ASHRAE Journal - August 2014 - 86

Column Iaq applIcatIons
Roger Hedrick

Standard 62.1 Update & Plans
By RogeR HedRick, BeMP, MeMBeR ASHRAe

ASHRAE's principal ventilation standard, Standard 62.1-2013, Ventilation for
Acceptable Indoor Air Quality, was recently republished with a number of updates. A
number of years ago, Standard 62.1 went through some fairly significant changes.
The transition from the advisory language of 62-1989 to today's mandatory, codeintended language, which includes much more extensive requirements was long,
difficult and contentious.
Fortunately, or perhaps naturally, revisions to 62.12007 and 62.1-2010 have been much more straightforward. In large part, this is because the major issues have
been resolved and the changes are focused on improving
the details of the standard. For example, changes to 62.12010 that resulted in 62.1-2013 include:
* Table 6.2.2.2, "Zone Air Distribution Effectiveness,"
is modified to increase the effectiveness of underfloor
air-distribution systems that meet certain conditions.
The "Zone Air Distribution Effectiveness" (Ez) is a factor
used in calculating the amount of outdoor air needed at
the zone that accounts for how well the ventilation air
gets from the diffuser to the occupant breathing zone.
For underfloor air distribution systems that have vertical
throws of less than 50 fpm (0.25 m/s) at a height of 4.5 ft
(1.37 m) above the floor, the standard now allows an Ez of
1.2. These systems may then meet the standard with less
outdoor air than systems with lower Ez values, depending
on the Ez value in the critical zone.
* The requirements for the quality of water used in
humidification systems is modified and clarified. In
previous versions of the standard, the language regarding water used in humidification systems was unclear,
"Water shall originate directly from a potable source or
from a source with equal or better water quality." In particular, it was not clear to users what water treatment
chemicals might be allowed. The language was clarified
that no chemicals could be added other than those that
meet either of two other standards (NSF/ANSI 60-2012,
Drinking Water Treatment Chemicals-Health Effects and 21
CFR 173.310, Secondary Direct Food Additives Permitted In Food
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For Human Consumption). For chemicals meeting 21 CFR
173.310, automated dosing equipment is required to be
used to control the chemical concentrations in the water.
* Building-level pressurization requirements were
clarified, and a definition of "exfiltration" was added.
Standard 62.1-2010 required that total building outdoor
air intake exceed total building exhaust airflow "whenever the mechanical air-conditioning systems are dehumidifying." The wording was revised for the 2013 version
such that the requirement applies except "When outdoor
air dry-bulb temperature is below the indoor zone dewpoint design temperature."
* A performance alternative to the prescriptive exhaust rates is added. This approach is similar to the IAQP
in that it allows a performance approach. It differs, however, in that monitoring of the concentrations of contaminants of concern is required and provides the basis for control of exhaust flow rates. Standard 90.1-2010
includes a requirement that garage ventilation systems
must vary flow rates based on monitored contaminant
levels. Standard 62.1, on the other hand, provided a required exhaust rate for parking garages, but no allowance for reducing this flow. Thus, Standards 90.1 and 62.1
contained conflicting requirements. 62.1-2013 was modified to include a performance approach for exhaust systems, to address the conflict. This approach requires that
contaminants of concern be identified based on sources
in the zone, that concentration limits be specified, and
Roger Hedrick is principal engineer at Architectural Energy Corporation, a member of
NORESCO Energy and Sustainability Services. He is chair of SSPC 62.1, Ventilation for
Acceptable Indoor Air Quality.

ASHRAE Journal - August 2014

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