Recent cedr items

Evaluating Indoor Air Quality Impacts of Far-UVC (222 nm) in a Controlled Full-Scale Office Environment with Human Subjects

Mon, 29 Jun 2026 00:00:00 +0000

Far-UVC (222 nm) irradiation effectively inactivates airborne pathogens, but photolyzes oxygen to generate ozone, potentially initiating indoor chemistry that may form secondary pollutants. To evaluate these impacts in a realistic setting, we conducted experiments in a full-scale (158 m3) office chamber. The study involved 13 sessions with human subjects (n=4–8) under typical mechanical ventilation (0.7–0.8 h⁻¹). We monitored ozone, ultrafine particles, and nitrogen oxides, and took time-integrated volatile organic compounds (VOCs) samples before and after the lamps on. We found that while far-UVC operation increased ozone concentrations, the elevation in the occupied room was modest (median increase 1.44 ppb). We didn’t observe discernible secondary aerosol and VOCs formation. Participant surveys indicated that air quality remained acceptable throughout the experiments. These results suggest that in ventilated, occupied offices, far-UVC can be deployed with minimal impact on...

Decarbonizing large commercial buildings through heat recovery

Thu, 25 Jun 2026 00:00:00 +0000

Presented at the CEC EPRI Electrification Summit on June 10, 2026, this poster describes an ongoing California Energy Commission-funded research initiative (Grant Award #EPC-23-032) led by the California Institute for Energy and Environment (CIEE) and the Center for the Built Environment (CBE) at the University of California, Berkeley, which aims to provide a cost-effective pathway to substantially reduce carbon emissions from large commercial buildings through heat pumps and thermal storage, with key project components including the demonstration of a large, new heat recovery chiller using an ultra-low GWP refrigerant (R-1234ze, GWP=1, zero ozone depletion) at the Kaiser Permanente South San Francisco Medical Center — where the system is designed to provide chilled water while simultaneously rejecting heat at 140–170°F for building heating at a combined COP as high as 6.7 and cover greater than 50% of the annual heating load — alongside data-driven analysis of operating data...

Mainstreaming Personal Comfort Devices (PCDs): Enabling Modular Personal Controls for a Wide Range of Energy and Comfort Applications

Thu, 25 Jun 2026 00:00:00 +0000

This poster, presented at the 2026 CEC EPRI Electrification Summit, details an ongoing project (Grant Award #: EPC-23-033) aimed at mainstreaming Personal Comfort Devices (PCDs) to provide targeted occupant comfort and reduce HVAC energy and emissions in large commercial buildings. The research focuses on developing a "Personal Control Ecosystem" centered on a Personal Control Hub (PC Hub), an open-source hub built on an ESP32 microcontroller with integrated sensors for occupancy, temperature, humidity, PM2.5, CO2, and VOCs. Novel PCDs developed include a nanofabric handwarmer using nanotube material and a heated/cooled desktop pad for wrist comfort. Integration strategies with Building Management Systems (BMS) utilize networking (BACnet) and semantic layers (Brick or ASHRAE 223) to facilitate load shifting and widened temperature deadbands. Field study results indicate that using PCDs can maintain equivalent comfort while achieving over 30% savings in heating energy by lowering...

Envelope-driven comfort risk in residential demand response

Fri, 12 Jun 2026 00:00:00 +0000

Residential demand response (DR) is a valuable resource for grid reliability, but remains challenging because the highly heterogeneous residential building stock leads to widely varying and hard-to-predict load and comfort responses during DR events. Although prior research has estimated the technical potential of DR-capable technologies for achieving energy demand savings, little is known about how they affect thermal comfort. In particular, it remains unclear how indoor thermal conditions due to DR depend on the thermal envelope characteristics of the housing stock. To address this gap, this study provides a systematic, location-specific assessment of indoor thermal performance during DR-events across the US housing stock using both typical DR weather data and detailed building metadata. We evaluate how envelope characteristics influence indoor temperatures during realistic simulated summer and winter DR events across 37 US locations, applying both temperature threshold and...

Personal comfort systems for adults with intellectual disabilities

Fri, 12 Jun 2026 00:00:00 +0000

This study examines how personal comfort systems (PCS) support thermal adaptation among adults with intellectual disabilities living in energy-poor households in Chile. Participants (n = 8) in two identical social-housing units completed two in-home field campaigns: winter (June–August 2023; 10 weeks) and summer (December 2023–March 2024; 14 weeks). The study combined an adapted daily point-in-time thermal comfort questionnaire, continuous indoor dry-bulb temperature monitoring (15 min), and pre-/post-season interviews. Indoor conditions frequently fell outside reference comfort thresholds (92.6% of winter temperatures < 21.5°C; 64.1% of summer temperatures > 26°C). Using participant-level paired comparisons with thermal preference ‘No change’ as a comfort proxy, PCS use showed no systematic winter increase (median Δ = –0.014; p = 0.944) but a consistent summer increase (median Δ = 0.126; p = 0.014). Interview accounts indicated that PCS supported everyday adaptation, while...

A simulation study on condensation risk in radiant cooling panels with elevated air movement

Mon, 8 Jun 2026 00:00:00 +0000

Radiant cooling panels are an energy-efficient heating, ventilation, and air conditioning (HVAC) alternative to conventional all-air systems, as they operate with higher chilled water temperatures and rely on water as the primary heat transfer medium. However, their wider adoption has been constrained by the risk of surface condensation, which limits allowable surface temperatures and reduces cooling capacity. Elevated air movement, such as that induced by ceiling fans, has been proposed as a strategy to enhance cooling capacity and maintain thermal comfort, yet its impact on condensation behavior remains insufficiently understood, particularly under conditions where panel surfaces operate below the dew point. This study employs transient computational fluid dynamics (CFD) simulations using the interThermalPhaseChangeFoam solver in OpenFOAM to investigate the effects of air speed on condensation phenomena over a uniformly cooled radiant panel. A simplified numerical wind tunnel...

