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New requirements of ASHRAE standard 62.1-2010.


ASHRAE Standard 62 was first published in 1973. It was revised and republished in 1981, 1989. 1999 and 2001. The standard was placed on continuous maintenance in 1997. Under continuous maintenance the standard is revised continually and by policy is republished every three years. The standard number was revised flora 62 to 62.1 to allow for separation of the low-rise residential provisions into new standard 62.2. Standard 62.1 Ventilation for Acceptable Indoor Air Quality was published in 2004, 2007 and 2010. There were significant changes in ventilation rates in the 1981, 1989, and 2004 versions of the standard. While the ventilation rates did not change markedly between 2007 and 2010, there are significant changes in the procedures. This purpose of this paper is to explain some of the changes that occurred and document the rational for some of the changes.


From the initial publication of ASHRAE's ventilation standard, there was an allowance for different methods of providing for indoor air quality. The standard recognized the use of natural ventilation, mechanical ventilation and exhaust, and credit was given for advanced filtration in the 1973 version. In the 1981 version the filtration credit was incorporated into a new indoor air quality procedure. The approaches are now the natural ventilation procedure, the ventilation rate procedure (VRP) and the indoor air quality procedure (IAQP).


The natural ventilation procedure is established in 62.1-2010 through addendum n. Natural ventilation requirements were removed from Section 5 (Systems and Equipment) and a new section 6.4 was written. Natural ventilation systems shall include mechanical ventilation systems with a couple of exceptions. This requirement is new. It is analogous to the requirement for mechanical ventilation in ASHRAE Standard 62.2-2007.

As mixed mode or hybrid ventilation systems become more attractive design options, the standard was updated to reflect that using mechanical ventilation to supplement natural ventilation should be the rule rather than the exception. An extended discussion of design of such systems can be found in Strategy 8.4 of the recently published Indoor Air Quality Guide - Best Practices for Design, Construction, and Commissioning.

The exeptions where mechanical ventilation is not required to supplement natural ventilation systems are:

* The engineered natural ventilation system is approved by the authority having jurisdiction

* The natural ventilation system complies with the requirements in section 6.4 and the openings cannot be closed during periods of occupancy

* The zone is not served by heating or cooling equipment


The ventilation rate procedure is the most commonly used procedure. This procedure is used to calculate minimum ventilation rates for occupied spaces and the minimum ventilation rate required at the outdoor air intake of each ventilation system. There are three types of changes to this procedure between 2007 and 2010: changes to occupancy rates, clarification of the multiple zone calculations, and additional requirements for demand control ventilation.


Several occupancy categories were modified or added with addendum d. The storage category was modified to differentiate between occupiable storage rooms for liquids or gels and storage rooms for dry materials. Kitchen (cooking): Breakrooms; Banks or bank lobbies: Sorting, packing, light assembly; and general manufacturing (excludes heavy industrial and processes using chemicals) were added to Table 6-1. Electrical equipment rooms and elevator machine rooms were deleted from Table 6-1.

Addendum f clarified pool deck areas. Addendum m deleted Appendix E as health care facilities are now included in Standard 170-2008. Addendum s modified ventilation rates in shipping/receiving, warehouses, coin-operated laundries, and disco/dance floors.

Multiple Zone Systems

Parts of section 6.2 the Ventilation Rate Procedure, along with relevant definitions and Appendix A were modified by addendum t. The intent was to clarify the requirements for designing multiple zone systems without any major changes in requirements.

In any design, a distinction between "design" conditions and operating conditions is implied and the revisions are intended to clarify the requirements for "design". Just as a cooling system is sized for the "design" conditions for peak outdoor temperatures and related variables, a ventilation system must be sized for the "design" conditions of occupancy, air distribution, and related variables. The system may be operated to meet the current ventilation loads and not the design load if the current load is different from design. The same equations are used for determining the air quantities required at the outdoor air intake for part (ventilation) load conditions. Details of what can be varied are covered in the following section on demand control ventilation.

The other clarification in the language modifications in addendum t is to reinforce the requirement to design VAV systems using the minimum expected primary airflow in the critical zone. The system ventilation efficiency ([E.sub.v]) for variable air volume (VAV) systems is by their nature less than equivalent constant volume (CV) systems. However, the overall energy consumption efficiency of VAV systems can be much better than CV systems, which is why they are systems of choice in many applications. It is important that designers use the proper airflow values for VAV system design so that the minimum required ventilation air ([]) is supplied to the breathing zone of each ventilation zone. Instructions on how to design are not a part of the standard, but many resources are available including articles in the ASHRAE Journal (see references) and courses from the ASHRAE Learning Institute.

Demand Control Ventilation

Demand control ventilation (DCV) is now defined as "any means by which the breathing zone outdoor air flow ([]) can be varied to the occupied space or spaces based on the actual or estimated number of occupants and/or ventilation requirements of the occupied zone." A baseline of no less than the building component (Ra*Az) of the DCV zone is required for any zone and the system must provide each zone with no less than the breathing zone outdoor airflow for the current zone population. Addendum g also changed the standard to require documentation of assumptions and sequences and setpoints for any DCV system.


