Dec 19, 2022

On Dec. 8, Daikin hosted a webinar in which Hoy Bohanon, PE, LEED AP and past chair of ASHRAE SSPC 62.1, discussed recent updates to ASHRAE Standard 62.1-2022. Over 700 people registered for the session, which highlighted updates to the standard related to humidity control and the IAQ Procedure.

The Standard, “Ventilation and Acceptable Indoor Air Quality,” sets out three procedures to calculate mechanical ventilation rates for commercial buildings: the Natural Ventilation Procedure (NVP), the Ventilation Rate Procedure (VRP) and the IAQ Procedure (IAQP). While the 2019 version of Standard 62.1 introduced important updates to the NVP and VRP, the most significant updates in the 2022 version relate to the IAQP, including:

1. Specifying Design Compounds (previously referred to as “contaminants of concern”) commonly found in indoor air and their Design Limits
2. Listing acceptable methods to verify the efficiency of air cleaning systems that may be used with the IAQP such as ASHRAE Standard 145.2 (see Addendum n)
3. Adding the requirement for both successful subjective evaluation of IAQ and objective evaluation of air quality post occupancy.

Why Choose the IAQP?

According to the Standard 62.1 User’s Manual, “The VRP is a prescriptive procedure in which outdoor air intake rates are predetermined for various space types (occupancy categories) based on contaminant sources and source emission rates that are typical for the space type.” (Pg. 63) When the VRP is used, IAQ is achieved by diluting contaminated indoor air with outside air without consideration of actual contaminant emission rates, the use of air cleaning, or other environmental factors that could impact IAQ.

In contrast, the IAQP is a “performance-based procedure” that allows “any method to be used to achieve the contaminant concentration limits, including source control, air cleaning, or dilution of indoor contaminants with outside air.” Because it is performance-based, the User’s Manual states that “the IAQP may allow for a more cost-effective solution to providing good air quality” (pg. 100) and “could allow for a reduction in the amount of outdoor air required with a concurrent reduction in associated energy costs.” (pg. 20) In addition, it “may also be used to achieve better air quality than the VRP” (pg. 101), and “If outdoor air is deemed to be unacceptable for general ventilation,” the Manual recommends that engineers “consider using air cleaning and the IAQP in lieu of the VRP for the ventilation system design.” (pg. 20)

Making the IAQP Easier to Use

Even though the IAQP is a more direct way to ensure good IAQ and is often more cost effective and energy efficient than the VRP, many engineers have yet to use the IAQP because it requires them to identify specific contaminants and appropriate concentration limits, which is outside the area of expertise for most engineers

As Mr. Bohanon discussed, ASHRAE recognized this barrier to adoption of the IAQP and has now prescribed a list of fourteen Design Compounds plus PM2.5 and their Design Limits. Engineers now simply need to ensure any air cleaning system used with the IAQP can maintain these Design Compounds and PM2.5 within the Design Limits. Calculators developed by Daikin and companies like enVerid Systems can be used to run calculations on a zonal basis to determine how much outside air can be displaced with cleaned indoor air using the IAQP.

As Mr. Bohanon also discussed, the updated standard now also lists specific test methods that must be followed to verify the efficiency of any air cleaning system used with the IAQP. Perhaps the most common test method for gas-phase air cleaning systems is ASHRAE Standard 145.2.

The other important update to the standard that Mr. Bohanon highlighted is the new requirement to perform an objective IAQ verification post occupancy and an update to the subjective verification requirement that now requires least 80% of occupants to be satisfied with the IAQ as measured on a survey. These new verification requirements can be a great way for engineers to demonstrate the quality of the indoor air from an IAQP design.

Given the heightened focus on both IAQ and building decarbonization, these updates to the IAQP make the procedure a much more attractive option to improve energy efficiency and deliver good IAQ. We thank Mr. Bohanon for an informative and timely webinar.

Click here to watch the recorded webinar and see a list of helpful resources.