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Net-Zero Energy, High-Performance Buildings Program
The Net-Zero Energy, High-Performance Buildings Program is one of two programs that are being pursued within the Energy and Environment Division. The program objective is to develop and deploy advances in measurement science to move the nation toward net-zero energy, high-performance buildings while maintaining healthy indoor environments. The program has four technical thrusts—whole building metrics, building load reduction, equipment efficiency, and onsite energy generation.
The division consists of 11 projects led by 11 separate project leaders. There are 25 full-time permanent staff members (20 scientists and engineers and 5 technicians); 8 other employees (term employees, postdoctoral researcher, and students); and 6 NIST associates.
TECHNICAL MERIT OF THE PROGRAM
Accomplishments
The program demonstrated significant accomplishments across all four technical thrusts.
The Whole Building Metrics thrust displayed technical accomplishments across the spectrum of building sustainability areas, including the development of metrics and evaluation tools for indoor air quality (IAQ) applicable to low-energy buildings. Of special note is the flexibility and speed exhibited in responding to the COVID-19 pandemic in several ways, including by incorporating the CONTAMX engine into the FaTIMA tool developed to assist in evaluating the impacts of aerosol exposure controls in response to COVID-19.
The unique Net Zero Energy Residential Test Facility (NZERTF) offers tremendous opportunities to test low-energy systems with the goal of demonstrating net-zero energy performance. Systems tested included space conditioning equipment, air distribution, domestic water, and demand-controlled ventilation. The NZERTF is expected to be used to support the Chemical Assessment of Surface and Air (CASA) project in fiscal year (FY) 2022, which is a collaborative, multi-institution field effort to quantify indoor air chemistry issues (connected to the Sloan Foundation Indoor Chemistry program).
Significant contributions in high-performance buildings include the following: the production of formaldehyde measurement and reference material production—formaldehyde is one of the most common and most concerning volatile organic compounds (VOCs) emitted by many building materials, and it is the only VOC that is regulated currently—and the study of emissions from cigarette butts, which is new science directed at assessing a potential health risk, conducted with sponsorship of the U.S. Food and Drug Administration (FDA) as well as internal NIST funds.
The initiation of a project to understand factors that contribute to water quality under the operational parameters of high-performance buildings is necessary to achieve the net-zero goal. In net-zero energy, high-performance buildings, the reduction in water usage leads to unintended, undesired consequences, such as pipe corrosion, deposition of corrosion byproducts, decreased waste conveyance, increased biofilm formation, and pathogen growth.
NIST continues to develop software programs (BEES, BIRDS, BIRDS NEST, and E3) for use in valuation of economic performance (life-cycle cost) and environmental performance (life-cycle assessment). BIRDS NEST (Building Industry Reporting and Design for Sustainability Neutral Environmental Software Tool) software will replace BIRDS (which measures the environmental performance of building products by using the life-cycle assessment approach specified in the ISO 14040) and is interoperable with the Department of Energy’s OpenStudio, the Athena Sustainable Materials Institute’s (ASMI’s) Impact Estimator for Buildings, and compatible with a variety of other software tools. It is used by building designers and architects familiar with building energy modeling E3 is an economic evaluation engine that will provide economic calculations to academics and software developers.
Under the Building Load Reduction thrust, the IAQ research group developed the important extensions of IAQ analysis tools (specifically CONTAM) to couple with energy simulation software (EnergyPlus and TRNSYS) to provide improved characterization and analysis of net-zero energy buildings. The NIST program on evaluation of insulation materials remains the world’s leading program for the measurement science of current, widely used insulation materials. Insulation is a key component in the energy efficiency of the building envelope, which is a long-lasting building system.
The Equipment Efficiency thrust’s accomplishments will enable the use of the low-global warming potential (GWP) refrigerants to be used safely in building applications. Development of heat transfer and system performance information will assist in the selection and implementation of the best replacements for high-GWP hydrofluorocarbon (HFC). The thrust has advanced testing and modeling of the fire behavior of low-GWP working fluids, which have higher flammability than the working fluids they are replacing. This work is among the best in the world and is globally integrated with collaborators. The thrust is also testing high-efficiency equipment (various kinds of heat pumps, including CO2, an emerging technology) in environmental chambers and the NZERTF. The data analysis and simulations identify climate-appropriate solutions and implement optimization in design software. Additionally, novel equipment (e.g., magnetic refrigeration) has been investigated.
