Recent cedr_cbe_hvac items

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...

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.

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...

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,...

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...

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.

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...

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...

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.

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

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...

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...

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

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...

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...

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’...

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...

Energy savings from temperature setpoints and deadband: Quantifying the influence of building and system properties on savings

Mon, 13 Jul 2020 00:00:00 +0000

This paper provides a systematic approach for quantifying the influence of building size, construction category, climate, occupancy schedule, setpoint, and deadband on HVAC energy consumption in office buildings. Simulating the DOE reference office buildings of three sizes and three construction categories in all United States climate zones, using the EnergyPlus, we conducted several N-way ANOVA analyses to study the interrelationships between setpoints, deadbands and several building related and environment related factors. In summary, daily optimal deadband selection of 0, 1, 2, 4, 5, and 6 K would result in an average energy savings of -70.0, -34.9, -13.7, 9.6, 16.4, and 21.2 %, respectively, compared to baseline deadline of 3 K. Selecting the daily optimal setpoint in the range of 22.5 ± 1 °C, 22.5 ± 2 °C, and 22.5 ± 3 °C would result in an average savings of 7.5, 12.7, and 16.4 %, respectively, compared to the baseline setpoint of 22.5 °C. Additionally, we found that when...

Optimizing Radiant Systems for Energy Efficiency and Comfort

Mon, 6 Jul 2020 00:00:00 +0000

Radiant cooling and heating systems provide an opportunity to achieve significant energy savings, peak demand reduction, load shifting, and thermal comfort improvements compared to conventional all-air systems. As a result, application of these systems has increased in recent years, particularly in zero-net-energy (ZNE) and other advanced low-energy buildings. Despite this growth, completed installations to date have demonstrated that controls and operation of radiant systems can be challenging due to a lack of familiarity within the heating, ventilation, and air-conditioning (HVAC) design and operations professions, often involving new concepts (particularly related to the slow response in high thermal mass radiant systems). To achieve the significant reductions in building energy use proposed by California Public Utilities Commission’s (CPUC’s) Energy Efficiency Strategic Plan that all new non-residential buildings be ZNE by 2030, it is critical that new technologies that...

Energy trade off analysis of optimized daily temperature setpoints

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

We introduce a systematic approach for analyzing the energy consumption of four control policies (i.e., zone level daily optimal control, zone level annual optimal control, building level daily optimal control, building level annual optimal control), which differed based on their temporal and spatial control scales. In order to integrate occupant thermal comfort requirements, we defined uniformly distributed random constraint functions on the setpoints. We used the DOE reference small office building in three U.S. climate zones for simulating the performances of control policies, using EnergyPlus. Among the four control policies, the building level annual control policy showed close to the highest energy efficiency (27.76% to 50.91% (average of 39.81%) savings depending on the climate) with comparatively small training data requirements. In addition, the building level daily optimal setpoint selection, subject to thermal comfort constraints, leads to 17.64 – 38.37% (average of...

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

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

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

Eliminating Overcooling Discomfort While Saving Energy

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

A large percentage of commercial buildings in North America use variable air volume (VAV) systems with reheat, and this system type is also common around the world. Summertime overcooling is widespread in such buildings and has received considerable media attention over the past few years. ASHRAE Research Project RP-1515, reported in this article, shows that much of today’s overcooling originates in unsubstantiated engineering assumptions about the performance of VAV boxes and diffusers at low-flow setpoints. These assumptions are that low flows will cause diffusers to dump cooled air and create drafts around occupants, ventilation air will be poorly mixed, and VAV airflow control will become unstable or inaccurate. Together, they have resulted in VAV minimums being commonly set at 20% to 50% of maximum. ASHRAE RP-1515 and other recent research have shown each of these assumptions to be unwarranted, and that far lower minimums are desirable.

A Prototype Toolkit For Evaluating Indoor Environmental Quality In Commercial Buildings

Wed, 18 Mar 2020 00:00:00 +0000

Measurement of building environmental parameters is often complex, expensive, and not easily proceduralized in a manner that covers all commercial buildings. Evaluating building indoor environmental quality performance is therefore not standard practice. This project developed a prototype toolkit that addressed existing barriers to widespread indoor environmental quality performance evaluation. A toolkit with both hardware and software elements was designed for practitioners around the indoor environmental quality requirements of the American Society of Heating, Refrigeration and Air Conditioning Engineers / Chartered Institution of Building Services / United States Green Building Council Performance Measurement Protocols. This unique toolkit was built on a wireless mesh network with a web-based data collection, analysis, and reporting application. The toolkit provided a fast, robust deployment of sensors, real-time data analysis, Performance Measurement Protocol-based analysis...

Ceiling-fan-integrated air conditioning: Airflow and temperature characteristics of a sidewall-supply jet interacting with a ceiling fan

Wed, 12 Feb 2020 00:00:00 +0000

Ceiling-Fan-Integrated Air Conditioning (CFIAC) is a proposed system that can greatly increase buildings’ cooling efficiency. In it, terminal supply ducts and diffusers are replaced by vents/nozzles, jetting supply air toward ceiling fans that serve to mix and distribute it within the room. Because of the fans’ air movement, the system provides comfort at higher room temperatures than in conventional commercial/ institutional/retail HVAC. We have experimentally evaluated CFIAC in a test room. This paper covers the distributions of air-speed, temperature, and calculated comfort level throughout the room. Two subsequent papers report tests of human subject comfort and ventilation effectiveness in the same experimental conditions. The room’s supply air emerged from a high-sidewall vent directed toward a ceiling fan on the jet centerline; we also tested this same jet on a fan located off to the side of the jet. Primary variables are: ceiling fan flow volumes in downward and upward...

Coordinated control of HVAC systems

Wed, 12 Feb 2020 00:00:00 +0000

This paper describes the development of new control logic for starting and stopping energy-intensive equipment in buildings such as staged air-conditioning units. The concept is to use pulse-width modulation (PWM) instead of level-crossing logic. A finite state machine is used to handle the case where a single unit has multiple stages of operation. An optimized coordinator determines the phase of the PWM signals of each unit so that peak demand for power is minimized over each PWM period. Control logic for the PWM function was developed so that the phase could be manipulated by the coordinator.

Computer simulations were used to assess the performance of the new strategy and to compare it to level-crossing logic. The following five metrics were used to assess the performance: 1) magnitude of the control error, 2) start/stop frequency, 3) average power consumption, 4) standard deviation of the power consumption, 5) peak power consumption. The computer simulations showed...

Influence Of Three Dynamic Predictive Clothing Insulation Models On Building Energy Use, HVAC Sizing And Thermal Comfort

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

In building energy simulation, indoor thermal comfort condition, energy use and equipment size are typically calculated based on the assumption that the clothing insulation is equal to a constant value of 0.5 clo during the cooling season and 1.0 clo during heating season. The assumption is not reflected in practice and thus it may lead to errors. In reality, occupants frequently adjust their clothing depending on the thermal conditions, as opposed to the assumption of constant clothing values above, indicating that the clothing insulation variation should be captured in building simulation software to obtain more reliable and accurate results. In this study, the impact of three newly developed dynamic clothing insulation models on the building simulation is quantitatively assessed using the detailed whole-building energy simulation program, EnergyPlus version 6.0. The results showed that when the HVAC is controlled based on indoor temperature the dynamic clothing models do not...

