Recent cedr_cbe_ieq items

Effects of window view attributes on occupants' view satisfaction: Findings from human subject experiments evaluating actual window views

Mon, 16 Mar 2026 00:00:00 +0000

The quality of window views influences building occupants’ well-being, yet little is known about what constitutes high view quality. We investigated eight factors: number of layers visible, presence of nature, object-to-glazing distance, observer proxy, window-to-wall ratio, horizontal and vertical view angles, and blind position. We conducted a human subject experiment in which 69 participants each evaluated 15 window views and rated their satisfaction. Views with equal to or more than 35% greenery or sky and unobstructed clear glazing were strongly associated with higher satisfaction. Blind position emerged as a key moderator, shaping how other factors influenced view quality. Under clear glazing, increasing the proportion of nature elements and extending the distance of visible objects from the glazing significantly improved satisfaction. However, when blinds were lowered, these changes offered no benefit. We also found that compliance with the LEED Quality Views guideline...

Acoustical Case Study: AIASF Headquarters Lecture Hall

Thu, 19 Feb 2026 00:00:00 +0000

This case study summarizes our efforts to optimize speech intelligibility in a medium-sized lecture hall. In addition to describing the acoustical design, we also interpret the results of our acoustical measurements. Speech intelligibility in the hall was assessed both subjectively and objectively using natural as well as amplified speech. We determined that natural speech could be clearly understood at the rear of the hall (about 50 feet from the speaker) without electronic amplification. Thus, one of our design goals was achieved. Adding sound-absorbing materials on the ceiling and selected walls reduced the reverberation time to 0.4 seconds, thereby meeting a project design goal. Due to the distributed sound absorption and low background noise level, exceptional speech intelligibility has been achieved in the room.

Effects of intermittent cooling on human thermophysiological and perceptual responses in a non-steady-state thermal environment

Thu, 13 Nov 2025 00:00:00 +0000

Intermittent cooling, characterized by the on-off cycling of air-conditioning systems, generates a non-steady-state indoor thermal environment. While widely adopted for energy conservation, its impact on human thermophysiological and perceptual dynamics remains insufficiently understood. To investigate this, we conducted chamber experiments in a simulated residential/office space using three cooling set-points (thermostat target temperature: 28 °C, 26 °C, and 20 °C). Each trial involved 70 minutes of active cooling followed by 50 minutes of shutdown. We continuously monitored indoor air temperature, skin temperature, blood pressure, heart rate, and subjective thermal responses from 12 participants throughout each cycle. Results show that cold exposure intensity significantly shaped the temporal dynamics of human thermal response. Under strong cooling (20 °C), skin temperature declined continuously without stabilization over 70 minutes, thermal sensation and acceptability remained...

Energy efficiency and comfort: analysis of thermal responses and behaviors of residents with high and low air conditioning dependency

Thu, 13 Nov 2025 00:00:00 +0000

The widespread use of split air conditioners (SAC) in Chinese residences has a significant impact on energy consumption. This study examines SAC usage behaviors in Jiaozuo, Henan Province, through environmental measurements and resident surveys. Using the entropy weight method, SAC users were classified into high air conditioning dependency (HACD) and low air conditioning dependency (LACD) groups. While both groups experienced similar outdoor heat conditions (P > 0.05), HACD residents maintained significantly lower indoor temperatures (P = 0.002). However, there were no significant differences in heat sensation, thermal comfort, or acceptability between the two groups (P > 0.05). LACD residents demonstrated greater adaptability to higher temperatures by adopting diverse low-carbon strategies, such as natural ventilation, fan usage, and clothing adjustments. As a result, they exhibited lower energy consumption compared to HACD residents, highlighting the potential for energy...

Ten questions concerning the application of adaptive thermal comfort in mixed-mode buildings

Mon, 4 Aug 2025 00:00:00 +0000

The recently completed IEA Annex 69 (Strategy and Practice of Adaptive Thermal Comfort in Low Energy Buildings) identified mixed-mode (MM) building design and operation as key strategies for the buildings sector in its transition towards a low-carbon mode. Mixed-mode is short-hand for naturally ventilated designs with supplemental air-conditioning that can be called upon whenever and wherever external climatic loads and/or internal loads dictate. Success of the MM strategy requires shifting the sector’s concept of thermal comfort away from a static comfort zone towards an adaptive approach in which the indoor comfort zone drifts in the same direction as external weather and seasonal trends. The potential for mixed-mode design arises from its applicability in both new construction and existing building stock. The objective of this paper is to elevate awareness of the mixed-mode design concept within the building sector and related research communities. Furthermore, it...

Window View Satisfaction Assessment Method: A Comparison of Physical Space, Virtual Reality, and Digital Image

Thu, 17 Jul 2025 00:00:00 +0000

Window view quality influences occupants' health, well-being, work performance, and real estate value. However, there is a lack of validation for view satisfaction assessment methods and no broad consensus on experiment protocols. Therefore, it is difficult to compare and combine experimental data from different research, hindering research advancement in the view quality assessment field. In this study, we compare widely used window view display techniques with actual window views in physical spaces to investigate the suitability of these techniques for evaluating view subcategories: content, access, clarity, privacy, and overall view satisfaction. Participants evaluated their satisfaction with these five subcategories using identical window views presented through three media: physical space (PS), virtual reality (VR), and digital images (IM). Additionally, we compared different rendering techniques of window views, including HDR photos, collages, images of 3D models rendered...

Field demonstration of a tracer method to track simulated exhaled air trajectories and mixing in three connected rooms with upper-room GUV

Tue, 29 Apr 2025 00:00:00 +0000

We conducted tracer gas experiments in three connected nursery rooms to track simulated exhaled air trajectories and mixing. We emulated exhaled air with a pulse release of ethanol and measured its concentration with 2s time resolution with spatially distributed metal oxide sensors in both the upper and occupied levels of the room. We found that the overhead cooling supply air enhanced vertical air mixing within the rooms. When a room had higher supply airflow than the others, the tracer gas mixed quickly in that room because the supply air dominated the room mixing, thereby isolating it from air mixing with the other rooms. When the forced air system was not operating, the tracer gas resided longer in the upper room before descending. The tracer method also depicts air trajectories from different release locations by detecting the release point and affecting nearby sensors. These experiments support the potential of this method to be used in the field for understanding air trajectories...

Causal effects estimation: Using natural experiments in observational field studies in building science

Fri, 4 Apr 2025 00:00:00 +0000

Correlational analysis, such as linear regression, does not imply causation. This paper introduces and applies a causal inference framework and a specific method, regression discontinuity, to thermal comfort field studies. The method utilizes policy thresholds in China, where the winter district heating policy is based on geographical location relative to the Huai River. The approximate latitude of the Huai River can be considered as a natural, geographical threshold, where cities near the threshold are quite similar, except for the availability of district heating in cities north of the threshold, creating a situation similar to a natural experiment. Using the regression discontinuity method, we quantify the causal effects of the experiment treatment (district heating) on the physical indoor environments and subjective responses of building occupants. We found that mean indoor operative temperatures were 4.3 °C higher, and mean thermal sensation votes were 0.6 warmer due to the...

The effects of personal comfort systems on sleep: A systematic review

Tue, 1 Apr 2025 00:00:00 +0000

Creating a comfortable thermal environment is the necessary measure to safeguard human sleep quality but it requires a substantial amount of energy. Personal comfort systems have the potential to improve sleep while significantly reducing energy consumption compared to typical air conditioning systems. Despite some studies reporting favorable outcomes when using personalized approaches to cooling or heating in bedrooms, a comprehensive summary of the impact of personal comfort systems on sleep is lacking. This systematic review of 25 sleep studies estimates the effect of personal comfort systems on sleep quality, sleep stages and sleeping thermal comfort. Configuration of personal comfort systems and sample characteristics are summarized and compared. Calculated effect sizes show that using personal comfort systems are generally effective in improving sleep quality and sleeping thermal comfort. However, there are potential negative effects of personal heating on slow wave sleep...

Implementation of desk fans in open office: Lessons learned and guidelines from a field study

Tue, 15 Oct 2024 00:00:00 +0000

Desk fans allow individual thermal adjustment in shared spaces which increases occupants’ thermal satisfaction. When associated with the increase of room conditioning system setpoint temperature, they can also reduce energy use. In comparison to other Personal Comfort Systems (PCS), low-power desk fans can be very efficient for cooling. Nevertheless, previous studies identify some barriers to their implementation and show no clear guidelines on how to overcome them. Therefore, this study presents the results of a field implementation of desk fans in an open office in Brazil. The intervention consisted of providing one desk fan for each occupant and progressively increasing the setpoint temperature. Indoor thermal conditions were recorded simultaneously with occupants’ thermal perception using sensors and surveys. Results show fans increased thermal satisfaction by 20 %. And, when fans were available, the preferred indoor air temperature increased by 1 °C. However, many constraints...

Experimental evaluation of thermal comfort, SBS symptoms and physiological responses in a radiant ceiling cooling environment under temperature step-changes

Thu, 13 Jun 2024 00:00:00 +0000

People usually experience transient thermal environments when entering or leaving a conditioned indoor environment. This has been previously explored but there is little knowledge on the impact of temperature step-changes on thermal comfort in a radiantly cooled environment. We aim to investigate human comfort and underlying physiological mechanism in such conditions. We assessed thermal comfort, sick building syndromes (SBS) symptoms, and physiological responses. Twenty healthy participants were exposed to three temperature step-change conditions with three outdoor air temperatures (29 ℃, 33 ℃ and 36 ℃) and one indoor air temperature of 26 ℃. Subjective evaluation was collected through a questionnaire. Blood oxygen saturation (SpO2), skin temperature, and electrocardiograph (ECG) were measured. As expected, the overall thermal sensation, comfort, acceptability, preference, and subjective air freshness changed significantly before and after temperature step-changes. Perceived...

