Ventilation and Indoor Air Quality in Low-Energy Buildings

Summary

NIST is developing tools to define and verify high-performance indoor air quality (IAQ) in buildings and is collecting the data needed to improve the application and effectiveness of these tools. NIST is working with key 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. The need to demonstrate the ability of potential IAQ metrics to quantify occupant health, occupancy patterns, and economic outcomes is needed in the building community. This project focuses on developing and applying NIST building airflow, IAQ, and energy analysis tools that can be utilized to evaluate these metrics.

NIST develops the whole-building IAQ and ventilation analysis software, CONTAM, which has been coupled with whole-building energy analysis tools to enable designers and analysts to simultaneously consider both the building design and operation holistically. Widespread use of these tools depends on improvements to the user interfaces, availability of required input data, building model development methods, validation studies, and training materials. The increased demand for the ability to integrate CONTAM with other analysis tools including chemical-biological, radiological, and nuclear (CBRN) defense and smoke management system design/analysis have spurred the need for methods to facilitate this integration. 

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 quantify and verify high-performance IAQ in buildings, provide input data to improve usability of the tools including building models, develop methods needed to support and verify the applicability of these tools to improving the effectiveness of high-performance building programs, and to evaluate the applicability of these tools to the control of building systems to meet IAQ and ventilation-related requirements.

What is the new technical idea?  
NIST is developing the tools that can be used to perform analysis of ventilation and IAQ within buildings, providing input data to improve the application of these and other relevant tools, facilitating the integration of these tools into relevant analysis platforms, and applying these tools to develop standards related to IAQ and ventilation and the means to facilitate meeting such standards during operation (e.g., via building system control).

Simulation tools have been under continuous development at NIST for several decades, with CONTAM being the flagship program. One of the most significant advancements in the transport physics of CONTAM has been to couple it with multizone, whole-building analysis software, EnergyPlus and TRNSYS. This coupling is important in that it addresses the interdependence between building airflow and heat transfer, which in turn affects contaminant transport and occupant exposure and enables the evaluation of the impacts of ventilation and infiltration and the IAQ impacts of building design and retrofit. Initial implementations of these coupling efforts have proved successful. Widespread use of these tools in practice will require improvements to the user interfaces; availability of guidance, training materials, input data, and reference models; applicability of output results of the tools; and validation studies.

What is the research plan? 
The planned products of this project include software tools, supporting data, and building model templates as well as integration of software into building controls to facilitate the design, analysis, and operation of IAQ and ventilation in the built environment in high-performance buildings. 

Software tools. The initial coupling methodology between CONTAM and energy software relied heavily on socket-based technology. This coupling method has been replaced by refactoring ContamX as a dynamic link library (contamx‑lib.dll) and providing it with an API, i.e., ContamX-API, which enables direct integration of the DLL into various software platforms and eliminates the need for socket-based functionality. Work has begun to use this refactored capability to replace the coupling method of existing co-simulation between CONTAM and both EnergyPlus and TRNSYS with a thread-safe version of contamx‑lib.dll. This thread-safe version 3.4.1.x of ContamX-API was incorporated into IU with updated Java bindings including documentation of updates to the API. This year, a new version of CONTAM 3.5 will be released including related utilities (i.e., ContamRV, Contam3DExport, ContamFMU, Type98, etc.) and updated documentation. CONTAM version 3.5 will incorporate new ContamW features including a 64-bit build, gnuPlot charting capabilities, redesigned controls definition procedures (removed SketchPad drawing component), and enhanced results file output definition. 

Supporting Data. NIST has maintained an informal database of air-tightness measurements in commercial buildings since 2010 [1]. NIST has begun assembling the Commercial Building Air-leakage Database (CBAD) to provide a web interface that enables users to search the database on a range of building properties such as year of construction, floor area, and whether it incorporates an air barrier. CBAD is soon to be formally released as an online database along with associated documentation.

Software integration. Recently, the development of application programming interfaces (APIs) to facilitate the integration of the CONTAM simulation engine via ContamX-‑API and development of CONTAM building models via ContamW-‑API into various analysis environments was begun. To incorporate ContamX-‑API into IU, NIST developed a Java native interface wrapper. Python bindings for ContamX-‑API were also developed in the form of the contamxpy module that was made available via the PyPI python packaging index (https://pypi.org/project/contamxpy/). The initial implementation of ContamW-‑API was incorporated into the Rhino/Grasshopper (RG) platform to facilitate the use of CONTAM within this architecture-centric platform. The initial implementation of the ANT plug-in (short for CONTAMinANT) was used to inform further development of ContamW-‑API and to demonstrate the feasibility of the use of CONTAM within RG.

Last year, a pre-release version of ANT was developed and made available for download (https://www.food4rhino.com/en/app/ant). Demonstration examples were developed along with a draft user guide and a paper was presented at the SimBuild 2024 Conference [2]. This conference paper presented the use of ANT along with other RG modules to address parametric analysis and community-scale IAQ analysis. 

NIST develops various LCA tools including the Building Industry Reporting and Design for Sustainability Neutral Environment Software Tool (BIRDS NEST). BIRDS NEST provides users with the ability to account for various building material properties and building energy usage via EnergyPlus simulations when performing LCA analysis on residential buildings. The applicability of incorporating IAQ-related factors in parallel with BIRDS NEST has been reviewed along with the ability to incorporate CONTAM analysis within the evaluation framework which currently leverages the OpenStudio software to perform said analysis, and a test case to be used when developing the initial implementation was identified. This year, an initial set of IAQ-related factors will be incorporated into the OpenStudio-BIRDS NEST framework/workflow

Work continues on CONTAM on a Chip (COAC) to implement the CONTAM simulation engine, ContamX, as well as demonstrating benchtop control of a variable speed fan via the Raspberry Pi system for real time ventilation control in homes.

REFERENCES:

1. Emmerich, S.J. and A.K. Persily, U.S. Commercial Building Airtightness Requirements and Measurements, in AIVC Conference 2011. 2011, AIVC: Brussels.
2. Shen, J., W.S. Dols, and B.P. Polidoro, ANT: A Multizone Indoor Air Quality (IAQ) and Ventilation Analysis Plug-in for Algorithm Aided Design, in SimBuild 2024. 2024, IBPSA-USA: Denver, CO, USA.
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 3.5 to be released this year
• Release of CONTAM APIs
• Release of ANT
• Clearing House for Infiltration Modeling Purposes published

Impact of Industry-Consensus Standards and Tools:

• CONTAM analysis was performed to aid in developing ventilation rates for corridors of educational facilities as they pertain to ASHRAE Standard 62.1.