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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Extraction and Analysis of Time Series Data from Building Automation Systems Using Large Language Models

Semantic schemas like Haystack 4, Brick and ASHRAE standard 223 enable the structured, standardized, and machine-readable representation of building data, facilitating interoperability, data integration, and advanced analytics. However, extracting information from these models requires specialized expertise in SPARQL and other programming languages, skills that are not commonly found among building professionals. Recent advancements in Large Language Models (LLMs), such as ChatGPT, enable the construction of queries using natural language, making it easier for individuals to interact with these systems in a manner that resembles everyday speech. However, these methods have not yet been tested on building semantic ontologies. This paper introduces a novel workflow and tool for enabling users to ask questions about a specific building's data, using natural language and receive answers automatically generated by GPT-4o. Our approach integrates semantic ontologies with advanced LLM capabilities to automate three critical steps: (1) generating SPARQL queries to retrieve time series references from ontological models, (2) extracting the corresponding time series data from the Building Automation System, and (3) performing computations and visualizations tailored to the user's query. The proposed method simplifies access to BAS data, allowing both domain experts and non-specialists to conduct sophisticated analyses without needing extensive technical knowledge of semantic web technologies. By demonstrating this pipeline, we facilitate more accessible and scalable data-driven decision-making in building operations and management.

Mulayim, Ozan Baris↗
DOE OSTI2017

Assessing Occupant and Outdoor Air Impacts on Indoor Air Quality in New California Homes

In 2008 the State of California adopted new building codes that required the use of mechanical ventilation systems in homes that meet the requirements of ASHRAE Standard 62.2. The standard requires both a dwelling unit mechanical ventilation system and exhaust fans in kitchens and bathrooms. A field study was undertaken to evaluate the IAQ and ventilation performance of homes built to these requirements. For ventilation system performance, the airflows of all mechanical ventilation systems were measured and their use was monitored for a one-week period. To evaluate IAQ, key pollutants were measured indoors and outdoors during the week, and occupants completed satisfaction surveys. The key pollutants included: formaldehyde, humidity, PM2.5 and NO2. Passive samplers were used to determine average concentrations for the week. Active samplers were used to develop time-series results that can be used to correlate pollutant concentrations with occupant activities. Other ventilation/IAQ related parameters were also recorded, such as stove top temperatures to indicate cooking, exterior door contact switches to know when large openings were being used for ventilation and sensors to determine when clothes dryers were being used. The building envelope and duct leakage were measured to enable estimates of infiltration and duct leakage effects. This paper presents an overview of the test procedures and preliminary results from several homes. The results show that although average concentrations may be reasonable compared to available standards (with the exception of formaldehyde), occupants have a strong impact on pollutant variability and source strength and that outdoor concentrations cannot be ignored. Overall, these mechanically ventilated homes have reasonable IAQ. The homes and duct systems are moderately tight, though not excessively so, by US standards. Significant concerns have been expressed regarding compliance with the ventilation requirements in the California building code. However, almost all the ventilation systems in this study complied with the ventilation air flow requirements and on average were significantly higher than the minimum required air flow rates.

Walker, IS↗
DOE OSTI2020

Re-Envisioning RCx: Achieving Max Potential HVAC Controls Retrofits through Modernized BAS Hardware and Software