Causal Thinking: Uncovering Hidden Assumptions and Interpretations ofStatistical Analysis in Building Science

Thu, 13 Jun 2024 00:00:00 +0000

Causal thinking emphasizes the understanding of asymmetric causal relationships between variables, requiring us to specify which variable is the cause (independent variable) and which is the effect (dependent variable). Reversing the causal relationship direction can lead to profoundly different assumptions and interpretations. We demonstrate this by comparing two linear regression approaches used in thermal comfort research: Approach (a), which regresses thermal sensation votes (y-axis) on indoor temperature (x-axis); Approach (b), which does the reverse, regressing indoor temperature (y-axis) on thermal sensation votes (x-axis). From a correlational perspective, they may appear interchangeable, but causal thinking reveals substantial and practical differences between them. Approach (a) represents occupants’ thermal sensations as responses to indoor temperature. In contrast, Approach (b), rooted in adaptive comfort theory, suggests that thermal sensations can trigger behavioral...

Numerical simulation of cooling performance of radiant ceiling system interacting with a ceiling fan

Tue, 12 Mar 2024 00:00:00 +0000

We evaluate the heat transfer from radiant ceilings that have suspended acoustical panels present for noise reduction. An upward-directed ceiling fan is added to offset the reduction of heat exchange due to the acoustical panels. We systematically simulate the indoor thermal environment and the changes to heat transfer coefficients caused by the interaction between radiant ceiling panels, acoustical panels, and ceiling fan under four influencing factors: (1) coverage ratio of acoustical panels, (2) fan rotational speed, (3) radiation panel temperature and (4) room height. The simulation method is validated with experimental data. Numerical results show that the augmented air speed increases convective and total heat transfer for radiant panel. Simulated temperature non-uniformity, air and operative temperature in the occupied part of the room is reduced with increased fan speed, and with decreased acoustical panel coverage ratio. The PMV increased with increased acoustical panel...

Field Study of Thermal Infrared Sensing for Office Temperature Control

Tue, 23 Jan 2024 00:00:00 +0000

The purpose of this paper is to evaluate the performance of a novel office temperature control system. To make occupants more comfortable with less energy, we have been developing a new system that uses an inexpensive infrared camera to evaluate occupants’ thermal sensation and optimize room temperature. The system (1) detects the positions of a person’s face, nose, and hands in a thermal image taken by an infrared camera and measures temperatures in those areas; (2) predicts thermal sensation using measured skin temperatures; and (3) adjusts an HVAC set-point temperature based on the predicted sensation to optimize occupant thermal comfort. We compared the comfort and energy performance of the new system to conventional control using a fixed setpoint of 72.0 °F (22.2 °C) in a small conference room. The results indicate that the conventional control often overcooled the occupants, whereas our system reduced cooling energy consumption and made the occupants more thermally neutral...

Acoustical Intervention Study for a Small University Conference Room

Mon, 24 Jul 2023 00:00:00 +0000

Small conference rooms are often used for either face-to-face communication or for virtual meetings involving an electroacoustical link between a talker and a listener. The intelligibility of speech in such environments depends on a number of factors, one of which is the nature of the reverberant sound within the space. Treating such a room with sound-absorbing materials helps reduce the so-called “cognitive load” for people who are spaced some distance away from a talker or who are listening to monaural speech reproduced by a loudspeaker. This study describes an acoustical retrofit of a small conference room to attain the reverberation time criterion found in LEED version 4.1 ID+C. Several mathematical models were used to predict the reverberation time before and after adding soundabsorbing treatment. In addition, measurements were conducted to quantify the before and after room reverberation characteristics. We found that speech was always intelligible both before and after...

The Effects of Ventilation, Humidity, and Temperature on Bacterial Growth and Bacterial Genera Distribution

Thu, 2 Mar 2023 00:00:00 +0000

The Effects of Ventilation, Humidity, and Temperature on Bacterial Growth and Bacterial Genera Distribution

Ceiling-fan-integrated air-conditioning: thermal comfort evaluations

Thu, 2 Mar 2023 00:00:00 +0000

Ceiling-fan-integrated air-conditioning: thermal comfort evaluations

Smart detection of indoor occupant thermal state via infrared thermography, computer vision, and machine learning

Thu, 2 Mar 2023 00:00:00 +0000

Smart detection of indoor occupant thermal state via infrared thermography, computer vision, and machine learning

Enabling Portable and Reproducible Long-term Thermal Comfort Evaluation with Brick Schema and Mortar Testbed

Wed, 23 Mar 2022 00:00:00 +0000

Thermal comfort in buildings is typically assessed through occupant surveys, especially for short-term thermal comfort. For long-term thermal comfort, thermal comfort standards and recent research suggest continuous physical monitoring of temperature is sufficient. However, a lack of formal rules for data representation in building automation systems and the high costs of analytical application development for buildings impede predicting long-term thermal comfort at scale. This paper demonstrates portable and reproducible application development techniques for evaluating long-term thermal comfort with the Brick metadata schema and Mortar data testbed. We take advantage of the relatively large Mortar dataset containing over 25 buildings to improve the generalizability of long-term thermal comfort evaluation. Previous research often performs analysis on limited datasets.The design of Mortar enables running the same software applications across many heterogeneous buildings, simplifying...

Visual Task Difficulty and Temporal Influences in Glare Response

Tue, 15 Mar 2022 00:00:00 +0000

The literature suggests that glare sensation may be influenced by visual task difficulty. Previous research by the authors provided reasons to infer that the perceived level of visual discomfort may vary with time of day and be affected by temporal and personal factors. The study presented here explores the postulated relationships between visual task difficulty, temporal variables, and glare response as the day progresses. Under controlled laboratory conditions, twenty subjects were exposed to a constant artificial source luminance at four times of day and gave glare sensation votes while completing twelve visual tasks of various difficulties. Self-assessments of temporal variables (fatigue, food intake, caffeine ingestion, mood, previous daylight exposure and sky condition) were provided by test subjects together with their glare judgements. Statistical analysis of responses confirmed that the time interval between test sessions showed a direct relationship to the increased...

Impacts of life satisfaction, job satisfaction and the Big Five personality traits on satisfaction with the indoor environment

Mon, 7 Feb 2022 00:00:00 +0000

Providing indoor environmental quality (IEQ) that satisfies building occupants is an essential component for sustainable and healthy buildings. Existing studies mainly analyse the importance of environmental factors on occupant satisfaction but often overlook the influence of personal factors. Here, we aim to explore the impact of personal factors like life satisfaction, job satisfaction, the Big Five personality traits, sex, and age on occupant IEQ satisfaction. We conducted a cross-sectional assessment in nine air-conditioned commercial buildings in Singapore and surveyed 1162 individuals on their satisfaction with 18 IEQ parameters. Using proportional odds ordinal logistic regression, we found that occupants with higher job and life satisfactions were, respectively, 1.3 – 2.3 and 1.3 – 2 times more likely satisfied with the 18 IEQ parameters. The odds ratios (OR) for overall environment satisfaction and job and life satisfaction were 2.1 (95% CI: 1.8 – 2.6) and 1.9 (95% CI:...

Creating alliesthesia in cool environments using personal comfort systems

Wed, 12 Jan 2022 00:00:00 +0000

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 room volume. Twenty subjects experienced three modes of heating (AC only, AC together with PCS, and PCS only) at three initial room air temperatures (14, 16, and 18°C) and were given some control options throughout the testing. Skin temperatures, thermal pleasantness, and thermal sensation votes were recorded during the exposures. The PCS heating was more effective than AC control at alleviating occupant discomfort. With PCS present, the three initial room temperatures produced equivalent positive perceptions of thermal pleasantness and sensation. Providing occupants with AC control did not influence this result. AC alone did not produce...

An Examination of Range Effects When Evaluating Discomfort Due to Glare in Singaporean Buildings

Mon, 10 Jan 2022 00:00:00 +0000

This article discusses ratings of visual discomfort from glare across different buildings located in Singapore. These data were used to determine if range effects influence the vertical illuminance values for the same ratings of visual discomfort when the category rating procedure is used. The effect occurs when maxima and minima vertical illuminance (i.e. the range) vary across buildings. Our analyses showed that with a higher vertical illuminance range in a building, the mean vertical illuminance value for the same criterion of visual discomfort also increased. The results suggest that the effect caused by different ranges of measured vertical illuminance present across the buildings biased the ratings of visual discomfort. Although these effects may be unavoidable in some buildings that have vastly different levels of light, the data suggest that the overall range of vertical illuminance must be carefully evaluated when predicting visual discomfort. Matching these conditions...

Overcooling of Offices Reveals Gender Inequity in Thermal Comfort

Wed, 15 Dec 2021 00:00:00 +0000

Growth in energy use for indoor cooling tripled between 1990 and 2016 to outpace any other end use in buildings. Part of this energy demand is wasted on excessive cooling of offices, a practice known as overcooling. Overcooling has been attributed to poorly designed or managed air-conditioning systems with thermostats that are often set below recommended comfort temperatures. Prior research has reported lower thermal comfort for women in office buildings, but there is insufficient evidence to explain the reasons for this disparity. We use two large and independent datasets from US buildings to show that office temperatures are less comfortable for women largely due to overcooling. Survey responses show that uncomfortable temperatures are more likely to be cold than hot regardless of season. Crowdsourced data suggests that overcooling is a common problem in warm weather in offices across the US. The associated impacts of this pervasive overcooling on well-being and performance...

A sex/age anomaly in thermal comfort observed in an office worker field study: A menopausal effect?

Wed, 15 Dec 2021 00:00:00 +0000

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 each questionnaire according to time and location. During exploratory data analyses we observed that female subjects aged over 40 and 50 or younger registered significantly warmer sensations than other subjects, male and female, from other age ranges. To further explore this phenomenon, the sample of building occupants were classified into two groups – women of perimenopausal age (over 40 and 50 or younger) while the remaining respondents served as a reference group for comparison. Women in the perimenopausal age range demonstrated an increased perception of warmth (p<0.01) and expressed thermal dissatisfaction more frequently (p<0.01)...

Sunlight and Indoor Thermal Comfort

Wed, 22 Sep 2021 00:00:00 +0000

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 Section 5.3 of the Standard.

