Center for the Built Environment

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

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

To evaluate performance, the research team conducted measurement and verification using measured energy data and regression modeling with typical meteorological weather data to calculate weather-normalized annual energy consumption. G36 implementation resulted in weather-normalized annual energy savings of 7 percent and 11 percent in the two hot water plants, corresponding to $ 0.095 per square foot per year and $0.17 per square foot per year cost savings. The implementation also led to 15 percent energy savings in the chilled water plant, corresponding to $0.12 per square foot cost savings—excluding June through August—when compared to existing controls strategy.

These results confirm both the energy efficiency benefits and the technical viability of using a modular and scalable approach for adopting G36. The findings also highlight the importance of reviewing existing systems and performing thorough retro-commissioning to ensure system operation as expected, especially in critical environments, before deploying advanced control strategies.

ASHRAE Guideline 36 defines standardized high-performance control sequences for heating, ventilation, and air conditioning (HVAC) systems, yet limited field evidence exists on its plant-level applications. In this project, the team implemented Guideline 36 supply water temperature reset sequences for two hot water plants and a chilled water plant using a layered architecture of supervisory control, Building Automation and Control Networks (BACnet) communication, Control Description Language (CDL) based programming developed by ASHRAE Standard 231p, and Brick ontology to ensure scalability and interoperability. Measurement and verification (M&V) with weather normalization showed savings of 3.28 kBTU/ft²-year (10.38 kWh/m2-year)(7.5%) and 10.15 kBTU/ft²-year(32 kWh/m2-year) (11.5%) for the hot water plants, and 6.61 kWh/m2 (2,097 BTU/ft2) (14.6%) for the chilled water plant, translating to cost reductions of $0.095/ft2-year ($1.02/m2-year), $0.17/ft2-year ($1.82/m2-year), and $0.12/ft2 ($1.29/m2), respectively. These results provide empirical evidence of Guideline 36’s effectiveness in plant applications and highlight its potential for broader adoption. Additionally, retro-commissioning efforts in one building reduced chilled water energy use by 16%, demonstrating the importance of addressing existing operational inefficiencies to fully realize the benefits of advanced control strategies.

Heating, ventilation, and air-conditioning (HVAC) system functional performance test is a critical commissioning step in ensuring the design, installation, and operation of the building's mechanical system is verified against its intent. HVAC systems in commercial buildings are complex and traditional methods, which are manual and time-consuming, are sometimes incomplete. This is particularly concerning for HVAC controls, where an analyst would first identify all relevant sensor measurements from the building management system, cross-reference them with design drawings, and then compile a sequence of operations to test before implementation and analysis. This process becomes harder to manage as the system scales. In this study, we demonstrate it is possible to enhance HVAC equipment and control sequence commissioning by using a metadata schema called Brick in the performance test. The Brick schema allows for querying required measurement points from the BMS in a standardized, machine-readable format. By further connecting the Brick model to the building's BACnet network, most performance tests can be streamlined to increase the commissioning efficiency. In this study, we developed a generalized workflow based on Brick metadata schema that commissioning agents can directly apply with minimal manual adjustment. We demonstrated the framework by testing the air handling unit functions of a climate chamber at UC Berkeley. The performance tests include adjusting the supply fan speed and damper position and analyzing their impact on the airflow rate at terminal units. By using the Brick schema, the HVAC performance tests can be highly automated and generalized to a variety of buildings, yielding time and cost savings during commissioning while improving robustness.

The operational carbon emissions intensity of the electricity used in a building is commonly treated as a fixed value but grid carbon emissions factors have temporal and geographical variations, which makes building operating emissions dependent on when and where electricity is used. Grid electricity carbon characteristics can be quantified by either average or marginal emission rates, leading to an increasing debate about which metric provides more accurate results for determining the effect of various decarbonization strategies. We advocate for the use of the marginal operating emissions rate (MOER) to evaluate the impacts of demand-side management because it considers the generating plants' dispatch order and is able to reflect the change in emissions induced by demand management. In this study, we examined the benefits of emission-based load-shifting strategies by first analyzing the annual temporal variations of the Northern California grid region and developed a virtual chiller load shift strategy similar to demand response but interacting with the grid MOER signal. We then assessed its effect on the case study building by calculating the avoided emissions on a seasonal and annual basis through a numerical simulation. As a result, we found that for the Northern California region, shifting load is most effective during the spring season with 18% avoided carbon emissions when the grid has more renewable supply. However, the simulated annual result shows 2% avoided carbon emissions indicating the seasonal characteristics of the proposed strategy and the limitation of considering load shift strategy as the single solution to decarbonize.

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

Charging infrastructure availability is a major concern for plug-in electric vehicle users. Nowadays, the limited public chargers are commonly occupied by vehicles which have already been fully charged. Such phenomenon, known as overstay, hinders other vehicles’ accessibility to charging resources. In this paper, we analyze a charging facility innovation to tackle the challenge of overstay, leveraging the idea of Robo-chargers -automated chargers that can rotate in a charging station and proactively plug or unplug plug-in electric vehicles. We formalize an operation model for stations incorporating Fixed-chargers and Robo-chargers. Optimal scheduling can be solved with the recognition of the combinatorial nature of vehicle-charger assignments, charging dynamics, and customer waiting behaviors. Then, with operation model nested, we develop a planning model to guide economical investment on both types of chargers so that the total cost of ownership is minimized. In the planning phase, it further considers charging demand variances and service capacity requirements. In this paper, we provide systematic techno-economical methods to evaluate if introducing Robo-chargers is beneficial given a specific application scenario. Comprehensive sensitivity analysis based on real-world data highlights the advantages of Robo-chargers, especially in a scenario where overstay is severe. Validations also suggest the tractability of operation model and robustness of planning results for real-time application under reasonable model mismatches, uncertainties and disturbances.

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

Many commercial buildings have a vast network of sensors as part of their building automation systems (BAS) that allows opportunities for energy consumption and cost savings by deploying advanced control sequences. However, this resource is often underutilized since BAS are typically programmed with simple control sequences with limited potential to deliver on these opportunities. The recent availability of ASHRAE Guideline 36 (G36) with advanced HVAC control sequences supports control retrofits in existing buildings to unlock much of the savings potential. However, barriers such as the lack of standard naming convention of building assets and data points, proprietary equipment and BAS, and the inherent uniqueness of buildings and their systems prevent building stakeholders from adopting any “plug-and-play” implementation of G36. Instead, control vendors must often undertake the manual and labor-intensive point mapping process to identify a data stream’s functional and spatial relationship within the HVAC system along with other relevant contexts and map it to the new control sequences. The vendor must carry out the point mapping process in each individual building since the mapping is unlikely to port over to another building. Even for the same building, the point mapping process can occur multiple times if various control vendors implement different control retrofits and/or multiple control retrofits happen over the lifecycle of the building. Then, there is the likelihood that G36 control sequences are programmed uniquely to the building, preventing the same implementation from being reused in another. Therefore, this paper presents a field demonstration of how we leveraged the Brick ontology with BACnet, OpenBuildingControl’s Control Description Language (CDL), and open-source support tools to implement scalable and portable advanced building controls. These tools provide standardized semantic descriptions and relationships of the building’s assets and data points (Brick), standardized communication protocol to read from and write to the building’s BAS (BACnet), and standardized code implementations (CDL) of standardized advanced control strategies (G36). We implemented G36’s hot water supply temperature setpoint reset in a Berkeley, CA building for this field demonstration. This field demonstration aims to show how integrating these tools may streamline the deployment of advanced control sequences such as G36 in a consistent manner regardless of differences found across buildings.