NIST is developing the tools to define and verify high-performance indoor air quality (IAQ) as well as the broader indoor environmental quality (IEQ) in low-energy buildings and the data needed to improve the effectiveness of high-performance building standards and programs. NIST has been working with other stakeholders to develop IAQ-related metrics for high performance buildings as well as details on how to document high performance IAQ in design, construction, commissioning, and operation. These metrics and documentation approaches need to be applied to actual buildings and evaluated by stakeholders, e.g. designers, manufacturers and building owners, before they are used in standards and other high performance building programs. Recent stakeholder feedback revealed the need to identify, develop and demonstrate the effectiveness of potential IAQ metrics as ultimately related to occupant health, occupancy patterns, and economic outcomes. NIST building energy, airflow, and IAQ analysis tools will be utilized to evaluate these metrics.
Additionally, coupled building energy and multizone airflow and IAQ modeling tools have been developed to enable designers to simultaneously consider both the energy and IAQ impacts of building design features. However, widespread use of these tools will require improvements to the user interfaces, availability of required input data and reference models, and validation studies.
Two sets of coupled building models will be developed as products of this project: one representing commercial and the other residential buildings. These models will be based on the Pacific Northwest National Laboratory (PNNL) commercial and residential prototype buildings that were developed for the U.S. Department of Energy (DOE). These building models, meant to represent a majority of the U.S. building stock, are used to evaluate the continually evolving energy standards including ASHRAE Standard 90.1 and the International Energy Conservation Code (IECC) NIST will develop infiltration correlations based on multizone analysis of the commercial prototype buildings under various envelope leakage rates and U.S. climate zones. These infiltration rate correlations will then be made accessible as building energy measures for use via OpenStudio (developed by the National Renewable Energy Laboratory) which provides a front end to EnergyPlus. Coupled residential building models will be made available to enable combined analysis of IAQ and energy use in both single and multi-family dwellings.
Objective: To develop tools to define and verify high-performance indoor air quality in low-energy buildings and data needed to improve the effectiveness of high-performance building standards and programs.
What is the new technical idea?
The ASHRAE Position Document on Indoor Air Quality (ASHRAE 2017) indicates that even though energy efficiency and IAQ are often considered contradictory goals, high-performing, energy efficient buildings with good IAQ can still be achieved via integrated design. The document further indicates the need for simulation tools that enable integrated building system design that achieves low energy and high indoor environmental quality. Emmerich and Schoen (2013) discussed the tools that are available and those that are needed for supporting occupant health, comfort, and productivity in low energy buildings and concluded that a critical need exists in the area of tool development and application for the measurement and verification of IAQ in low-energy (including net zero energy) buildings. Recent analysis of the treatment of IAQ in high-performance building case studies, and in standards and guidance documents, revealed that IAQ was not covered in a comprehensive manner and when it was, it was not consistent with high-performance goals (Emmerich, Teichman et al. 2017). In response to these needs, metrics associated with high performance IAQ are being developed as are details on how to document high performance IAQ in design, construction, commissioning, and operation. These metrics and documentation approaches need to be applied to actual buildings and evaluated by stakeholders, e.g. designers, manufacturers, and building owners, before they are used in standards and other high performance building programs. Additionally, coupled building energy and multizone airflow and IAQ modeling tools have been developed to enable designers to simultaneously consider both the energy and IAQ impacts of building design features. However, widespread use of these tools in design practice will require improvements to the user interfaces, availability of required input data and reference models, and validation studies.
What is the research plan?
The planned products of this project are tools, data, standards, and guidance on verifying the achievement of high performance IAQ and ventilation. During a previous project, we analyzed the treatment of IAQ in high-performance building case studies, standards, and guidance documents and developed details on how to document the implementation of high performance IAQ. Additionally, a literature review was performed on field studies of ventilation and IAQ performance verification in high performance buildings. A workshop on whole-building performance metrics was held during the 2016 ASHRAE IAQ Conference aimed at identifying areas of focus for future development of non-energy related building performance metrics, e.g., IAQ-related metrics. This conference/workshop revealed the need to “translate science into practice” by identifying, developing, and demonstrating reliable and effective IAQ metrics as ultimately related to occupant health and productivity. NIST building energy, airflow and IAQ analysis tools will be utilized to evaluate the applicability of such metrics and to identify modeling requirements and improved simulation tools necessary to enable users to readily perform building IAQ modeling studies that address occupant health and productivity, IEQ and energy use.
