Edward Arens

University of California, Berkeley | UCB · Center for the Built Environment

Within Annex 80, there is a manifold need to use key performance indicators (KPI, i.e. performance met rics). This is relevant to all Subtasks. The “Task Group KPI” is established to coordinate and clarify the KPIs, used within Annex 80. The Task Group shall collect and coordinate KPIs, relevant to Resilient Cool ing. It shall develop and constantl...

Heating and cooling in buildings accounts for over 20% of total energy consumption in China. Therefore, it is essential to understand the thermal requirements of building occupants when establishing building energy codes that would save energy while maintaining occupants’ thermal comfort. This paper introduces the Chinese thermal comfort dataset, e...

The Predicted Mean Vote (PMV) model developed by Fanger predicts thermal sensation. It is used in the ISO-7730, while the ASHRAE-55 uses a modified version (PMVCE) to better account for cooling provided by air movement. We compared the PMV and PMVCE results against 64,825 thermal sensation votes collected in buildings. We found that for V > 0.1 m/s...

Global climate change is predicted to increase the number and intensity of heatwaves. Fans can be used instead of or in combination with compressor-based air conditioning (AC) to reduce heat strain on people, while reducing energy consumption, environmental impact, and electricity grid stress. In extremely hot and dry environments, fan use becomes...

The ability to measure occupants’ thermal state in real time will enable major advances in the control of air conditioning systems. This study proposes predicting occupant thermal state by a combination of infrared thermography, computer vision, and machine learning. The approach 1) uses cheek, nose and hand temperatures because they are least subj...

The world is facing a rapid increase of air conditioning of buildings. It is the motivation of Annex 80 to develop, assess and communicate solutions of resilient cooling and overheating protection. Resilient Cooling is used to denote low energy and low carbon cooling solutions that strengthen the ability of individuals and our community to withstan...

Ceiling-fan-integrated air-conditioning (CFIAC) is a concept in which terminal supply ducts and diffusers are replaced by vents/nozzles that jet supply air into the vicinity of ceiling fans to be mixed and distributed within the room. CFIAC distributes the supply air within the room and convectively cools the occupants. This could allow raised ther...

Personal Comfort Systems (PCS) promise to reduce the energy needed to condition indoor environments, while also enhancing their occupants’ thermal pleasure. To explore these potentials in heating conditions, we compared the effectiveness of PCS heating various portions of the occupant against the normal Air Conditioning (AC) practice of warming the...

The global effects of climate change will increase the frequency and intensity of extreme events such as heatwaves and power outages, which have consequences for buildings and their cooling systems. Buildings and their cooling systems should be designed and operated to be resilient under such events to protect occupants from potentially dangerous i...

Heatwaves are one of the most dangerous natural hazards causing more than 166,000 deaths from 1998–2017. Their frequency is increasing, and they are becoming more intense. Electric fans are an efficient, and sustainable solution to cool people. They are, for most applications, the cheapest cooling technology available. However, many national and in...

In a field study conducted in office settings in Sydney, Australia, background survey and right-here-right-now thermal comfort questionnaires were collected from a sample of office workers. Indoor environmental observations, including air temperature, mean radiant temperature, air velocity, and relative humidity, were also recorded and matched with...

Human metabolic rate is a fundamental and essential aspect of thermal comfort, and gender differences in metabolic rate may underlie gender differences in comfort. This study explores gender differences in physiological and subjective responses to a wide range of cold to hot temperatures. Forty healthy college students (20 females and 20 males) par...

The layout of ceiling fans in buildings is challenging because of the need to co-ordinate with other elements in the ceiling space, and because the resulting airflows within the occupied space interact with furniture. This study conducted detailed air speed measurements in four buildings with different room sizes, furniture configurations, ceiling...

Research into human thermal perception indoors has focused on “neutrality” under steady‐state conditions. Recent interest in thermal alliesthesia has highlighted the hedonic dimension of our thermal world that has been largely overlooked by science. Here, we show the activity of sensory neurons can predict thermal pleasure under dynamic exposures....

Solar radiation affects occupant comfort and building energy consumption in ways that have received relatively little attention in environmental design and energy simulation. Direct, diffuse, and reflected irradiation on the body have warming effects that can be equated to increases in the mean radiant temperature (MRT) of the occupant's surroundin...

Indoor carbon dioxide (CO2) is a critical parameter in the design and control of ventilation, and in monitoring fresh air levels in buildings. Building occupants are primary sources for indoors CO2, and the rate at which CO2 is generated depends on the occupants’ physical activities. In the past, CO2 generation rates have been indirectly calculated...

Digital and physical prototypes are commonly used across a broad range of industries for product development and user experience testing. Prototyping processes are also used in scientific research to generate ideas and test hypotheses. However, these creative activities receive less attention in research papers than the quantitative methods and fin...

A vertical thermally stratified environment provides opportunities for improved ventilation effectiveness and energy efficiency, but vertical temperature gradient can also cause local thermal discomfort. ASHRAE 55 and ISO 7730 prescribe a 3 °C/m limit between head and feet for seated persons. However, an increasing amount of evidence suggests that...