Measured influence of supply airflow rate and supply air temperature on air mixing time in a room with overhead mixed system

Mon, 8 Jun 2026 00:00:00 +0000

Air mixing and movement are often driven by the design and operating conditions of the heating, ventilation, and air conditioning (HVAC) system, and are influenced by occupants and thermal gradients at windows and walls. Air mixing affects the indoor-generated pollutants dispersion and thus influences the effectiveness of ventilation and within-room air cleaning systems, including upper-room germicidal ultraviolet disinfection (GUV). In rooms with a ceiling exhaust and/or upper-room GUV, upward airflow from occupants can enable faster pollutant removal compared to well-mixed conditions. We used pulsed ethanol as a tracer and measured concentration at 2 s time resolution using fast-response metal oxide sensors at three levels: near the floor at 0.1–0.4 m, mid-height at 1.1–1.4 m, and at 2.4 m, 0.3 m from the 2.74 m ceiling. Forty experiments were conducted under the following conditions: HVAC off; supply air at ~380 (low) or ~1200 m3 h-1 (high) at neutral, cooling, or heating temperatures...

Room surface convective heat transfer with ceiling fans and its effect on radiant cooling systems

Mon, 8 Jun 2026 00:00:00 +0000

The integration of ceiling fans with radiant systems remains underexplored despite their potential to address cooling capacity limitations. This study adopts a two-step approach to quantify the impact of elevated air movement on thermally activated building systems (TABS). First, we used OpenFOAM to calculate convective heat transfer coefficients under varying airflows, air-to-surface temperature differences, and zone sizes. These coefficients also apply to ceiling fans in buildings without radiant systems. Second, we implemented these coefficients in EnergyPlus to evaluate key radiant design parameters. Scenario 1 results show median steady-state cooling heat transfer rates increase of up to 47% relative to the no-fan cases when operative temperature is held constant. Scenario 2 demonstrates a median cooling effect of up to 4.8 K under fixed capacity, reflecting both lower zone temperatures and direct air movement on occupants. Overall, TABS-fans systems offer a scalable strategy...

Energy Performance of ASHRAE Guideline 36 Hydronic Sequences in Existing HVAC Systems Enabled by Portable, Semantic Interoperability Tools

Fri, 3 Apr 2026 00:00:00 +0000

ASHRAE Guideline 36 defines standardized high-performance control sequences for heating, ventilation, and air conditioning (HVAC) systems, yet limited field evidence exists on its plant-level applications. In this project, the team implemented Guideline 36 supply water temperature reset sequences for two hot water plants and a chilled water plant using a layered architecture of supervisory control, Building Automation and Control Networks (BACnet) communication, Control Description Language (CDL) based programming developed by ASHRAE Standard 231p, and Brick ontology to ensure scalability and interoperability. Measurement and verification (M&V) with weather normalization showed savings of 3.28 kBTU/ft²-year (10.38 kWh/m2-year)(7.5%) and 10.15 kBTU/ft²-year(32 kWh/m2-year) (11.5%) for the hot water plants, and 6.61 kWh/m2 (2,097 BTU/ft2) (14.6%) for the chilled water plant, translating to cost reductions of $0.095/ft2-year ($1.02/m2-year), $0.17/ft2-year ($1.82/m2-year), and...

Temporal resolution matters: Evaluating carbon emission factors for accurate accounting in commercial buildings

Fri, 3 Apr 2026 00:00:00 +0000

Accurately quantifying operational carbon emissions from buildings is essential to verify that decarbonization targets are met. Yet many current practices rely on overly simplified yearly average emission factors that overlook the temporal variability of the electrical grid generation. This issue becomes increasingly critical with the rising penetration of renewable energy and the adoption of demand-side strategies in buildings, such as load shifting. Existing literature on net-zero carbon buildings rarely examines how the temporal resolution of emission factors affects accounting accuracy. In this study, we evaluated a range of grid emission factors (annual, seasonal, time-of-day, season-hour, and month-hour) and quantified their impact on carbon emissions accounting accuracy for commercial buildings across 18 U.S. grid regions. These emission factors, derived from publicly available datasets, are applied to measured hourly electricity consumption profiles from over 600 real...

Cross-climate analysis of energy flexibility in high thermal mass radiant systems

Fri, 3 Apr 2026 00:00:00 +0000

High thermal mass radiant systems have strong potential for energy flexibility, but key parameter relationships remain unclear. This study conducts a comprehensive parameter sensitivity analysis of Thermally Activated Building Systems (TABS) and Embedded Surface Systems (ESS) using hundreds of thousands of simulations. Two representative cases, Hangzhou, China (humid subtropical) and San Francisco, USA (marine), are analyzed in depth, followed by cross-climate testing in eight additional cities spanning hot to mild climates. Results show that start/stop is the primary driver of load shifting potential, while start time has little effect on cooling energy supply. For Floor ESS, however, operation duration is critical: extending operation from 8 to 24 hours increases daily cooling supply by 25.9% in Hangzhou and 35.4% in San Francisco, compared to only 5-9% in other terminal types. Using San Francisco as an example, a comparison of fixed nighttime pre-cooling and flexible scheduling...

ASHRAE Guideline 36 Open Source Supervisory Control Technology Development and Demonstration

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

ASHRAE Guideline 36 (G36) establishes industry best practice standardized sequence of operations for heating, ventilation, and air conditioning systems, including airside systems, chilled water plants, and hot water plants. Previous research studies have implemented airside system sequence of operations to show up to 35 percent energy savings over existing control strategies. This project demonstrated a scalable approach to implementing G36 sequence of operations for chilled water and hot water plants in existing buildings.

The team used the supervisory control layer to coordinate G36 logic with existing building automation systems without requiring major infrastructure changes. Using Control Description Language, the team implemented control logic to promote transparency, modularity, and alignment with G36 specifications, and applied Brick ontology to tag heating, ventilation, and air conditioning system data points.

To evaluate performance, the research team conducted...

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...

Quick Guide on Changing Refrigerant Requirements

Mon, 23 Feb 2026 00:00:00 +0000

This quick guide is intended to provide a simple summary of changing refrigerant requirements for HVAC applications based on Federal and California regulations. Though there are broader implications for other industries (including industrial and transportation), this guide focuses on commercial HVAC applications.

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.

