be higher than the efficiency of the portable in-duct UVGI apparatus. Based on the results for the tested UVGI-equipped HVAC system, the expected efficiency was at least 88% for Bacillus subtilis var. niger spores, a common surrogate for Bacillus anthracis spores.

The CABA Building Intelligence Quotient programme

The article describes the web-based Building Intelligence Quotient (BiQ) programme, developed for the Continental Automated Buildings Association (CABA). The initial BiQ beta testing and the BiQ corporate portfolio analysis are reported. The BiQ rates building automation systems in existing large office buildings and supports the integrated design and life-cycle costing processes. It contributes to the increasing convergence of green and intelligent building programmes. Using the BiQ for rating the intelligence of building automation contributes to the knowledge of building performance and enhances intelligence within the building industry. The BiQ reflects the convergence of information technology to all building and business enterprise systems contributing to the acquisition of knowledge that can positively guide future decision making and action. Using the BiQ and comparing the BiQs across corporate portfolios provides new ways that various stakeholders can learn from actual building performance and improve decision making for the automation systems of future buildings. The BiQ can be a key part of developing individual and collective intelligence in relation to building design and operation. The BiQ report is a feedback mechanism that shows what is working and what is not. The BiQ and other CABA programmes contribute to the notion of feedback and intelligence.

Evaluation of plume potential and plume abatement of evaporative cooling towers in a subtropical region

Hong Kong is a typical subtropical region with frequently high humidity in late spring and summer seasons. Plume from evaporative cooling towers, which service air-conditioning systems of civil buildings, has aroused public concerns since 2000 when the fresh water evaporative cooling towers were allowed to be used for high energy efficiency and environmental issues. This paper presents the evaluation of the plume potential and its effect on the sizing of the plume abatement system in a large commercial office building in Hong Kong for practical application. This evaluation was conducted based on a dynamic simulation platform using the typical meteorological year of Hong Kong since the occurrence of the plume heavily depends on the state conditions of the exhaust air from cooling towers and the ambient air, while the state condition of the exhaust air is determined by the total building cooling load and the control strategies of cooling towers employed mainly for improving energy efficiency. The results show that the control strategies have a significant effect on the plume potential and further affect the system design and sizing of the plume abatement system.

Continuous-time model identification for closed loop control performance assessment

The paper describes a system identification procedure for continuous-time transfer function models and demonstrates how it can be used for control performance assessment. Two normalized indices are derived for detecting oscillations and sluggish performance. The methods are designed for single-input single-output (SISO) control loops that experience periodic setpoint changes. An advantage of the system identification procedure is that it can operate on irregularly sampled data. The paper presents results from simulation tests and from tests on an heating, ventilating, and air-conditioning (HVAC) system serving a large commercial office building.

The Use of Relative Risk-Based Assessment to Identify Cost-Effective Fire Safety Design Options for a Large Office Building

The Use of Relative Risk-Based Assessment to Identify Cost-Effective Fire Safety Design Options for a Large Office Building

Volatile Organic Compounds in the Indoor Air of Warsaw Office Buildings

The aim of this study was to assess exposure to volatile organic compounds (VOCs) in office buildings. Five large office buildings in different areas of Warsaw were selected for the investigation. The identification and the determination of VOCs in the working environment were carried out twice during the year - in the spring-summer time and in the autumn-winter time in 50 offices. The most abundant compounds found were aliphatic and aromatic hydrocarbons. The carcinogenic compounds, benzene and formaldehyde were among the VOCs found in the offices. Because of the absence of health based indoor air quality standards for the office working environment in Poland and in the world, the exposure assessment for 50 workers employed in 5 office buildings was carried out with reference to ambient air quality standards and standards established for rooms in public utility buildings under Polish law. Notice was also taken of the recommended standard for total VOCs proposed by Seifert and Mølhave. The analysis of the results of the exposure assessment of VOCs in offices in the buildings investigated shows what these compounds occur in at levels which could contribute to the “sick building syndrome” (SBS), particularly in those buildings that were not air-conditioned.