The On-Site Energy Generation thrust’s accomplishments include the characterization of photovoltaic components and materials within them. The NIST research team has designed and built SI-traceable reference cells for terrestrial one-sun (AM1.5) condition. The United States was behind other nations (e.g., Germany and Singapore) in developing photovoltaic (PV) standards. This brings the United States to parity with other countries. There is a need for U.S. researchers to obtain reference cells to validate their PV performance. This is a very important function of this group of researchers. NIST Campus PV arrays and weather station data (https://doi.org/10.18434/M3S67G) are good resources. Polymeric materials are used widely in PV modules. While the silicon light absorber can last for a long time, less is known about the long-term performance of these polymers in encapsulants and back sheets. This project helps develop and implement facilities and measurement techniques to study these supporting, but critical, materials in the PV modules.
Challenges and Opportunities
The Assessment of Insulation Thermal Performance project is expanding into the measurement of innovative insulation materials. Because some of these new insulation materials have different mechanisms of thermal transport, current test methods may not provide a complete characterization of the material performance. For example, phase change materials need to have a procedure that accounts for the energy storage in the phase change.
There is no mention of a thermoelectric program to harvest waste heat, which might be an important aspect of low-energy buildings.
There are concerns about safety issues, in particular fire safety, associated with materials used in low-energy buildings. Cross-division collaborations would be productive in gathering data to better understand these issues.
The Engineering Laboratory’s (EL’s) capabilities for developing a flammability metric for low-GWP working fluids are unique and would offer benefits if the capabilities were deployed in other applications—for example, the use of low-GWP processing aids in industrial processes.
The NIST PV research group has started to investigate indoor PV standards and reference cells. Low-light studies and indoor white light harvesting will be important for wide deployment of Internet of Things (IoT) devices and sensors needed to monitor energy usage in low-energy buildings. Indoor PV measurement standards are urgently needed.
The PV performance project so far has worked only on traditional inorganic PV materials, (e.g., Si, GaAs, and Ge); second-generation and third-generation PVs (e.g., organic PVs and halide perovskite PVs) have now achieved very high efficiencies under AM1.5. They might be even more applicable for indoor PV applications.
Understanding the compounding effects of multiple stresses—for example, thermal and mechanical, on degradation mechanism of the polymers used in PV systems is important. Understanding how to use laboratory results to predict field service outcome is necessary for the next phase of the study.
The renewed awareness of indoor air quality created by the COVID-19 pandemic combined with the growing use of simulation in engineering practice is an opportunity for further development of the capabilities and integration with other tools of CONTAMW.
PORTFOLIO OF SCIENTIFIC EXPERTISE
Accomplishments
The Net-Zero Energy, High-Performance Buildings team is one of the leading modeling tool development groups in IAQ, complemented by experimental/field investigation capabilities of the group.
A staff member has been recognized by a prestigious Presidential Early Career Award for Scientists and Engineers (PECASE) in 2019 and is the driver of the NIST PV program. Collaboration with researchers who specialize in the net-zero buildings to implement indoor light harvesting for IoT devices is beneficial for the next phase of the electrical performance of solar PV cells and arrays project.
Non-destructive optical and chemical characterizations are important for studies into the service life prediction of polymers used in PV systems. The laboratory expertise and field studies are both necessary to achieve the objective.
The combination of experimental and simulation capabilities has led to achievements necessary for the industry to fully utilize the low-GWP refrigerants.
The development of metrics and tools for sustainable buildings, such as BEES, BIRDS, BIRDS NEST, and E3, requires close collaboration between economists and engineers. NIST is an ideal environment for such an interdisciplinary project.
NIST is long recognized as the leader in insulation measurement and standards.
EL has very good expertise in laboratory, field measurements, and modeling in contaminant control and IAQ.
The water use in high-performance buildings project builds on NIST’s existing building water heating energy efficiency study on testing methods for water heaters.
Challenges and Opportunities
NIST is no longer making organic PVs, and so there is no internal collaboration for the PV group in EL to explore newer technologies. The group needs to seek collaborations outside of NIST.
In the insulation thermal performance project, succession planning for retiring personnel is critical. It appears that principal investigator succession transition has been successful, but it is less clear what the plans are for succession planning for the technician resource.
The water use in high-performance buildings project requires expertise in fluid dynamics, heat transfer, biology, and modeling. The information provided did not show a multidisciplinary team.
ADEQUACY OF RESOURCES
Accomplishments
The NZERTF is a unique facility that provides opportunities for a multitude of high-performance building studies, including equipment testing, energy efficiency, and IAQ. Although built several years ago, significant foresight into the design of the building has allowed the structure to maintain building loads that remain lower than current code-compliant building. The three ground-source heat pumps in the NZERTF are impressive and will allow quantitative comparison of different technologies. Additionally, side-by-side, small-duct high-velocity, and conventional heat pump systems will provide valuable comparison data.