ASHRAE Standard 55 has been evolving in recent years to encourage more sustainable building designs and operational practices. A series of changes address issues for which past design practice has been deficient or overly constrained. Some of the changes were enabled by findings from field studies of comfort and energy-efficiency, and others by new...

The project goal was to identify and test the integration of smart ceiling fans and communicating thermostats. These highly efficient ceiling fans use as much power as an LED light bulb and have onboard temperature and occupancy sensors for automatic operationbased on space conditions. The Center for the Environment (CBE) at UC Berkeley led the res...

Ceiling-Fan-Integrated Air Conditioning (CFIAC) is a proposed system that can greatly increase buildings’ cooling efficiency. In it, terminal supply ducts and diffusers are replaced by vents/nozzles, jetting supply air toward ceiling fans that serve to mix and distribute it within the room. Because of the fans’ air movement, the system provides com...

The ability to inexpensively monitor indoor air speed and direction on a continuous basis would transform the control of environmental quality and energy use in buildings. Air motion transports energy, ventilation air, and pollutants around building interiors and their occupants, and measured feedback about it could be used in numerous ways to impr...

During exercise, comfort requirements are different because of the elevated metabolic heat production. It is essential to know the preferable thermal environment to give environmental design suggestions to sports facilities. Experimental studies on preferred temperature were conducted on 20 healthy human subjects walking on a treadmill at 4, 5, and...

'Personal comfort systems' and thermally active clothing are able to warm and cool individual building occupants by transferring heat directly to and from their body surfaces. Such systems would ideally target local body surfaces with high-temperature sensitivities. Such sensitivities have not been quantified in detail before. Here we report local...

Naturally ventilated buildings have been found to be comfortable over a wider range of indoor temperatures than in air-conditioned buildings, while using less energy. The mechanisms underlying this are not well understood. Through a longitudinal field study of a naturally ventilated office in Alameda, CA, we obtained insights into how occupants exe...

Thermal discomfort is a widespread problem in the built environment, due in part to the variability of individual occupants' thermal preferences. Personal comfort systems (PCS) address this individual variability, and also enable more energy-efficient thermal conditioning in buildings by reducing the need for tight indoor temperature control. This...

People often feel uncomfortably warm and sweaty in their workspace after commuting there by walking or cycling in summer. This is because body heat stored during the commute takes a substantial time to dissipate. People complaining about this uncomfortable transition may cause operators to lower the thermostat setpoint, causing long-term overcoolin...

We mapped thermal sensitivities of 318 skin spots over 15 body parts, in 48 college students. The results show that body parts had wide variance in thermal sensitivity. The foot, lower leg and upper chest are much less sensitive than average, while the cheek, neck back, and seat area are very sensitive to both cooling and warming stimuli. To examin...

Indoor air movement affects many functions of buildings, including ventilation and air quality, comfort and health of occupants, fire safety, and building energy use. Accurately measuring air movement has been difficult and expensive over extended periods of time, especially for velocities below 1 m/s. A new type of high frequency ultrasonic transc...

A large percentage of commercial buildings in North America use variable air volume (VAV) systems with reheat, and this system type is also common around the world. Summertime overcooling is widespread in such buildings [Mendell and Mirer 2009] and has received considerable media attention over the past few years. ASHRAE Research Project RP-1515, r...

We measured indoor air speeds generated by ceiling fans in 78 full-scale laboratory tests. The factors were the room size, fan diameter, type, speed, direction (up or down), blade height, and mount distance (i.e. blade to ceiling height). We demonstrated the influence of these factors, showing that the most significant are speed, diameter and direc...

Thermal-comfort modeling has traditionally incorporated radiant effects via the metrics mean radiant temperature (MRT) and radiant temperature asymmetry. These metrics have not until recently, considered the effect of incoming solar radiation directly heating the occupants, though it significantly affects their thermal comfort. In this paper, we de...

Metabolic rate was measured on 60 college students (30 women and 30 men) while reclining at rest (Re), sitting (quiet-SQ, typing-ST and filing-SF), standing (quiet-STQ, typing-STT and filing-STF), and walking on a treadmill at 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 km/h. Each activity was measured for 10 min (30 min for Re) using a wearable high-precision...

This paper explores the ability of a low-energy wearable thermal device to improve whole body thermal comfort. The wearable device is a wristwatch-like thermal device with a 25mm * 25mm contact heating and cooling surface. Twenty-three subjects were recruited for testing in a climate chamber, with each participating in three 2-hour tests. The three...

Over-cooling happens commonly in air-conditioned buildings that costs energy and results in discomfort complaints. There are many reasons causing overcooling, and HVAC engineers and researchers have proposed several approaches to prevent it from happening. In this paper, we describe a field study to show how the overcooling and energy use were sign...