Concentrations of cat and dust-mite allergens in dust samples from 92 large US office buildings from the BASE Study

The concentrations of cat (Fel d1) and dust-mite (Der f1 and Der p1) allergens were measured in 92 large office buildings in the US Environmental Protection Agency's Building Assessment Survey and Evaluation (BASE) Study (251 dust samples; one to four samples per building). Fel d1 was detected in almost all buildings and samples (91 buildings, 99%; 235 samples, 94%; range: <0.01-19 microg/g; median: 0.3 microg/g). Cat allergen exceeded 1 microg/g (a lower symptom threshold) in 56 samples (22%) from 45 buildings, but exceeded 8 microg/g (a sensitization threshold) in only two samples (1%) from two buildings. Der f1 or Der p1 was found in approximately half of all buildings and samples (63 and 70% of buildings; 45 and 51% of samples; range: <0.01-53 microg/g and <0.01-25 microg/g; median: <0.02 and 0.03 microg/g, respectively). Mite allergen exceeded 2 microg/g (a sensitization threshold) in seven samples (3%) from five buildings and exceeded 10 microg/g (a symptom threshold) in three samples (1%) from three buildings. Fel d1 concentration was significantly higher in samples collected in summer (June to September, 48 buildings), but cat allergen was not correlated with either mite allergen. Der f1, but not Der p1, concentration tended to be higher in samples collected in winter (December to April, 44 buildings), and the two mite allergens were significantly correlated only in winter. Cat and mite allergens were detected in 78% of representative US office buildings, but the concentrations seldom exceeded levels associated with sensitization or symptom provocation. The information on the concentrations of cat and dust-mite allergens in representative large US offices has expanded the baseline data available for interpretation of measurements from other building investigations. With suggested refinements, the BASE protocol for measurement of allergen concentrations in dust samples may serve as a guide to future studies of building characteristics, bioaerosol concentrations, and occupant perceptions of the indoor environment.

Concentrations of airborne culturable bacteria in 100 large US office buildings from the BASE study

This paper presents summary statistics of airborne culturable bacteria from the US Environmental Protection Agency Building Assessment Survey and Evaluation (BASE) study. Air samples were collected with single-stage, multiple-hole, agar impactors in 100 large office buildings in 1994-1998 to obtain normative data on indoor environmental quality. Bacterial concentrations were compared by incubation temperature, location, season, and climate zone. Forty-one percent of the samples were below the 2- or 5-min detection limits (18 or 7 CFU/m3, respectively) but less than 1% were overgrown. Mesophilic bacteria (30 degrees C) accounted for >95% of culturable bacteria, both indoors and outdoors. Average concentrations were higher outdoors, except for Gram-positive cocci, which were the only group that were significantly higher indoors (39 vs. 24 CFU/m3), and Gram-negative cocci, for which both concentrations were low and the difference were not significant. Outdoor concentrations of culturable bacteria were somewhat higher in winter (194 vs.165 CFU/m3), and the two dominant outdoor groups were unknown bacteria and Gram-positive rods. Conversely, indoor concentrations were significantly higher in summer (116 vs. 87 CFU/m3), consisting primarily of unknown bacteria and Gram-positive cocci. Bacterial concentrations were within the ranges reported in previous studies of non-problem buildings, and the extreme aggregated indoor concentrations (e.g. the 90th percentile, 175 CFU/m3) of these 100 representative buildings may serve as upper bounds to develop interpretation guidelines for office environments and similar non-manufacturing workplaces in various climate zones. The Building Assessment Survey and Evaluation (BASE) study was one of the most comprehensive investigations of indoor environmental quality in which a standardized protocol was used to measure bioaerosols in 100 typical US office buildings. The information on the indoor and outdoor concentrations of airborne bacteria in different climate zones during the heating and cooling seasons has expanded the baseline data available for interpretation of measurements from building investigations. With suggested refinements, the BASE protocol may serve as a guide for future studies of bioaerosol concentrations, building characteristics, and occupant perceptions of the indoor environment.