Field Implementation of a Cost-Optimized Supply Air Temperature Reset Strategy in Multizone VAV Systems

Wed, 4 Feb 2026 00:00:00 +0000

Multi-zone variable air volume (MZ VAV) heating, ventilation, and air conditioning (HVAC) systems are commonly used in commercial buildings, but their performance varies widely, leading to a significant performance gap between best practice and typical operation. The supply air temperature (SAT) reset strategy significantly influences the energy efficiency of VAV systems. This paper presents the field implementation and validation of a novel SAT control method, Cost-Optimized Reset (CORE) in three commercial buildings in California. To evaluate the real-world performance of CORE, we conducted a measurement and verification (M&V) analysis using a randomized crossover trial approach over the course of the monitoring period. Energy consumption, HVAC operational parameters, and utility rates were analyzed and showed 5-22% energy savings in combined heating, cooling and fan energy, and 1-20% savings in related energy cost for CORE compared to the existing SAT reset strategy with...

Real-World Performance of Heat Recovery Chillers with Exhaust Air Coils in an All-Electric Medical Building

Thu, 20 Nov 2025 00:00:00 +0000

Heat recovery chillers (HRCs) are systems that utilize waste heat from the condenser side for heating purposes. As an electrification strategy, they offer the potential to reduce operational carbon emissions associated with heating, while providing higher coefficient of performance (COP) than air-to-water heat pumps and a much smaller equipment footprint. However, limited research has been published on the real-world performance of HRCs in this configuration. This study investigates the performance of HRCs in a newly constructed all-electric building located in ASHRAE climate zone 3C. The building is a five-story, 182,800 ft2 (17,000 m2) outpatient surgery and medical office facility. In this facility, HRCs serve as the primary plant equipment to meet the building’s heating and cooling loads, with exhaust air coils functioning as either a heat sink or source to balance loads on the HRCs. The building entirely relies on the HRCs and exhaust air coils for all cooling capacity and...

Field Study of HVAC Cost Optimized Supply Air Temperature Reset (CORE)

Thu, 20 Nov 2025 00:00:00 +0000

Multi-zone variable air volume heating, ventilation, and air-conditioning systems are widely used in commercial buildings, but their performance varies significantly. Recent studies have found 4 to 15 percent variation in heating, ventilation, and air-conditioning energy consumption between different supply air temperature reset strategies in multi-zone variable air volume heating, ventilation, and air conditioning systems. Cost Optimized Reset is a dynamic, cost-responsive, supply-air-temperature set solution that minimizes heating, ventilation, and air conditioning cost by optimizing heating, cooling, and fan energy use. The objectives of this research demonstration project were to 1) refine the Cost Optimized Reset algorithm for wider adoption in commercial buildings in California, and 2) demonstrate the operation of Cost Optimized Reset in at least two buildings, evaluating energy and cost impacts.

The results indicated that Cost Optimized Reset, when compared to...

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...

Simulation-Based evaluation of Cost-Responsive supply air temperature control strategy for office buildings across different climates

Thu, 6 Nov 2025 00:00:00 +0000

The supply air temperature (SAT) setpoint control strategy is a vital part of a variable air volume (VAV) system. This paper presents a new cost-responsive (CORE) SAT control algorithm for the VAV system which does not require discharge air temperature data for easier implementation, along with a new humidity control strategy that constrains the maximum SAT based on outdoor dewpoint temperature to meet dehumidification requirements in humid climates. We conducted a comprehensive parametric simulation study using a representative office building model to assess energy cost savings of the new CORE control algorithm against other widely adopted control strategies, including the best industry practice ASHRAE Guideline 36 (G36). We created an EnergyPlus-Python-based simulation environment to implement all control algorithms. Results showed that the new CORE algorithm consistently yielded higher energy cost savings than others, despite variations in climate, energy tariff structure,...

Teaching Life Cycle Assessment: An Accessible Approach for Future Architects and Building Professionals

Wed, 17 Sep 2025 00:00:00 +0000

Architects play a vital role in decarbonization efforts. Architects need the skills to assess the environmental impacts of their designs while understanding how early-stage design decisions shape the environmental impacts of their final designs. However, most academic structures do not provide future architects with the skills and knowledge needed to perform life cycle assessment (LCA) nor understand the linkages between design decisions and environmental impacts. Based on experiences from teaching LCA and life cycle thinking to architecture students in Brazil and the United Kingdom, we outline our vision for providing architecture students with the skills needed by industry to navigate the ever-changing climate crisis. We highlight that not everyone needs to do a full-scale assessment, but everyone should be able to engage in conversations related to sustainability and impact reduction.

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...

Assessment of Embodied Water Impacts for Landscape Architecture Strategies: A Life Cycle Assessment Approach

Thu, 24 Jul 2025 00:00:00 +0000

Addressing the pressing issue of water scarcity and environmental impact, this research investigates the embodied water impacts of landscape architecture strategies. Employing life cycle assessment (LCA) and water footprint methodologies, the study explores hardscape, vegetation, and building elements within urban landscapes. Through a case study of the Bauer Wurster Hall East Courtyard at UC Berkeley, various landscape design scenarios are analyzed for their embodied water impacts. The findings reveal large differentials in embodied water between scenarios. The original site design showcases a total of 1440 kL embodied water, while the remodeled version amplifies to 5820 kL. Notably, concrete and steel emerge as primary contributors to embodied water, despite their relatively low mass proportions on-site. Concrete paving, in particular, demonstrates a significant impact, outweighing other paving materials like asphalt and brick. The findings emphasize the need for informed decision-making...

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...

Commercial Building HVAC Functional Performance Test Automation Using Brick Metadata Schema

Mon, 23 Jun 2025 00:00:00 +0000

Heating, ventilation, and air-conditioning (HVAC) system functional performance test is a critical commissioning step in ensuring the design, installation, and operation of the building's mechanical system is verified against its intent. HVAC systems in commercial buildings are complex and traditional methods, which are manual and time-consuming, are sometimes incomplete. This is particularly concerning for HVAC controls, where an analyst would first identify all relevant sensor measurements from the building management system, cross-reference them with design drawings, and then compile a sequence of operations to test before implementation and analysis. This process becomes harder to manage as the system scales. In this study, we demonstrate it is possible to enhance HVAC equipment and control sequence commissioning by using a metadata schema called Brick in the performance test. The Brick schema allows for querying required measurement points from the BMS in a standardized,...

