How to Use the IAQP: A Streamlined Approach Based on the New ASHRAE 62.1 User’s Manual and Addendum aa

Published 07/28/2021
By Doug Engel
ASHRAE 62.1-2019 User's Manual

This blog post has been updated to reflect a simplification to how the IAQP is applied based on Addendum aa to Standard 62.1-2019, which was published by ASHRAE on 2/14/22.

This is the second blog post in our series on ASHRAE’s performance-based ventilation design standard, the Indoor Air Quality Procedure (IAQP). In our first blog post, we summarized what the new 62.1-2019 User’s Manual published in June 2021 says about when to apply the IAQP. In this post, we summarize how to apply the IAQP, citing guidance from the updated User’s Manual and Addendum aa to Standard 62.1-2019, which was published in February 2022.

The new User’s Manual and Addendum aa are an invaluable resource for HVAC designers and building owners applying Standard 62.1 as they provide helpful guidance on when to use the IAQP and simple tables to make applying the IAQP as easy as applying the Ventilation Rate Procedure.

You can learn more about the most important updates to the User’s Manual by watching our webinar with Dr. Marwa Zaatari, a voting member of the ASHRAE committee that oversees Standard 62.1, and Anurag Goel, enVerid’s Director of Sales & Application Engineering.

How to Apply the Indoor Air Quality Procedure (IAQP) 

How to apply the IAQP can be summarized in the following 4 steps:  

4 Steps to Apply the IAQ Procedure 

Steps 1-3 involve collecting inputs for the mass balance calculation performed in Step 4, which determines the minimum ventilation rate for each applicable zone using the IAQP.  

enVerid has developed tools to make completing these 4 steps as simple as calculating ventilation rates using the Ventilation Rate Procedure. enVerid’s tools also generate compliance reports for code officials with all the documentation required to comply with the IAQP.

Step 1: Confirm Design Compounds & Design Limits

The first step to apply the IAQP is identifying the appropriate Design Compounds (formerly called contaminants of concern) and associated Design Limits.

Before Addendum aa, coming up with a list of contaminants and design limits was the responsibility of the designer. Addendum aa simplified this step by prescribing 14 Design Compounds and PM2.5 and their associated Design Limits to be used when applying the IAQP, removing this responsibility from the designer. The list is provided in Table 6-5 of Addendum aa.

 Here is the list of COCs and Concentration Limits provided in the User’s Manual (pg. 106): 

ASHRAE Standard 62.1-2019 Addendum aa Table 6-5 Design Compounts, PM2.5 and their Design Limits

While Addendum aa lists 14 Design Compounds and PM2.5, formaldehyde usually drives the ventilation rate for typical commercial building applications. Thus, controlling formaldehyde is key to an efficient IAQP design. ASHRAE has not listed CO2 as a Design Compound, but CO2 may be added to the list by the designer if desired. When CO2 is added, then either CO2 or formaldehyde usually drive the ventilation rate for an IAQP design.

The only requirement for the designer in this first step is to decide whether more stringent LEED or WELL Design Limits should be used based on project goals and to confirm there are no unusual site-specific sources of pollution need to be considered.

When an enhanced IAQ design is desired, more stringent Design Limits may be specified to calculate the minimum ventilation rate using the IAQP. These more stringent requirements can be applied using enVerid’s IAQP Calculator.

According to the 62.1-2019 User’s Manual, “If a ventilation zone will have unusual contaminant sources or sources where emissions will be unusually high, additional ventilation or air cleaning must be included in the design” and “The additional ventilation or air cleaning required must be designed using the IAQP….” (Pg. 76)

Step 2: Apply Emission Rates

The second step is applying indoor emission rates and outdoor concentrations for each Design Compound. The updated 62.1-2019 User’s Manual simplifies this step by providing a list of emission rates and outdoor concentrations for a typical office space. Using peer-reviewed papers provided in Appendix N of Standard 62.1-2019, enVerid has replicated this list for other common applications of air cleaning. enVerid’s IAQP Calculator automatically applies the appropriate emissions rates based on the User’s Manual table and sources provided in Appendix N.

Generation Rates & Outdoor Air Concentrations

Step 3: Apply Air Cleaning Efficiency

Step three is to determine the air cleaning efficiency for the full list of Design Compounds. This information can be provided by the manufacturer and should be based on third-party verified efficiencies using nationally recognized standard test methods such as ASHRAE 145.2 for gas-phase air-cleaning systems and ASHRAE 52.2 for particle removal systems. ASHRAE 145.2 testing is required for any device used to earn points under LEED pilot credit EQpc124.

The following table lists the third-party validated air cleaning efficiencies for enVerid Sorbent Ventilation TechnologyTM for the full range of Design Compounds prescribed in Addendum aa plus CO2 and SARS-CoV-2 based on ASHRAE 145.2 and 52.2 test methods. As the table shows, Sorbent Ventilation Technology is very efficient at removing formaldehyde, which makes it ideal for use with the IAQP.

Design Compounds, Design Limits and Efficiencies - Addendum aa to ASHRAE Standard 62.1 - 2019

Step 4 – Mass Balance Analysis

The final step is to apply the data confirmed in the previous steps to the mass balance analysis for all the zones served by the HVAC system. The mass balance analysis is used to calculate the minimum outdoor air volume such that the Design Limits for all Design Compounds are not exceeded.

Given the number of calculations required for each Design Compound and each zone, enVerid recommends that designers use an IAQP Calculator to simplify this step. Using enVerid’s IAQP Calculator, designers simply enter basic design parameters for the whole system and any zones. The IAQP Calculator applies the appropriate emission rates for the appropriate Design Compounds and calculates the minimum outside air according to the IAQP accounting for the cleaning efficiency of the chosen air cleaning system. This easy-to-use calculator shares most of the same inputs as Ventilation Rate Procedure for simple use by designers.

Here is an example input tab for enVerid’s IAQP Calculator:

enVerid IAQP Calculator Input

And here is a sample output from for enVerid’s IAQP Calculator. HLR modules refer to the enVerid air cleaning systems used to clean indoor air.

enVerid IAQP Calculator OutputIAQP Validation

The final requirement of the IAQP, as defined in Addendum aa, is to conduct a subjective and objective evaluation to ensure the design maintains Design Compounds below the Design Limits post occupancy. As explained in the new User’s Manual, 62.1-2019 made it easier to comply by providing flexibility on when to test and how many occupants or independent observers to survey. 62.1-2019 also allows the use of previous surveys from “substantially similar zones” to comply with this requirement.

Importantly, the User’s Manual clarifies that, “For the purposes of the IAQP, acceptable perceived IAQ excludes dissatisfaction related to thermal comfort, noise and vibration, lighting, and psychological stressors” as these factors are “beyond the scope of the standard.” (pg. 103-104)

enVerid can help designers complete the subjective and objective IAQP validation requirements. For more information, contact your enVerid representative or contact enVerid directly.


As the market seeks ways to improve indoor air quality and reduce building carbon emissions, the IAQP provides a compelling pathway to use proven air cleaning systems to achieve good indoor air quality cost-effectively and energy efficiently. Thanks to the updated User’s Manual, Addendum aa, and tools to simplify calculations such as enVerid’s IAQP Calculator, applying the IAQP is now easier than it has ever been.

Learn more about how Addendum aa makes improving indoor air quality and building energy efficiency using the IAQP much easier by reading our blog post ASHRAE Makes Adopting the IAQ Procedure Easier with Addendum aa.


Doug Engel

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