Ventilation and Indoor Air Quality in Low-Energy Buildings Project

NIST is developing tools and metrics to both reduce the building heating and cooling loads associated with ventilation and infiltration and to evaluate the indoor air quality (IAQ) impacts of designs and technologies used in low-energy buildings. This work is intended to reduce the likelihood that efforts to reduce building energy use will negatively impact IAQ, and to support the application of approaches that can simultaneously reduce energy use and improve IAQ. Simulation capabilities and analysis tools are being developed to enable airflow and IAQ analysis in conjunction with energy design and analysis tools. In addition, reference cases and data are being developed to support ventilation, infiltration, and IAQ analyses of low-energy building designs and retrofits.

Objective:  To develop the tools and data required to determine the ventilation and IAQ impacts of strategies to achieve low-energy buildings, as well as to achieve heating and cooling load reductions through the application of technologies and designs based on ventilation, infiltration, and IAQ control by 2014.

What is the new technical idea?  To develop the capabilities needed to assess the IAQ impacts of low-energy building designs and technologies, as well as to support the implementation of strategies that can both save energy and improve IAQ, current energy design and analysis software tools need to have the capability to better quantify airflow, ventilation, and indoor contaminant concentrations. Achieving this goal will require coordination with the developers and users of energy design and analysis tools to incorporate enhanced capabilities into their tools. To this end, the project will also address the need to improve the measurement science embodied in multizone airflow and IAQ modeling, building thermal simulation, and computational fluid dynamics (CFD), including the integration of these simulation capabilities to support the analysis of the complex building and ventilation system designs and retrofits being applied in high performance, sustainable buildings. These advanced tools will be applied to study the potential energy and IAQ performance of important but challenging building and ventilation design approaches, including natural and hybrid ventilation. In order to advance the consideration of airflow and IAQ impacts in current efforts to investigate energy savings opportunities in existing and new buildings, supporting models, data and metrics will also be developed.

What is the research plan?  To improve the ability to evaluate the energy impacts of ventilation and infiltration and the IAQ impacts of low-energy building designs and technologies, this project focuses on developing engineering tools and data to integrate multizone airflow and IAQ modeling, building thermal simulation, and CFD analysis. This includes collaborations with the developers of both TRNSYS and EnergyPlus – the most widely used tools for building energy analysis. In FY12, the new version of the TRNSYS/CONTAM coupled thermal/airflow analysis tool was published, a second phase of the CRADA on the TRNSYS/CONTAM tool (to be completed in FY13) was defined and work was initiated to improve the modeling of airflows in the EnergyPlus simulation program. In FY13, NIST will initiate simulation studies employing the new TRNSYS/CONTAM coupled tool, and define and implement graphic user interface capabilities for creating coupled models.

Based on discussions with DOE and the EnergyPlus development team, in FY12, NIST supported improvement of the airflow and IAQ modeling capabilities of EnergyPlus by developing a graphic capability using CONTAM to create an EnergyPlus AirflowNetwork input file. In FY13, NIST will continue this work by developing a plan to incorporate CONTAM’s full suite of airflow and contaminant transport modeling capabilities into EnergyPlus. This plan will include coupling CONTAM and EnergyPlus modeling through co-simulation, i.e., use of an external program that controls individual simulation programs which will be demonstrated in FY14.

Previously under this project, NIST created CONTAM models of the 16 DOE reference buildings, which have been developed for DOE within EnergyPlus for use in assessing the impacts of energy efficiency measures and to support standards development. Using CONTAM, correlations of infiltration rates with weather were developed for these buildings and will be provided to NREL to improve future energy analyses. A simulation plan was also developed in co-operation with NREL to use these building models to examine the energy and IAQ impacts of efficient ventilation options to support future requirements in ASRHAE Standard 189.1. In FY13, NIST will publish a journal article on the infiltration correlations and will execute the simulation study with NREL.

Additionally, the ASHRAE SSPC 90.1 committee has asked NIST to support the performance-based design of low-energy buildings by updating the commercial building air leakage database. In FY12, NIST updated the existing database by gathering and analyzing the latest air leakage data and information on achieving airtightness to support the design and construction of low-energy buildings. In FY13, the results will be published in a journal article.

Another key aspect of this project is to define the role of IAQ in low-energy buildings. Part of this goal is being pursued through NIST’s involvement in ASHRAE Standard 189.1, on which Andrew Persily serves as vice-chair. In FY13, an air barrier commissioning addendum for 189.1 will be submitted for publication, a new addendum to 189.1 updating the IAQ requirements will be submitted for public review and a proposal for a residential high-performance building standard (189.2) will be submitted to ASHRAE and other co-sponsoring organizations. During FY2012, Steven Emmerich was named a co-chair of ASHRAE’s IAQ 2013 conference, which will focus on IAQ in low-energy buildings. This conference is intended to document both the progress made toward desired project impacts such as IAQ analysis adopted into best-practice building design and increased adoption of ventilation strategies and technologies that simultaneously reduce energy and improve IAQ. In addition, shortcomings that still need to be addressed will be identified. In FY13, the detailed goals and program for the conference, which is scheduled for October 2013, will be developed. Also in FY13, NIST will develop a proposal for a new ASHRAE Residential IAQ Guide (similar to the ASHRAE IAQ Guide which was developed by a committee led by Persily) and Emmerich will lead the committee overseeing its development.

Recent Results:

2010-2012 Outputs: 5 Journal articles, 5 Conference/workshop talks, 3 Tech Notes

2012

Outputs:

• Updated existing commercial building air leakage data to support ASHRAE 90.1 Appendix G addendum and analyzed new data to support low-energy building design
• Created CONTAM-based capability to create EnergyPlus AirflowNetwork input file for easier coupled energy/airflow modeling
• Developed correlations of infiltration with weather for DOE reference buildings to enable  more accurate energy modeling
• Developed simulation plan (with NREL) to examine energy and IAQ impacts of energy efficiency measures for DOE reference buildings

Outcomes:

• Published new TRNSYS/CONTAM coupled energy/airflow simulation tool
• Published new version of LEED-referenced natural ventilation design and analysis tool (LoopDA 3.0) 
• Proposed changes to Standard 189.1 to strengthen consideration of IAQ

2011

Outcomes:

• Created CONTAM models of standard reference buildings for energy and IAQ analysis
• Performance credit for improved airtightness addendum for ASHRAE 90.1 released for public review

Impacts:

• CONTAM modeling used for residential indoor air quality and exposure studies to support improved requirements and performance-based options in Standard 62.2
• New addenda on multifamily buildings (to support LEED for Homes Multifamily Midrise Guidance) and performance-based ventilation option included in Standard 62.2

2010

Outcome:

• ASHRAE IAQ Design Guide published

Standards and Codes:

This project provides input to ASHRAE energy, ventilation and sustainable building standards (90.1, 90.2, 62.2, 62.1 and 189.1) and green building programs such as LEED and EPA Indoor Air Plus. Emmerich is the new chair of ASHRAE Guideline 10, Interactions Affecting the Achievement of Acceptable Indoor Environments, and Persily is vice-chair of Standard 189.1 as well as chair of its IEQ working group. Specific input to date has included development of new addenda on multifamily buildings and performance-based ventilation options for Standard 62.2, support of new air barrier requirement and energy modeling performance credit for improved airtightness for Standard 90.1, changes to strengthen consideration of IAQ in Standard 189.1, and technical input to EPA Indoor Air Plus and Standard 90.2.