ASHRAE Journal - September 2023 - 19

COLUMN IEQ APPLICATIONS
Procedure (IAQP) in Standard
62.1-2022.
Our goal is to provide
users of Standard 241 with
an understanding of the
impact of implementing
different strategies to meet
the required equivalent
clean airfl ow on energy
consumption, life-cycle costs
and carbon emissions. As
we show, these goals can all
be achieved by using hybrid
ventilation design strategies
that combine outdoor air
ventilation with air cleaning
for bioaerosols, particulate
and gases.
Methodology
The analysis presented
here is based on a large-scale simulation of prototypical
building energy models to approximate the typical
energy consumption and carbon emission of outdoor
air ventilation and fi ltration of commercial buildings in
the U.S. for six building groups: large offi ce, small offi ce,
primary school, secondary school, retail stand-alone and
retail strip mall in 15 different ASHRAE climate zones.3
For the simulation we reviewed a number of analysis
options with the goal of balancing repeatability,
reproducibility, transparency, credibility,
conservativeness and accuracy. We selected the SCOUT
software tool. SCOUT is an open-source software
program developed and supported by the U.S.
Department of Energy (DOE) that is used to estimate
the impacts of various energy conservation measures
(ECMs) across the U.S. residential and commercial
building sectors. Fifty custom SCOUT ECMs were used,
and 210 unique OpenStudio/EnergyPlus " Commercial
Prototype " models were constructed.*
The annual thermal energy was extracted from
each of these models. A separate calculation based on
results from a previously published study on energy
use of fi brous fi lters was used to approximate typical
*5 SCOUT building types × 2 SCOUT building scenarios ×
5 SCOUT AIA climate zones. For this study, 2 Market Segments ×
7 Building Types × 15 ASHRAE/IECC Climate Zones = 210
energy consumption and carbon emission of HVAC air
fi ltration.4 Table 1 summarizes the prototypes considered
in the model.
Discussion of Findings
Figure 1 summarizes total thermal energy savings
by replacing 1,000 cfm (472 L/s) of outdoor airfl ow
with cleaned recirculated indoor air, broken out by
ASHRAE climate zone for (a) retrofi t buildings and (b)
new construction buildings. This metric can be used
to quickly understand where conditioning outdoor
airfl ow is the most energy and carbon intensive and
to easily extrapolate potential savings for individual
buildings. The complete study3 shows the potential
energy savings and carbon emission reduction that can
be achieved when offsetting outdoor air with fi ltration
and air cleaning.
Table 2 shows the cost per cfm of outdoor air and
particulate fi ltration (MERV 7 and MERV 13) installed
in the recirculated airstream for 15 climate zones.
The costs presented here can be extrapolated to
different building types. The key observation from
this analysis is that outdoor air is much more energy
intensive (on average 10 times more) than upgrading
particulate fi ltration from low effi ciency (MERV 7)
to high effi ciency (MERV 13). If a building is already
S E PTEM B E R 2 0 2 3 ashrae.org ASHRAE JOURNAL
19
TABLE 1 Overview of prototypes, floor area, prerequisite outdoor air and ASHRAE Standard 241 and CDC guidance.
PREREQUISITE ASHRAE
STANDARD 62.1-2022
OUTDOOR AIR
PROTOTYPE
BUILDING
TYPEa
SCOUT
COMMERCIAL
SECTOR
PROTOTYPE
FLOOR AREA
(ft2)
HEIGHT
(ft)
TOTAL
OCCUPANTS
VRP
(cfm/
Large Offi ce Large Offi ce 498,588
Small Offi ce Small Offi ce
5,502
Stand-Alone
Retail
Strip
Mall
Secondary
School
Education
Primary
School
73,959
10
1,478
18
5 - 10
40
42
aNew Construction: DOE 90.1-2016 and retrofi t DOE 90.1-2004.
bIAQP outdoor air requirement is represented as a range as it can vary based on the effectiveness of gaseous air cleaning solution
used.
cThe cfm/person presented for CDC is derived from 5 ach for the assumed volume and number of occupants. Therefore, the values
will be different if the assumptions vary from the prototype building presented in this table.
Mercantile/
Service
24,692
22,500
210,887
9
9
30
30
10
2,429
28
370
337
6,095
PERSON)
17
17
14
16
15
IAQPb
(cfm/
PERSON)
5 - 10
5 - 10
5 - 10
5 - 10
5 - 10
INFECTION RISK MITIGATION
MODE
ECAi
ASHRAE
STANDARD 241
(cfm/
PERSON)
30
30
40
40
40
CDCc
VENTILATION
GUIDANCE
(cfm/
PERSON)
154
147
167
167
29

http://www.ashrae.org

ASHRAE Journal - September 2023

Table of Contents for the Digital Edition of ASHRAE Journal - September 2023