Side-by-side laboratory comparison of radiant and all-air cooling: How natural ventilation cooling and heat gain characteristics impact space heat extraction rates and daily thermal energy use

Thu, 5 Dec 2019 00:00:00 +0000

For radiant cooling to maintain equivalent comfort conditions as all-air cooling it must remove more heat from a space, the peak space heat extraction rate must be larger, and the peak must occur earlier. In this article, we assess how the magnitudes of these differences are influenced by heat gain characteristics and by the use of natural ventilation night precooling. We present measurements from a series of multi-day side-by-side comparisons of radiant cooling and all-air cooling in a pair of experimental testbed buildings, with equal heat gains, and maintained at equivalent comfort conditions. In a five-day experiment with mixed internal heat gains, solar gains, and natural ventilation night precooling, radiant cooling had to remove 35% more heat than the all-air system in equivalent circumstances; and the peak heat extraction rate was 20% larger (median difference on multiple days). In a similar experiment with highly convective internal gains the differences were smaller...

Cooling Load and Design Sizing Report

Thu, 5 Dec 2019 00:00:00 +0000

The current standard procedure for design sizing of cooling systems is not well suited for design of buildings with radiant cooling. There are several reasons that the standard design procedure for radiant cooling systems (ASHRAE Systems & Equipment 2016 Chapter 6: Radiant Heating and Cooling) is flawed, including that the current standard definition of space cooling load (ASHRAE Fundamentals 2017 Chapter 18: Nonresidential Cooling and Heating Load Calculations) omits fundamental principles that are essential to the operation of radiant cooling. This report identifies several specific shortcomings with the current standard cooling load definition and with the standard cooling system design sizing procedure. We explain the fundamental flaws with each, discuss why addressing these shortcomings is especially important to the optimal design and operation of radiant cooling systems, and provide general recommendations for how the procedures ought to be improved. The issues and...

Thermal comfort in buildings using radiant vs. all-air systems: A critical literature review

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

Hydronic radiant heating and cooling systems are considered as an energy efficient technology to condition buildings. We performed a literature review to assess if radiant systems provide better, equal or lower thermal comfort than all-air systems. We included only peer-reviewed articles and articles published in proceedings of scientific conferences. The publications found have been classified based on research methods used. These include: (1) building performance simulation (BPS), (2) physical measurements (in laboratory test chambers and in buildings) and (3) human subject testing / occupant based surveys. This review identified eight conclusive studies: five studies that could not establish a thermal comfort preference between all-air and radiant systems and three studies showing a preference for radiant systems. Very few studies were based on occupant feedback in real buildings suggesting a significant research need. Overall, we found...

A review of advanced air distribution methods - theory, practice, limitations and solutions

Mon, 7 Oct 2019 00:00:00 +0000
Ventilation and air distribution methods are important for indoor thermal environments and air quality. Effective distribution of airflow for indoor built environments with the aim of simultaneously offsetting thermal and ventilation loads in an energy efficient manner has been the research focus in the past several decades. Based on airflow characteristics, ventilation methods can be categorized as fully mixed or non-uniform. Non-uniform methods can be further divided into piston, stratified and task zone ventilation. In this paper, the theory, performance, practical applications, limitations and solutions pertaining to ventilation and air distribution methods are critically reviewed. Since many ventilation methods are buoyancy driving that confines their use for heating mode, some methods suitable for heating are discussed. Furthermore, measuring and evaluating methods for ventilation and air distribution are also discussed to give a comprehensive framework of the review.

Codes and standards report

Wed, 8 May 2019 00:00:00 +0000

The goal of this study was to (1) propose changes to Title 24 to support improved modeling capabilities and help achieve significant energy efficiency goals for radiant systems in California, and (2) propose changes, as needed, to relevant ASHRAE Standards, Handbooks, and Guidelines to provide new information and guidance on radiant systems. The current version of California Building Energy Efficiency Standards, Part 6 of the California Building Standards Code (Title 24) does not address factors specific to high thermal mass radiant systems within the body of the Standards. The alternative compliance method references some limited aspects relating to radiant systems but it is incomplete and not practically applicable, and has not yet been implemented in the associated compliance software. In addition, there are some modeling limitations for radiant systems in EnergyPlus, which is the simulation engine underlying the compliance software for the Title 24 performance approach....

Comparison of construction and energy costs for radiant vs. VAV systems in the California Bay Area

Wed, 8 May 2019 00:00:00 +0000

The goal of this study was to perform a design stage cost analysis comparing a selected radiant building against an identical building with a traditional variable air volume (VAV) system. Major findings from the cost estimates include:
• The radiant HVAC design has a total cost of $38.9/ft² compared to $29.9/ft² for the VAV design, representing a $9.0/ft²premium for the radiant design.
• The higher costs for the radiant system can largely be attributed to higher piping labor costs for piping and radiant equipment, which itself is $9.8/ft² higher than that for the VAV design.
• Since labor rates are higher in the San Francisco Bay Area, for the estimated national average labor rate, the premium for radiant is $6.8/ft², compared to the VAV system. The high installed cost for the radiant equipment is partly a reflection of the current radiant manufacturers’ pricing strategies and the contractors’ bidding...

Ceiling fans: Predicting indoor air speeds based on full scale laboratory measurements

Mon, 6 May 2019 00:00:00 +0000
We measured indoor air speeds generated by ceiling fans in 78 full-scale laboratory tests. The factors were the room size, fan diameter, type, speed, direction (up or down), blade height, and mount distance (i.e. blade to ceiling height). We demonstrated the influence of these factors, showing that the most significant are speed, diameter and direction. With other factors fixed, the average room air speed in the occupied zone increases proportionally with fan air speed and diameter. Blowing fans upwards yields lower but far more uniform air speeds than downwards. We show that for the same fan diameter and airflow, fan type has little effect on the air speed distribution in the region outside the fan blades. We developed several new dimensionless representations and demonstrate that they are appropriate for comparisons over a wide range of fan and room characteristics. Dimensionless linear models predict the lowest, average, and highest air speeds in a room with a median (and 90th...

Current practice for design and control of high thermal mass radiant cooling systems, and opportunities for future improvements

Mon, 1 Apr 2019 00:00:00 +0000
Radiant cooling and heating have the potential for improved energy efficiency, demand response, comfort, indoor environmental quality, and architectural design. Many radiant buildings have demonstrated outstanding performance in these regards. However, there are no well-established best practices for design of radiant buildings and their control systems, and most industry professionals are unfamiliar with radiant systems. This study summarizes interviews with eleven professionals with substantial experience with design and operation of radiant buildings in North America. Interviews focused specifically on high thermal mass radiant buildings, referred to as thermally active building systems (TABS). Interviews revealed a diverse range of approaches for design and control of TABS buildings. While interviewees expressed many similar approaches, they also have manyunique preferences. Examples of consistent themes include the use of dedicated outdoor air systems for ventilation and...