Integrating symbolic neural networks with building physics: A study and proposal

Thu, 19 Jun 2025 00:00:00 +0000

Symbolic neural networks, such as Kolmogorov–Arnold Networks (KAN), offer a promising approach for integrating prior knowledge with data-driven methods, making them valuable for addressing inverse problems in scientific and engineering domains. This study explores the application of KAN in building physics, focusing on predictive modeling, knowledge discovery, and continuous learning. Through four case studies, we demonstrate KAN’s ability to rediscover fundamental equations, approximate complex formulas, and capture time-dependent dynamics in heat transfer. While there are challenges in extrapolation and interpretability, we highlight KAN’s potential to combine advanced modeling methods for knowledge augmentation, which benefits energy efficiency, system optimization, and sustainability assessments beyond the personal knowledge constraints of the modelers. Additionally, we propose a model selection decision tree to guide practitioners in appropriate applications for building physics.

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...

Building and occupant characteristics as predictors of temperature-related health hazards in American homes

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

Many cities and regions are making significant investments towards planning for extreme temperature and in particular extreme heat. A heat vulnerability index (HVI) is a metric to track spatial variation in extreme temperature risk to target mitigation interventions. Most HVIs focus on demographic characteristics, which generally relate to vulnerability, and lack information about the building stock, which mediate the occupant’s exposure to extreme temperatures. In this study, we use the Energy Information Administration’s (EIA) Residential Energy Consumption Survey (RECS) to estimate prevalence of temperature-related illness in the United States and develop machine learning models using climate, demographic, and building characteristics to predict them. Temperature-related illness affects approximately 2 million households annually, around 1% of the total population. The models we developed predict temperature-related illness with up to 85% accuracy. The most important feature...

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...

The Villages at 995 East Santa Clara St, San Jose: Energy & Emission Report

Tue, 18 Feb 2025 00:00:00 +0000

Our study uses EnergyPlus simulations to examine whole-building demand and energy end-use profiles for different design options and then uses these outputs to evaluate cost and carbon impacts of each scenario in Xendee, a modeling platform designed to “right size” and balance investments in distributed energy resources (DER).

Our results show that efficiency measures are key to meet the ambitious performance metrics for this project; however, most of the technology potential occurs for heating, ventilation and air conditioning (HVAC) or domestic hot water (DHW) loads which are a relatively small portion of a mid-rise multifamily building’s overall energy use. The most meaningful strategies to reduce or shift loads for this building include DHW load shifting, energy recovery ventilation, dynamic ventilation, and ceiling fans. Envelope strategies improve overall annual building performance but become an issue when lower heat loss increases cooling during the...

How high can You Go: Determining the warmest supply water temperature for high thermal mass radiant cooling systems under thermal comfort constraints

Fri, 14 Feb 2025 00:00:00 +0000

The need for cooling in buildings is mainly handled using systems based on the refrigeration cycle, often an energy- and cost-intensive process. High thermal mass radiant systems (HTMR) enable the use of warmer than typical chilled water temperatures to provide cooling. In favorable weather conditions, the cooled water can be produced through low-energy and low-cost cooling devices. In this two-phased study, we first determined the warmest supply water temperature (SWT) needed in HTMR that maintains thermally comfortable conditions on the cooling design day. Then, we investigated the potential of replacing the refrigeration cycle with evaporative cooling devices in the primary cooling system. We performed a quasi-random sampling of building and HTMR system design parameters representing typical building characteristics and design cooling loads for lighting, people, and plug loads to create 360,900 single zone EnergyPlus models. We iteratively simulated the models on the climate...

Assessing thermal comfort and participation in residential demand flexibility programs

Tue, 14 Jan 2025 00:00:00 +0000

Residential space-conditioning-based demand flexibility (DF) has become an increasingly sought-after method for demand-side load management to enhance grid reliability and facilitate integration of renewable energy generation. However, predicting the effectiveness and flexibility of residential DF resources is challenging. Current estimates show that only 50% of projected savings from DF resources are actualized. Currently, there is a very limited understanding of how thermal comfort during space-conditioning-based DF events in real-world settings impacts household energy use behaviors and, consequently, the success of DF programs in achieving targeted savings. This paper proposes a method to comprehensively assess the thermal comfort implications of DF strategies and presents results of their impacts on DF event participation decisions and demand savings. The study's key findings are: 1) DF event setpoint offsets that maintain indoor operative temperatures between 18 to 22°C...

Results from Lab Testing: Rethinking VAV Hot Water Terminal Unit Design

Mon, 13 Jan 2025 00:00:00 +0000

A number of operational issues exist with typical variable air volume (VAV) reheat terminal units. These include temperature stratification at the heating coil discharge and the reduced capacity and higher flow rates required for increasingly popular low temperature hot water systems. This article summarizes the findings of a recent research project that sought to better understand and help overcome these issues.

Quantifying Office Building HVAC Marginal Operating Carbon Emissions and Load Shift Potential: A Case Study in California

Tue, 7 Jan 2025 00:00:00 +0000

The operational carbon emissions intensity of the electricity used in a building is commonly treated as a fixed value but grid carbon emissions factors have temporal and geographical variations, which makes building operating emissions dependent on when and where electricity is used. Grid electricity carbon characteristics can be quantified by either average or marginal emission rates, leading to an increasing debate about which metric provides more accurate results for determining the effect of various decarbonization strategies. We advocate for the use of the marginal operating emissions rate (MOER) to evaluate the impacts of demand-side management because it considers the generating plants' dispatch order and is able to reflect the change in emissions induced by demand management. In this study, we examined the benefits of emission-based load-shifting strategies by first analyzing the annual temporal variations of the Northern California grid region and developed a virtual...

Field Study of Thermal Infrared Sensing for Office Temperature Control

Tue, 7 Jan 2025 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...

Robo-Chargers: Optimal Operation and Planning ofa Robotic Charging System to Alleviate Overstay

Tue, 7 Jan 2025 00:00:00 +0000

Charging infrastructure availability is a major concern for plug-in electric vehicle users. Nowadays, the limited public chargers are commonly occupied by vehicles which have already been fully charged. Such phenomenon, known as overstay, hinders other vehicles’ accessibility to charging resources. In this paper, we analyze a charging facility innovation to tackle the challenge of overstay, leveraging the idea of Robo-chargers -automated chargers that can rotate in a charging station and proactively plug or unplug plug-in electric vehicles. We formalize an operation model for stations incorporating Fixed-chargers and Robo-chargers. Optimal scheduling can be solved with the recognition of the combinatorial nature of vehicle-charger assignments, charging dynamics, and customer waiting behaviors. Then, with operation model nested, we develop a planning model to guide economical investment on both types of chargers so that the total cost of ownership is minimized. In the planning...