A data-driven analysis of occupant workspace dissatisfaction

Mon, 23 Aug 2021 00:00:00 +0000

Studies often aim to determine which indoor environmental quality parameters best predict the overall workspace assessment. However, this method overlooks important differences distinguishing satisfied and dissatisfied occupant groups. We used a new analytical approach on 36671 post-occupancy evaluation responses to overcome this problem and better understand workspace satisfaction in office buildings. Principal components analysis reduced satisfaction votes with 15 different IEQ items into two principal components related to: 1) privacy and amount of space, and 2) cleanliness and maintenance. We grouped the data by occupants that were either satisfied or dissatisfied with their workspace. Principal component 1 explained half of the variability in the dataset and reliably distinguished occupants satisfied with their workspace from those that were dissatisfied. We used support vector machine to classify the satisfied and dissatisfied groups based on principal components 1 and 2....

Respiratory Performance of Humans Exposed to Moderate Levels of Carbon Dioxide

Wed, 23 Jun 2021 00:00:00 +0000

In a business as usual scenario, atmospheric carbon dioxide concentration (CO₂) could reach 950 parts per million (ppm) by 2100. Indoor CO₂ concentrations will rise consequently, given its dependence on atmospheric CO₂ levels. If buildings are ventilated following current standards in 2100, indoor CO₂ concentration could be over 1300 ppm, depending on specific ventilation codes. Such exposure to CO₂ could have physiological and psychological effects on building occupants. We conducted a randomized, within-subject study, examining the physiological effects on the respiratory functions of 15 persons. We examined three exposures, each 150 min long, with CO₂ of: 900 ppm (reference), 1450 ppm (decreased ventilation), and 1450 ppm (reference condition with added pure CO₂). We measured respiratory parameters with capnometry and forced vital capacity (FVC) tests. End-tidal CO₂...

Detailed measured air speed distribution in four commercial buildings with ceiling fans

Wed, 2 Jun 2021 00:00:00 +0000

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 fan types, and ceiling-fan-to-floor-area ratios. We measured air speeds across the occupied spaces at four heights while varying ceiling fan operation modes such as fan rotational speed, operating direction, and the number of operating fans. In total, we collected 207,080 air speed samples at 343 sites under 20 test conditions. This paper presents the magnitude and distribution of air speeds, cooling effects, and their influencing factors. The Airspeed Coverage Index (ACI= (Fan air speed (SF)× Fan diameter (D))/√(Average area served per ceiling fan (A))) describes the combined effects of multiple influencing factors on the magnitude...

Predicting thermal pleasure experienced in dynamic environments from simulated cutaneous thermoreceptor activity

Wed, 2 Jun 2021 00:00:00 +0000

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. A numerical model of cutaneous thermoreceptors was applied to skin temperature measurements from 12 human subjects. A random forest model trained on simulated thermoreceptor impulses could classify pleasure responses (F1-score of 67%) with low false positives/negatives (4%). Accuracy increased (83%) when excluding the few extreme (dis)pleasure responses. Validation on an independent dataset confirmed model reliability. This is the first empirical demonstration of the relationship between thermoreceptors and pleasure arising from thermal stimuli. Insights into the neurophysiology of thermal perception can enhance the experience of built...

Field Evaluation of Thermal and Acoustical Comfort in Eight North-American Buildings Using Embedded Radiant Systems

Wed, 3 Feb 2021 00:00:00 +0000

We performed a post-occupancy assessment based on 500 occupant surveys in eight buildings using embedded radiant heating and cooling systems. This study follows-up on a quantitative assessment of 60 office buildings that found radiant and all-air buildings have comparable temperature and acoustic satisfaction with a tendency for increased temperature satisfaction in radiant buildings. Our objective was to investigate reasons of comfort and discomfort in the radiant buildings, and to relate these to building characteristics and operations strategies. The primary sources of thermal discomfort are lack of control over the thermal environment (both temperature and air movement) and slow system response, both of which were seen to be alleviated with fast-response adaptive opportunities such as operable windows and personal fans. There was no optimal radiant design or operation that maximized thermal comfort, and building operators were pleased with reduced repair and maintenance associated...

Prototyping Solutions to Improve Comfort and Enable HVAC Energy Savings

Wed, 20 Jan 2021 00:00:00 +0000

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 findings. This paper describes a resourceful and iterative process of building, refining and testing a variety of ‘personal comfort devices’ that were used in a series of research studies in labs and in occupied non-residential buildings. The studies demonstrated that when building users have the ability to individualize their thermal environments, they can accept wider temperature ranges, potentially leading to reductions in HVAC energy consumption while also improving comfort. The devices tested include office chairs with battery-powered heating and cooling, IoT-connected desk fans and low-energy heating devices. This paper describes...

Modeling solar radiation on a human body indoors by a novel mathematical model

Mon, 4 Jan 2021 00:00:00 +0000

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 surroundings. A simplified occupant-centered model (SolarCal Model, i.e., SC Model) has recently been adopted in ASHRAE Standard 55, followed by a comprehensive simulation procedure combining detailed room- and manikin geometries using the Daylight Coefficient Model (DC Model). This paper presents an intermediate-level mathematical model (the HNU Solar Model) capable of rapid annual calculations of the MRT increases. Both the room and occupant geometries are simplified but consistent with those of the SC Model. Novel strategies of the calculation include a sky-annulus fraction, virtual body shadow, and equivalent window. Modeled results are compared...

Transient human thermophysiological and comfort responses indoors after simulated summer commutes

Mon, 4 Jan 2021 00:00:00 +0000

The current study investigates the transient human physiological and comfort responses during sedentary activity following a period of elevated activity in a hot condition. Such metabolic and thermal down-steps are common in buildings as occupants arrive after commuting in summer. It creates a serious problem for thermostatic control, since arriving occupants find their transition uncomfortably warm at temperatures that resident occupants find comfortable. Fifty-nine participants (29 men, 30 women) dressed in 0.6 clo were tested while sedentary for 60 min in 26 °C, after having been exposed to 30 °C for 15min, during which they performed activities metabolically simulating commuting: sitting (SE- 1.2 met), or doing three levels of stair-step exercises: low (LEx- 2.2 met), medium (MEx - 3.0 met), and high (HEx - 4.4 met). Subjective comfort and physiological responses (metabolic rate, skin temperature, skin blood flow rate, heart rate, core temperature, and skin wettedness) were...

Skin Temperature Sampling Period for Longitudinal Thermal Comfort Studies

Wed, 9 Dec 2020 00:00:00 +0000

There is limited scientific evidence on what is the optimal sampling period to measure skin temperature in longitudinal thermal comfort studies, and how this sampling period selection affects the results. iButtons® are among the most widely used wireless sensors in field and lab studies to measure skin temperature, since they are accurate, reliable, and cause minimal discomfort. However, their use is significantly limited by their memory capacity. We aimed to determine what is the optimal sampling period of skin temperature in studies which use iButtons®. We measured wrist skin temperature of 14 participants at 60 s intervals for a period of 1 month and wrist temperature of 5 participants at 20 s intervals for a week. Results showed that the selection of a 300 s sampling period would provide reasonably accurate results while limiting the number of times data needs to be downloaded.

Occupant satisfaction with the indoor environment in seven commercial buildings in Singapore

Thu, 12 Nov 2020 00:00:00 +0000

Understanding occupants’ satisfaction with their environment is an important step to improve indoor environmental quality (IEQ). These satisfaction data are limited to Singaporean commercial buildings. We surveyed (N = 666) occupant satisfaction with 18 IEQ parameters in seven Green Mark certified air-conditioned commercial buildings in Singapore. About 78 % of the participants expressed satisfaction with their overall workspace environment. Occupants were most satisfied with flexibility of dress code (86 % satisfaction), electrical lighting (84 %) and cleanliness (82 %), and most dissatisfied with sound privacy (42 % dissatisfaction), personal control (32 %) and temperature (30 %). We found that satisfaction with cleanliness has the highest impact to overall workspace environment satisfaction. Our results suggest achieving high occupant satisfaction for some IEQ factors is harder than others, which suggests the premise of singular satisfaction rating (e.g., 80 %) that applies...

Experimental evaluation of the effect of body mass on thermal comfort perception

Tue, 6 Oct 2020 00:00:00 +0000

Globally 39% of adults are overweight, 13% are obese, and 9% are underweight. Current thermal comfort standards, catering to the normal weight occupant, may hence be ignoring nearly 60% of the population. This could have significant comfort, productivity and energy implications. We performed a climate chamber study of the thermal response of 76 subjects in all the body mass index (BMI) categories, from 17 and 37 kg/m2. Every participant underwent the same four sessions at average operative temperatures of 19.9, 22.4, 25.3, and 28.2 °C. We obtained subjective feedback from participants on their thermal sensation and preference, humidity sensation and preference, thermal comfort rating, and air quality perception. We also measured skin temperature, blood pressure, pulse rate, blood glucose level, weight, height, waist and hip circumferences and body composition. Overall, we did not find significant impact of BMI on the thermal sensation. However, the overweight and obese participants...

Size-resolved dynamics of indoor and outdoor fluorescent biological aerosol particles in a bedroom: A one-month case study in Singapore

Mon, 28 Sep 2020 00:00:00 +0000

This study evaluated the interrelations between indoor and outdoor bioaerosols in a bedroom under a living condition. Two wideband integrated bioaerosol sensors were utilized to measure indoor and outdoor particulate matter (PM) and fluorescent biological airborne particles (FBAPs), which were within a size range of 0.5-20 μm. Throughout this one-month case study, the median proportion of FBAPs in PM by number was 19% (5%; the interquartile range, hereafter) and 17% (3%) for indoors and outdoors, respectively, and those by mass were 78% (12%) and 55% (9%). According to the size-resolved data, FBAPs dominated above 2 and 3.5 μm indoors and outdoors, respectively. Comparing indoor upon outdoor ratios among occupancy and window conditions, the indoor FBAPs larger than 3.16 μm was dominated by indoor sources, while non-FBAPs were mainly from outdoors. The occupant dominated the indoor source of both FBAPs and non-FBAPs. Under awake and asleep, count- and mass-based mean emission rates...

