For Release:
March 27, 2012
Contact: Jodi Scott
Public Relations
678-539-1140
Public Input Sought on Alternative to ASHRAE Standard
62.1 Ventilation Rate Procedure Proposed
ATLANTA – A proposed change to the ventilation rate
procedure in ASHRAE’s indoor air quality standard is open for review after
changes were made based on public input last year.
ANSI/ASHRAE Standard 62.1-2010, Ventilation for
Acceptable Indoor Air Quality, sets minimum ventilation rates and other
requirements for commercial and institutional buildings.
The ventilation rate procedure provides a prescriptive
method for determining minimum ventilation requirements. It accounts for
pollutant sources from both the building and its occupants, and allows the
designer to account for the efficiency of different ventilation systems when
delivering outdoor air to the breathing zone.
Proposed addendum f was first released for public comment
in September 2011 after some users of Standard 62.1 indicated the ventilation
rate procedure was “too complicated,” according to Standard 62.1 chair Roger
Hedrick. He said the 62.1 committee agreed that application of the
multiple-zone recirculating system equations described in Section 6.2.5 and
Appendix A can be complex.
“When designing multiple zone recirculating ventilation
systems, Table 6-3 provides a default value of Ventilation Efficiency (Ev)
based on the largest value of the zone primary (Zp) outdoor air fraction, for
all the zones served by the system,” he said. “However, if Max (Zp) exceeds
0.55, then Appendix A must be used to design the system outdoor airflow. Addendum f attempts to simplify the design
process by providing a simplified default approach for cases with Max (Zp)
greater than 0.55.”
The earlier review draft set the default value of the
zone primary outdoor air fraction based on a default minimum zone primary
airflow set as 30 percent of the zone design primary airflow.
“The public review comments pointed out that this
formulation did not work mathematically under certain conditions,” Hedrick
said. “This new public review version instead simply allows Ev to be set to
0.6, unless a higher value is provided by Table 6-3 or by using Appendix
A. Use of a relatively low value of Ev
will result in higher outdoor airflow rates, but using the default will
simplify the system design process.”
Also open for review is addendum i, which would add
limits for low humidity. Recent studies have shown that excessively low
humidity may result in unacceptable indoor air quality. The Standard 62.1
committee is interested in the appropriateness of the relative humidity limit
and the climate zones where the requirement applies. The addendum is open for an advisory public
review, meaning comments received allow for constructive input and need not be
resolved or formally acted on by the project committee.
In addition to addenda f and i, three additional addenda
are open for public review from March 23 until April 22. For more information,
visit www.ashrae.org/publicreviews.
They are:
• Addendum h
–Table 6-1, includes ventilation rates for “Sports arena (play area)” and “Gym,
stadium (play area).” Both space types have ventilation rates based on floor
area only, the per person rate is zero. Users of the standard have expressed
interest in applying demand controlled ventilation to these space types, which
is effectively prohibited by the lack of a per person component to the
ventilation rate. This proposed addendum replaces both of these space types
with “Gym, Sports Arena (play area)”, with Rp = 20 cfm/person and Ra = 0.06
cfm/ft² and assigns this new space type with an air class of 2 rather than
class 1 from the first publication public review version.
• Addendum k
adds an exception to the recirculation limits on Class 4 exhaust airstreams
from laboratory hoods which would allow use of heat wheel energy recovery in
some cases. The exception defines
several criteria which the airstream must meet before such heat recovery can be
used, and the heat recovery system must limit recirculation airflow to less
than 0.5 percent of the outdoor air intake flow.
• Addendum l
adds a refrigerated warehouse space type to Table 6-1, providing revised
ventilation rates for these spaces. These rates include a “People Outdoor Air
Rate, Rp” which will require ventilation during periods of expected occupancy,
but do not include an “Area Outdoor Air Rate, Ra” which will allow the
ventilation rate to be zero for refrigerated warehouses with no occupants.
In addition, addendum j is open for public review from
March 23 until May 7. The proposed addendum would add requirements to the
Indoor Air Quality Procedure (IAQP) for determining minimum ventilation rates
which require consideration of the combined effects of multiple contaminants of
concern on individual organ systems. This “additive” effect is already implicit
in the Ventilation Rate Procedure. This proposed change is intended to improve
the IAQP by requiring consideration of these additive effects that are well
established in the literature for many organ systems, according to Hedrick.
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