Published 07/15/2021
In late June, ASHRAE published its revised Standard 62.1 User’s Manual, bringing it up to date with the ANSI/ASHRAE Standard 62.1-2019, the current version of the non-residential ventilation standard for acceptable indoor air quality.
As ASHRAE explained in its press release, Standard 62.1 “is written to be code enforceable and contains only mandatory language.” As a companion document, the User’s Manual is a “crucial supplement for professionals concerned with ventilation and indoor air quality.”
We could not agree more: the guide is an invaluable resource for engineers applying Standard 62.1. In particular, the latest version of the User’s Manual provides helpful guidance on when to use the performance-based Indoor Air Quality Procedure (IAQP) and when to use the prescriptive Ventilation Rate Procedure (VRP) to calculate ventilation rates.
The newest version of the User’s Manual also includes a helpful example of how to apply the IAQP with air cleaning technology to deliver good indoor air quality more cost effectively than with the VRP. The example includes a helpful reference table of indoor contaminants, emission rates, and design limits.
In this blog post, we summarize what the User’s Manual says about when to apply the IAQP. In the next blog post, we summarize what the User Manual says about how to apply the IAQP.
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.
IAQP vs. VRP
Let’s start with the latest language from the User’s Manual explaining the difference between the IAQP and the VRP (all bolding is ours).
“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) In other words, the VRP is based on the idea that the solution to pollution is dilution. Indoor air quality is achieved by bringing in “fresh” outside air with limited consideration for the quality of outside air, emissions from building materials, or other environmental factors impacting indoor air quality.
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 IAQP allows ventilation air to be reduced below rates that would have been required by the VRP if it can be reliably demonstrated that the resulting air quality meets the required criteria described in Section 6.3.4.” (Pg. 100)
According to Standard 62.1-2019 itself,
“Although the intake airflow determined using each of these approaches may differ significantly…any of these approaches is a valid basis for design.” (Section 6.1)
So when should designers use the IAQP rather than the VRP?
When to use the IAQP
The updated User’s Guide points to four cases when the IAQP is more appropriate that the VRP, and we’ve added a fifth based on our experiences:
1. When outdoor air is not “fresh air”
“When the quality of outdoor air is poor, ventilation may not be effective in improving indoor air quality. Bringing in contaminated outdoor air may result in diluting one group of pollutants while increasing levels of another.” (Pg. 17)
“If outdoor air is deemed to be unacceptable for general ventilation, consider using air cleaning and the IAQ Procedure (Section 6.3) in lieu of the VRP (Section 6.2) for the ventilation system design.” (Pg. 20)
According to the American Lung Association’s 2021 State of the Air report, over 40% of Americans live with unhealthy air. The now seemingly annual wildfires in the West are exhibit A for this, but there are many other examples in cities across the country.
2. When spaces may have unusual contaminant sources
“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. The additional ventilation or air cleaning required must be designed using the IAQ Procedure in Section 6.3 of the standard or based on environmental safety standards where there is an environmental health and safety professional responsible to the owner who has determined appropriate criteria.” (Pg. 76)
The presence of “unusual contaminant sources” should be determined relative to what is considered typical for a breathing zone as per Table I-1 in Appendix I of Standard 62.1. For example, for office space Table I-1 says, “Occupant activity is primarily sedentary (seated). There are no significant space-related contaminants.” If there is the possibility for any atypical emissions from things like furniture, printers, cleaning products, personal products, the heating of food that may be consumed at cubicles, etc., then additional ventilation or air cleaning must be included in the design using the IAQ Procedure.
Whereas the first two cases may be obvious scenarios to apply the IAQP, the next two cases are perhaps less obvious but more widely applicable, especially given the growing focus on indoor air quality and energy efficiency.
3. When better indoor air quality (IAQ) is desired
“…If a higher or lower level of acceptance is desired, then the IAQP may be the more appropriate design procedure.” (Pg. 63)
“The IAQP may also be used to achieve better air quality than the VRP….” (Pg. 101)
While many of the gaseous contaminants referenced in the User’s Guide are less familiar to the public, there is growing awareness that lower levels of CO2, which is generated by people, and volatile organic compounds (VOCs) from building materials and furniture lead to improved decision making. (Read more here). Using the IAQP to design to a specific CO2 or VOC performance level is a great example of where the performance-based approach is more appropriate than the prescriptive VRP.
Read our University of Miami case study for a great example of how applying the IAQP with HLR air scrubbers improved indoor air quality while also saving money.
4. When a more cost-effective ventilation solution for good air quality is desired
“The use of air cleaning with recirculation could allow for a reduction in the amount of outdoor air required with a concurrent reduction in associated operational energy costs.” (Pg. 20)
“The IAQP may allow for a more cost-effective solution to providing good air quality, as all design strategies may be considered and compared…” (Pg. 100)
This is the application of the IAQP that we see most often on our projects.
By combining the IAQP with our HLR modules to remove indoor generated contaminants, we can deliver good indoor air quality with less outside air and therefore smaller HVAC systems and lower ventilation energy consumptions, which lead to life cycle cost savings.
As a 2020 report by NREL found, “The HLR technology was shown to control contaminants of concern below exposure limits with lower ventilation rates, which leads to energy savings.” According to NREL, “Cooling savings were measured to range from 6% to 37% during the peak cooling month.”
Similarly, Slipstream recently presented a webinar entitled “Absorbent Air Cleaning: A New Way to Think about Ventilation”, which presented a case study that showed that “air cleaning can substitute for outdoor air ventilation, leading to energy savings.”
5. To earn LEED points without increasing project cost
While not called out specifically in the User Manual, the other common application of IAQP and air scrubbing has increasingly been LEED projects. USGBC has developed the LEED BD+C Performance based indoor air quality design and asse