The indoor air quality procedure was modified with addendum r. The modifications make clearer that the procedure is an alternate method for calculating ventilation rates that can provide (ventilation reduction) credit for reduction of concentrations of contaminants in the indoor air by means other than ventilation. Typical alternatives include filtration and air cleaning.

The procedure was strengthened by removing an approach that merely required that it be proved "successful in similar buildings," without a definition of success or similar. As revised, the procedure now requires calculations for any application of the IAQP. It is now clear that the IAQP can be combined with or used to enhance results provided by the VRP.

Informative Appendix D Acceptable Mass Balance Equations for use with the IAQ Procedure was modified by addenda b and 1. Certain errors were corrected and nomenclature was revised to be consistent with the body of the standard. Informative Appendix B Summary of Selected Air Quality Guidelines was updated and revised through addendum q. Tables B-l and B-2 were updated while Table B-3 was added.


Exhaust ventilation is now a stand-alone section within section 6 Procedures. The new section 6.4 Exhaust Ventilation applies to all zones or systems regardless of the design procedure used (natural. VRP, or IAQP).


Several addenda related to improving indoor air quality were added including those addressing system operations, outdoor air quality, separation distances, and environmental tobacco smoke.

Ventilation System Operation

The ventilation system will not be effective if it is not operated. Among other changes, addendum j included the requirement that "Systems shall be operated such that all spaces are ventilated when they are expected to be occupied.

Outdoor Air Quality

The existing requirement for filtering outdoor air in non-attainment areas for [PM.sub.10] with a minimum of MERV 6 filters was reworded. A new requirement for filtering outdoor air in non-attainment areas for [PM.sub.2.5] was added by addendum c. In an area where the national standard for [PM.sub.2.5] is exceeded, filters of MERV 11 or higher must be used to clean the air prior to its introduction into occupied spaces. Addendum c also modified the requirements for filtering ozone from outdoor air by changing the referenced ozone NAAQS standard from the old one-hour average to the current eight-hour average. The trigger concentration for requiring air cleaning was revised to be consistent with classifications of areas (69FedReg 23998) that are serious, severe-15, severe-17, or extreme. Areas that are classified as either marginal or moderate for 8-hour ozone nonattainment do not require air cleaning.

Table 4-1 National Primary Ambient Air Quality Standards for Outdoor Air was relocated to a new appendix J and values were updated.

Separation Distances Between Outdoor Air Intakes and Outdoor Sources

Addendum p added language to equate openings for natural ventilation systems with outdoor air intakes. It also added minimum separation distances for exhaust of classes 2, 3, and 4 air from outdoor air intakes. Separation distances from plumbing vents and outdoor air intakes were also added to Table 5-1.

Environmental Tobacco Smoke (ETS)

The requirement for venilation of smoking areas in section 6.2.9 was deleted by addendum i. Addendum k modified note 2 in Table 6-1 regarding environmental tobacco smoke.
Table of Addenda

62.1a  General cleanup of 62.1-2004, adding clarity and removing
       errors and inconsistencies. No significant new requirements.

62.1b  This addendum addresses compliance issues that may result from
       unclear wording or phrasing in Appendices C. D, and F.

62.1i  Deletes language stating that smoking areas shall have more
       ventilation than comparable no-smoking areas.

62.1c  Addendum requires MERV-11 particle filtration in PM2.5
       nonattainment areas. The U.S. EPA changed to an eight-hour
       average ozone concentration as the basis for compliance with
       the ozone NAAQS. Selection of a design value of 0.107 ppm or
       more (corresponding to Serious, Severe, or Extreme by the U.S.
       EPA) is based on limiting this requirement to the worst
       ambient air quality areas for ozone.

62.1d  Addendum adds the following Occupancy Categories to Table
       6-1:Kitchens (cooking); Banks or Bank Lobbies; Breakrooms;
       Sorting. Packing, Light Assembly: General Manufacturing
       (excludes heavy industrial and processes using chemicals): and
       Storage rooms (dry).

62.1e  This addendum updates the references to industry standards and
       documents within the body of Standard 62.1-2007.

62.1f  This addendum clarifies the meaning of "pool deck area" and
       associated outdoor airflow rate requirements.

62.1g  This addendum adds information for demand controlled
       ventilation (DCV) systems to augment Section 6.2.7 Dynamic

62.1h  This addendum relocates Table 4-1 to a new informative
       appendix so that changes to the NAAQS can be updated quickly.

62.1j  This addendum to Section 8 clarifies when, at a minimum, the
       ventilation systems shall be operated.

62.1k  This addendum corrects language in Note 2 of Table 6-1
       (smoking) to make it consistent with terminology used
       elsewhere in the standard.