HVAC system energy optimization using an adaptive hybrid metaheuristic

Fri, 15 Mar 2019 00:00:00 +0000
Previous research efforts for optimizing energy usage of HVAC systems require either mathematical models of HVAC systems to be built or they require substantial historical operational data for learning the optimal operational settings. We introduce a model-free control policy that begins learning optimal settings with no prior historical data and optimizes HVAC operations. The control policy is an adaptive hybrid metaheuristic that uses real-time data, stored in building automation systems (e.g., gas/electricity consumption, weather, and occupancy), to find optimal setpoints at the building level and controls the setpoints accordingly. The algorithm consists of metaheuristic (k-nearest neighbor stochastic hill climbing), machine learning (regression decision tree), and self-tuning (recursive brute-force search) components. The control policy uses smart selection of daily setpoints as the control basis, making the control schema complementary to legacy building management systems....

Quantifying energy losses in hot water reheat systems

Tue, 30 Oct 2018 00:00:00 +0000
We developed a new method to estimate useful versus wasted hot water reheat energy using data obtained from typically installed instrumentation that applies to all pressure independent VAV terminal units with discharge air temperature sensors. We evaluated the method using a year of 1-minute interval data for a 11,000 m2 building with 98 terminal reheat units, and found a 14% upper bound for the uncertainty associated with this method. We found that just 21% of gas energy is converted to useful reheat energy in this building. The distribution losses alone were 44% of the heat output from the boiler. The results raise questions regarding the tradeoffs between hot water heating systems, which have significant distribution losses, and electric heating systems, which effectively have zero distribution losses. In this building, and likely many others, an electric reheat system supplied by a small photovoltaic panel system would have a lower operating energy cost and a lower initial...

Side-by-side laboratory comparison of space heat extraction rates and thermal energy use for radiant and all-air systems

Mon, 27 Aug 2018 00:00:00 +0000
Radiant cooling systems extract heat from buildings differently than all-air cooling systems. These differences impact the time and rate at which heat is removed from a space, as well as the total amount of thermal energy that a mechanical system must process each day. In this article we present measurements from a series of multi-day side-by-side comparisons of radiant cooling and all-air cooling in a pair of experimental testbed buildings, with equal heat gains, and maintained at equivalent comfort conditions (operative temperature). The results show that radiant cooling must remove more heat than all-air cooling – 2% more in an experiment with constant internal heat gains, and 7% more with periodic scheduled internal heat gains. Moreover, the peak sensible space heat extraction rate for radiant cooling (heat transfer at the cooled surface, not the cooling plant) must be larger than the peak sensible space heat extraction rate for all-air systems, and it must occur earlier....

How High Can You Go? Determining the Highest Supply Water Temperature for High Thermal Mass Radiant Cooling Systems in California

Thu, 5 Apr 2018 00:00:00 +0000
Cooling demands are a major driver of energy consumption in buildings, and is mostly performed using systems based on the refrigeration cycle, an energy and cost intensive process. To investigate the potential of eliminating the refrigeration cycle from a building design in Californian climates, we created a single zone EnergyPlus model that uses a high thermal mass radiant system as the primary conditioning system, and that meets California’s energy code requirements. On the cooling design day, we randomly selected the start and number of hours of radiant system operation, lighting and plug load power densities, and occupant density for a set of models to determine the supply water temperature (SWT) that maintained comfortable temperatures. About 67% of tested models required SWT at or above 18 °C indicating that high thermal mass radiant systems have a high potential to use less energy and lower cost cooling devices like evaporative cooling towers in most California climates.

Effect of acoustical clouds coverage and air movement on radiant chilled ceiling cooling capacity

Wed, 7 Mar 2018 00:00:00 +0000
Thermally activated building systems have the potential to achieve significant energy savings, yet, the exposed concrete may also create acoustical challenges due to the high reflectivity of the hard surface. Free-hanging acoustical clouds reduce the acoustical issues, but also the cooling capacity of a radiant chilled ceiling system. Fan-induced air movement can be used to compensate for the cooling capacity reduction. We experimentally assess the combined effect of acoustical clouds and fans on the cooling capacity for an office room. We installed a ceiling fan between the clouds (blowing in the upward or downward direction) and small fans above the clouds (blowing horizontally) at the ceiling level to increase the convective heat transfer along the cooled ceiling. We tested the different fan configurations against a reference case with no elevated air movement. The tests conducted without fans showed that cooling capacity decreased, but only by 11%, when acoustical cloud coverage...

Evaluation of a cost-responsive supply air temperature reset strategy in an office building

Mon, 4 Dec 2017 00:00:00 +0000
This paper describes a new supply air temperature control strategy for multi-zone variable air volume systems. We developed the strategy with the intent that it is simple enough to implement within existing building management systems. At 5-minute intervals, the strategy estimates the cost of fan, heating and cooling energy at three different supply air temperatures (current, higher, lower), and chooses the one with the lowest cost as the setpoint. We then implemented this strategy in a seven floor, 13,000 m2 office building and compared the energy costs to the industry best practice control strategy in a randomized (daily) controlled trial over a 6-month period. We showed that the new control strategy reduced total HVAC energy costs by approximately 29%, when normalized to the typical annual climate data for this location and operating only during typical office hours. These findings indicate that the current industry best practice control strategy does not find the optimal energy...

Cooling capacity and acoustic performance of radiant slab systems with free-hanging acoustical clouds

Mon, 20 Nov 2017 00:00:00 +0000
Radiant slab systems have the potential to achieve significant energy savings, yet, when applied in the ceiling (e.g., thermally activated building system) the exposed concrete may also create acoustical challenges due to the high reflectivity of the hard surface. Balancing all of the building indoor environmental quality factors is important in the design of an effective workspace for the occupants, and so we need to consider the interactions between thermal and acoustic comfort. We assessed the cooling capacity in a hydronic test chamber and the sound absorption in a reverberation chamber to study the effects, for an office room, of different coverage areas of free-hanging acoustical clouds below a radiant chilled ceiling. The cooling experiments showed that for 47% cloud coverage of the ceiling area, we measured only an 11% reduction in cooling capacity caused by the blockage of radiant exchange between the ceiling and the room. The acoustical results showed that if the cloud...

Adaptable cooling coil performance during part loads in the tropics—A computational evaluation

Thu, 16 Nov 2017 00:00:00 +0000
Air conditioning and mechanical ventilation systems may be oversized in commercial buildings in the Tropics. Oversized cooling coils may lead to reduced dehumidifying performance, indoor air quality and thermal comfort and increased energy consumption. In this paper, an adaptable cooling coil design is assessed with a general-purpose coil selection software tool, in which the number of active rows changes as a function of the load. For a 100% oversized coil, it is shown that the adaptable cooling coil is able to provide small but relevant improved humidity control down to 25% of the design load. This was obtained without affecting energy performance in typical variable air volume design and control. For specific applications, where variable air volume systems mainly control space humidity, there are also energy savings. The adaptable cooling coil could be seen as providing additional flexibility in the operation of HVAC systems, particularly in the tropics.