Most existing buildings have sub-optimal heating, ventilation, and air conditioning (HVAC) controls, resulting in wasted energy and occupant discomfort. Retro-commissioning (RCx) addresses many of these issues, but it is a lengthy and highly customized process. Limited capabilities of existing building automation system hardware restricts the scope of most RCx projects. Incentive programs consider building automation system (BAS) hardware retrofits to be high-capital investments and do not allow them in typical RCx programs. This paper describes work that the authors are leading to facilitate technical and market innovation in the BAS industry to unlock large savings in existing commercial buildings through deep retrofits of BAS hardware and software. California and New York research projects are demonstrating BAS retrofits leveraging the American Society of Heating, Refrigeration, and Air Conditioning Engineers’ (ASHRAE) new Guideline 36 high performance sequences of operation to achieve greater than 20 percent whole building energy savings, while saving costs and reducing risk through streamlined processes and standardization across BAS manufacturer product lines and across implementation practices. This paper describes market barriers that impede achieving deep savings from BAS retrofits in custom incentive and traditional RCx programs and presents a new maximum potential BAS retrofit model that addresses these barriers. The new model leverages the authors’ efforts in market enablement through open standards, BAS industry partnerships, and tools for cost-effective scaling that includes tools for project screening, savings calculations, and measurement and verification (M&V). This approach is widely applicable and will be ready for at-scale implementation within two years.

Paliaga, Gwelen↗
DOE OSTI2025

HP-FLEX: Field demonstration of the semantics-driven configuration of a Model Predictive Control system to make heat pumps flexible

Model Predictive Control (MPC) has demonstrated significant potential for optimizing building operations and enabling demand flexibility. However, the widespread adoption of MPC is hindered by complex manual configuration and commissioning processes that must be conducted by control experts working alongside building operators. These challenges drive up costs and reduce scalability, particularly when technical human resources and building automation systems are limited, such as in small and medium commercial buildings (SMCBs). This paper demonstrates how semantic standards, specifically ASHRAE 223P, can accelerate the adoption of MPC applications for load flexibility in SMCBs. The authors present a replicable control framework, titled “HP-FLEX” that leverages a building’s semantic model to bootstrap the required data configuration for an MPC controller developed for optimizing heat pump systems as flexible grid resources. The semantic model helps streamline the deployment workflow, particularly for site setup, data/control commissioning, and model setup. This integration enhances portability, transferability, and scalability of the HP-FLEX MPC, which has been developed to support MPC-based supervisory HVAC controllers in SMCBs. Additionally, the paper details the required building and thermostat metadata information to enable the HP-FLEX MPC based on field demonstrations. The new workflow was tested in a small commercial building located in California, U.S., and demonstrated a load shifting performance of 9% based on a dynamic pricing signal that varies by the hour. This work provides a practical pathway for transitioning sophisticated building applications from custom to standardized semantic representations, supporting the broader adoption of advanced control strategies like MPC. The framework also establishes a foundation for evolving metadata requirements as applications mature while maintaining compatibility with industry standards.

Paul, Lazlo↗
DOE OSTI2013

Energy and Energy Cost Savings Analysis of the IECC for Commercial Buildings

The purpose of this analysis is to assess the relative energy and energy cost performance of commercial buildings designed to meet the requirements found in the commercial energy efficiency provisions of the International Energy Conservation Code (IECC). Section 304(b) of the Energy Conservation and Production Act (ECPA), as amended, requires the Secretary of Energy to make a determination each time a revised version of ASHRAE Standard 90.1 is published with respect to whether the revised standard would improve energy efficiency in commercial buildings. As many states have historically adopted the IECC for both residential and commercial buildings, PNNL has evaluated the impacts of the commercial provisions of the 2006, 2009, and 2012 editions of the IECC. PNNL also compared energy performance with corresponding editions of ANSI/ASHRAE/IES Standard 90.1 to help states and local jurisdictions make informed decisions regarding model code adoption.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2013

Simulation Analyses in Support of DOE’s Fossil Fuel Rule for Single Component Equipment and Lighting Replacements