The emission testing laboratory used for formaldehyde and cigarette butt studies has excellent capabilities.
A substantial multiyear overhaul of the unique guarded hot-box facilities was completed this year.
The HVAC&R research group has a combination of capabilities in material property characterization, application testing (mini-breadboard heat pump [MB-HP]) and modeling. Equipment modifications were made to accommodate new refrigerant flammability concerns.
The laboratory’s experimental apparatus and modeling capabilities for the investigation of flammability of low-GWP refrigerants are excellent and unique.
There are advanced measurement capabilities, including LED array sources, complete I-V-T (current versus voltage versus temperature) measurement stations, and wide-field hyperspectral imaging system, open up the ability to study different PV materials and devices.
The state-of-the-art accelerated laboratory weather chamber is critical for study of long-term polymer degradation.
Challenges and Opportunities
Additional equipment is needed for measuring non-steady state material thermal transfer properties.
Several facilities are necessary for the successful completion of projects, including the environmental chambers, which are aging and need maintenance and possibly upgrade and enhancement.
A single researcher is listed for the water use in high-performance buildings project. For something this complex, it seems that a team is needed.
EFFECTIVENESS OF DISSEMINATION OF OUTPUTS
Accomplishments
There are many instances of collaboration with universities and others outside of NIST to apply tools in their research. Some examples include the following: collaboration with the Boston University School of Public Health to study of interventions to reduce multifamily housing energy use and contaminant exposures using coupled simulations; collaboration with the New Jersey Institute of Technology on the analysis of comfort data from prior heat pump (HP) system tests; and participation in
the multi-institution Chemical Assessment of Surface and Air (CASA) project that will be widely disseminated under Sloan Foundation sponsorship.
The NIST PV research group publishes in appropriate journals (e.g., IEEE Journal of Photovoltaics and Applied Physics Letters). As part of the group’s outreach, members attend PV specialist conferences.
Applications of tools (e.g., CONTAM) are frequently published in journals and presented at conferences. In FY 2018, stakeholders from the building energy efficiency, water efficiency, and water quality communities were convened to formulate measurement science research needs for plumbing systems. The result was a roadmap published by NIST (https://doi.org/10.6028/NIST.TN.2088). Staff participate in the International Thermal Conductivity Conference and publish in relevant journals such as Metrologia, Journal of ASTM International, and ASHRAE Journal. Staff regularly present at the International Society of Indoor Air Quality and Climate Indoor Air conference, the largest and most important conference for indoor air quality science.
Staff members are active participants in the development of several ASTM standards on standardized test methods for improving materials testing, laboratory weathering, and service life prediction of PV polymers and components. Additionally, they actively contribute to several ASTM standards on chemical emissions from building materials, including formaldehyde; they provide continuing leadership insulation standard reference materials that are widely used by industry (1450e Fibrous Glass Board, 1452 Fibrous Glass Blanket, 1453 Expanded Polystyrene and 1459 Fumed Silica Board); and contribute to thick calibration transfer specimens for manufacturers of residential insulation (linked to ASTM Committee C16 on Thermal Insulation).
Staff have been significant participants in interactions with refrigerant stakeholders and standards development. Within ASHRAE, staff are active on: T.C. 3.1—Refrigerants and Secondary Coolants, Research Subcommittee; SSPC 34, Flammability Subcommittee; the Project Management Subcommittee for ASHRAE-RP1806; the Project Management Subcommittee for new HF formation project; and presenting at ASHRAE meetings. For the Air-Conditioning, Heating, and Refrigeration Institute (AHRI), staff hold membership on the AHRI Flammable Refrigerants Subcommittee and are helping to identify and guide new research on refrigerant flammability. For the International Organization for Standardization (ISO), staff hold membership in TC86, SC 8/WG8: Burning Velocity Test Methods, providing on-going detailed input to new ISO standard test methods on LBV (laminar burning velocity). Staff are technical points of contact for two NIST Standard Reference HVAC& R Databases: (1) CYCLE_D, for evaluating refrigerant cycle performance based on thermodynamic properties (https://www.nist.gov/srd/nist-standard-reference-database-49), and (2) REFLEAK, for estimating the composition shift of zeotropic refrigerant blends resulting from the leak/recharge processes (https://www.nist.gov/srd/nist-standard-reference-database-73).