Energy Use, Occupant Surveys and Case Study Summary: Radiant Cooling and Heating in Commercial Buildings

Tue, 17 Oct 2017 00:00:00 +0000

While forced-air distribution systems remain the predominant approach to heating and cooling in U.S. commercial buildings, radiant systems are emerging as a part of high performance buildings. Radiant systems transfer energy via a surface that contains piping with warmed or cooled water, or a water/glycol mix and separate ventilation through a dedicated outside air system. These systems can contribute to significant energy savings due to relatively small temperature differences between the room set-point and cooling/heating source, and the efficiency of using water rather than air for thermal distribution1. They can also offer peak demand reduction, load shifting, and improved comfort compared to conventional all-air systems.
The California Energy Commission (CEC) EPIC program funded a radiant research project from 2016-2018 to better characterize the energy use, occupant perceptions, opportunities for improvement, and provide data and resources to increase market adoption...

Development of whole building energy models for detailed energy insights of a large office building with green certification rating in Singapore

Tue, 10 Oct 2017 00:00:00 +0000
Detailed insights on energy use are missing for the building stock in Singapore which may aid with energy consumption reductions through a targeted approach. Therefore, we created two whole building energy models for a large commercial office building in the tropics; representing a fully glazed and a concrete façade. We used Singapore’s current building codes, which includes compliance with local green rating system, and collaboration between two entities with first-hand experience with design, construction, and operation of buildings in the tropics to define the models. The models provide a first step towards a set of standardized inputs and assumptions for office buildings in the tropics. The results show an energy use intensity of 146 kWh m-2·a. The three highest energy consumers are air conditioning and mechanical ventilation (43%), lighting (29%), and plug loads (21%) while the two main sources of cooling loads are ventilation (29%) and conduction and radiation through windows...

Development of a Personal Heater Efficiency Index

Wed, 4 Oct 2017 00:00:00 +0000
There is currently no quantitative method for evaluating the effectiveness and efficiency of personal heaters, which are commonly used in workplace situations to achieve thermal comfort. Instead, personal heaters are currently evaluated by their total energy use and heating method. We propose a new index and method of test by which efficiency of personal heaters may be calculated and assessed, taking into account both heating effectiveness and power use. This method was tested on a sample of 12 personal heaters, of various types: conductive, radiant, and convective. Each heater was tested in an environmental chamber, using a thermal manikin to quantitatively determine the amount of heat delivered to a subject. Heater location was standardized across the heaters prior to testing, so that all results are comparable. Results indicated that convective heaters were the least efficient, radiant heaters approximately twice as efficient, and conductive heaters 20 times more efficient...

Field Study of Capitol Area East End Complex (CAEEC) Sacramento, California

Tue, 26 Sep 2017 00:00:00 +0000
The energy and comfort performance of buildings using underfloor air distribution (UFAD) has been of interest, with some contention, in the building industry for many years. It is not often that an opportunity to address that question directly appears. This project represented such an opportunity to compare and contrast two similarly designed buildings in the same climate and co-located near one another, both occupied by California state employees, one with a UFAD system (B225) and the other with an overhead (OH) variable air volume (VAV) system (B172). At the outset there was hope that we could settle the question definitively due to the highly instrumented systems in these buildings that afforded an opportunity to use measured data for the comparison. This report contains a detailed description of the measured data and simulated analyses used to compare the energy performance of UFAD vs. OH systems, and a summary of the post occupancy evaluations (POE) used to study and compare...

Changing the Rules: Innovative Low-Energy Occupant-Responsive HVAC Controls and Systems

Tue, 12 Sep 2017 00:00:00 +0000
The overall goal of this Project was to create a new occupant-based paradigm for Heating, Ventilation, and Air Conditioning (HVAC) control that will reduce HVAC energy use in buildings while improving occupant comfort. The Project explored integrating low-energy personal comfort systems (PCS) into HVAC operations, advanced variable-air volume (VAV) control algorithms, and innovative open-source software for monitoring and control. The Project investigated deployment of commercially available occupant-vote based ambient temperature control technology alongside the other innovations. To accomplish this the research team developed, tested and demonstrated, through the performance of three detailed case studies, new products and HVAC control & operation practices, and performed work to identify market transformation potential for these innovative technologies in standards, codes, and common practice. Key research activities and findings are summarized below.• Fifty low-energy...

A new control strategy for high thermal mass radiant systems

Thu, 3 Aug 2017 00:00:00 +0000
This paper presents a new controller for high thermal mass radiant systems that can be implemented within a typical Building Automation System. We illustrate its performance using an EnergyPlus model representing a single zone, middle floor of an office building in Sacramento, California. The results of a small sensitivity analysis show that when compared to common practice in the US this approach reduces electricity cost and energy consumption by up to 40% and 35%, respectively, while maintaining comparable comfort conditions in the zone. Furthermore, this design & control approach could eliminate the need for a chiller in most California climate zones for typical office design loads.

Energy Performance of Commercial Buildings with Radiant Heating and Cooling

Fri, 14 Jul 2017 00:00:00 +0000
This report is part of the California Energy Commission (CEC) EPIC project (EPIC-14-009), Optimizing Radiant Systems for Energy Efficiency and Comfort. The main goal of this research was to determine the building characteristics of projects with radiant heating and cooling and assess their real world energy use compared to standard benchmarks for building energy performance. The energy use was self-reported through surveys and utility data and is based on whole building site energy use for a minimum of 12 months. The report describes the general building characteristics including type, size, location and climate zone of 23 buildings in North America with radiant distribution systems for both heating and cooling the predominant area of the building. The study found that almost all of the 23 buildings outperformed peer buildings and national benchmarks, suggesting that radiant systems are part of the integrated approach that can lead to low energy consumption in commercial buildings....

TABS Radiant Cooling Design & Control in North America: Results from Expert Interviews

Fri, 16 Jun 2017 00:00:00 +0000

Radiant cooling and heating has the potential for improved energy efficiency, demand response, comfort, indoor environmental quality, and architectural design. Many radiant buildings have demonstrated outstanding performance in these regards, and application of the technology in commercial buildings is expanding. However, there are no well-established best practices for design of radiant buildings and their control systems, and most professionals in the building industry are unfamiliar with radiant systems.
In this study, TRC Energy Services and the UC Berkeley Center for the Built Environment interviewed eleven prominent professionals who have substantial experience with design, construction, and operation of radiant buildings in North America, having collectively designed more than 330 radiant cooled buildings. The objective of the study was to document the variety of design and control approaches currently used for radiant cooled buildings, highlight themes of common...

Recent trends in radiant system technology in North America

Wed, 19 Apr 2017 00:00:00 +0000
Radiant cooling and heating systems provide an opportunity to achieve significant energy savings, peak demand reduction, load shifting, and thermal comfort improvements compared to conventional all-air systems, and as a result, application of these systems has increased in recent years. However, due to the relatively new and unfamiliar nature of radiant system technology compared to other traditional HVAC systems, there is a lack of energy, cost, and occupant satisfaction data to provide real world examples of energy efficient, affordable, and comfortable buildings using radiant systems. The overarching goal of this research is to make a first step to fill that information gap. This paper specifically (1) describes a new expanded database with over 400 buildings using radiant cooling and heating systems, (2) presents the CBE online radiant systems world map that displays all buildings from the database, and (3) summarizes the results and trends from this radiant map dataset, which...