Personal comfort systems (PCS) aim to efficiently fulfill building occupants’ personal thermal comfort demands, but to date not many have been manufactured and evaluated. Based on the observation that foot/hand warming are most effective in cool conditions, and head cooling is most effective in warm environments, we built and tested a suite of PCS...

ASHRAE Standard 55 has adopted new provisions to assure thermal comfort for occupants exposed to solar radiation indoors. They are included in the recently-released 2017 version of the Standard [1]. Normative Appendix C provides the analytical method, and both prescriptive and performance-basedapproaches to compliance are incorporated within Sectio...

The ability of hands and feet to convey skin thermal sensations is an important contributor to our experience of the surrounding world. Surprisingly, the detailed topographical distribution of warm and cold thermosensitivity across hands and feet has not been mapped, although sensitivity maps exist for touch and pain. Using a recently developed qua...

Recognizing the value of open-source research databases in advancing the art and science of HVAC, in 2014 the ASHRAE Global Thermal Comfort Database II project was launched under the leadership of University of California at Berkeley's Center for the Built Environment and The University of Sydney's Indoor Environmental Quality (IEQ) Laboratory. The...

Comfort cooling by ceiling fans is cost-effective and energy-efficient compared to compressor-based cooling and fans are commonly used in tropical and subtropical countries. There are however limited data and design tools supporting the design of fan systems, especially for situations where there are multiple fans. In this paper, we investigate air...

Ceiling fans provide cooling to indoor occupants and improve their thermal comfort in warm environments at very low energy consumption. Understanding indoor air distribution associated with ceiling fans helps designs when ceiling fans are used. In this study, we systematically investigate the air movement distribution in an unoccupied office room i...

Subjects were tested under a set of air speed setpoints as might be used in automated control of ceiling fans. At lower temperatures the fan speeds were slightly higher than needed for thermal neutrality, to account for occasional non-sedentary metabolic rates associated with getting up, standing, or moving about. At higher temperatures the air spe...

Smart buildings and autonomous vehicles are expected to see rapid growth and adoption in the coming decades. Americans spend over 90% of their lives in buildings or automobiles, meaning that 90% of their lives could be spent interfacing with intelligent environments. EMBR Labs has developed EMBR WaveTM, a wearable thermoelectric system, for introdu...

Skin temperature detection thresholds have been used to measure human cold and warm sensitivity across the temperature continuum. They exhibit a sensory zone within which neither warm nor cold sensations prevail. This zone has been widely assumed to coincide with steady-state local skin temperatures between 32-34ᵒC, but its underlying neurophysiolo...

Inefficient controlling strategies in heating and cooling systems have given rise to a large amount of energy waste and to widespread complaints about the thermal environment in buildings. An intelligent control method based on a support vector machine (SVM) classifier is proposed in this paper. Skin temperatures are the only inputs to the model an...

The classic or deterministic understanding of thermal comfort contends that it is driven exclusively by the physics of the body’s heat exchange with its immediate thermal environment. But in recent decades there has been widespread recognition that a person’s thermal history and adaptation level, including behavioral, physiological and psychologica...

This paper quantifies the greenhouse gas (GHG) emissions co-benefits associated with water, waste and transportation usage in certified green commercial office buildings in California. The study compares the measured values of water, waste and transportation usage self-reported by office buildings certified under the Leadership in Energy and Enviro...

Indoor sports facilities are energy-intensive in warm climates, cooling the interior to low temperatures that are comfortable for exercise. There is little existing guidance on how to do this efficiently. This study investigated thermal comfort with air movement at elevated activity levels, and the energy saving potentials with elevated setpoint te...

As the climate changes, global use of air-conditioning will proliferate as solutions are sought for maintaining thermal comfort in buildings. This rises alongside increased purchasing power as economies grow, harbouring the potential to unleash an unprecedented growth in energy demand. Encouraging higher levels of air movement at warmer temperature...

As the climate changes, global use of airconditioning will proliferate as solutions are sought for maintaining thermal comfort in buildings. This rises alongside increased purchasing power as economies grow, harbouring the potential to unleash an unprecedented growth in energy demand. Encouraging higher levels of air movement at warmer temperatures...

The assignments of basal metabolic rates (BMR), basal cardiac output (BCO), and basal blood perfusion rates (BBPR) were compared in nine multi-compartment, whole-body thermoregulation models. The data are presented at three levels of detail: total body, specific body regions, and regional body tissue layers. Differences in the assignment of these q...

Personal Comfort Systems (PCS) are capable of maintaining occupant comfort in buildings despite large deviations from recommended "comfortable" temperatures. We present a novel digital controller for a well-studied (previously analog) PCS, allowing it to report real-time telemetry and respond to programmatic actuation requests. This enables the est...

The effects of air movement from ceiling fans on subjective thermal comfort and perceived air quality (PAQ) were examined for warm-humid environments. In a climate chamber controlled at three temperatures (26 °C, 28 °C and 30 °C) and two relative humidity (RH 60% and 80%), sixteen subjects (8 males and 8 females) dressed in summer clothing (0.5 clo...