Field Study of Thermal Infrared Sensing for Office Temperature Control

Tue, 7 Jan 2025 00:00:00 +0000

Field Study of Thermal Infrared Sensing for Office Temperature Control

Energy Flexibility and Sensitivity Analysis of High Thermal Mass Radiant Terminals

Tue, 3 Dec 2024 00:00:00 +0000

High thermal mass radiant systems as a hydronic thermal mass activation method have many opportunities for cost-effective demand management. The system is regarded with the possibility of long-term transferring peak heating and cooling loads to off-peak hours and peak load reductions. This study conducted over 300,000 case calculations for a sensitivity analysis of load shifting parameters in radiant space conditioning systems across 16 climate zones in California, 14 different climatic cities outside California. The parameters analyzed include building geometric parameters (building length, width, window-to-wall ratio, orientation), internal heat source levels (from people, lights, plugs), control parameters (start and stop times), and the design construction of radiant terminals. A comparative analysis was also conducted across cities in different climatic conditions to explore the impact of climate on the load shifting capabilities of radiant space conditioning. The results...

Assessing Overheating Risk and Energy Impacts in California's Residential Buildings

Sun, 24 Nov 2024 00:00:00 +0000

Extreme heat causes more weather-related deaths in the United States than any other natural hazard, and these events are projected to increase in frequency, intensity, and duration. As a result, it is critical to ensure safe thermal conditions in homes while minimizing excessive cooling energy use. In California, where the median age of homes is 45 years and nearly 40% lack mechanical cooling, this deficiency undermines one of the most essential goals of housing: to shelter people from outdoor weather of a warming planet. We aim to quantify the overheating risk in the housing sector to support the development of public policies related to maximum safe indoor thermal limits and building energy use. Using the ResStock modeling framework, we created over 52,000 building models to represent California's residential housing stock and assessed overheating risks by simulating indoor temperatures and analyzing the energy impacts of adding cooling systems.Our findings reveal significant...

Passive and low-energy strategies to improve sleep thermal comfort and energy resilience during heat waves and cold snaps

Mon, 4 Nov 2024 00:00:00 +0000

In high- and middle-income countries, there is a great reliance on heating, ventilation, and air conditioning systems (HVAC) to control the interior thermal environment. However, these systems are expensive to buy, maintain, and operate while being energy and environmentally intensive. Easily-accessible passive and low-energy strategies, such as fans and electrical heated blankets, address these challenges but their comparative effectiveness for providing comfort in sleep environments has not been studied. Using passive strategies in combination with low-energy strategies that elevate air movement like ceiling or pedestal fans enhances the cooling effect by three times compared to using fans alone. We extrapolated our experimental findings to estimate heating and cooling effects in two historical case studies: the 2015 Pakistan heat wave and the 2021 Texas power crisis. Passive and low-energy strategies reduced sleep-time heat or cold exposure by 69-91%. The low-energy strategies...

Spatial Thermal Autonomy (sTA): A New Metric for Enhancing Building Design Towards Comfort, Heat Resilience and Energy Autonomy

Mon, 4 Nov 2024 00:00:00 +0000

Achieving thermal comfort in buildings while maintaining energy efficiency is a critical challenge in architecture and engineering design and operation. Traditional thermal comfort metrics used in the early stages of design tend to neglect two key aspects: spatial variability of thermal conditions within buildings and the promotion of passive design strategies over active conditioning systems. This oversight leads to localized discomfort, excessive energy use, and increased vulnerability to overheating. To address these issues, we propose a novel metric called spatial Thermal Autonomy (sTA). The primary advantage of sTA is its ability to capture spatial variability in thermal conditions, offering a more comprehensive view of comfort across different building zones. Additionally, sTA supports passive design by quantifying a building's capacity to maintain comfort without active energy use. We performed a simulation case study evaluating sTA for different thermal zone sizes, passive...

Material Selection and System Layout to Lower Embodied Carbon of Pipe in an Office Building

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

The use of life cycle assessment (LCA) to evaluate the environmental impacts of buildings has largely ignored the embodied impacts of mechanical, electrical and plumbing (MEP) systems that rely on significant proportions of metals and contain a multitude of complex components. A better understanding of the environmental impacts of MEP systems is needed to achieve a net-zero carbon future. The study serves as an initial step in developing benchmarks and impact reduction strategies for MEP systems. It considers the material substitution from standard practice to PEX pipe throughout (Radiant: PEX in slab, copper and steel elsewhere; VAV: steel and copper) and for both typical single-riser pipe layout and multi-riser layout for both HVAC system types. When assessed for a four-story office building, the A1-A4 GWP100 impacts for the pipe in the standard layout for the radiant and VAV systems are 1.1 kgCO2e/m2 and 0.8 kgCO2e/m2, respectively. Implementing a like-for-like material...

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...

Harmonized Resilience at Roosevelt Village: How Futuristic Grid-Interactivity and Resilience Come Together in Senior Affordable Housing

Fri, 11 Oct 2024 00:00:00 +0000

To decarbonize the buildings and electricity sectors at a pace consistent with state and national climate goals, buildings must become grid resources, capable of morphing load profiles to accommodate variable renewable generation, facilitate cost-effective grid decarbonization, and help ensure reliable power system operation. Simultaneously, the changing climate poses increasing risks of extreme weather events and resulting power outages that developers, designers, and building operators must plan for. This yield s new questions around the best approaches to achieve these outcomes, what it costs, who benefits, and what barriers there are to widespread adoption.We seek to answer these questions by adopting a futuristic set of grid-interactive design requirements for a mid-rise affordable housing, mixed-use development: to sustain critical loads during an outage and to consume no grid electricity for residential end-uses between 4-9pm every day. We present an approach that achieves...

Load Shifting and Enhancing Energy Savings with Dynamic Ventilation Strategies in Multi-Family Residential Buildings

Fri, 20 Sep 2024 00:00:00 +0000

There is an increasing focus on the time at which energy is used in buildings both to reduce utility costs and carbon emissions in response to time-dependent grid signals. One method to shift electrical load out of peak pricing hours is to use batteries, but they have high first costs and also incur an energy penalty due to round trip efficiency and other losses. Another method is to use thermal storage to offset heating and cooling. Similarly, mechanical ventilation systems can also be controlled to shift energy use to periods of the day with lower energy, cost, and environmental impacts by varying the ventilation rate while still meeting ventilation code requirements. Mechanical ventilation systems in large multi-family residential buildings are mostly central air systems with either manually balanced dampers or constant airflow regulator (CAR) dampers that aim to provide a constant ventilation airflow rate to each apartment. ASHRAE 62.2 allows for dynamic ventilation rate systems...