A novel classification scheme for design and control of radiant system based on thermal response time

Wed, 25 Jan 2017 00:00:00 +0000
Radiant system design and control standards and guidebooks currently classify radiant systems as a function of their structure and geometry. We assume that design solutions, testing methods, and control strategies of radiant systems can be more clearly described and classified based on their thermal parameters. In this study, we use the thermal response time to evaluate the dynamic thermal performance of radiant systems. We defined the response time (τ ₉₅) as the time it takes for the surface temperature of a radiant system to reach 95% of the difference between final and initial values when a step change in control of the system is applied as input. The state space and thermal resistance models are used to calculate the response time for different radiant system types with a variety of configurations and boundary conditions. We performed 56,874 simulations. Concrete thickness, pipe spacing, and concrete properties have significant impact on the response...

New method for the design of radiant floor cooling systems with solar radiation

Tue, 17 May 2016 00:00:00 +0000
Impacts of solar shortwave radiation are not taken into account in the standardized design methods in the current radiant system design guidelines. Therefore, the current methods are not applicable for cases where incident solar is significant. The goals of this study are to: 1) use dynamic simulation tools to investigate the impacts of solar radiation on floor cooling capacity, and 2) develop a new simplified method to calculate radiant floor cooling capacity when direct solar radiation is present. We used EnergyPlus to assess the impacts of solar for different design conditions. The simulation results showed that the actual cooling capacities are in average 1.44 times higher than the values calculated with the ISO 11855 method, and 1.2 times higher than the ASHRAE method. A simplified regression model is developed to improve the predictability of ISO methods. The new model calculates the increased capacity as a function of the zone transmitted solar and the characteristic temperature...

SinBerBEST Technology Energy Assessment Report

Thu, 28 Apr 2016 00:00:00 +0000
SinBerBEST Technology Energy Assessment Report

Predicting thermal comfort of people in naturally ventilated buildings

Thu, 5 Nov 2015 00:00:00 +0000
A new procedure for predicting the thermal comfort of people in naturally ventilated buildings is described. The procedure starts by obtaining, for each important wind direction, velocity ratios between points of interest inside the proposed building and the wind-measuring height outside. Th~s is best done with a wind-tunnel test of a scale model of the building, but there are also published sources of such ratios. The ratios, plus building-induced temperature changes, are applied to a weather tape representing the site, in order to produce an hour-by-hour record of indoor climate. This record is used in a program simulating human thermal com-fort. The program puts out the percentage of time, by season and by periods of day, that thermal comfort is expected in the proposed building. This information enables architects and engineers to make more rational decisions in designing naturally ventilated buildings.

Air-change effectiveness: theory and calculation

Thu, 5 Nov 2015 00:00:00 +0000

This paper reports the development of methods for calculating a ventilation performance metric that is a measure of the airflow pattern in a room or zone of a multi-zone ventilation system. Temporal mixing theory is used as the basis for these methods. The methods are applicable to all ventilated systems that can be modeled as a set of interconnected chambers. Relations between the ventilation performance metric defined in this paper and those defined previously are derived. The theoretical results of this paper are consistent with published experimental findings. They also illustrate that the conclusions in some experimental studies about the airflow patterns in working buildings may be incorrect. Re-analysis of previously published detail illustrates how common features of mechanically ventilated buildings, such as recirculation of return air and multiple chambers, confound information about airflow patterns in tracer gas data. The calculation methods developed in this paper...

Air leakage test report: EPA region 8 headquarters, Denver, CO

Mon, 2 Nov 2015 00:00:00 +0000

On May 16-18, 2008, CBE researchers working in collaboration with key personnel from Engineered Interiors Group (EIG), Opus NW Management/GPT, and the Environmental Protection Agency (EPA), conducted air leakage tests in the EPA Region 8 Headquarters Building in Denver, CO. There were two primary objectives for this testing:
1. Determine the characteristic air flow leakage rate from the underfloor air distribution system on the 7th floor, and
2. Using alternative testing methods assess the overall accuracy and effectiveness of the GSA leak testing protocol.
We begin this report with a description of the EPA building, a background description of the basic leakage types, discussion of airflow measurement methods, and a description of the GSA protocol. This is followed with a section that documents the results of all testing accomplished and includes discussions of these results and their implications for the GSA protocol. In the Appendices, we provide a detailed...

Comparison of Zone Cooling Load for Radiant and All-Air Conditioning Systems

Mon, 2 Nov 2015 00:00:00 +0000
By actively cooling down one or more surfaces in a space, water-based embedded surface cooling (radiant) systems remove heat both by convection and radiation. Therefore, unlike the case of well-mixed air distribution systems where the cooling load is purely convective, the cooling load for radiant systems is comprised of both convective and radiant components. However, in current practice, the same design cooling load calculation methods for the radiant systems are used as the convection based air systems. The purpose of this energy simulation study was to investigate if there are differences in peak zone cooling load and 24-hour total zone cooling energy generated by all-air distribution systems in comparison to radiant cooling systems. Sensitivity studies were performed for different load and boundary conditions. Simulation results show that total zone cooling energy for the radiant cooling systems studied can be 2.7-6.5% higher than the all-air systems, and peak zone cooling...

Modeling transient contaminant transport in HVAC systems and buildings.

Mon, 2 Nov 2015 00:00:00 +0000

A mathematical model of the contaminant transport in HVAC systems and buildings is described. The model accounts for transients introduced by control elements such as fans and control dampers. The contaminant transport equations are coupled to momentum equations and mass continuity equations of the air. To avoid modeling variable transport delays directly, ducts are divided into a large number of small sections. Perfect mixing is assumed in each section. Contaminant transport equations are integrated with momentum equations in a way that guarantees mass continuity by using two non-negative velocities for computing the mass transport between elements. Computer simulations illustrate how the model may be used to analyze and design control systems that respond to a sudden release of a toxic contaminant near a building. By coupling transient flow prediction with transient contaminant prediction, the model overcomes a number of problems with existing contaminant transport codes.

Sizing Thermally Activated Building Systems (TABS): A Brief Literature Review and Model Evaluation

Mon, 2 Nov 2015 00:00:00 +0000
While Thermally Activated Building Systems (TABS) is a recognized low-energy HVAC candidate system for net-zero-energy buildings, sizing of these systems is complex due to their slow thermal response. In this paper, seven design and control models have been reviewed and characterized systematically with an aim to investigate their applicability in various design scenarios and at different design stages. The design scenarios include variable space heat gain, different building thermal mass and varying pump operating hours. Three design stages were considered, including feasibility study, early design decisions and detailed sizing. The applicability to different design stages was evaluated based on a compromise between accuracy and ease of implementation of the design methods. Five of the models were shortlisted for a future simulation-based evaluation and recommendation.

Advanced Integrated Systems Technology Development

Mon, 2 Nov 2015 00:00:00 +0000

To achieve the radical improvements in building energy efficiency being called for by the State of California, it will be necessary to apply an integrated approach involving new designs, new technologies, new ways of operating buildings, new tools for design, commissioning and monitoring, and new understanding of what comprises a comfortable and productive indoor environment. All of these themes define important goals that have guided the broad and comprehensive research effort described in this report. Research methods have included field studies, laboratory studies, energy and thermal comfort modeling, and technology transfer through participation on American Society of Heating, Refrigerating and Air Conditioning Engineers standards and technical committees. Center for the Built Environment research is also guided by its 40 industry partners, who serve as the project advisory board for the project.
The work done under this project has advanced the understanding of...