At the request of the US Department of Energy’s (DOE) Federal Energy Management Program (FEMP), Pacific Northwest National Laboratory (PNNL) conducted a series of building energy simulations using a large office model to investigate the potential savings that could be accrued from a typical chiller, boiler, or lighting replacement in a Federal office building. FEMP’s interest was in knowing whether or not single component replacements like these would have any chance of achieving the fossil- fuel-based energy consumption reduction requirements specified in Section 433 of the Energy Independence and Security Act (EISA) of 20071. Specifically, FEMP was interested in whether an older Federal building, built in the 1980s or 1990s and designed to meet energy standards in place at the time the building was designed, could meet the requirements of Section 433 of EISA for renovations. Many single component renovations like chiller replacements, boiler replacements, and lighting retrofits may meet the minimum cost requirement of Section 433 of EISA but may not offer any opportunity to achieve fossil-fuel-generated energy consumption reductions on the order of 55% or more. If single component renovations such as these would not achieve the necessary reductions, then FEMP would consider modifying rules based on Section 433 of EISA to exempt these types of single component renovations from the overall fossil-fuel-generated energy consumption reduction provisions. FEMP would instead require Federal agencies to ensure that these renovations use FEMP-designated efficiencies for chillers and boilers or the lighting power density requirements found in ASHRAE Standard 90.1-2010. The results of PNNL’s analysis indicated that it is unlikely that a combined boiler and chiller replacement, or an individual boiler or chiller replacement in an older existing Federal building would meet the requirements of Section 433 of EISA. While buildings can achieve up to 34% reduction in cooling and 11% reduction in heating load with this type of retrofit, these savings fall well short of the minimum savings specified in Section 433 of EISA. Similarly, a lighting retrofit in an older existing Federal building would also not likely meet the requirements of Section 433 of EISA. While buildings can save up to 52% on lighting loads, the whole buildings savings would be well short of the minimum savings specified in Section 433 of EISA.

Halverson, Mark A.↗
DOE OSTI2013

Multifamily Individual Heating and Ventilation Systems, Lawrence, Massachusetts (Fact Sheet)

The conversion of an older Massachusetts building into condominiums illustrates a safe, durable, and cost-effective solution for heating and ventilation systems that can potentially benefit millions of multifamily buildings. Merrimack Valley Habitat for Humanity (MVHfH) partnered with U.S. Department of Energy Building America team Building Science Corporation (BSC) to provide high performance affordable housing for 10 families in the retrofit of an existing mass masonry building (a former convent). The original ventilation design for the project was provided by a local engineer and consisted of a single large heat recovery ventilator (HRV) located in a mechanical room in the basement with a centralized duct system providing supply air to the main living space and exhausting stale air from the single bathroom in each apartment. This design was deemed to be far too costly to install and operate for several reasons: the large central HRV was oversized and the specified flows to each apartment were much higher than the ASHRAE 62.2 rate; an extensive system of ductwork, smoke and fire dampers, and duct chases were specified; ductwork required a significant area of dropped ceilings; and the system lacked individual ventilation control in the apartments.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Moisture performance of sealed attics in the mixed-humid climate

Oak Ridge National Laboratory studied 8 homes in the mixed-humid climate, 4 with vented attics and 4 with sealed attics. ORNL wanted to understand the moisture performance of the sealed attic and how it affected the interior environment. We found that the attic and interior of sealed attic homes were more humid than the attic and interior observed in vented attic homes. This is due to the lack of ventilation in the sealed attic. Historically attics have been vented to dehumidify the attic and interior of the home. A sealed attic design greatly reduces the venting potential and thus this drying pathway and can cause elevated interior moisture over a vented attic home. Despite the elevated attic and interior moisture in the sealed attic homes, so far no mold or material degradation has been found. The roof sheathing moisture content has stayed below 20%, indicating low potential for material degradation. Also the relative humidity at the roof sheathing has stayed within the ASHRAE 160 design criteria except for a short time during the 2011/2012 winter. This was due to a combination of the sealed attic design (minimal venting to the outside) and the duct work not being operated in the attic which usually provides a dehumidification pathway. It was also found that when the humidity was controlled using the HVAC system, it resulted in 7% more cooling energy consumption. In the mixed-humid climate this reduces the cost effectiveness of the sealed attic design as a solution for bringing ducts into a semi-conditioned space. Because of this we are recommending the other alternatives be used to bringing ducts into the conditioned space in both new construction and retrofit work in the mixed-humid climate.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Hydronic Heating Coil Versus Propane Furnace, Rehoboth Beach, Delaware (Fact Sheet)