Are we prioritizing the right thing? Cutting carbon emissions in California's large office buildings before installing a heat pump

Tue, 27 Aug 2024 00:00:00 +0000

We studied a combination of heating system measures in two large commercial officebuildings in San Francisco (110,000 and 120,000 ft 2 respectively) within a project funded by the California Energy Commission’s Public Interest Efficiency Research program. We retrofitted theexisting heating plants and updated the HVAC controls to ASHRAE Guideline 36-2021 as closely as possible while retaining the existing controller hardware. These measures decreased annual natural gas consumption by about 70 percent while also reducing HVAC electricity consumption. The results reinforce previous work showing significant natural gas reductions in 3 other buildings that underwent full controls retrofits (including controller hardware), and large savings from another 3 buildings that underwent partial controls upgrades. We show that on today’s electricity grid, which is quite dirty during the winter and early morning hours when most heating occurs, the carbon emissions reduction from these measures...

Re-optimizing Optimal Start and Morning Warmup

Tue, 27 Aug 2024 00:00:00 +0000

Conventional wisdom and standard industry practice is to setback zone temperature setpoints when commercial buildings are unoccupied at night. The HVAC systems then operate in warmup mode to recover zone temperatures prior to the start of occupancy, sometimes with an optimal start algorithm. These strategies were intended to reduce HVAC energy consumption when originally developed decades ago but are due for re-examination given the significant changes in HVAC systems that have since occurred. In particular, the changes currently underway with the movement toward electrification present new design considerations and priorities. Warming up a building as fast as possible may not be the best strategy in terms of energy use, operating cost, or carbon emissions. This article discusses some of the downfalls of conventional morning warmup practices, suggests an improved strategy, and shows the results from a pilot field demonstration test.

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...

Reducing Gas Consumption in Existing Large Commercial Buildings

Thu, 23 May 2024 00:00:00 +0000

Natural gas combustion to serve space heating hot water systems causes approximately one third of large commercial building energy use in California. This project evaluated an innovative set of non-proprietary, cost-effective methods to reduce energy consumption and associated emissions from these systems. The project demonstrated 70% natural gas savings and substantial electricity savings in two large office buildings, yielding total utility cost savings of approximately $110,000 (or $0.5/ft²) per year. The project also conducted detailed studies on distribution losses and boiler efficiency in several buildings; measured performance of key components in laboratory tests; gathered and analyzed data from hundreds of buildings to evaluate actual performance of these systems; and provided a public dataset to inform future retrofits, research, and code development. The research also highlighted characteristics that make a building a good candidate for retrofit so these results can...

Hot Water Heating: Design and Retrofit Guide

Tue, 21 May 2024 00:00:00 +0000

Hot Water Heating: Design and Retrofit Guide

Impact of Window vs Windowless Exam Rooms on Cognitive Performance: A Field Study During a University Exam

Thu, 11 Apr 2024 00:00:00 +0000

This study aims to measure the impact of having visual connections to nature through windows on the cognitive performance of university students, as assessed by their final exam scores. To build upon prior research conducted in controlled laboratory and climate chamber settings, which may have a gap between findings and real-world contexts, demonstrating the positive effects of window views on occupants, this study addressed the limitations of lab-based experiments by conducting a field test in university lecture rooms with 121 students enrolled in STEM classes, taking their actual final exam. In the field test, we randomly assigned the students to either of two conditions: one with windows and one without, while monitoring indoor environmental factors. The results revealed no significant difference in cognitive performance—whether measured by scores or cognitive efficiency gauged by the time taken to complete the exam—between students in conditions with and without window views....

Heating Hot Water Policy Recommendations

Thu, 28 Mar 2024 00:00:00 +0000

Heating Hot Water Policy Recommendations

Fans for cooling people guidebook

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

Using fans alone or in coordination with HVAC systems to cool people offers several significant enhancements compared to conventional HVAC systems, including improved thermal comfort, indoor air quality, air distribution, energy savings, and initial cost savings. Despite the numerous benefits of fans and fan-integrated systems, comprehensive resources are unavailable to guide engineers and architects in designing and implementing such systems. The purpose of this guideline is to address this gap and provide practitioners with valuable materials and answers to common questions. What are the available fan options? Various fan types are available in the market, such as ceiling fans, desk fans, and pedestal fans. This guideline provides a comprehensive overview of the criteria for fan type selection. These criteria cover blade characteristics, fan size, airflow patterns, fan performance metrics, motors and drives, power and efficiency, and control strategies. Ceiling fans are generally...

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...

Variable Air Volume Hot Water Reheat Terminal Units: Temperature Stratification, Performance at Low Hot Water Supply Temperature, and Myths from the Field

Tue, 6 Feb 2024 00:00:00 +0000

Variable Air Volume Hot Water Reheat Terminal Units: Temperature Stratification, Performance at Low Hot Water Supply Temperature, and Myths from the Field

Heating Hot Water Distribution Heat Losses: Detailed Measurement

Fri, 2 Feb 2024 00:00:00 +0000

Variable air volume systems with hydronic reheat at terminal units are a common Heating Ventilation Air Conditioning (HVAC) system type in medium and large commercial buildings. This study measured HHW heat loss in detail in a 66,000 ft² (6,200 m²) office and lab building, built in 2000, in Davis, California. We used methods adapted from Raftery et al. (Raftery, Geronazzo, et al. 2018) to calculate the HHW distribution losses from BAS measured data, and then measured unintentional heat loss at the whole building level including losses from distribution and passing HHW valves. We further measured HHW distribution losses in greater detail on a single HHW distribution branch removing loss contributions from other potential issues, such as passing HHW valves.

For the whole building, using newly installed, calibrated water flow meter and matched pair calibrated RTD HHW supply and return temperature sensors, typical HHW setpoints, with all air handlers...

Fans for cooling people guidebook

Fri, 2 Feb 2024 00:00:00 +0000

What are the available fan options?Various fan types are available in the market, such as ceiling fans, desk fans, and pedestal fans. This guideline provides a comprehensive overview of the criteria for fan type selection. These criteria cover blade characteristics, fan size, airflow patterns, fan performance metrics, motors and drives, power and efficiency, and control strategies. Ceiling fans are...