Teledesic broadband center field study

Mon, 2 Nov 2015 00:00:00 +0000

The design of many unconventional internet and technology office spaces in the late 90’s has challenged many standard conventions of workplace protocol. Although it is easy to poke fun at the free café lattes, foosball machines, and dogs in the office, the desire to create a workplace that is healthier, more functional, and casual is seen by many as a positive and continuing trend. The question then arises, how well do these new innovative workplaces actually perform?
The Teledesic Broadband Center, in Bellevue, Washington, is one example of this new office paradigm. Designed by the architecture firm NBBJ of Seattle in conjunction with mechanical engineering firm Arup of San Francisco, the project is an adaptive reuse of an industrial building to create the new headquarters for Teledesic, a company that is building a global broadband communications network. The design of the 70,000-square foot space incorporates many new workplace features, including a high loft-style...

CBE UFAD cost analysis tool: Life cycle cost model, issues and assumptions

Mon, 2 Nov 2015 00:00:00 +0000

This report, a companion to the first cost model assumptions report [Webster et. al. 2008] documents the issues and assumptions upon which the CBE UFAD life cycle cost (LCC) modeling tool were based. In this first section we provide and overview of the model structure and a brief description of its main parts. In Section 2 we summarize highlights of the literature search that we conducted to inform our model development work. Section 3 summarizes the major issues and assumptions for the model approach as well as pertinent LCC elements. Section 4 contains more detailed descriptions of the model elements as implemented in the accompanying tool.
The issues and assumptions provide a wealth of information about what things need to be considered when constructing a tool but also serve as a guide for considerations important to any LCC methods that attempt to compare system types.
Our intent in designing this tool was to provide a comprehensive tool with flexibility to...

Case study report: David Brower Center

Mon, 2 Nov 2015 00:00:00 +0000

The David Brower Center (DBC) is a 4-story 45,000-ft2 office building located in downtown Berkeley, California (Figure 1). The building was completed and first occupied in May 2009. It contains lobby and public meeting space on the first floor and open plan office spaces on the 2nd-4th floors, which primarily house non-profit environmental activist organizations. Integral Group (formerly Rumsey Engineers) was the mechanical design engineer on the project and, working with the architect (Solomon E.T.C. – WRT) and other design specialists, put together a design promoting low energy consumption.
The goal of a low energy building was achieved through an integrated design process that combined thermal mass, shading, and insulation into an efficient building envelope, implemented daylighting and efficient lighting control strategies, and used a low energy HVAC system. The primary space conditioning subsystem is hydronic in-slab radiant cooling and heating, which is installed...

Technical Report on California State Teachers Retirement System Building: UFAD Performance and Blinds Study

Mon, 2 Nov 2015 00:00:00 +0000

For the week of July 19-23, 2010 members from CBE traveled to the California State Teachers Retirement System (CalSTRS) building in Sacramento with two main goals in mind: (1) help validate the CBE UFAD design tool with measured building data and (2) evaluate the performance of the CalSTRS UFAD system during different blinds setting scenarios (open, horizontal, and closed). During certain times of year, CalSTRS building engineers have had trouble meeting setpoints because of solar loading. Two spaces were monitored: (1) a conference room on the 3rd floor and (2) an open plan space on the 11th floor.
This project was funded by CBE and the Public Interest Energy Research program.

Effects of furniture and contents on peak cooling load

Mon, 2 Nov 2015 00:00:00 +0000
We assess the impact that furniture and contents (i.e. internal mass) have on zone peak cooling loads using a perimeter zone model in EnergyPlus across 5400 parametric simulation runs. The zone parameters were HVAC system type (overhead, underfloor, and thermally activated building system (TABS)), orientation, window to wall ratio, and building envelope mass. The internal mass parameters were the amount, area, and the material type used. We also evaluated a new internal mass modeling method, which models direct solar radiation on the internal mass surface, an effect that is missing in current methods. We show how each of these parameters affect peak cooling load, highlighting previously unpublished effects. Overall, adding internal mass changed peak cooling load by a median value of -2.28% (-5.45% and -0.67% lower and upper quartiles respectively) across the studied parameter space. Though the median is quite low, this study highlights the range of effects that internal mass can...

Design and Control of Hydronic Radiant Cooling Systems

Mon, 2 Nov 2015 00:00:00 +0000

Improving energy efficiency in the Heating Ventilation and Air conditioning (HVAC) systems in buildings is critical to achieve the energy reduction in the building sector, which consumes 41% of all primary energy produced in the United States, and was responsible for nearly half of U.S. CO2 emissions. Based on a report by the New Building Institute (NBI), when HVAC systems are used, about half of the zero net energy (ZNE) buildings report using a radiant cooling/heating system, often in conjunction with ground source heat pumps. Radiant systems differ from air systems in the main heat transfer mechanism used to remove heat from a space, and in their control characteristics when responding to changes in control signals and room thermal conditions. This dissertation investigates three related design and control topics: cooling load calculations, cooling capacity estimation, and control for the heavyweight radiant systems. These three issues are fundamental to the development...

A comparison between two underfloor air distribution (UFAD) design tools

Mon, 2 Nov 2015 00:00:00 +0000
The purpose of this study is to compare the capabilities and accuracy of two publicly available underfloor air distribution (UFAD) design tools (ASHRAE RP-1522 and CBE). The comparison is based on the air distribution models, diffuser types, ability to predict the design cooling load, supply plenum heat balance, temperature profile and setpoint, plenum configuration, and air distribution effectiveness. A combined database is fed into each tool’s air distribution model to assess their accuracy. The results show the RP-1522 model predicts thermal stratification slightly more accurately than the CBE model in cases using swirl and square diffusers, but both results are comparably accurate for design purposes. The CBE UFAD tool has the key advantage of being able to predict the UFAD cooling load and model four different plenum configurations and both interior and perimeter zones. The RP-1522 tool is able to calculate the air distribution effectiveness.

Temperature stratification and air change effectiveness in a high cooling load office with two heat source heights in a combined chilled ceiling and displacement ventilation system

Mon, 2 Nov 2015 00:00:00 +0000
Radiant chilled ceilings (CC) with displacement ventilation (DV) represent a promising integrated system design that combines the energy efficiency of both sub-systems with the opportunity for improved ventilation performance resulting from the thermally stratified environment of DV systems. Their combined cooling capacity is thought to be limited. The purpose of this study is to conduct laboratory experiments for a U.S. interior zone office with a very high cooling load (91.0 W/m²) and with two different heat source heights represented by computer CPUs (at floor level and at 1.52 m) to investigate their influence on room air stratification and air change effectiveness. The experiments were carried out in a climatic chamber equipped with 12 radiant panels, covering 73.5% of the ceiling, installed in the suspended ceiling. The cooling load removed by the panels varied between 0 and 92 W/m²(based on radiant panel area) or between 0 and 68 W/m²(based...