A practical method for assessing the performance of control loops subject to random load changes

A method is described for detecting load changes and characterizing subsequent responses in single-input-single-output (SISO) feedback control loops. The method is computationally simple and suitable for on-line implementation in a controller. Load changes are detected using a statistical change detection procedure that uses zero-crossings information to account for autocorrelation. Responses are characterized by a normalized index that can be related to a damping ratio in a second-order model. Results are presented from applying the method to data from a simulated control loop and two temperature control loops in a large office building.

Changing microbial concentrations are associated with ventilation performance in Taiwan's air-conditioned office buildings

Our study conducted serial environmental measurements in 12 large office buildings with two different ventilation designs to obtain airborne microbial concentrations in typical office buildings, and to examine the effects of occupant density, ventilation type and air exchange efficiency on indoor microbial concentrations. Duplicate samples of airborne fungi and bacteria, a total of 2477 measurements, were collected based on a scheme of conducting sampling three times a day for at least seven consecutive days at every study building. Air change rates (ACHs) were also estimated by tracer gas concentration decay method, and measured by continuous Multi-Gas monitor for each building. Most sampling sites were with total fungal and bacteria concentrations higher than 1000 CFU/m(3), an often-quoted guideline in earlier research. Significantly higher concentrations of fungi and bacteria, as well as higher indoor/outdoor (I/O) ratios across most groups of airborne microbes, were identified in buildings with fan coil unit (FCU) system than those with air-handling unit (AHU) system (Student's t test, P < 0.0001). Older buildings and higher air exchange rates were statistically associated with greater indoor bacteria levels in FCU ventilated buildings (R(2) = 0.452); a pattern not found in AHU buildings. Increasing ACH seemed to be the determinant factor for rising indoor fungal and Cladosporium concentrations in those FCU buildings (R(2) = 0.346; 0.518). Our data indicated that FCU ventilated buildings might have provided more outdoor matters into indoor environments through direct penetration of outdoor air. Results also demonstrated a quantitative association between rising numbers of occupants and increasing indoor levels of yeast in both FCU and AHU ventilated buildings. The regression model identified in this study may be considered a reference value for proposing an optimal ACH, while with adequate filtration of fresh air, as an effective strategy in lowering indoor microbial concentrations in air-conditioned buildings. As control of indoor microbial contamination has become an increasing concern around the world, feasibility and effectiveness of adopting ventilation approach has attracted a significant interest. This field investigation demonstrated, quantitatively, critical variables to be taken into consideration while applying such a measure, including the kinds of microbes to be removed and the types of ventilation system already in place.

Modeling occupancy in single person offices

This paper examines the statistical properties of occupancy in single person offices of a large office building in San Francisco. A probabilistic model to predict and simulate occupancy in single person offices is proposed. It is found that vacancy intervals are exponentially distributed and that the coefficient of the exponential distribution for a single office could be treated as a constant over the day. Occupancy intervals are more complex than vacancy intervals. The distribution of occupancy intervals is time varying. Variations among different offices are examined. The implications of the findings on thermal and air quality control are discussed.

Extract and Supply Air Flow Rates in a Large Office Building Before and After Balancing

One of the two air distribution systems serving the office rooms of a 25-year-old large office building was balanced in autumn 2002. The supply and extract air flow rates of 173 office rooms were measured before and after balancing. Before balancing, the air flow rates varied considerably from room to room and many of the office rooms were over pressurised. The average extract air flow rate in the whole of the building was 20.7 L/s.person and the standard deviation 11.0 L/s.person. The aim of the balancing process was to meet the design values dating from 1978. The original air distribution plan was very disparate, presumably taking into consideration both room size and number of occupants in the room. Balancing achieved the design air flow rates remarkably well but the person-specific air flow values still varied considerably between the office rooms. After balancing, the average extract air flow rate was 29.3 L/s.person and the standard deviation 13.6 L/s.person. The paper discusses whether design air flow values should be followed when the occupancy within the building has changed and whether energy saving aspects should be taken into account. Balancing is recommended after duct cleaning or major building renovations to accommodate for changes that have taken place in the air distribution system.