Staff make their NIST-developed simulation tools publicly available. The development of software is driven by industry needs, and these tools are widely used in academia. CYCLE_D-HX has been completed, and validated with extensive testing, and placed on the NIST EL website in FY 2018 for free download (https://www.nist.gov/services-resources/software/cycled-hx-nist-vapor-compressioncycle-modelaccounting-refrigerant). BEES, BIRDS NEST, and E3 are associated with the metrics program and sustainability and economic analysis of projects. CONTAM is one of the most widely used multizone modeling tools for the study of air and contaminant flows in buildings. It has been coupled with multiple complementary tools for energy simulation and also with CFD software. The CONTAMX computational engine has been used in special purpose tools including LoopDA for natural ventilation analysis and FaTIMA for exposure analysis.
Challenges and Opportunities
Since NIST is not an academic institution and needs to balance publications, standards, reference materials, and research, the productivity cannot be measured by publications alone. However, it should be
clear to the researchers whether they are measured by the number of publications or the number of citations from their publications. The Net-Zero Energy, High-Performance Buildings program’s only publication from 2018, associated with the Measurement Science for Service Life Prediction of Polymers Uses PV Systems project, seems to be below expectation.
Little work is being done with standards development on the electrical performance of solar PV cells and arrays, and it seems this is potentially a fruitful area for standards.
CONCLUSIONS AND RECOMMENDATIONS
Many of the accomplishments of the Net-Zero Energy, High-Performance Buildings program involve the measurement, characterization, and modeling of indoor air quality in high-performance buildings. Indoor air quality concerns related to COVID-19 and smoke from wildfires lately have increased the urgency of research in this area. Creating a separate technical thrust in IAQ may allow NIST’s EL-unique capabilities to be used to address a greater number of applications.
RECOMMENDATION: The Net-Zero Energy, High-Performance Buildings program should organize a specific technical thrust in indoor air quality (IAQ) in order to increase the program’s ability to provide a focused and effective response to urgent IAQ issues.
The NZERTF is a unique facility that provides benefits both to NIST and to external researchers and collaborators. There is potential to expand the use of the facility to further develop the program’s interactions with external collaborators.
RECOMMENDATION: The Engineering Laboratory should proactively seek opportunities to fully utilize the capabilities of Net Zero Energy Residential Test Facility to expand collaborations between the program researchers and other researchers.
The EL’s unique position in the development of IAQ analysis tools (especially CONTAM) and the coupling of CONTAM with energy simulation software has provided improved analysis capabilities of net-zero energy building performance. These capabilities can be extended with an improved CONTAM user interface and continued projects that analyze the interaction between indoor environment and energy efficiency.
RECOMMENDATION: The Engineering Laboratory should improve the CONTAM user interface and seek opportunities to demonstrate the interaction between indoor air quality and energy efficiency analyses.
The EL has long been the industry leader in the metrication and standardization of insulation and HVAC&R equipment. To maintain this leadership position, the testing facilities need to be maintained and upgraded to match the innovation occurring in industry.
RECOMMENDATION: The Engineering Laboratory should seek adequate funding of facilities maintenance to ensure that NIST can continue its industry leadership position in measurement and standardization of energy-efficient materials and systems.
The work of the EL to understand the performance, especially the flammability, of low-GWP working fluids is critical for the successful transition to low-GWP fluids. As the transition to low-GWP fluids is occurring across industrial sectors, this research can be expanded to support industrial processing.
RECOMMENDATION: The work to develop a flammability metric for low- global warming potential working fluids should be expanded to include additional industrial applications.
The creation of calibrated standard reference solar cells by the EL researchers established an SI-traceable reference instrument and brought the United States on par with other countries. However, it is prudent to look ahead, rather than playing catch-up. In the past decade, there have been many breakthroughs in third-generation photovoltaic cells, in particular organic and perovskite solar cells. Additionally, standards need to be established for new applications beyond one-sun conditions (e.g., indoor IoT applications). If expertise does not exist within NIST, outside collaborations should be sought.
RECOMMENDATION: The NIST Photovoltaics research group should establish standards for solar cells based on materials beyond traditional inorganic semiconductor solar cells and for testing conditions beyond terrestrial one-sun illumination. If expertise does not exist within NIST, outside collaborations should be pursued.
Dissemination of EL results takes on several different forms—for example, publication in referred journals or NIST technical notes, software, standards, and reference materials. Depending on the nature of the work, groups naturally have different portfolios. The dissemination activities are not uniformly high across all projects. It would also be helpful for the staff to know the precise metric for evaluation. In terms of publication of refereed papers, the EL needs internal clarification as to whether the number of papers or the number of citations of the papers that is important. Additionally, the number of standards adopted has not been tracked.
RECOMMENDATION: The Engineering Laboratory should articulate clear evaluation criteria for output and use these criteria to determine whether to encourage or to sunset a project. Since NIST is unique in setting standards, adoption of standards by industrial groups should be tracked.
