Ventilation Performance for Novel Sustainability and Resilience Challenges

Summary

Building ventilation and indoor air quality (IAQ) performance must account for many new challenges related to sustainability and resilience goals, including airborne infectious disease transmission indoors, elevated outdoor pollutant concentrations such as those associated with Wildfire Urban Interface (WUI) smoke, and climate change-driven extreme events such as heat waves, floods, and power outages. At the same time, providing effective ventilation and controlling IAQ involves complex relationships with building energy consumption and greenhouse gas (GHG) emissions, highlighting the need to understand the potential energy impacts associated with improving IAQ. Increasing building energy efficiency in response to climate change pressures while maintaining indoor environmental conditions that support occupant health, safety, and productivity is a major issue for the building community. The existence of these multiple, complex, and interrelated challenges has led to calls for improvements in building ventilation, advancements in IAQ requirements in standards, and more flexible and effective strategies for operation and maintenance. Identifying the most effective approaches and their potential impacts requires a deeper technical understanding of the interactions of airflow, energy use, and indoor contaminant transport and the development of new assessment methodologies using advanced building simulation methods and performance metrics. In response to these needs, this project is focused on developing tools, metrics, and data to advance energy efficient building ventilation and IAQ systems, including supporting changes to existing ventilation and IAQ standards and guidelines and developing new ones that are needed.

Description

Objective:
To develop tools, metrics, and data to enable sustainable, resilient, high-performance building and ventilation system design and operation in response to current and future challenges driven by climate change, airborne disease transmission, and other developing hazards. Also, to develop a methodology to evaluate potential changes to ventilation and IAQ standards so their impacts can be better understood and evaluated before they are adopted and implemented.

What is the new technical idea? 
The design and operation of building and ventilation systems have long been essential to building energy efficiency and occupant health, safety, and productivity through their impacts on building airflows and indoor pollutant concentrations. Nevertheless, efforts to reduce building energy consumption have not always recognized the role of ventilation system performance and the importance of envelope infiltration, nor have they fully acknowledged the critical need to maintain high quality indoor environments. Even though energy efficiency and IAQ are often considered contradictory goals, high-performing, energy-efficient buildings with good IAQ can be achieved via integrated design, sound operation, and regular maintenance. Nevertheless, more advanced design approaches and simulation tools are needed to enable such integrated building design to achieve both energy efficiency and IAQ goals. Emmerich and Schoen  discussed available tools and those still required to support occupant health, comfort, and productivity in low-energy buildings. They also identified a critical need for tools and data for measuring and verifying IAQ performance. A recent analysis of the consideration of IAQ in high-performance building case studies and in standards and guidance documents revealed that IAQ was often not addressed in a manner that was consistent with high-performance goals . In response to these needs, metrics of high-performance IAQ are required, as are tools for assessing and documenting high-performance IAQ in design, construction, commissioning, and operation. In addition, the development of ventilation and IAQ standards has been limited by the inability to estimate the impacts of proposed requirements on building energy consumption and occupant exposure, which new simulation tools and metrics would support.

What is the research plan?
The new tools and metrics in response to new ventilation and IAQ drivers will focus on the evaluation of new technologies and approaches to design, operation and maintenance that are being proposed to address airborne disease transmission, WUI smoke and other hazards. Given that discussions of these new drivers have stressed the importance of building ventilation performance, during FY24 this effort will continue the analysis of approaches to evaluating ventilation in buildings, focusing on the impacts of building configuration and ventilation system design and the standards and guidelines relevant to conducting these evaluations. NIST will continue to pursue a potential collaboration with GSA to convert NIST research on ventilation assessment into a protocol that they can use for the federal building stock, which will also be useful to other building owners and operators. During FY24, this project will also continue the review and critical assessment of the technologies, design approaches and O&M strategies that have been proposed to manage airborne infection risk and indoor exposure to elevated outdoor pollution episodes from WUI smoke and other developing concerns. This assessment will focus on their technical underpinnings, practicality and consistency with current standards and codes. Included among these technologies is the use of indoor CO2 measurement to assess ventilation adequacy, which is an implementation of the well-established tracer gas dilution technology described in ASTM Standards D6245  and E741 . As part of this project, proposed revisions to both of these standards will be pursued to address the more widespread applications of CO2 to assess the adequacy of ventilation. These applications of indoor CO2 require reliable values of the rate of CO2 generation by building occupants that account for their characteristics and the activities in which they are engaged. During FY24, measurements of CO2 generation rates obtained from energy expenditure researchers will be used to evaluate the predictive accuracy of the CO2 generation rate approach developed by NIST, which will be reflected in subsequent revisions to ASTM D6245 and other relevant standards.

The other major technical area of this project will involve performance metrics, simulation methodology, and benchmarking criteria to support the development of ventilation and IAQ standards. As these standards are updated to reflect current and future ventilation and IAQ challenges, a flexible and technically-sound approach is needed to consistently evaluate the impact of new requirements. Building energy efficiency standards, such as ANSI/ASHRAE/IES Standard 90.1 Energy Standard for Buildings Except Low-Rise Residential Buildings, use prototype commercial EnergyPlus models to evaluate the potential energy savings from changes to the standard , . Under this project CONTAM models of these prototype buildings  will be utilized to investigate the impacts of potential ventilation and IAQ requirements on indoor exposure to specific contaminants of interest. In support of these analyses, emission rates of these contaminants and other key input data for these modeling efforts will be gathered from the literature. During FY24 a simulation methodology and analysis plan will be developed to compare new standard requirements, with baseline simulations providing an initial set of benchmark data for evaluating measurements in the literature and IAQ measurement protocols for commercial buildings. These simulations will also be used to investigate the impacts of other standard requirements, such as envelope airtightness requirements in energy standards. As part of this multi-year effort, the simulation methodology will enable the evaluation of the national benefits for IAQ improvement with respect to productivity and absenteeism. Another task during FY24 will be to complete a draft of Guideline 45P Measurement of Whole Building Performance for Occupied Buildings except Low-Rise Residential Buildings, on how to perform ventilation and IAQ assessments in commercial buildings.

Major Accomplishments

• Quick Indoor CO2 (QICO2) Tool https://www.nist.gov/services-resources/software/quick-indoor-co2-qico2-tool
• Indoor Environmental Quality (IEQ) Guidelines Database https://www.isiaq.org/stc34_ieq_guidelines.php

Impact of Standards and Tools:

• Address IAQ/ventilation challenges
  • Exposure to WUI smoke & other extreme events
  • Climate drivers such as increased heating and cooling loads; outdoor pollution
  • Reducing airborne transmission  in buildings
• Develop more flexible, effective, and advanced building and system operation and maintenance guidance
  • Clearer understanding on how to use CO2
  • Development of metrics to evaluate impacts of ventilation changes on IAQ
  • Research contributing to changes in building-related standards