62.11  This addendum modifies Informative Appendix D as follows: (1)
       Improve variable-name consistency with body of the standard
       and Appendix A. (2) Delete one figure, replace with two
       improved figures. (3) Delete "proportional" systems from Table
       D-l. since VAV systems with fixed-position outdoor air dampers
       are unlikely to meet the requirements of the standard and
       should be discouraged.

62.1m  This addendum removes ventilation requirements for healthcare
       spaces from the Standard since ventilation requirements for
       these types of spaces are now covered in Standard 170-2008.
       "Ventilation of Health Care Facilities".

62.1n  This addendum modifies Section 5.1 and 6.0 to relocate Natural
       Ventilation requirements into Section 6, to add prescriptive
       requirements for naturally ventilated systems, and to require
       both passive and mechanical ventilation (mixed-mode or hybrid)
       ventilation for most buildings in most climates.

62.1o  This addendum moves the existing 6.2.8 and the corresponding
       Table 6-4 (exhaust) into a new Section 6.5 such that it
       applies to all spaces regardless of the method used to provide
       ventilation to the occupied spaces (Ventilation Rate
       Procedure, IAQ Procedure, Natural Ventilation).

62.1p  This addendum modifies and adds separation distance
       requirements between outdoor air intakes and sources of
       contaminants including exhaust and relief airstreams
       characterized using the Classes of An already defined in the

62.1q  This addendum updates and modifies informative appendix B that
       provides reference information for IAQ procedure contaminants
       of concern.

62.1r  This addendum modifies the IAQ procedure description in
       Section 6.l and its requirements in Section 6.3. It addresses
       compliance issues that may result from unclear wording or
       phrasing, requires a mass balance analysis, and requires a
       subjective analysis after construction. It eliminates
       compliance using "design approaches that have proved
       successful in similar buildings."

62.1s  Modifies ventilation rates for shipping/receiving areas,
       warehouses, and coin-operated laundries.

62.1t  This proposed addendum modifies normative Appendix A, and
       associated Section 6.2 requirements, as follows:

       * It reduces compliance issues that may result from unclear
         wording or phrasing, especially for VAV systems.

       * It improves nomenclature consistency between the body of the
         standard and the appendix.

       * It moves key equations from textual definitions to the body
         of the Appendix.

       * It clarifies the design conditions (including minimum
         expected discharge airflow and highest expected system primary
         airflow) used to calculate worst-case intake airflow for
         multiple-zone recirculating systems.


ASHRAE. 1973. ASHRAE Standard 62-73, ANSI B194.1-1977, Standards for Natural and Mechanical Ventilation. New York: American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc.Inc.

ASHRAE. 1981. ASHRAE Standard 62-1981, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society of Heating. Refrigerating and Air-conditioning Engineers. Inc.

ASHRAE. 1989. ANSI/ASHRAE Standard 62-1989, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society of Heating. Refrigerating and Air-conditioning Engineers. Inc.

ASHRAE. 1999. ANSI/ASHRAE Standard 62-1999, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society of Heating. Refrigerating and Air-conditioning Engineers. Inc.

ASHRAE. 2001. ANSI/ASHRAE Standard 62-2001, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society of Heating. Refrigerating and Air-conditioning Engineers. Inc.

ASHRAE. 2004. ANSI/ASHRAE Standard 62.1-2004, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society of Heating. Refrigerating and Air-conditioning Engineers, Inc.

ASHRAE. 2007. ANSI/ASHRAE Standard 62.1-2007, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society of Heating. Refrigerating and Air-conditioning Engineers, Inc.

ASHRAE. 2007. ANSI/ASHRAE Standard 62.2-2007, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings. Atlanta: American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc.

ASHRAE. 2008. ANSI/ASHRAE/ASHE Standard 170-2008, Ventilation of Health Care Facilities. Atlanta: American Society of Heating. Refrigerating and Air-conditioning Engineers, Inc.

ASHRAE. 2009. Indoor Air Quality Guide: Best Practices for Design, Construction, and Commissioning. Atlanta: American Society of Heating. Refrigerating and Air-conditioning Engineers, Inc.

Federal Register Vol 69. No. 84, April 30, 2004. 23998 Table 1 - Classification for 8-hour ozone NAAQS for areas subject to [section] 51.902A

Stanke. D. "Addendum n. Single Zone and Dedicated OA Systems," ASHRAE Journal, October 2004

Stanke, D. "Standard 62-2001 Addendum 62n -Ventilation for Changeover-Bypass VAV Systems" ASHRAE Journal. November 2004

Stanke, D. "Single-Path Multiple-Zone System Design," ASHRAE Journal January 2005

Stanke, D. "Standard 62.1-2004 - Designing Dual-Path, Multiple-Zone Systems." ASHRAE Journal, May 2005

Hoy Bohanon, PE. LEED-AP is Director of Carolinas Region for Working Buildings, LLC

Hoy Bohanon, P.E.

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Author:Bohanon, Hoy
Publication:ASHRAE Transactions
Article Type:Report
Geographic Code:1USA
Date:Jul 1, 2010
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