Air-conditioning use behaviors when elevated air movement is available

Thu, 13 Aug 2020 00:00:00 +0000

Many experimental studies demonstrated that elevating indoor temperatures to 28 or 30°C is comfortable if fans are used, while this elevation often is not applied in practice. This study aims to investigate AC thermostat use behaviors when elevated air movement is available, as well as to provide insights at guiding occupants to select warmer environments without reducing their comfort. 20 subjects participated in a series of tests at three initial ambient temperatures (26, 28, and 30°C) with different settings of an AC thermostat and a ceiling fan: (1) a free-controlled thermostat without a fan, (2) a free-controlled thermostat with a free-controlled fan, (3) a free-controlled thermostat with an always-on fan (controllable but not allowed to turn off), (4) a limited thermostat (no lower than 28°C) with a free-controlled fan, and (5) a limited thermostat with an always-on fan. The results show that without the ceiling fan, subjects used AC to lower indoor temperatures to 25.7°C....

Evaluation of the effect of landscape distance seen in window views on visual satisfaction

Thu, 13 Aug 2020 00:00:00 +0000

Daylighting standards dictate that the view seen through a window can be evaluated using several criteria. Among one of them is the distance at which the visual content can be seen. However, not enough guidance is given on how this criterion can be applied in practice. We used two approaches to address this problem: online surveys and human subject assessment in a controlled experiment using an artificial window. Images were used in both cases to represent window views. Two independent groups of participants took part in either study and both gave subjective satisfaction ratings to three parameters, namely, connection to the outside, visual content and visual privacy. Eighteen images were evaluated in the online surveys by a total of 91 participants while eight images were rated by 50 participants that took part in the controlled experiment. We developed a calculation method, named the Observer Landscape Distance (OLD), to quantify the distance of the window view landscape from...

Experimental evaluation of visual flicker caused by ceiling fans

Mon, 3 Aug 2020 00:00:00 +0000

Significant energy savings can be achieved by promoting elevated air speed using ceiling fans by increasing the cooling set-point temperature of an air-conditioning system. However, fan blades that obstruct the light from an artificial ceiling fixture from the relative viewing position of a building occupant could causes problems of visual flicker. We performed experiment to identify the effects of visual flicker caused by ceiling fans. Two different designs were used that had either opaque or transparent blades, which created different levels of visual flicker. These were installed in two test-rooms with similar environmental conditions. Forty-six participants took part in the study under a crossover design. Participants completed three cognitive visual tasks in both conditions: Stroop-test, switcher and digit-span tasks, respectively. Before and after completing the tasks, subjective evaluations were also given to several variables. Comparisons across the two ceiling fans showed...

Improved long-term thermal comfort indices for continuous monitoring

Wed, 15 Jul 2020 00:00:00 +0000

Thermal comfort standards have suggested a number of physical indices which can be calculated from either building simulations or in situ physical monitoring to assess the long-term thermal comfort of a space. However, the prohibitively high cost of sensor technologies has limited the applications of these physical indices, and their usefulness has never been established using data collected in real buildings. This paper is the first assessment of the six types of existing indices (23 total) found in standards and five types of new indices (36 total) and their correlation with the long-term thermal satisfaction of building occupants. Correlation analyses were based on continuous thermal comfort measurements and post-occupancy evaluation surveys from four air-conditioned office buildings in Sydney, Australia. We found that the majority of existing indices, especially those based on predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) metrics, have a weak correlation...

Targeted occupant surveys: A novel method to effectively relate occupant feedback with environmental conditions

Wed, 1 Jul 2020 00:00:00 +0000

Occupant satisfaction surveys are widely used in laboratory and field research studies of indoor environmental quality. Field studies pose several challenges because researchers usually have no control over the indoor environments experienced by building occupants, it is difficult to recruit and retain participants, and data collection methods can be cumbersome. With this in mind, we developed a survey platform that uses real-time feedback to send targeted occupant surveys (TOS) at specific indoor environmental conditions and stops sending survey requests when collected responses reach the maximum surveys required. We performed a pilot study of the TOS platform with occupants of a radiant heated and cooled building to target survey responses at 16 radiant slab surface (infrared) temperatures evenly distributed from 15 to 30 °C. We developed metrics and ideal datasets to compare the TOS platform against other occupant survey distribution methods. The results show that this novel...

An online learning approach for quantifying personalized thermal comfort via adaptive stochastic modeling

Wed, 1 Jul 2020 00:00:00 +0000

HVAC systems are the major energy consumers in commercial buildings in the United States. These systems are operated to provide comfortable thermal conditions for building occupants. The common practice of defining operational settings for HVAC systems is to use fixed set points, which assume occupants have static comfort requirements. However, thermal comfort has been shown to vary from person to person and also change over time due to climatic variations or acclimation. In this paper, we introduce an online learning approach for modeling and quantifying personalized thermal comfort. In this approach, we fit a probability distribution to each comfort condition (i.e., uncomfortably warm, comfortable, and uncomfortably cool) data set and define the overall comfort of an individual through combing these distributions in a Bayesian network. In order to identify comfort variations over time, Kolmogorov–Smirnov test is used on the joint probability distributions. In order to identify...

Ceiling Fan Design Guide

Mon, 18 May 2020 00:00:00 +0000

This guide enables architects, designers, and engineers to maximize the many benefits of integrating ceiling fans into building systems. It introduces the advantages of using ceiling fans, describes how ceiling fans work, provides guidance and resources for designing spaces with ceiling fans and specifying ceiling fan products.

Integrating Smart Ceiling Fans and Communicating Thermostats to Provide Energy-Efficient Comfort

Mon, 4 May 2020 00:00:00 +0000

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 research team including TRC, Association for Energy Affordability (AEA), and Big Ass Fans (BAF). The research team conducted laboratory tests, installed99 ceiling fans and 12 thermostats in four affordable multifamily housing sites in California’s Central Valley, interviewed stakeholders to develop a case study, developed an online design tool and design guide, outlined codes and standards outreach, and published several papers.The project team raised indoor cooling temperature setpoints and used ceiling fans as the first stage of cooling; this sequencing of ceiling fans and air conditioningreducesenergy consumption, especially during peak...

Predicted percentage dissatisfied with vertical temperature gradient

Mon, 4 May 2020 00:00:00 +0000

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 this limit is too restrictive. To revisit how vertical temperature gradient affects local thermal comfort, we conducted laboratory tests with four nominal vertical temperature gradients (0.4, 2.9, 5.9, and 8.4 °C/m). Ninety-eight seated college-age students participated in a blind within-subject experiment. Cold-feet discomfort is more frequently rated than warm-head discomfort with increasing temperature gradients. By using logistic regression modeling, we show that the whole-body dissatisfaction increases only slightly (< 10 %) with vertical temperature gradient, even up to 8.4 °C/m. Sex does not significantly affect the results...

Artificial Intelligence for Efficient Thermal Comfort Systems: Requirements, Current Applications and Future Directions

Wed, 29 Apr 2020 00:00:00 +0000

In buildings, one or a combination of systems (e.g., central HVAC system, ceiling fan, desk fan, personal heater, and foot warmer) are often responsible for providing thermal comfort to the occupants. While thermal comfort has been shown to differ from person to person and vary over time, these systems are often operated based on preﬁxed setpoints and schedule of operations or at the request/routine of each individual. This leads to occupants’ discomfort and energy wastes. To enable the improvements in both comfort and energy efﬁciency autonomously, in this paper, we describe the necessity of an integrated system of sensors (e.g., wearable sensors/infrared sensors), infrastructure for enabling system interoperability, learning and control algorithms, and actuators (e.g., HVAC system setpoints, ceiling fans) to work under a governing central intelligent system. To assist readers with little to no exposure to artiﬁcial intelligence (AI), we describe the fundamentals of an intelligent...

Advances to ASHRAE Standard 55 to encourage more effective building practice

Mon, 20 Apr 2020 00:00:00 +0000

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 developments in the design- and building-management professions. The changes have been influencing practice and spurring follow-on research.

The Standard now addresses effects of elevated air movement, solar gain on the occupant, and draft at the ankles, each with several impacts on energy-efficient design and operation. It also addresses the most important source of discomfort in modern buildings, the large inter- and intra-personal variability in thermal comfort requirements, by classifying the occupants’ personal control and adaptive options in a form that can be used in building rating systems. In order to facilitate design,...

Spatial Uniformity of Thermal Comfort from Ceiling Fans Blowing Upwards

Thu, 6 Feb 2020 00:00:00 +0000

Air movement from fans is an effective way to deliver thermal comfort in warm air temperatures. We measured air speeds in a shared office at 15 siteswhere an occupant would typically be located. The fan speed and direction were changed to operate in either the upwards or downwards direction. Mean airspeeds in the occupied zone were higher when fans were blowing downwards, but the spatial distribution across the space was less uniform. When fans areblowing upwards, thermal comfort estimates using SET indicate less risk of discomfort from high airspeed locations directly under the fans compared withthe downward case. Vertical air speed gradients showed higher air speeds at head height and lower air speeds at ankle height in the upwards direction, butthe opposite profile for fans blowing in the downward direction. The positive vertical gradient in the upwards direction is favorable to reduce the potential fordraft at the ankles. These results suggest that despite lower air speeds,...

Localized cooling for human comfort

Wed, 22 Jan 2020 00:00:00 +0000

Traditional vehicle air conditioning systems condition the entire cabin to a comfortable range of temperature and humidity regardless of the number of passengers in the vehicle. The A/C system is designed to have enough capacity to provide comfort for transient periods when cooling down a soaked car. Similarly for heating, the entire cabin is typically warmed up to achieve comfort.

Localized heating and cooling, on the other hand, focuses on keeping the passenger comfortable by forming a micro climate around the passenger. This is more energy efficient since the system only needs to cool the person instead of the entire cabin space and cabin thermal mass. It also provides accelerated comfort for the passenger during the cooling down periods of soaked cars. Additionally, the system adapts to the number of passengers in the car, so as to not purposely condition areas that are not occupied.

The present paper reports on a fundamental study of localized cooling to achieve...