In the previous project, a method was developed to provide improved infiltration modeling in an easy to use format. This method, using correlations based on multizone analysis, has been expanded upon to include a larger set of non-low-rise residential building models and climate zones for incorporation into EnergyPlus models via OpenStudio measures. Additionally, CONTAM simulations were performed for seven of the DOE commercial prototype buildings at four airtightness levels in 62 cities in collaboration with Oak Ridge National Laboratory, the Air Barrier Association of America, and the US-China Clean Energy Research Center for Building Energy Efficiency Consortium. These simulations were used to develop an initial version of the Oak Ridge National Laboratory Infiltration Calculator (ORNL 2019), which is an online tool that provides estimates of the potential energy and cost savings due to improvements in building envelope airtightness. A revised version of the Infiltration Calculator was developed in FY19 to estimate the amount of moisture transport through the building envelope attributable to air leakage. NIST has proposed that this tool be improved by expanding it to include more buildings and climate zones.
Another focus of the previous project was the integration of multizone airflow and IAQ modeling with building thermal simulation to improve the evaluation of the energy impacts of ventilation and infiltration and of the IAQ impacts of low-energy building (LEB) designs. Previously, a new version of the TRNSYS/CONTAM coupled tool was published, and NIST subsequently developed and demonstrated co-simulation coupling of CONTAM and EnergyPlus. Enabling widespread use of these tools will require improvements to their user interfaces, the availability of required input data and reference models, and validation studies. NIST conducted a model validation study of the new coupled thermal/airflow/IAQ analysis capabilities including an analytical case study, identification of empirical validation dataset(s), simulations to generate predictions for comparison to the measured data, and inter-model prediction comparisons. The Medium Office Building model will be used to compare various methods of accounting for infiltration in building energy modeling, including correlations and fully coupled models, with consideration given to improving existing methods of accounting for building airflow in these models. The residential building models developed by NIST will be used by the Boston University School of Public Health to perform an epidemiological study of interventions intended to reduce energy consumption and exposure to indoor pollutants associated with diseases such as asthma. Further, a coupled model of the NIST Net-Zero Energy Residential Test Facility will be developed for use in evaluating CO2-based demand-controlled ventilation. In FY20, this work will be validated against measurements made in the NZERTF using a CO2 monitoring system to be installed within the NZERTF during FY19.
A database of commercial building air-tightness measurements will be vetted, formalized and provided on the NIST website for use by building modelers as a resource in selecting model input values based on building measurements. In coming years, improvements to model usability will be completed, including better synchronization of airflow/IAQ and energy models as changes are made during design development, better integration with Open Studio, enabling CONTAM users to utilize existing building plans when creating building models, and developing a web-based set of verification, validation, and demonstration cases that will enable users to utilize the NIST-developed toolset.
During FY20, this project will include preliminary undertakings related to developing a web-based application of the CONTAM simulation engine, ContamX. ContamX will be converted to web-assembly in order to run as a client-side program within browsers. This will allow the development of web-based tools that can utilize ContamX to address specific building design and analysis problems. Multiple web-based utilities are being considered to take advantage of CONTAM on the web, including a building pressurization tool, a CO2-based building ventilation metric tool and an ASHRAE Standard 62.2 equivalent exposure analysis tool. Further, the ability to implement multizone analysis within building controls systems will be investigated which will include the implementation of ContamX within a microcontroller-based environment.
ASHRAE (2017). ASHRAE Position Document on Indoor Air Quality. R. American Society of Heating, Air-conditioning Engineers. Atlanta, GA.
Emmerich, S. J. and L. Schoen (2013). IAQ 2013 Tools Topic Overview. ASHRAE IAQ 2013. Vancouver, BC, Canada, ASHRAE.
Emmerich, S. J., K. Y. Teichman and A. K. Persily (2017). "Literature review on field study of ventilation and indoor air quality performance verification in high-performance commercial buildings in North America." Science and Technology for the Built Environment: 1-8.
ORNL (2019). https://airleakage-calc.ornl.gov/. Oak Ridge National Laboratory Energy Savings and Moisture Transport Calculator.