Variable Air Volume Hot Water Reheat Terminal Units: Temperature Stratification, Performance at Low Hot Water Supply Temperature, and Myths from the Field

Fri, 2 Feb 2024 00:00:00 +0000

Hot water coils are common in commercial building HVAC systems. Nevertheless, their design, installation, and control are frequently sub-optimal, with respect to maximizing heat exchange effectiveness and air temperature setpoint control. For example, conditions on-site sometimes lead to coils being installed in parallel flow instead of counter flow configuration, and temperature stratification in the leaving air can lead to control issues. Additionally, low hot water supply temperatures (HWST) of ~120⁰F (49⁰C) are becoming more common with the rise of heat pump and efficiency retrofits. As hot water systems are typically designed for high HWST (160 - 180⁰F, 71 - 82⁰C), lower waterside “delta T” temperature differences (HWST – HWRT) would occur using low HWST in retrofits of conventional hot water heating systems. If buildings retain existing coils for the low-HWST systems common to efficiency retrofits, they will be unable to maintain the same design heat capacity without replacing...

Screening Method to Identify High VAV Minimum Airflow Rates and Retrofit Opportunities

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

Excessively high minimum airflow setpoints for Variable Air Volume (VAV) boxes, caused by outdated energy codes stipulating they should be 30% or higher of the maximum airflow, led to significant energy waste. Lower setpoints meet the ventilation code requirements while minimizing recirculation and reheat energy waste. ASHRAE RP-1515 showcased this by correcting VAV minimums in 1,000,000 ft² (92903 m²) of California office space which yielded 10-30% HVAC energy savings and improved thermal comfort. Consequently, the Title 24 Energy Standards and ASHRAE 90.1 were updated to mandate minimum airflows match ventilation requirements. Beyond increased reheat energy waste caused by elevated VAV minimums, boiler operation issues can also contribute to avoidable energy waste. Despite energy codes mandating low VAV minimums for several years, these issues remain common in new construction and existing buildings. Our goal is to simplify retrofit decision-making for...

Field Study of Thermal Infrared Sensing for Office Temperature Control

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

Field Demonstration of the Brick Ontology to Scale up the Deployment of ASHRAE Guideline 36 Control Sequences

Fri, 1 Sep 2023 00:00:00 +0000

Many commercial buildings have a vast network of sensors as part of their building automation systems (BAS) that allows opportunities for energy consumption and cost savings by deploying advanced control sequences. However, this resource is often underutilized since BAS are typically programmed with simple control sequences with limited potential to deliver on these opportunities. The recent availability of ASHRAE Guideline 36 (G36) with advanced HVAC control sequences supports control retrofits in existing buildings to unlock much of the savings potential. However, barriers such as the lack of standard naming convention of building assets and data points, proprietary equipment and BAS, and the inherent uniqueness of buildings and their systems prevent building stakeholders from adopting any “plug-and-play” implementation of G36. Instead, control vendors must often undertake the manual and labor-intensive point mapping process to identify a data stream’s functional and spatial...

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...

Toward Design Automation for Building Models

Mon, 17 Jul 2023 00:00:00 +0000

Building performance simulation is an important tool in building design and operations. Its purpose is to evaluate and optimize energy use, environmental impact, and occupant comfort of buildings. However, the current state of building performance simulation tools is highly fragmented, and the models themselves can be of low quality. In this paper, we present a platform-based design paradigm for building performance models. This approach offers a standardized design flow to ensure that the models are developed in a consistent and systematic way. Addition- ally, our approach addresses the lack of model performance metrics, allowing for the quantification of model performance. We explore the design flow and model performance quantification with a case study, demonstrating the use of the platform-based design paradigm.

Skewering the silos: using Brick to enable portable analytics, modeling and controls in buildings

Mon, 5 Jun 2023 00:00:00 +0000

Skewering the silos: using Brick to enable portable analytics, modeling and controls in buildings

View Access Index: The effects of geometric variables of window views on occupants’ satisfaction

Tue, 14 Mar 2023 00:00:00 +0000

View Access Index: The effects of geometric variables of window views on occupants’ satisfaction

Measured Space Heating Hot Water Distribution Losses in Large Commercial Buildings

Tue, 14 Mar 2023 00:00:00 +0000

Measured Space Heating Hot Water Distribution Losses in Large Commercial Buildings

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

Boiler Retrofits and Decarbonization in Existing Buildings: HVAC Designer Interviews

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

In this study, we investigate methods to reduce carbon emissions from existing large commercial buildings with central natural gas-fired boilers used for space heating. This research explores opportunities to reduce natural gas use through improved building operations and through building decarbonization. We conducted one-hour interviews with 17 mechanical HVAC designers, together having over 350 years of industry experience, professional tenures at engineering consulting firms and design/build firms, and project work in California, New York, Texas, Alaska, the United Kingdom, and Canada. We asked a mix of quantitative and qualitative questions, covering four topic areas: General Background, Peak Heating Load and Boiler Selection, Boiler Controls, and Existing Building Decarbonization. The interviews yielded insight into industry practices, including determining peak heating load, equipment redundancy, boiler staging controls, Heating Hot Water temperature resets, challenges of...

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...

The effect of thermochromic windows on visual performance and sustained attention

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

Thermochromic windows have been widely studied as a technology that can potentially offer increases in energy conservation and provide a desirable luminous environment inside buildings. However, there has been little attention placed on how the tinted states of thermochromic glazing influence occupant behaviour and visual perception. An experiment under controlled conditions was designed to test the influence of different thermochromic tint states on human response. By using a controllable artificial window, five typical luminous conditions were set up, including clear (no tint) and two different levels of blue and bronze tint states, respectively, which produced different room colour temperatures. Thirty-one subjects were recruited who completed three visual tasks, including a visual acuity and a colour naming tasks using the coloured Landolt ring chart and a sustained attention test using the d2 test. Subjective assessments were also collected using questionnaires. Statistical...

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)...