A dimensionality reduction method to select the most representative daylight illuminance distributions

Wed, 22 Jan 2020 00:00:00 +0000

One challenge when evaluating daylight distribution is dealing with the large amount of temporal and spatial data, visualisations and variability in illuminances that are assessed in buildings. Using a dimensionality reduction method based on principal component analysis, we identified the most representative annual daylight distributions. We modelled a rectangular room containing an analysis grid of 3200 illuminance sensor points and simulated 3285 different temporal daylight conditions using an annual occupancy schedule ranging from 08:00 to 17:00 with one-hour sampling intervals in two locations: Singapore and Oakland, California. Our approach explained 98 % of the illuminance variability with three daylight distributions in Singapore, and 92 % using six in Oakland, California. Our dimensionality reduction strategy was also generalised using a complex building geometry showing the utility of the method. We think this approach can be used to provide a more efficient and reliable...

Using air movement for comfort during moderate exercise

Mon, 2 Dec 2019 00:00:00 +0000

Fitness centers 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. However it is well-known that significant energy can be saved by cooling sedentary occupants with air movement at elevated setpoint temperatures. This experiment investigated thermal comfort and air movement at elevated activity levels. Comfort votes were obtained from 20 subjects pedaling a bicycle ergometer at 2, 4, and 6 MET exercise intensities in four temperatures (20, 22, 24, 26 °C, RH 50%) under personal controlled ceiling fan airflow, as well as in a 20 °C still-air reference condition. An additional test of frontal airflow was conducted at 26 °C. The hypothesis, that air movement together with higher temperatures would produce equal or better comfort and perceived air quality below the reference condition, Center for the...

Longitudinal assessment of thermal and perceived air quality acceptability in relation to temperature, humidity, and CO2 exposure in Singapore

Mon, 2 Dec 2019 00:00:00 +0000

Thermal acceptability (TA) and perceived air quality acceptability (PAQA) are typically analysed in climate chambers or cross-sectional field studies. Individual factors, such as expectations and perceived environment history, may influence the acceptability response. Longitudinal studies with multi-day design are absent in the literature. Fifteen Singaporean subjects participated in a 7-day longitudinal experiment in which they carried a portable sensor that continuously recorded personal air temperature, relative humidity and carbon dioxide concentration at 1-minute intervals. Instantaneous TA and PAQA were regularly sampled by survey for each subject. High acceptability was found at home, restaurants and workplaces, whereas low acceptability was found for outdoor and transport environments. The participants from Singapore’s modern tropical environment spent an average of 96% of their time indoors. Weak associations were reported between acceptabilities and measured physical...

Use of adaptive control and its effects on human comfort in a naturally ventilated office in Alameda, California

Mon, 18 Nov 2019 00:00:00 +0000

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 exercise various adaptive control opportunities to meet their comfort needs in the absence of a mechanical HVAC system. Continuous measurements were made of adaptive behaviors such as window state, ceiling fan usage, heater usage, and indoor and outdoor climate (dry-bulb air temperature, relative humidity, CO2, outdoor temperature). Over 1400 thermal comfort survey responses were collected, which showed that the building provided acceptable thermal conditions for 98% of the survey period, covering an indoor temperature range of 16–28°C. Occupants wore clothing between 0.5 and 0.6 clo in summer, and 0.7–0.8 in winter. Occupants opened windows...

Nudging the adaptive thermal comfort model

Mon, 18 Nov 2019 00:00:00 +0000

The recent release of the largest database of thermal comfort field studies (ASHRAE Global Thermal Comfort Database II) presents an opportunity to perform a quality assurance exercise on the first generation adaptive comfort standards (ASHRAE 55 and EN15251). The analytical procedure used to develop the ASHRAE 55 adaptive standard was replicated on 60,321 comfort questionnaire records with accompanying measurement data. Results validated the standard's current adaptive comfort model for naturally ventilated buildings, while suggesting several potential nudges relating to the adaptive comfort standards, adaptive comfort theory, and building operational strategies. Adaptive comfort effects were observed in all regions represented in the new global database, but the neutral (comfort) temperatures in the Asian subset trended 1–2°C higher than in Western countries. Moreover, sufficient data allowed the development of an adaptive model for mixed-mode buildings that closely aligned to...

Transient human thermophysiological and comfort responses indoors after simulated summer commutes

Wed, 6 Nov 2019 00:00:00 +0000

Using personally controlled air movement to improve comfort after simulated summer commute

Wed, 6 Nov 2019 00:00:00 +0000

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 overcooling and wasting energy. In addition, space cooling is slow, requiring minutes to take effect. This study addresses how to improve comfort in the transition by increasing the availability of convective cooling, where the response time is in seconds. Thirty-five subjects (17 men and 18 women) dressed in 0.6 clo en-tered a test room after exercising at 4.4 met for 15 min in 30 ºC. The exercise emulates the commute activity in summer. The test room was controlled to 24, 26, and 28 ºC, with and without the option of cooling using fan-produced horizontal airflow. Subjects were sedentary for 60 minutes, during which subjective thermal responses...

High-density thermal sensitivity maps of the human body

Mon, 14 Oct 2019 00:00:00 +0000

‘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 thermal sensations and sensitivities for 318 local skin spots distributed over one side of the body, measured on a large number of subjects. Skin temperature changes were induced with a thermal probe 14 mm in diameter, and subjective thermal sensations were surveyed after 10 s. Our neutral base temperature was 31 °C and the spot stimulus was ±5 °C. Cool and warm sensitivities are seen to vary widely by body part. The foot, lower leg and upper chest are much less sensitive than average; in comparison, the cheek, neck back, and seat area are 2–3 times as sensitive to both cooling and warming stimuli. Every body part exhibits stronger sensitivity...

Evaluating the comfort of thermally dynamic wearable devices

Mon, 7 Oct 2019 00:00:00 +0000

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 study evaluates a novel approach to PCS that leverages the time-dependence of human thermal perception. A 6.25 cm2 wearable device, Embr Wave, delivers dynamic waveforms of cooling or warming to the inner wrist. In three thermal comfort tests conducted in a climate chamber with N = 49 subjects and temperatures between 20 and 28 ºC, the device exhibited a corrective potential of 2.5 ºC within 3 minutes for both warm and cool populations, while consuming ~1 W of power. The effect is even more pronounced (corrective potential up to 3.3 ºC over periods of 3- and 45-minutes) when subjects are given control of the device’s operation. Subjects...

Review of fan-use rates in field studies and their effects on thermal comfort, energy conservation, and human productivity

Mon, 30 Sep 2019 00:00:00 +0000

This paper is a literature review of field studies on fan-use rates and their effects on thermal comfort, energy conservation, and human productivity. In the assessed literature, fans are more popular in Asia, and more used in mixed-mode (MM) and naturally ventilated (NV) buildings than in air-conditioned (AC) buildings. On the basis of collected fan-use models, probit regression models of fan-use rates and ambient environments were obtained and indicate that the essential trigger of fan-use is a warm environment rather than building types. This result helps us to understand the control behaviors and comfort requirements of occupants. Also, fans could provide benefits in three aspects: widening neutral temperatures, saving energy, and improving occupants’ productivity. First, using fans in buildings elevates the neutral temperature and the upper limit of neutral zone (0.5 thermal sensation scale) averages by about 3 K in ranges from 25.7℃ to 28.7℃ and 27.5℃ to 30.7℃, respectively....

Effect of sensor position on the performance of CO2-based demand controlled ventilation

Mon, 9 Sep 2019 00:00:00 +0000

CO2–based demand controlled ventilation (DCV) can save energy while maintaining acceptable indoor air quality. CO2 concentration may vary within an occupied space and it is unclear how sensor location influences the ventilation and energy performances. The objective of the present study is to investigate the effect of CO2 sensor position on the performance of DCV systems under mixing and displacement ventilation. Experimentally validated computational fluid dynamics (CFD) models were simulated under representative indoor ventilation and occupancy conditions. The results show that the ventilation strategy, occupancy level, and air change rate have notable impacts on the CO2 sensing performance. Under mixing ventilation, CO2 sensors placed at the room exhaust can meet the requirements of sensor accuracy defined by ASTM E741 and California Title 24. However, the sensor errors associated with sensor location can be higher than the acceptable threshold under displacement ventilation,...

Personal thermal comfort models with wearable sensors

Mon, 26 Aug 2019 00:00:00 +0000

A personal comfort model is an approach to thermal comfort modeling, for thermal environmental design and control, that predicts an individual's thermal comfort response, instead of the average response of a large population. We developed personal thermal comfort models using lab grade wearable in normal daily activities. We collected physiological signals (e.g., skin temperature, heart rate) of 14 subjects (6 female and 8 male adults) and environmental parameters (e.g., air temperature, relative humidity) for 2–4 weeks (at least 20 h per day). Then we trained 14 models for each subject with different machine-learning algorithms to predict their thermal preference. The results show that the median prediction power could be up to 24%/78%/0.79 (Cohen's kappa/accuracy/AUC) with all features considered. The median prediction power reaches 21%/71%/0.7 after 200 subjective votes. We explored the importance of different features on the prediction performance by considering all subjects...

Measuring air speed with a low-power MEMS ultrasonic anemometer via adaptive phase tracking

Wed, 3 Jul 2019 00:00:00 +0000

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 transceiver provides high sensitivity measurements and low cost through microelectromechanical systems (MEMS) manufacturing. However, at high frequencies, conventional ultrasonic signal processing algorithms function only over small ranges of ambient temperature and velocity. In this paper, we describe three algorithms that use the complex phase angle of an ultrasonic pulse to measure velocity and temperature over extended ranges of temperature and velocity. They employ heuristics to track the vibration cycle of the measured phase angle. These methods are applied in a pulse-based anemometer whose 176kHz MEMS transceivers both transmit and...

