ASHRAE Journal - September 2023 - 20

COLUMN IEQ APPLICATIONS
receiving the minimum
outdoor air per the
applicable standard, then
air cleaning strategies
should be evaluated
before providing more
outdoor air.
Primary School Example
(73,959 ft2 [6871 m2],
1,478 People)
To put the above results
into context, results
for a typical existing
secondary school located
in the Northeast and the
Southeast are presented
in Figure 2 for multiple
hybrid ventilation
scenarios:
* Increased outdoor
FIGURE 1 Annual thermal load by ASHRAE Climate Zone per 1,000 cfm of outdoor airflow for retrofit (ASHRAE/IESNA Standard
90.1-2004) and new construction buildings (ASHRAE/IES Standard 90.1-2016).
A
Total Thermal Load Reduced by Replacing 1,000 cfm of Outdoor Air by Clean Recirculated Air Retrofit: ASHRAE/IESNA Standard 90.1-2004
(kBtu/1,000 cfm/year)
1,000
Washington
4C
20,300
Montana
6B
41,000
Minnesota
6A
&
7A
60,200
Colorado
5B
California
3C
2,000
22,000
Arizona
2B
22,000
Alaska
8A
90,000
air per the Standard
62.1-2022 prescriptive
approach Ventilation Rate
Procedure (VRP) by 50%;
* Outdoor air per
the Standard 62.1-2022
prescriptive approach
(VRP);
* Outdoor air per
the Standard 62.1-2022
prescriptive approach
(VRP) with energy
recovery ventilation (ERV)
at a 60% total efficiency;
* Outdoor air per
the Standard 62.1-2022
performance-based
approach (IAQ Procedure
[IAQP]) with sorbent filters capable of removing
formaldehyde (HCHO) at efficiency of 70%;
* Outdoor air per the Standard 62.1-2022
Washington
4C
12,000
California
3C
1,300
Alaska
8A
21,000
New Mexico
4B
20,000
Texas
3B
Hawaii
1A
40,000
Total Thermal Load Reduced by Replacing 1,000 cfm of Outdoor Air by Clean Recirculated Air New Construction: ASHRAE/IES Standard 90.1-2016
B
(kBtu/1,000 cfm/year)
1,000
Montana
6B
13,000
Minnesota
6A
&
7A
16,000
Colorado
5B
17,000
Arizona
2B
10,000
New Mexico
4B
9,500
Texas
3B
Hawaii
1A
16,000
performance-based approach (IAQP with sorbent filters
capable of removing formaldehyde at efficiency of 70%
with energy recovery at a 60% total efficiency).
For each of the five scenarios presented above, we ran
the model for MERV 7 and MERV 13. Following Standard
20
ASHRAE JOURNAL ashrae.org S E PTEM B ER 2023
241 requirements, MERV 7 particulate filtration does not
contribute to the equivalent clean airflow number.
From simulated results, all of the outdoor air scenarios
presented coupled with MERV 13 complied with
Standard 241 for educational facilities (40 cfm [19 L/s])
of clean air/person) and CDC guidance (42 cfm [20 L/s]
of clean air/person†
†5 ach, 73,959 ft2, 10 ft (3 m) ceiling height, and 1,478 occupants.
9,500
Georgia
3A
11,000
FL
2A
22,400
18,000
90,000
New
York
4A
&
5A
12,500
9,500
15,000
Georgia
3A
12,000
FL
2A
42,000
52,000
90,000
New
York
4A
&
5A
31,000
42,000
). In contrast, none of the outdoor air
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ASHRAE Journal - September 2023

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