Quantification on Fuel Cell Degradation and Techno-Economic Analysis of a Hydrogen-Based Grid-Interactive Residential Energy Sharing Network with Fuel-Cell-Powered Vehicles

Wed, 1 Dec 2021 00:00:00 +0000

Hydrogen-based (H2-based) interactive energy networks for buildings and transportations provide novel solutions for carbon-neutrality transition, regional energy flexibility and independence on fossil fuel consumption, where vehicle fuel cells are key components for H2-electricity conversion and clean power supply. However, due to the complexity in thermodynamic working environments and frequent on/off operations, the proton exchange membrane fuel cells (PEMFCs) suffer from performance degradation, depending on cabin heat balance and power requirements, and the ignorance of the degradation may lead to the performance overestimation. In order to quantify fuel cell degradation in both daily cruise and vehicle-to-grid (V2G) interactions, this study firstly proposes a two-space cabin thermal model to quantify the ambient temperature of vehicle PEMFCs and the power supply from PEMFCs to vehicle HVAC systems. Afterwards, a stack voltage model is proposed to quantify the fuel cell degradation...

Transformation Towards a Carbon-Neutral Residential Community with Hydrogen Economy and Advanced Energy Management Strategies

Wed, 1 Dec 2021 00:00:00 +0000

Cleaner power production, distributed renewable generation, building-vehicle integration, hydrogen storage and associated infrastructures are promising for transformation towards a carbon-neutral community, whereas the academia provides limited information through integrated solutions, like intermittent renewable integration, hydrogen sharing network, smart operation on electrolyzer and fuel cell, seasonal hydrogen storage and advanced heat recovery. This study proposes a hybrid electricity-hydrogen sharing system in California, United States, with synergistic electric, thermal and hydrogen interactions, including low-rise houses, rooftop photovoltaic panels, hydrogen vehicles, a hydrogen station, micro and utility power grid and hydrogen pipelines. Advanced energy management strategies were proposed to enhance energy flexibility and grid stability. Besides, simulation-based optimizations on smart power flows of vehicle-to-grid interaction and electrolyzer are conducted for further...

Application of Gagge’s Energy Balance Model to Determine Humidity-Dependent Temperature Thresholds for Healthy Adults Using Electric Fans During Heatwaves

Mon, 1 Nov 2021 00:00:00 +0000

Heatwaves are one of the most dangerous natural hazards causing more than 166,000 deaths from 1998–2017. Their frequency is increasing, and they are becoming more intense. Electric fans are an efficient, and sustainable solution to cool people. They are, for most applications, the cheapest cooling technology available. However, many national and international health guidelines actively advise people not to use them when indoor air temperatures exceed the skin temperature, approximately 35°C. We used a human energy balance model, to verify the validity of those recommendations and to determine under which environmental (air temperature, relative humidity, air speed and mean radiant temperature) and personal (metabolic rate, clothing) conditions the use of fans would be beneficial. We found that current guidelines are too restrictive. Electric fans can be used safely even if the indoor dry-bulb temperature exceeds 35°C since they significantly increase the...

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.

Cooling Energy Savings and Occupant Feedback in a Two Year Retrofit Evaluation of 99 Automated Ceiling Fans Staged With Air Conditioning

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

Controlled air movement is an effective strategy for maintaining occupant comfort while reducing energy consumption, since comfort at moderately warmer temperatures requires less space cooling. Modern ceiling fans provide a 2–4 °C cooling effect at power consumption comparable to LED lightbulbs (2–30 W) with gentle air speeds (0.5–1 m/s). However, very limited design guidance and performance data are available for using ceiling fans and air conditioning together, especially in commercial buildings. We present results from a 29-month field study of 99 automated ceiling fans and 12 thermostats installed in ten air-conditioned buildings in a hot/dry climate in California. Staging ceiling fans to automatically cool before, and then operate together with air conditioning enabled raising air conditioning cooling temperature setpoints in most zones, with overall positive occupant interview and survey responses. Overall measured cooling season (April– October) compressor energy savings...

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...

Full Scale Laboratory Experiment on the Cooling Capacity of a Radiant Floor System

Mon, 14 Jun 2021 00:00:00 +0000

Direct solar radiation on a cooled radiant floor increases its cooling capacity. There is limited measured evidence of this phenomenon reported in the literature. We assessed the effect of solar radiation, increased air movement, and carpet on the cooling capacity of the radiant floor in a laboratory exposed to the outside environment. We performed experiments for different chilled water supply temperature. The cooling capacity of the chilled radiant floor was measured to increase from 32 up to 110 W/m² under direct solar radiation. The surface temperature region exposed to solar radiation reached a peak temperature of 26 °C while the unexposed areas were between 20 and 21 °C. Increasing the chilled water supply temperature from 12 to 18 °C caused a decrease in cooling capacity from ~110 to ~95 W/m². Higher air speeds along the floor created by ceiling fans increased the radiant slab cooling capacity by ~12 % (from 32 to 36 W/m²) when the operative...

Capturing Energy Savings from Correcting VAV Box Minimums on Campus

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

The Office of Sustainability at UC Berkeley leads energy and water saving campaigns on campus and has set the goal to reduce energy use intensity by an average of at least 2% annually. One of the proposed energy conservation practices is to improve ventilation efficiency. Our project primarily addresses wasted fan, cooling, and heating energy through excessive air recirculation in campus buildings. By correcting the variable air volume minimum airflow setpoints, we anticipate up to 10-30% HVAC energy savings. As a pilot project, this report documented how to implement these changes step by step and lower the barrier to entry for Facilities Services to implement this change in other campus buildings. We developed a comprehensive campus building evaluation matrix and reviewed all 31 campus buildings in the building automation system. We conducted three rounds of analysis, including screening each of the buildings in the building automation system, further reviewing building candidates’...

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...

Design and control of high thermal mass radiant systems

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

Heating, ventilation, and air-conditioning (HVAC) systems play a key role in providing healthy, productive, and thermally comfortable built environment for the occupants. Improper HVAC design will degrade occupants’ satisfaction with the built environment, potentially affecting their performance which can be valued up to 200 times the building’s energy costs. In the top two energy consuming countries, the US and China, over 40% of the energy use in buildings with HVAC systems can be attributed to those systems. Moreover, 13% of total greenhouse gas emissions in the US can also be ascribed to HVAC systems. On a global scale, electricity demand for space cooling could increase by up to 210% by 2050 from 2016 levels. This rapid growth prediction is driven by the fact that most of the world’s population and wealth growth is happening in the tropics and in middle-income countries where air-conditioning has relatively small penetration in buildings. There are serious implications to...