Predicting older people's thermal sensation in building environment through a machine learning approach: Modelling, interpretation, and application

Mon, 1 Jul 2019 00:00:00 +0000

There is insufficient knowledge on how environmental and physiological factors affect older people's thermal perceptions. In this paper, we present two data-driven models (a field study model and a lab study model) using the algorithm of random forests to predict older people's thermal sensation. These two models were developed from a field study dataset and a lab study dataset separately. The field study dataset was collected from 1040 old subjects (70 + years) who lived in 19 aged-care homes, which contains multi-dimension factors such as environmental parameters, subjects' demographic information, health condition, acclimatization degrees, living habits and thermal perceptions' votes. The lab study dataset was collected from a lab study and contains 18 old subjects' (65 + years) eight local skin temperatures and thermal perceptions' votes under five thermal environments (21/23/26/29/32 °C). After the procedure of feature selection, the field study model was developed with four...

Chinese older people's subjective and physiological responses to moderate cold and warm temperature steps

Mon, 1 Jul 2019 00:00:00 +0000

Older people are very likely to experience transitions among spaces with different temperatures in daily life. But little has been known about their thermal comfort and physiological responses to these temperature steps. This study investigated 18 healthy older people's thermal perceptions and physiological parameters under cold and warm exposures with 3/5/6 °C temperature steps. The results showed that subjects' thermal sensation was sensitive to all moderate temperature steps, but their thermal comfort perception could only distinguish temperature changes greater than 5 °C. Thermal unacceptability was only observed when subjects' tympanic temperature reached at 37.08 °C. Also, we found older people need more than 50 min time to get their mean skin temperature steady after cold stimuli, while they only need <24 min after warm ones. Cold stimuli could significantly boost subjects' blood pressure, respiratory rate, blood oxygen saturation, and depress heart rate. To predict...

Comparison of mean radiant and air temperatures in mechanically-conditioned commercial buildings from over 200,000 field and laboratory measurements

Thu, 20 Jun 2019 00:00:00 +0000

We assessed the difference between mean radiant temperature ((t_r ) ̅) and air temperature (t_a) in conditioned office buildings to provide guidance on whether practitioners should separately measure (t_r ) ̅ or operative temperature to control heating and cooling systems. We used measurements from 48 office buildings in the ASHRAE Global Thermal Comfort Database, five field studies in radiant and all-air buildings, and five test conditions from a laboratory experiment, including both radiant and all-air spaces. Considering only the ASHRAE Global Thermal Comfort Database because it is the largest and most representative dataset, under typical office conditions, the median absolute difference (e.g., disregarding direction of the difference) between (t_r ) ̅ and t_a was 0.4 ℃ (with interquartile range = 0.4 ℃), and more specifically, the median difference shows that (t_r ) ̅ was 0.4 ℃ (with interquartile range = 0.4 °C) warmer than t_a. In the radiant cooled laboratory tests, (t_r...

Field evaluation of occupant satisfaction and energy performance in eight LEED-certified buildings using radiant systems

Wed, 19 Jun 2019 00:00:00 +0000

In this study, we present the results of a post-occupancy assessment on thermal comfort, indoor air quality, and acoustical quality from 568 occupant surveys in eight LEED-certified buildings with radiant heating and cooling systems, and trends in low-energy consuming buildings based on building characteristics, radiant design, and building operator interviews. This study follows-up on a quantitative assessment of 60 office buildings that found radiant and all-air buildings have equal satisfaction with indoor environmental quality, with a tendency for increased thermal satisfaction in radiant buildings. Our objective was to investigate reasons of comfort and discomfort in the radiant subset, and to relate these to building characteristics and operations strategies. Our analysis revealed that the primary sources of temperature dissatisfaction are lack of control over the thermal environment (both temperature and air movement) and slow system response, both of which were seen to...

Ceiling fans in commercial buildings: In situ airspeeds & practitioner experience

Wed, 5 Jun 2019 00:00:00 +0000

Ceiling fans are a traditional approach for increasing occupant comfort and are well-established in residential application in many parts of the world. However, they are infrequently included in commercial spaces even though they have the potential to bring benefits including increased occupant comfort and decreased energy use either through raised setpoints in cooling or destratification in heating. This study provides practical insights into the case of ceiling fans in commercial spaces. We conducted 13 interviews with architects, engineers, and facilities managers from California and around the country to compile common themes of experience. These professionals provided lessons learned from 20 operational projects that include ceiling fans serving a wide set of functions in commercial spaces. Understanding the challenges they faced and the lessons they learned from these projects will facilitate prioritization of research and communication efforts. We also took in situ airspeed...

Continuous IEQ monitoring system: Performance specifications and thermal comfort classification

Tue, 2 Apr 2019 00:00:00 +0000

The quality of buildings can be assessed in terms of the indoor air quality, thermal comfort, lighting quality, acoustic comfort afforded the occupants, collectively referred to as Indoor Environmental Quality (IEQ). A major barrier to a more thoroughly representative audit of actual IEQ performance are the expense and complexity of the measurement instrumentation required. Rapid developments in sensor technology in recent years present the opportunity for continuous and pervasive IEQ monitoring to deliver truly representative characterisations of building performance at a modest cost. The last remaining obstacle to realising these developments seems to be a concern about instrument accuracy. In this paper we test the performance of a low-cost IEQ monitoring system (SAMBA) introduced in an earlier paper. Calibration data from 100 devices was analysed to calculate the standard error of the estimate as a measure of equipment accuracy. Those performance specifications were used in...

A thermal comfort environmental chamber study of older and younger people

Tue, 2 Apr 2019 00:00:00 +0000

We investigated whether or not, when exposed to the same conditions, older people (those aged 65 and over) had different thermal sensations, comfort, acceptability and preferences from their younger counterparts. The study was conducted in a thermal comfort environmental chamber, involving 22 older (average 69.7 years old) and 20 younger (29.6 years old) subjects, exposed to four test conditions between slightly cool and slightly warm. Subjective thermal comfort perceptions for local body parts and whole-body were surveyed. Skin temperatures were measured at four body locations: neck, right scapula, left hand, and right shin. We also investigated the correlation between the frailty level of the subjects and their thermal comfort levels. The study found no significant difference between the thermal sensation, comfort and acceptability of older and younger subjects. We also found no correlation between subjects’ frailty level and their thermal sensation, comfort, acceptability and...

Analysis of the accuracy on PMV – PPD model using the ASHRAE Global Thermal Comfort Database II

Mon, 1 Apr 2019 00:00:00 +0000

The predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) are the most widely used thermal comfort indices. Yet, their performance remains a contested topic. The ASHRAE Global Thermal Comfort Database II, the largest of its kind, was used to evaluate the prediction accuracy of the PMV/PPD model. We focused on: (i) the accuracy of PMV in predicting both observed thermal sensation (OTS) or observed mean vote (OMV) and (ii) comparing the PMV-PPD relationship with binned OTS – observed percentage of unacceptability (OPU). The accuracy of PMV in predicting OTS was only 34%, meaning that the thermal sensation is incorrectly predicted two out of three times. PMV had a mean absolute error of one unit on the thermal sensation scale and its accuracy decreased towards the ends of the thermal sensation scale. The accuracy of PMV was similarly low for air-conditioned, naturally ventilated and mixed-mode buildings. In addition, the PPD was not able to predict the dissatisfaction...

Thermosensory micromapping of warm and cold sensitivity across glabrous and hairy skin of male and female hands and feet

Mon, 18 Mar 2019 00:00:00 +0000

The ability of human 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 such sensitivity maps exist for touch and pain. Using a recently developed quantitative sensory test, we mapped warm and cold thermosensitivity of 103 skin sites over glabrous and hairy skin of handsand feet in male (30.2±5.8y) and female (27.7±5.1y) adults matched for body surface area (M 1.77±0.2m2; F 1.64±0.1m2; p=0.155). Our findings indicated that warm and cold thermosensitivity varies by 5-fold across glabrous and hairy skin of hands and feet, and that hands are twice as sensitive as the feet. Opposite to what is known for touch and pain sensitivity, we observed a characteristic distal-to-proximal increase in thermosensitivity over both hairy and glabrous skin (i.e. from fingers/toes to body of...

Personal CO2 bubble: Context-dependent variations and wearable sensors usability

Fri, 15 Mar 2019 00:00:00 +0000

High CO2 concentration in inhaled air has been shown to negatively impact work performance and increase acute health symptoms. As respiratory CO2 is constantly exhaled, it may not dissipate in surrounding air in absence of adequate air movement and is instead re-inhaled into the airways (breathing in a CO2-rich bubble). In this study, we explored the impacts of context-dependent factors such as office activities, desk settings, and personal differences on the inhalation zone CO2 concentration and on concentrations at a below-neck wearable sensor. While all factors were found to significantly impact measurements at both measuring points, desk settings (empty desk, desk with a fan, desk with laptop, desk with monitor) was found to be the most dominant factor. Presence of a small portable desk fan was found to significantly reduce the CO2 concentration. On average, we observed a 177 ppm reduction in CO2 concentration when using a fan, which is 25 ppm higher than the background CO2...

Towards unsupervised learning of thermal comfort using infrared thermography

Thu, 14 Mar 2019 00:00:00 +0000

Maintaining thermal comfort in built environments is important for occupant health, well-being, and productivity, and also for efficient HVAC system operations. Most of the existing personal thermal comfort learning methods require occupants to provide feedback via a survey to label the monitored environmental or physiological conditions in order to train the prediction models. However, the accuracy of these models usually drops after the training process as personal thermal comfort is dynamic and changes over time due to climatic variations and/or acclimation. In this paper, we present a hidden Markov model (HMM) based learning method to capture personal thermal comfort using infrared thermography of human face. We chose human face since its blood vessels has a higher density and it is not covered while performing regular activities in built environments. Learning algorithm has 3 hidden states (i.e., uncomfortably warm, comfortable, uncomfortably cool) and uses discretization...