Insight Homes constructed two houses in Rehoboth Beach, Delaware, with identical floor plans and thermal envelopes but different heating and domestic hot water (DHW) systems. Each house is 1,715-ft 2 with a single story, three bedrooms, two bathrooms, and the heating, ventilation, and air conditioning (HVAC) systems and ductwork located in conditioned crawlspaces. The standard house, which the builder offers as its standard production house, uses an air source heat pump (ASHP) with supplemental propane furnace heating. The Building America test house uses the same ASHP unit with supplemental heat provided by the DHW heater (a combined DHW and hydronic heating system, where the hydronic heating element is in the air handler). Both houses were occupied during the test period. Results indicate that efficiency of the two heating systems was not significantly different. Three issues dominate these results; lower system design performance resulting from the indoor refrigerant coil selected for the standard house, an incorrectly functioning defrost cycle in the standard house, and the low resolution of the natural gas monitoring equipment. The thermal comfort of both houses fell outside the ASHRAE Standard 55 heating range but was within the ACCA room-to-room temperature range when compared to the thermostat temperature. The monitored DHW draw schedules were input into EnergyPlus to evaluate the efficiency of the tankless hot water heater model using the two monitored profiles and the Building America House Simulation Protocols. The results indicate that the simulation is not significantly impacted by the draw profiles.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

Ventilation System Effectiveness and Tested Indoor Air Quality Impacts

Ventilation system effectiveness testing was conducted at two unoccupied, single-family, detached lab homes at the University of Texas - Tyler. Five ventilation system tests were conducted with various whole-building ventilation systems. Multizone fan pressurization testing characterized building and zone enclosure leakage. PFT testing showed multizone air change rates and interzonal airflow. Cumulative particle counts for six particle sizes, and formaldehyde and other Top 20 VOC concentrations were measured in multiple zones. The testing showed that single-point exhaust ventilation was inferior as a whole-house ventilation strategy. It was inferior because the source of outside air was not direct from outside, the ventilation air was not distributed, and no provision existed for air filtration. Indoor air recirculation by a central air distribution system can help improve the exhaust ventilation system by way of air mixing and filtration. In contrast, the supply and balanced ventilation systems showed that there is a significant benefit to drawing outside air from a known outside location, and filtering and distributing that air. Compared to the Exhaust systems, the CFIS and ERV systems showed better ventilation air distribution and lower concentrations of particulates, formaldehyde and other VOCs. System improvement percentages were estimated based on four System Factor Categories: Balance, Distribution, Outside Air Source, and Recirculation Filtration. Recommended System Factors could be applied to reduce ventilation fan airflow rates relative to ASHRAE Standard 62.2 to save energy and reduce moisture control risk in humid climates. HVAC energy savings were predicted to be 8-10%, or $50-$75/year.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

Addressing Kitchen Contaminants for Healthy, Low-Energy Homes

Cooking and cooking burners emit pollutants that can adversely affect indoor air quality in residences and significantly impact occupant health. Effective kitchen exhaust ventilation can reduce exposure to cooking-related air pollutants as an enabling step to healthier, low-energy homes. This report identifies barriers to the widespread adoption of kitchen exhaust ventilation technologies and practice and proposes a suite of strategies to overcome these barriers. The recommendations have been vetted by a group of industry, regulatory, health, and research experts and stakeholders who convened for two web-based meetings and provided input and feedback to early drafts of this document. The most fundamental barriers are (1) the common misconception, based on a sensory perception of risk, that kitchen exhaust when cooking is unnecessary and (2) the lack of a code requirement for kitchen ventilation in most US locations. Highest priority objectives include the following: (1) Raise awareness among the public and the building industry of the need to install and routinely use kitchen ventilation; (2) Incorporate kitchen exhaust ventilation as a requirement of building codes and improve the mechanisms for code enforcement; (3) Provide best practice product and use-behavior guidance to ventilation equipment purchasers and installers, and; (4) Develop test methods and performance targets to advance development of high performance products. A specific, urgent need is the development of an over-the-range microwave that meets the airflow and sound requirements of ASHRAE Standard 62.2.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

A Meta-Analysis of Single-Family Deep Energy Retrofit Performance in the U.S.

