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ASHRAE62.1-2004_Analysis_1
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Update, Analysis and Recommendations -

ANSI/ASHRAE STANDARD 62.1 2004,

Ventilation for Acceptable Indoor
Air Quality

Len Damiano, VP Sales & Marketing





December 2005
David S. Dougan, President,

EBTRON, Inc.




BACKGROUND

This paper is an updated version of a similar one published for Standard 62-2001. Please study
the complete documents discussed in this paper and review the bibliography. This short paper
should not be considered a substitute for the complete document, nor is it a shortcut to
compliance with the standard. There are many other issues to consider that are not discussed
here.

ANSI/ASHRAE Standard 62.1-2004 is an often misunderstood document outlining ventilation
requirements intended to provide acceptable indoor air quality for new buildings or those with
major renovations. Because of the rate-based nature of both procedures allowed for
compliance, this analysis focuses on the needs for reliable intake rate control and the risks of
some popular indirect controls. Design recommendations offered are intended to increase the
potential for both predictable compliance and for the flexibility to accommodate future changes,
while providing the greatest control reliability with the most energy efficient methods.
INTRODUCTION

This is a brief summary of ASHRAE Standard 62.1-2004, Ventilation for Acceptable Indoor Air
Quality (IAQ) in Commercial, Institutional, Industrial and High Rise Residential Buildings [1], as
it impacts and is influenced by ventilation control requirements, methods and equipment.
Operational implementation of these requirements can have a sizeable influence on energy
usage, when applied improperly or incompletely. Operational precision and design reliability are
essential to minimize energy usage, when compliance with 62.1 and energy codes are
simultaneous goals.

This ANSI-approved standard has been developed by a Standing Standards Project Committee
(SSPC) of the American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc.
(ASHRAE), under a continuous maintenance protocol. At any point in time, the official
Standard is comprised of both the most recently published parent document and all current
addenda. The latest parent document was republished earlier this year to combine 17 addenda
that had been approved subsequent to the original release of the 62-2001 parent document in
January 2002. The result is a final version that is substantially different from the basic ventilation
standard we have used since 1989.

In 2003, the scope of the Standard officially changed and a separate ASHRAE committee was
formed to address the specific needs of Low-Rise Residential Buildings. The existing Standard
became known as 62.1 and the new residential standard became 62.2.

The long promised 62.1 Users Manual was recently published and is now available at
www.ASHRAE.org. Work continues on Guideline 19P, which is intended to provide design
guidance for methods of compliance that exceed the minimum requirements of the Standard.
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Both of these supplemental documents should assist the designer and facility operator in the
understanding of and compliance with the Standard.
ANALYSIS AND RECOMMENDATIONS

Our discussion of Standard 62.1 will mimic most of its structure, provide recommendations for
compliance and highlight methods and assumptions to avoid. Our objectives have determined
the content.

The Standards Purpose and Scope are covered in Sections 1 and 2. To comply with the
Standard, designers of mechanical ventilation systems are tasked to provide specific minimum
rates of acceptable outdoor air to the breathing level of the occupied structures. In doing so, an
acceptable indoor environment may be achieved providing improved occupant comfort,
productivity and health. The procedures allowed for compliance with our national standard on
ventilation are prescriptive or performance-based. Your selection should be evaluated for IAQ
risk by the design practitioner.

DEFINITIONS

Section 3 addresses the definition of terms used within the Standard. Noteworthy is the
Standards definition of acceptable indoor air quality which is provided as


air in which there are no known contaminants at harmful concentrations as determined by
cognizant authorities and with which a substantial majority (80% or more) of the people exposed
do not express dissatisfaction
[1]
.



This means that 62.1, like all ASHRAE Standards, assumes one out of five occupants (20%)
may not be satisfied with the results of compliance and may express dissatisfaction with the
indoor air quality, even if the Standard is followed perfectly. Many sources have concluded that
the majority of HVAC systems designed in the U.S. do not meet the minimum ventilation rates
prescribed during operation. In which case, the actual occupant dissatisfaction level is
exponentially greater in practice [2]. It is not uncommon for rates to fall below levels that result
in occupant dissatisfaction significantly greater than 50%. Many systems cannot meet the
minimum airflow requirements at the occupied space during operation because of design
choices and equipment limitations, or due to the dynamic nature of mechanical ventilation
systems and the constant external forces acting on the building envelope.

The impacts from these continuously changing external conditions are not limited to Variable Air
Volume (VAV) systems [2]. Outdoor airflow rates will also vary for systems that provide a
Constant Volume of supply air (CAV) to the conditioned space, as a result of:

a) changes in wind and/or stack conditions on the intake system [3],
b) changes in filter loading,
c) changes in airflow requirements during an economizer cycle.

The lack of specific guidelines to overcome the effect of changing system dynamics on
ventilation rates and air distribution for todays HVAC systems is partially to blame for many
design deficiencies observed.

Unlike thermal comfort, the effect of indoor air quality is difficult to measure.
1
Many believe that
the outdoor air levels specified by ASHRAE are too low and should actually be increased, as
indicated by published research and reflected in European standards from CEN Technical
Committee 156 and their publication CR1752 [4].
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OUTDOOR AIR QUALITY

Section 4 of the Standard describes a three-step process to evaluate outdoor air for
acceptability. One of those steps requires examination of both the regional and local air quality
by the building owner. The section also specifies the documentation required to support the
conclusions of this preliminary review.

If the outdoor air quality is found to be unsuitable per Section 4, then treatment may be required
as indicated in §6.2.1. Outdoor air treatment involves removal of the particulates and/or gases
encountered that are in excess of the minimum standards cited by cognizant authorities in §4.1.

SYSTEMS AND EQUIPMENT

1

The work item that caused most controversy was an attempt to standardise [sic] design criteria for the
indoor environment. The criteria developed in the process have been published as a CEN Technical
Report CR 1752.
It specifies the levels of temperature, air velocity, noise, and ventilation for occupied
spaces.
Values are given for three categories of environmental quality: A - a high level of expectation, B -
a medium level and C - a moderate level. Supporting information is given on the derivations of the
specified values of the parameters as well as to enable alternatives, such as different clothing levels, to
be accommodated in the design assumptions.
The most debatable section is on indoor air quality. Here,
prominence is given to the evaluation of the required ventilation rate for comfort based on perceived air
quality, the method developed by Professor Fanger and his colleagues in Denmark. While some data is
presented, it is acknowledged that more research is needed to provide reliable information on pollution
loads from materials and on the additive effects of emissions from multiple sources."
Source:
http://www.aivc.org/frameset/frameset.html?../Air/20_3/jackman.html~mainFrame
accessed June 2005.

Section 5 specifies the minimum systems and equipment required under Standard 62.1. §5.4
states,
Mechanical ventilation systems shall include controls, manual or automatic, that enable the fan
system to operate whenever the spaces served are occupied. The system shall be designed to
maintain the minimum outdoor airflow as required by Section 6 under any

load condition. Note:
VAV systems with fixed outdoor air damper positions must comply with this requirement at
minimum supply airflow
[1]
.


Because the requirements in the Standard for compliance are set forth under any load
condition, we are being asked to maintain a constant rate of outdoor airflow in dynamic
systems. Logically, there should also be a requirement for continuous airflow measurement at
the intake of all air-handling units with automatic controls providing a space with a constant rate
of outdoor air, regardless of the system size, type or point of operation. Doing so would al