Thermal comfort under radiant asymmetries of floor cooling system in 2 h and 8 h exposure durations

Mon, 25 Feb 2019 00:00:00 +0000

Radiant heating and cooling systems inherently exhibit radiant asymmetries. Although many researchers have investigated the thermal comfort effects of asymmetric radiant environments, the exposure duration has not been emphasized, especially under floor heating and cooling scenarios. In this study, we conducted a series of tests in a climate chamber with floor cooling radiant asymmetries with human participants to investigate their thermal comfort effects from short-term (2 h) and long-term (8 h) exposure perspectives. The 2 h exposure test indicates that the floor cooling systems cause discomfort complaints more easily than other radiant systems such as ceiling heating/cooling because of its stronger cooling effects on the lower body parts. The cold floor resulted in significantly colder local thermal sensations and lower local skin temperatures in the foot, calf, and thigh areas. The comparison between the 2 h and 8 h exposures suggests that exposure duration affects both the...

A data-driven approach to defining acceptable temperature ranges in buildings

Mon, 25 Feb 2019 00:00:00 +0000

Current thermal comfort standards use Predicted Mean Vote (PMV) classes as the compliance criteria despite previous critiques. The implicit assumption is that a narrower PMV range ensures higher thermal acceptability among building occupants. However, our analysis of a global database of thermal comfort field studies demonstrates that PMV classes are not appropriate design compliance criteria, and reinforces the need for a new and robust approach to thermal comfort compliance assessment. We compared two statistical methods to derive acceptable temperature ranges from occupant responses applied one to the ASHRAE Global Thermal Comfort Database II. Derived acceptable temperature ranges in real buildings (7.4K-12.2K) using this new method are wider than the current standards mandate (2K-6K). Our findings support the call for a relaxation of suggested temperature ranges in thermal comfort standards so as to minimize unnecessary space conditioning. The proposed data-driven statistical...

Measurement of airflow pattern induced by ceiling fan with quad-view colour sequence particle streak velocimetry

Mon, 25 Feb 2019 00:00:00 +0000

Ceiling fans have been widely used for a long time as an effective cooling equipment to create sustainable indoor environment. However, it is rather difficult for the current measuring techniques to capture such a complicated airflow field in a whole-room scale. In this study, a novel large-scale airflow measurement technology, quad-view colour sequence particle streak velocimetry (CSPSV), is developed and applied to measure the airflow induced by a ceiling fan in a 4 m × 2.5 m × 3 m chamber. Four cameras were used in the new method, two at the higher position measuring airflow near the ceiling while the other two at the lower position measuring airflow near the floor, to capture the room-scale flow field. After reconstructing the vectors from each camera pair, the airflow vectors are merged to fill the blind zone near the ceiling and floor. Based on the three-dimensional three-component vector field measurement data, the averaged velocity vector, turbulence intensity, and vorticity...

The Squeaky Wheel: Machine learning for anomaly detection in subjective thermal comfort votes

Fri, 22 Feb 2019 00:00:00 +0000

Anomalous patterns in subjective votes can bias thermal comfort models built using data-driven approaches. A stochastic-based two-step framework to detect outliers in subjective thermal comfort data is proposed to address this problem. The anomaly detection technique involves defining similar conditions using a k-Nearest Neighbor (KNN) method and then quantifying the dissimilarity of the occupants’ votes from their peers under similar thermal conditions through a Multivariate Gaussian approach. This framework is used to detect outliers in the ASHRAE Global Thermal Comfort Database I & II. The resulting anomaly-free dataset produced more robust comfort models avoiding dubious predictions. The proposed method has been proven to effectively distinguish outliers from inter-individual variabilities in thermal demand. The proposed anomaly detection framework could easily be applied to other applications with different variables or subjective metrics. Such a tool holds great promise...

Heating and cooling the human body with energy-efficient personal com-fort systems (PCS)

Mon, 28 Jan 2019 00:00:00 +0000

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 devices--heated in-sole, heated/cooled wristpad, small deskfan, heated/cooled chair--and evaluated the thermal effect of each device and of combinations of the four. Human-subject and thermal-manikin tests in a climate chamber under cool and warm conditions (18oC and 29oC) investigated the thermal comfort improvement and heating/cooling performance of these devices. The results show the devices to have remarkable heating/cooling efficiencies, with combined cooling COP of 3.6 and heating COP of 0.88. They significantly improved subjects’ whole body thermal acceptance and thermal comfort perception, with more than 80% of people accepting...

The Effect of a Low-Energy Wearable Thermal Device on Human Comfort

Mon, 28 Jan 2019 00:00:00 +0000

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 tests were at 20, 23, and 26ºC ambient conditions. It was found that the local warming and cooling had a signifi-cant effect for subjects who felt cool or warm before using the device. The wearable device was able to improve whole-body thermal sensation about 1 scale unit towards neutral. The whole body thermal comfort was also improved significantly by the wearable device if sub-jects felt discomfort before using it. For people who felt neutral prior to use, the improvement of using the wearable device was small but also statistically significant. The concept of local-ized, individually-controlled thermal wearable devices is promising...

Reducing building over-cooling by adjusting HVAC supply airflow setpoints and providing personal comfort systems

Mon, 28 Jan 2019 00:00:00 +0000

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 significantly reduced by lowering maximum and minimum supply air flowrate setpoints, while providing personal comfort systems for occupants. The study was conducted over 16 months in two office spaces of a campus building with high HVAC energy expenditure and frequent cold complaints. The initial visit and measurements showed that the spaces were over-ventilated, causing cold discomfort in several workstations. We provided personal comfort systems to 26 occupants (heated/cooled chair, footwarmer, legwarmer based on occupants’ own choices) to maintain comfort, and gradually reduced the maximum and minimum supply air volume setpoints, to reduce...

Continuous IEQ monitoring system: Context and development

Thu, 24 Jan 2019 00:00:00 +0000

Addressing two common challenges for building performance – reducing the carbon footprint attached to the provision of comfortable indoor environments, and improving the health and wellbeing of occupants – requires a more comprehensive understanding of how the indoor environments of buildings are operated. This paper introduces SAMBA, a state-of-the-art monitoring station for continuous, real-time measurements of indoor environmental quality (IEQ) parameters from occupants’ work desks. It combines a hardware solution that integrates a low-cost suite of sensors with a software platform designed to automatically analyse and visualize data for quick interpretation of IEQ performance by non-scientist. In addition to feeding a massive IEQ database for research, the resulting data may be used to better inform the metrological requirements for popular international IEQ rating schemes. This new era of indoor environmental monitoring based upon systems such as SAMBA affords a fundamentally...

Occupant comfort and behavior: High-resolution data from a 6-month field study of personal comfort systems with 37 real office workers

Wed, 5 Dec 2018 00:00:00 +0000

Personal Comfort Systems (PCS) provide individual occupants local heating and cooling to meet their comfort needs without affecting others in the same space. It saves energy by relaxing ambient temperature requirements for the HVAC system. Aside from these benefits, PCS offers a wealth of data that can describe how individuals interact with heating/cooling devices in their own environment. Recently developed Internet-connected PCS chairs have unlocked this opportunity by generating continuous streams of heating and cooling usage data, along with occupancy status and environmental measurements via embedded sensors. The data allow individuals’ comfort and behavior to be learned, and can inform centralized systems to provide ‘just the right’ amount of conditioning to meet occupant needs. In summer 2016, we carried out a study with PCS chairs involving 37 occupants in an office building in California. During the study period, we collected >5 million chair usage data-points and...

The importance of window view: Using an exploratory factor analysis to uncover the underlying latent dimensions

Wed, 5 Dec 2018 00:00:00 +0000

This report outlines a statistical method used to evaluate the subjective ratings given to an image of a window view. An online survey containing questionnaire items that I believe influence the observer’s perception of the view were listed and distributed online. In total, 181 subjective responses were collected. Participants were asked to rate each item in the survey based on the perceived level of agreement or importance for each question. To analyse the data, I used an exploratory factor analysis. Of the 30 question items listed in the survey, four underlying latent factors were extracted. Namely: ‘subjective responses to the window view’, ‘physical features of the view’, ‘physical features of the window’, and ‘work-related responses’, respectively. These are listed in order of the amount of variance that they could explain within the data. The results of the analysis show how responses to several different questionnaire items refer to the same latent factor. I believe that...

Indoor climate experience, migration, and thermal comfort expectation in buildings

Sat, 28 Jul 2018 00:00:00 +0000

Advances in heating, ventilation and air conditioning (HVAC) technologies have dramatically improved the indoor thermal environment, but attention should be paid on how this would affect building occupants' thermal comfort perception. In this paper, we studied the mutually dependent relationship between indoor climate experience and occupants' comfort expectation. An intriguing experiment was conducted in China where wintertime indoor thermal environments in northern cities (with district heating) are much warmer than in southern region (without district heating). By analyzing the 4411 responses from four college-aged subject groups with different indoor thermal history, two interesting findings emerged. Firstly, people's understandings of thermal comfort change with their indoor thermal experiences. Those permanently live in lower-grade non-neutral thermal environment can achieve similar thermal comfort perception as those who live in long-term comfortable thermal conditions....

Thermal comfort evaluated for combinations of energy-efficient personal heating and cooling devices

Sat, 28 Jul 2018 00:00:00 +0000

Personal comfort systems (PCS) have potential to fulfill building occupants' personal thermal comfort preferences with great efficiency. But to integrate them into building conditioning, there must be a broader selection of PCS devices available. Design guidance and standards are needed to assure that such devices provide high levels of comfort effectiveness and energy efficiency. This study addresses these needs. A suite of minimum-power PCS devices was built that target body parts significant to alliesthesia—a heated shoe insole, heated/cooled wristpad, small deskfan, and heated/cooled chair. They were tested in a climate chamber under cool and warm conditions using both thermal-manikin and human-subjects. Their efficiency at physically heating/cooling the body is high; the combined suite has a coefficient of performance (COP) of 3.6 for cooling and 0.88 for heating. The subjects' whole-body thermal acceptance and thermal comfort perception were improved by the devices in an...

Detailed experimental investigation of air speed field induced by ceiling fans

Tue, 17 Jul 2018 00:00:00 +0000

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 airflow profiles induced by a single fan and multiple fans using high spatial resolution air speed measurements (5,760 and 20,160 measuring points for the two cases respectively) in a climatic chamber. To authors' knowledge, this is the first time that interaction between multiple fans has been reported. We developed typical airflow patterns from the measurements and further validated them via smoke visualization. The singlefan results are consistent with previous studies of this configuration, providing additional refinements. For the multiple-fan case, both the difference of fan speed levels and the distance between the fans affect the...