The current state of Deep Energy Retrofit (DER) performance in the U.S. has been assessed in 116 homes in the United States (US), using actual and simulated data gathered from the available domestic literature. Substantial airtightness reductions averaging 63% (n=48) were reported (two- to three-times more than in conventional retrofits), with average post-retrofit airtightness of 4.7 Air Changes per House at 50 Pascal (ACH 50 ) (n=94). Yet, mechanical ventilation was not installed consistently. In order to avoid indoor air quality (IAQ) issues, all future DERs should comply with ASHRAE 62.2-2013 requirements or equivalent. Projects generally achieved good energy results, with average annual net-site and net-source energy savings of 47%±20% and 45%±24% (n=57 and n=35), respectively, and carbon emission reductions of 47%±22% (n=23). Net-energy reductions did not vary reliably with house age, airtightness, or reported project costs, but pre-retrofit energy usage was correlated with total reductions (MMBtu). Annual energy costs were reduced $\$1,283$ ± $\$804$ (n=31), from a pre-retrofit average of $\$2,738$ ± $\$1,065$ to $\$1,588$ ± $\$561$ post-retrofit (n=25 and n=39). The average reported incremental project cost was $\$40,420$ ± $\$30,358$ (n=59). When financed on a 30-year term, the median change in net-homeownership cost was only $\$1.00$ per month, ranging from $\$149$ in savings to an increase of $\$212$ (mean= $\$15.67$ ± $\$87.74$; n=28), and almost half of the projects resulted in reductions in net-cost. The economic value of a DER may be much greater than is suggested by these net-costs, because DERs entail substantial non-energy benefits (NEBs), and retrofit measures may add value to a home at resale similarly to general remodeling, PV panel installation, and green/energy efficient home labels. These results provide estimates of the potential of DERs to address energy use in existing homes across climate zones that can be used in future estimates of the technical potential to reduce household energy use and greenhouse gas emissions through DERs.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

Evaluation of the Efficacy of Bayesian Calibration: Interim Project Report

This project evaluated the efficacy of applying Bayesian calibration to EnergyPlus building energy models under different levels of data uncertainty. Small, medium, and large office buildings were modeled with input uncertainty consistent with data collection from the three standard ASHRAE audit levels. It was shown that Bayesian calibration both adjusts parameter values closer to the true values, while simultaneously reducing the uncertainty in the parameter values. Consequently, Bayesian-calibrated EnergyPlus models enhance the reliability of energy use predictions by more closely matching monthly utility bills with much reduced uncertainty compared with uncalibrated models.

Heo, Yeonsook↗
DOE OSTI2014

ANSI/ASHRAE/IES Standard 90.1-2013 Preliminary Determination: Qualitative Analysis

Section 304(b) of the Energy Conservation and Production Act (ECPA), as amended, requires the Secretary of Energy to make a determination each time a revised version of ASHRAE Standard 90.1 is published with respect to whether the revised standard would improve energy efficiency in commercial buildings. When the U.S. Department of Energy (DOE) issues an affirmative determination on Standard 90.1, states are statutorily required to certify within two years that they have reviewed and updated the commercial provisions of their building energy code, with respect to energy efficiency, to meet or exceed the revised standard. This report provides a preliminary qualitative analysis of all addenda to ANSI/ASHRAE/IES Standard 90.1-2010 (referred to as Standard 90.1-2010 or 2010 edition) that were included in ANSI/ASHRAE/IES Standard 90.1-2013 (referred to as Standard 90.1-2013 or 2013 edition).

