Ventilation and Indoor Air Quality in Low-Energy Buildings

Summary

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. 

Description

L researcher Steven Emmerich adjusts a multi-gas analyzer that will measure carbon monoxide, oxygen, carbon dioxide and hydrocarbons concentrations produced by such a generator located, against safety advice, in a garage.

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, improved simulation tools, and building models necessary to enable users to readily perform building IAQ modeling studies that address occupant health and productivity, IEQ and energy use.

A major component of this project improving the ability to measure and model the impact of infiltration on building energy usage and to provide resources related to these abilities. Previously, under this project, a method was developed to provide improved infiltration modeling in an easy to use format. This method implements correlations based on multizone analysis of both residential and non-residential building models (including DOE reference buildings) in multiple climate zones. This work included 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 to develop an initial version of the Oak Ridge National Laboratory Infiltration Calculator (ORNL 2019). The infiltration calculator is an online tool that provides estimates of the potential energy and cost savings due to improvements in building envelope airtightness and also provides estimates of the amount of moisture transport through the building envelope attributable to air leakage.

Funding levels of this project are in flux, and depending on the level of funding provided in FY21, NIST could continue to advance the use of these correlations by making them available within the Quick Energy Simulation Tool (eQuest) that is utilized to demonstrate compliance with the California Title 24 Building Energy Efficiency Standards. NIST could also contribute to the EnergyPlus documentation to provide users with the detailed methods and tools available to implement the correlations within EnergyPlus. NIST also continues to foster relationships associate with the ORNL Infiltration Calculator with the goal of improving the tool to include more buildings and climate zones.  During FY21, NIST could develop a website to act as a NIST Infiltration Modeling Clearinghouse (NIMCH) to provide a single, comprehensive source for information and resources for building energy modelers who have historically neglected to properly account for infiltration within their energy analysis. The NIMCH will provide access to tools, and data sets developed under this and other related projects include the Commercial Building Air-leakage Database (CBAD) developed under this project.

This project also addresses 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. CONTAM has been coupled with both EnergyPlus and TRNSYS, and these coupled software tools will continue to be enhanced to account for a broader range of simulation capabilities. Enabling widespread use of these tools will require improvements to their user interfaces; the availability of required input data, reference models, and training materials; and validation studies. In FY 20, NIST developed an initial set of coupled building models for both commercial and residential buildings (including the conversion of DOE/PNNL reference buildings and the NIST Suite of Homes). The Boston University School of Public Health worked together with NIST utilized couple, multifamily residential building models to perform studies of interventions intended to reduce energy consumption and exposure to indoor pollutants associated with diseases such as asthma. NIST has also worked with the Norwegian University of Science and Technology (NTNU) to perform coupled simulations to address the use of demand-controlled ventilation in office buildings in Norwegian climates. NIST models have also been used to inform ASHRAE research related to CO2-based demand-controlled ventilation in commercial buildings and to support ongoing US DOE funded efforts to evaluate interior and exterior air leakage in multifamily buildings. In FY21, NIST will continue work that was begun in FY20 to develop and publish training materials on the NIST Tube channel along with associated demonstration test cases, based on the above-mentioned work, for the use of the CONTAM family of programs.

Beginning in FY21, this project will encompass the modelling component of the NIST Net-Zero Energy Residential Test Facility (NZERTF). The NZERTF will be utilized to develop, measure the performance of, and simulate CO2-based demand-controlled ventilation. During FY19 and FY20, a CO2 monitoring system was installed within the NZERTF and a set of tests was defined to be performed and modeled using the EnergyPlus-CONTAM co-simulation capability. During FY21 this low-energy, residential model validation work will be performed and documented in a journal article. ContamHT (a non-release, developmental version of CONTAM) will also be enhanced to incorporate the full set of controls modeling capabilities that exist in the publicly available version of CONTAM, and these new capabilities could be verified using this DCV data as well.

During FY20, the ability to extend the applicability of CONTAM simulation engine, ContamX, to other analysis platforms was investigated (ContamXasm). ContamX was converted to web-assembly to run as a client-side program within browsers, and the initial implementation of ContamX within a microcontroller-based environment was carried out, i.e., CONTAM on a chip (COAC). These activities will be extended in FY21 to allow the development of web-based tools that can utilize ContamXasm 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, and initial demonstration of the capability will be performed within the Fate and Transport of Indoor Microbiological Aerosols software tool (FaTIMA) [4] that was developed during FY20 in response to the COVID-19 pandemic. FaTIMA version 2 will be developed to enhance the current capabilities based on feedback from users of the initial version of the tool along with a literature review aimed at maximizing the benefit and usability of the tool to the infectious transport modeling community.

Finally, support of standards development will continue mainly through involvement with ASHRAE. This includes the direct involvement of members of this project within various technical committees associated with various aspects of indoor air quality and ventilation (TCs 4.3 and 4.10) and standing standard project committees (SSPC 62.1, 62.2, 189.1 and 90.1). Members will also support higher level ASHRAE operations including the Tech Council, Technical Activities Committee (TAC), and the Epidemic Residential Task Force.

REFERENCES:

1. ASHRAE (2017). ASHRAE Position Document on Indoor Air Quality. R. American Society of Heating, Air-conditioning Engineers. Atlanta, GA.
2. Emmerich, S. J. and L. Schoen (2013). IAQ 2013 Tools Topic Overview. ASHRAE IAQ 2013. Vancouver, BC, Canada, ASHRAE.
3. 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.
4. Dols, W.S., B.J. Polidoro, D.G. Poppendieck, and S.J. Emmerich, A Tool to Model the Fate and Transport of Indoor Microbiological Aerosols (FaTIMA), TN 2095. 2020, National Institute of Standards and Technology: Gaithersburg, MD USA.

Major Accomplishments

• CONTAM version 3.2 published on website, September 2015
• Developed Open Studio Measure to allow users to model infiltration in energy simulations that will take into account HVAC system effects and weather

Impact of Standards and Tools:

• Climate Suitability Tool developed to identify opportunities for building designers to use natural or hybrid ventilation to reduce energy consumption in buildings.
• LoopDA software developed to provide building designers a tool to size openings for natural ventilation.
• CONTAM multizone airflow and contaminant transport analysis software used by building designers to assess ventilation effectiveness and indoor air quality.
• ASHRAE Standard 62.2, ventilation standard for residential buildings which was chaired by NIST staff, forms the basis for ventilation requirements in model codes.