A new modeling approach for the assessment of the effect of solar radiation on indoor thermal comfort

Tue, 17 Jul 2018 00:00:00 +0000

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 describe a new approach for the calculation of the hourly effective radiant field (ERF) and mean radiant temperature (MRT) for an occupant near various façade systems and office layouts. The new method uses Radiance to assess the hourly intensity of solar radiation that passes through a facade and lands on the human body. The proposed method, for commercial buildings, allows calculating with high accuracy the comfort effect of solar radiation on occupants throughout the year.

Preferred temperature with standing and treadmill workstations

Tue, 3 Jul 2018 00:00:00 +0000

Prolonged sedentary behavior has been shown to increase chronic diseases. Using standing and treadmill desk reduces sitting time, increases metabolic rate and thus has potential to improve health. There is little existing guidance on how to keep thermal comfort when using standing and treadmill desk. It is unknown what are the suitable ambient temperatures for occupants at elevated office activity levels. This experiment investigated thermal sensation and preferred temperature at elevated office activity levels, including sitting (SED), standing (STD), and two slow-walk speeds: walking at 1.2 km/h (TRD1) and walking at 2.4 km/h (TRD2). Comfort votes were obtained from 20 subjects under personal controlled ambient temperature. The active workstation significantly increased human metabolic level and reduced preferred temperature. The measured metabolic rates were 1.0, 1.1, 1.9 and 2.5 met for SED, STD, TRD 1 and TRD 2. The preferred ambient temperature reduced from 25.85 °C for...

Development of the ASHRAE Global Thermal Comfort Database II

Tue, 26 Jun 2018 00:00:00 +0000

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 exercise began with a systematic collection and harmonization of raw data from the last two decades of thermal comfort field studies around the world. The ASHRAE Global Thermal Comfort Database II (Comfort Database), now an online, open-source database, includes approximately 81,846 complete sets of objective indoor climatic observations with accompanying “right-here-right-now” subjective evaluations by the building occupants who were exposed to them. The database is intended to support diverse inquiries about thermal comfort in field settings. A simple web-based interface to the database enables filtering on multiple criteria,...

Percentage of commercial buildings showing at least 80% occupant satisfied with their thermal comfort

Thu, 31 May 2018 00:00:00 +0000

Most thermal comfort standards prescribe that buildings must provide satisfactory thermal comfort to at least 80% of their occupants. To assess how many buildings meet this criterion, we analysed temperature satisfaction votes from 52,980 occupants in 351 office buildings, obtained via a web-based seven-point satisfaction survey over 10 years, mainly in North America. 43% of the occupants are thermally dissatisfied, 19% neutral and 38% satisfied. The percentage of buildings meeting 80% satisfied occupants was only 2% if one considers votes from +1 to +3 (‘slightly satisfied to very satisfied’) as representing satisfaction, 8% if one includes votes from 0 to +3 (‘neutral to very satisfied’), and 33% if one includes votes from -1 to +3 (‘slightly dissatisfied to very satisfied’ – a seemingly generous criterion suggested in ASHRAE Standard 55). These results are concerning because they suggest that buildings are far from creating thermal environments that their occupants consider...

Advancing comfort technology and analytics to personalize thermal experience in the built environment

Thu, 31 May 2018 00:00:00 +0000

Nearly 60% of global energy consumption in buildings is used for space heating and cooling to provide occupant comfort. Yet, a large portion of occupants are dissatisfied with the buildings’ thermal environment. There are many reasons for thermal dissatisfaction in buildings, but a fundamental cause is the current practice of delivering uniform thermal conditions based on universal rules, without accounting for individual differences in comfort requirements. To address these issues, a growing body of research has emerged to better reflect individual’ comfort requirements. This dissertation contributes to this research by providing the following primary innovations: 1) Internet-connected personal comfort system (PCS) and 2) personal comfort models that can help to deliver personalized comfort experiences in occupied spaces. In particular, I developed and field-tested the new capabilities of PCS (data reporting, wireless connectivity) that could support individualized learning and...

Human metabolic rate and thermal comfort in buildings: The problem and challenge

Thu, 31 May 2018 00:00:00 +0000

Of the six fundamental parameters in the classic heat balance model of human thermal comfort, metabolic rate is probably the most important and yet it is the most crudely assessed in both research and practice. Most studies in thermal comfort domain to date have relied on simple activity diaries to estimate metabolic rate. To better understand the pros and cons of this convenient approach, a literature review of cognate disciplines was conducted with the aim of transferring developments in human metabolic science to the built environmental context. This review leads to the conclusion that the dairy methods prevalent in thermal comfort research and practice are probably not accurate enough to sustain common thermal comfort modeling with any semblance of precision. Additional research effort is needed to develop better metabolic rate estimation...

Thermal comfort and self-reported productivity in an office with ceiling fans in the tropics

Tue, 3 Apr 2018 00:00:00 +0000

Here we present a field study examining the impact of elevated room temperature and air movement on thermal comfort and self-reported productivity. This experiment was performed in three environmental conditions (one with a set-point of 23 °C—a typical set-point used in Singapore—and two elevated (up to 28 °C) room temperature conditions). Occupants had shared control of ceiling fans. The results show that the most comfortable thermal condition, with thermal sensation closest to neutral, is achieved at a room temperature of 26 °C with operating fans. Increasing the temperature set-point from 23 °C to 26 °C resulted in a significant increase in thermal acceptability (from 59% to 91%), and a 44 kWh/m2yr savings in electrical energy used for comfort cooling. We found that a room’s set-point temperature can be increased up to 27 °C without creating a negative impact when controllable air movement is provided compared to an environment with a set-point of 23 °C. Thermal...

Thermal comfort and acoustic quality in buildings using radiant systems

Tue, 3 Apr 2018 00:00:00 +0000

In the US, people spend about 90% of their time indoors. This long exposure to indoor conditions affects our well-being, performance and health. Design and operation of these spaces also impacts energy use in building which, in the US, accounts for 40% of primary energy use. With these dual challenges, researchers and building professionals seek design strategies to simultaneously address the challenge of indoor environmental quality (IEQ) and energy use. Radiant heating and cooling systems have the potential to achieve significant energy savings primarily due to the use of lower temperature differences between the space and the heating or cooling source. Compared to buildings with all-air systems, buildings with radiant systems have been commonly associated with increased thermal comfort but decreased acoustic quality. The concern of reduced acoustics is particularly the case with regard to massive radiant systems and the need to preserve heat transfer, thereby keeping radiant...

Comparing temperature and acoustic satisfaction in 60 radiant and all-air buildings

Wed, 7 Mar 2018 00:00:00 +0000

There is little knowledge from occupied buildings of the impact of radiant heating and cooling systems on indoor environmental quality aspects such as thermal comfort, indoor air quality, and acoustics. We present indoor environmental quality survey results from 3,892 respondents in 60 office buildings located in North America; 34 of which used all-air systems and 26 of which used radiant systems as the primary conditioning system. In the current study, we present the survey results of 1,645 occupants in buildings with radiant systems. To our knowledge, this is the largest dataset used in a comparison of occupant satisfaction in radiant buildings. We used an existing database to extract a subset of occupant responses from all-air buildings whose key characteristics match those radiant buildings. The results indicate that radiant and all-air spaces have equal indoor environmental quality, including acoustic satisfaction, with a tendency towards improved temperature satisfaction...

Global trends in thermal comfort in air conditioned and naturally ventilated offices in six climates

Tue, 13 Feb 2018 00:00:00 +0000

This paper compares occupants’ thermal response to naturally-ventilated and air-conditioned offices during the summer in four cool climate cities of developed economies (Midland in UK, San Francisco in US, and Melbourne and Brisbane in Australia) and four warm climate cities of developing economies (Bangkok in Thailand, and Bangalore, Jaipur and Chennai in India). This analysis is some of the first done using data from both the ASHRAE Global Thermal Comfort Databases I and II. Database II expands and is based on ASHRAE Database I (de Dear and Brager, 1998), led by teams at the Center for the Built Environment at University of California-Berkeley, University of Sydney, and Yongsei University Korea. Results confirmed one of the fundamental tenants of adaptive theory, that the outdoor climate context mattered. In the warm climate cities, occupants voted neutral at higher temperatures in both conditioning types, with a more distinct pattern for naturally ventilated buildings....

Personal comfort models—A new paradigm in thermal comfort for occupant-centric environmental control

Tue, 6 Feb 2018 00:00:00 +0000

A personal comfort model is a new approach to thermal comfort modeling that predicts an individual’s thermal comfort response, instead of the average response of a large population. It leverages the Internet of Things and machine learning to learn individuals’ comfort requirements directly from the data collected in their everyday environment. Its results could be aggregated to predict comfort of a population. To provide guidance on future efforts in this emerging research area, this paper presents a unified framework for personal comfort models. We first define the problem by providing a brief discussion of existing thermal comfort models and their limitations for real-world applications, and then review the current state of research on personal comfort models including a summary of key advances and gaps. We then describe a modeling framework to establish fundamental concepts and methodologies for developing and evaluating personal comfort models, followed by a discussion of...

Personal comfort models: Predicting individuals' thermal preference using occupant heating and cooling behavior and machine learning

Thu, 25 Jan 2018 00:00:00 +0000

A personal comfort model is a new approach to thermal comfort modeling that predicts individuals’ thermal comfort responses, instead of the average response of a large population. However, securing consistent occupant feedback for model development is challenging as the current methods of data collection rely on individuals’ survey participation. We explored the use of a new type of feedback, occupants’ heating and cooling behavior with a personal comfort system (PCS) for the development of personal comfort models to predict individuals’ thermal preference. The model development draws from field data including PCS control behavior, environmental conditions and mechanical system settings collected from 38 occupants in an office building, and employs six machine learning algorithms. The results showed that (1) personal comfort models based on all field data produced the median accuracy of 0.73 among all subjects and improved predictive accuracy compared to conventional...