determination↗
DOE OSTI2014

Case Study of a Heating Only Central GSHP System Using a Shallow Aquifer for a Warehouse

High initial cost and lack of public awareness of ground source heat pump (GSHP) technology are the two major barriers preventing rapid deployment of this energy saving technology in the United States. Under the American Recovery and Reinvestment Act (ARRA), 26 GSHP projects have been competitively selected and carried out to demonstrate the benefits of GSHP systems and innovative technologies for cost reduction and/or performance improvement. This paper highlights findings of a case study of one of the ARRA-funded GSHP demonstration projects, which is a heating only central GSHP system using shallow aquifer as heat source and installed at a warehouse and truck bay at Kalispell, MT. This case study is based on the analysis of measured performance data, utility bills, and calculations of energy consumptions of conventional central heating systems for providing the same heat outputs as the central GSHP system did. The evaluated performance metrics include energy efficiency of the heat pump equipment and the overall GSHP system, pumping performance, energy savings, carbon emission reductions, and cost-effectiveness of GSHP system compared with conventional heating systems. This case study also identified areas for reducing uncertainties in performance evaluation, improving operational efficiency, and reducing installed cost of similar GSHP systems in the future. Publication of ASHRAE at the annual conference in Seattle.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

RTU Comparison Calculator Enhancement Plan

Over the past two years, Department of Energy’s Building Technologies Office (BTO) has been investigating ways to increase the operating efficiency of the packaged rooftop units (RTUs) in the field. First, by issuing a challenge to the RTU manufactures to increase the integrated energy efficiency ratio (IEER) by 60% over the existing ASHRAE 90.1-2010 standard. Second, by evaluating the performance of an advanced RTU controller that reduces the energy consumption by over 40%. BTO has previously also funded development of a RTU comparison calculator (RTUCC). RTUCC is a web-based tool that provides the user a way to compare energy and cost savings for two units with different efficiencies. However, the RTUCC currently cannot compare savings associated with either the RTU Challenge unit or the advanced RTU controls retrofit. Therefore, BTO has asked PNNL to enhance the tool so building owners can compare energy and savings associated with this new class of products. This document provides the details of the enhancements that are required to support estimating energy savings from use of RTU challenge units or advanced controls on existing RTUs.

Miller, James D.↗
DOE OSTI2014

ANSI/ASHRAE/IES Standard 90.1-2013 Determination of Energy Savings: Quantitative Analysis

This report provides a final quantitative analysis to assess whether buildings constructed according to the requirements of ANSI/ASHRAE/IES Standard 90.1-2013 would result in improved energy efficiency in commercial buildings. The final analysis considered each of the 110 addenda to Standard 90.1-2010 that were included in Standard 90.1-2013. PNNL reviewed all addenda included by ASHRAE in creating Standard 90.1-2013 from Standard 90.1-2010, and considered their combined impact on a suite of prototype building models across all U.S. climate zones. Most addenda were deemed to have little quantifiable impact on building efficiency for the purpose of DOE’s final determination. However, out of the 110 total addenda, 30 were identified as having a measureable and quantifiable impact.

Halverson, Mark A.↗
DOE OSTI2013

The business of high performance: The USC Darla Moore School of Business

The University of South Carolina (USC), a public university in Columbia, South Carolina, partnered with the U.S. Department of Energy (DOE) to develop and implement solutions to build a new, low-energy educational building. The new Darla Moore School of Business (DMSB) will consume at least 50% less energy than requirements set by Energy Standard 90.1-2007 of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), the American National Standards Institute (ANSI), and the Illuminating Engineering Society of North America (IESNA) as part of DOE's Commerical Building Partnerships (CBP) program. 4 Lawrence Berkeley National Laboratory (LBNL) provided technical expertise in support of this DOE program.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