Energy performance of air distribution systems part II: room air stratification full scale testing

Mon, 2 Nov 2015 00:00:00 +0000

Room air stratification (RAS) is one of the key features of UFAD technology that determines how the benefits of low energy, good indoor comfort and ventilation performance are achieved. Understanding, accounting for, and controlling RAS are essential to successful design, installation, and operation of these systems. Likewise, modeling RAS is essential to simulating the energy performance of these systems. Although much research has been focused on RAS for displacement ventilation systems, relatively little has been done to develop a comprehensive model for UFAD systems, and no models currently exist within energy simulation programs commonly used by design and installation practitioners. Development of a model for RAS must be based on sound physical principles as well as also accurately representing the reality of how these systems are installed and operated. That is the purpose of the full scale testing effort we describe in this report.
CBE has been involved in RAS...

Assessment and Improvements of the CBE Underfloor Air Distribution (UFAD) Cooling Load Design Tool

Mon, 2 Nov 2015 00:00:00 +0000

The necessity of energy efficient Heating Ventilation and Air Conditioning (HVAC) technologies has been growing with the development of green buildings to reduce the impact of built environment on the US energy consumption. In this context, underfloor air distribution (UFAD) appears as an innovative air distribution method that has the potential benefits of reduced energy use, improved indoor air quality (IAQ) and thermal comfort. Currently, there are two UFAD design tools (CBE and RP-1522 tools) in the ASHRAE UFAD design guide to help HVAC designers predict thermal stratification and calculate air flow rate. The aim of this thesis is to comprehensively compare these two UFAD design tools and update the CBE UFAD Cooling Load Design Tool with new stratification models and extended capabilities. The comparison will provide HVAC designers with a reference when deciding which design tool to use.
The comparison consists of two parts. The first one compares features, including...

Thermal and air quality acceptability in buildings that reduce energy by reducing minimun airflow from overhead diffusers

Mon, 2 Nov 2015 00:00:00 +0000

There is great energy-saving potential in reducing variable air volume (VAV) box minimum airflow setpoints.
In the past, setpoints have been maintained at high levels because of three concerns: 1) low flows might cause the occupants draft discomfort from insufficient mixing of diffuser discharge air, 2) inability of VAV boxes to control at low flows, and 3) poor air quality resulting from a combination of poor control and insufficient diffuser mixing. It is worth examining these concerns to see whether they are justified. The controller accuracy and stability have recently been addressed by RP 1353, in which VAV boxes were found to control well at very low flow levels. The diffuser mixing issue and impact on comfort are addressed in this research project, RP 1515.
RP 1515 is a combined field and laboratory study, in which occupants’ thermal comfort and air quality satisfaction is evaluated in the field under reduced minimum VAV flow rate setpoints, and the mixing...

Radiant cooling research scoping study

Mon, 2 Nov 2015 00:00:00 +0000

The objective of this project is to characterize the opportunities and limitations of radiant cooling strategies for North America and identify research needs that CBE might most effectively address. Based on literature, case studies, and interviews with experienced designers, CBE has set out to determine the focus of radiant cooling research that will best address shortcomings of industry resources and thus provide the most benefit to CBE partners.

Air movement as an energy efficient means toward occupant comfort

Mon, 2 Nov 2015 00:00:00 +0000

Fans provide a major opportunity for buildings in that they enhance both energy efficiency and occupant comfort. Very low-wattage fans (3 watts) producing 1 m/s (2 mph) air movement near each occupant are capable of offsetting a 6ºF (3K) increase in indoor air temperature, while improving the comfort perceived by the occupants. Increasing the indoor temperature reduces a building’s total HVAC energy about 5% per degree F, or 10% per degree C, and even more in some climate zones if the higher indoor temperature permits natural ventilation or evaporative cooling systems to be used instead of compressor-based cooling.
The opportunities for new design approaches and new fan products are considerable. Room fans have many applications in both new and retrofit designs since they do not involve other HVAC systems, can be easily turned on and off (as with occupancy sensors or wireless controls), yet they can provide an instantaneous cooling effect for the occupant. They strengthen...

Impact of Solar Heat Gain on Radiant Floor Cooling System Design

Mon, 2 Nov 2015 00:00:00 +0000
Radiant floor cooling systems are increasingly being used in transition spaces with large glazed surfaces, such as atria, airports, and perimeter areas. For these cases, the cooling capacity can increase significantly according to the scientific literature. However, current design standards and test methods provide only limited guidance on sizing of radiant floor cooling systems and their associated air systems in the presence of solar radiation. The goals of this study are to 1) review current radiant surface cooling capacity estimation approaches; and 2) evaluate the impact of solar heat gain on radiant floor cooling capacity. Sensitivity simulation studies were conducted to investigate the influence of window-to-wall ratio, orientation, building aspect ratio, shading options, and floor material shortwave absorptivity. Review of current radiant system design standards showed that existing radiant cooling capacity estimation methods are insufficient when the system is exposed...

Supervisory control for energy savings and thermal comfort in commercial building HVAC systems.

Mon, 2 Nov 2015 00:00:00 +0000

The operation and maintenance of commercial building HVAC (heating, ventilation, and air-conditioning) systems is illustrative of an industry that can benefit from the insightful use of all available information sources. Modern HVAC systems using direct digital control can potentially provide useful performance data. Occupant feedback complaint data and HVAC system trend data are stored within modern maintenance management databases. This paper will address the specific issue of integration and application of these fundamental sources of information, using some modern and novel techniques. Examples are found in, but are not limited to the following areas: discrete-event, continuous, and hybrid control system theory, artificial intelligence, statistics, system identification, databases, etc. Methods specific to these areas can be used to synthesize a supervisory controller. The objective of this controller is to reduce energy costs, improve building occupant comfort, fault detection...

Energy performance of underfloor air distribution systems

Mon, 2 Nov 2015 00:00:00 +0000

This multi‐year project developed EnergyPlus/UFAD, a version the publicly available wholebuilding energy simulation program EnergyPlus that adds the capability for modeling underfloor air distribution systems. The project also developed a practical design tool for determining the cooling airflow quantity for underfloor air distribution systems. EnergyPlus/UFAD and the cooling airflow design tool are the first validated underfloor air distribution system tools of their kind. As such, they represent a significant advance in the state of the art of the design and energy analysis of such systems. This highly collaborative effort involved experts and facilities from four organizations, including the Center for the Built Environment at University of California, Berkeley; University of California, San Diego; Lawrence Berkeley National Laboratory; and York International.
This final report and seven appendices present experimental testing and analytical and computational fluid...

Laboratory testing of a displacement ventilation diffuser for underfloor air distribution systems

Mon, 21 Sep 2015 00:00:00 +0000
Underfloor air distribution (UFAD) systems use the underfloorplenum beneath a raised floor to provide conditioned air through floor-mounted diffusers, which typically discharge cool air with bothhorizontal and vertical momentum components. These systems usually createa vertical temperature stratification when in cooling mode and this hasan impact on energy, indoor air quality and thermal comfort. The purposeof this study was to characterize the stratification performance of apreviously unstudied type of floor diffuser that discharges airhorizontally, with almost no vertical velocity component, and aims tocombine the benefits of both UFAD and displacement ventilation (DV)strategies.We performed 19 full scale laboratory experiments in which we varied thenumber of diffusers and the internal loads over a range of valuestypically found in office spaces. We quantified the amount of thermalstratification by measuring the dimensionless temperature at ankle heightand found a...

A Classification Scheme for Radiant Systems based on Thermal TimeConstant

Mon, 14 Sep 2015 00:00:00 +0000
Radiant system design standards and guidebooks classify radiant systems as a function of their structure and geometry. We assume that design approaches, testing methods, and control strategies of radiant systems can be more clearly described and classified based on thermal parameters. We calculated using computational fluid dynamics method the thermal time con-stants for 66 radiant system cases. We found pipe spacing, thickness and material properties of structural layer have a significant impact on time constant, while operative temperature, water temperature and water flow regime do not. We found time constants of radiant ceiling panels vary between 30-91 s; for embedded surface systems between 0.25-3.5 h; for thermally activated building systems with pipes embedded in the massive concrete slabs, between 2.4-7.7 h; and for capillary pipes embedded in a layer at the inner surface, between 0.1-0.6 h. A preliminary radiant system classification scheme based on thermal time constant...

Advanced Integrated Systems Technology Development: Personal Comfort Systems and Radiant Slab Systems

Fri, 24 Jul 2015 00:00:00 +0000

To achieve the radical improvements in building energy efficiency being called for by the State of California, it will be necessary to apply an integrated approach involving new designs, new technologies, new ways of operating buildings, new tools for design, commissioning and monitoring, and new understanding of what comprises a comfortable and productive indoor environment. This project, which is an amendment to CEC Contract 500-08-044, has focused on two space conditioning technologies that were part of the original project and showed significant potential to dramatically improve traditional levels of energy efficiency while also increasing occupant satisfaction and thermal comfort. The amendment allowed us to extend our ongoing research on these two promising technologies: personal comfort systems , and radiant heating and cooling systems.
The work done under this project has advanced the understanding of personal comfort systems and radiant heating and cooling systems,...

Effects of Diffuser Airflow Minima on Occupant Comfort, Air Mixing, and Building Energy Use (RP-1515)

Tue, 14 Jul 2015 00:00:00 +0000

There is great energy-saving potential in reducing variable air volume (VAV) box minimum airflow setpoints to about 10% of maximum. Typical savings are on the order of 10-30% of total HVAC energy, remarkable for an inexpensive controls setpoint change that properly maintains outside air ventilation. However, there has long been concern whether comfort and room air mixing are maintained under low flows through diffusers, and this concern has prompted VAV minima to be typically set at 20-50% of maximum.
RP 1515 evaluated occupants’ thermal comfort and air quality satisfaction in operating buildings under both conventional and reduced minimum VAV flow setpoints, and measured the air diffusion performance index and air change effectiveness for typical diffuser types in the laboratory. The hypotheses were that lowered flow operation would not significantly reduce comfort or air quality, and that HVAC energy savings would be substantial. The hypotheses were almost...

Cooling efficiency of a brushless direct current stand fan

Thu, 2 Apr 2015 00:00:00 +0000
In warm environments, isothermal cooling by deliberately enhanced air movement can maintain thermal comfort using less energy than compressor-based air conditioning. To evaluate the performance of a brushless direct current (DC) stand fan, the cooling fan efficiency (CFE) index was measured in a climatic chamber under four dry-bulb temperatures (24, 26, 28, and 30 °C), six speed In warm environments, isothermal cooling by deliberately enhanced air movement can maintain thermal comfort using less energy than compressor-based air conditioning. To evaluate the performance of a brushless direct current (DC) stand fan, the cooling fan efficiency (CFE) index was measured in a climatic chamber under four dry-bulb temperatures (24, 26, 28, and 30 °C), six speed settings (corresponding to centreline speeds in the range 0.6-2.5 m/s at 1 m distance), two fan-manikin distances (1 and 2 m) and two orientations (front, side). The CFE index is defined as the ratio of the whole-body cooling...

Web application for thermal comfort visualization and calculation according to ASHRAE Standard 55

Thu, 12 Mar 2015 00:00:00 +0000
Thermal comfort is one of the fundamental aspects of indoor environmental quality and it is strongly related to occupant satisfaction and energy use in buildings. This paper describes a new web application for thermal comfort visualization and calculation according to ASHRAE Standard 55-2010 and 2013. Compared to existing software, the web application is free, cross-platform, and provides a visual and highly interactive accurate representation of the comfort zone. Its main features are: dynamic visualization of the comfort zone on psychrometric, temperature-relative humidity, and adaptive charts; new implementation of the Elevated Air Speed model; local thermal discomfort assessment; compliance document automation for LEED thermal comfort credits; metabolic activity and clothing insulation tables and dynamic models; and compliance with the standard. The tool can be used by architects, engineers, building operators, educators, and students.

Adventitious ventilation: a new definition for an old mode?

Mon, 5 Jan 2015 00:00:00 +0000
Adventitious ventilation: a new definition for an old mode?

Cooling load differences between radiant and air systems

Tue, 24 Jun 2014 00:00:00 +0000
Unlike the case of air systems where the cooling load is purely convective, the cooling load for radiant systems consists of both convective and radiant components. The main objectives of this energy simulation study were to investigate whether the same design cooling load calculation methods can be used for radiant and air systems by studying the magnitude of the cooling load differences between radiant and air systems over a range of configurations and to suggest potential improvements in current design guidelines. Simulation results show that 1) zone level 24-hour total cooling energy of radiant systems can be 5-15% higher than air systems due to differences in conduction load through the building envelope; 2) peak cooling load at the radiant system hydronic level can be 7-31% higher than air system for zones without solar load. The differences can increase up to 93% at the hydronic level for floor system in zones with solar load; 3) the cooling load differences between...

The development of a controlled environment chamber for the physical and subjective assessment of human comfort in office environments

Thu, 12 Jun 2014 00:00:00 +0000
The development of a controlled environment chamber for the physical and subjective assessment of human comfort in office environments

Development of guidelines for Modeling Underfloor Air Distribution (UFAD) Systems in EnergyPlus, eQUEST, and EnergyPro for use in California non-residential Building Energy Efficiency Standards

Thu, 22 May 2014 00:00:00 +0000
Development of guidelines for Modeling Underfloor Air Distribution (UFAD) Systems in EnergyPlus, eQUEST, and EnergyPro for use in California non-residential Building Energy Efficiency Standards

CBE EnergyPlus modeling methods for UFAD systems

Fri, 9 May 2014 00:00:00 +0000
This report documents the UFAD module specifications for EnergyPlus v3.1 and higher. We have conducted extensive validation of the interior zone model for Price swirl and York MIT1 variable area (VA) diffusers. These correlations should not be considered to be applicable to other diffuser types. (See below for user procedures to support other diffuser brands and types.)

Modeling of underfloor air distribution (UFAD) systems.

Fri, 9 May 2014 00:00:00 +0000
In this paper, we discuss the development of a module that is capable for the first time of simulatingUFAD systems in EnergyPlus. We describe the new models for EnergyPlus that simulate two important elements of these systems: underfloor air supply plenums and room air stratification under cooling operation. These algorithms were developed over a 5-year period of intensive interdisciplinary work consisting of theory, bench-scale and full-scale experimental testing, and computational fluid dynamics (CFD), analytical, and empirical modeling. We describe the modeling methods, show examples of a preliminary validation based on experimental data, and present results of research studies that have significantly contributed to a more complete understanding of the behavior of UFAD systems.