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ASHRAE STD 62.2

Ventilation and Acceptable Indoor Air Quality in Residential Buildings

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Organization: ASHRAE
Publication Date: 1 February 2020
Status: active
Page Count: 2
scope:

Background:

Since 2007, Section 4.1 (Ventilation Rate) of ASHRAE Standard 62.2 has stated that "each dwelling unit" is to be provided with "outdoor air" at the rate specified. This rate is understood to be the minimum amount of continuous outdoor air needed to achieve acceptable indoor air quality within a dwelling unit.

Outdoor air has a clear definition in the standard: "air, outdoor: air from outside the building taken into a ventilation system or air from outside the building that enters a space through infiltration or natural ventilation openings."

Transfer air also has a clear and intentionally separate definition in the standard: "air, transfer: air moved from one occupiable space to another, usually through doorways or grilles."

Based on the distinctly different definitions and the consistent use of the term "outdoor air" rather than "transfer air" in Section 4.1, the intent of the Standard seems clear that the "outdoor air" must come from outside the building and not from adjacent spaces such as other dwelling units or attached garages. This is also supported in:

- Section 4.1.2 Infiltration Credit, which limits infiltration credit to outdoor air that infiltrates through exterior envelope surface area that is not attached to garages or other dwelling units. No credit is provided for transfer air that infiltrates through common walls.

- Section 6.1, Adjacent Spaces and Transfer Air, which states: "Measures shall be taken to minimize air movement across envelope components to dwelling units from adjacent spaces such as garages, unconditioned crawlspaces, unconditioned attics, and other dwelling units." This is the only section which mentions transfer air and does so by stating that transfer air from other dwelling units shall be minimized. Section 4.1 sets a minimum requirement for an outdoor air flow rate, with the option of increasing without limit. Since Section 6.1 requires transfer air from adjacent dwelling units to be minimized, it seems logical to conclude that transfer air from adjacent dwelling units (what must be minimized) cannot be counted as outdoor air (which can be maximized).

Even with the text in these sections that implies that outdoor air is needed for acceptable indoor air quality and that transfer air shall be minimized, there is still confusion in the multifamily industry whether exhaust systems, when used in attached dwelling units, are actually in compliance with Section 4.1, since they seem to comply with Section 4.3.

Section 4.3 Airflow Measurement, seems to imply that measuring indoor air exhausted is how one confirms that the outdoor air rate required in Section 4.1 has been provided. However, in attached housing, one cannot assume that the amount of air exhausted from a dwelling unit is equal to the amount of outdoor air entering that same dwelling unit. Often the indoor air exhausted results in some outdoor air entering the dwelling unit, but also transfer air from adjacent dwelling units or other adjacent spaces (laundry room, trash closets, parking garages, or corridors), regardless of the steps taken to minimize that transfer air. Since the intent of 4.1 and 4.3 seems inconsistent, the industry needs clarification as to whether transfer air taken from adjacent spaces should be considered outdoor air.

Looking beyond ASHRAE 62.2 for context, ASHRAE Standard 62.1-2013, which applied to attached dwelling units in buildings 4 stories and greater, stated that "air from one residential dwelling shall not be recirculated or transferred to any other space outside of that dwelling." Additionally, the ASHRAE 62.1 committee responded "No" to the following interpretation request in 2016: "An exhaust-only ventilation system is an acceptable system for meeting the outdoor air ventilation requirements of high-rise multifamily dwelling units under ASHRAE Standard 62.1-2010, regardless of whether a dedicated outdoor air inlet is provided or whether the outdoor air flow rate is confirmed at an outdoor air inlet" (62.1-2010-7).

Given the background above, the intent of ASHRAE 62.2 seems clear. However, inconsistency remains in the standard causing confusion in the market, and an interpretation is being officially requested.

Document History

July 30, 2021
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Addendum f updates the references used for rating ventilation equipment. The revised references allow for ratings that better reflect installed performance and allow for improved...
July 30, 2021
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Addendum g deletes the reference to ASHRAE Guideline 24-2015, Ventilation and Indoor Air Quality in Low-Rise Residential Buildings, from Standard 62.2. Guideline 24-2015 was withdrawn by...
April 30, 2021
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Addendum e makes the air leakage rate for compartmentalization in multifamily dwellings more stringent. This change reduces air and contaminant transfer between dwelling units in...
April 30, 2021
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Disentangling the requirements of ventilation rate, control, and operation makes the standard easier to follow, enforce, and maintain over time. Addendum b clarifies an issue regarding to...
January 27, 2021
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Addendum y addresses concerns regarding ventilation of new multifamily dwellings that are accessed by an enclosed common corridor where the operation of exhaust systems may draw air from...
September 30, 2020
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Addendum d replaces the current definition of “readily accessible” with a new definition from the 2020 National Electrical Code (NEC) intended to be less ambiguous and more compatible with...
July 31, 2020
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Addendum v updates the normative references in Standard 62.2, Section 9. Note: In this addendum, changes to the current standard are indicated in the text by underlining (for additions)...
February 12, 2020
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
February 5, 2020
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Several questions have arisen from users of the standard and within the SSPC regarding requirements for installation and operation of mechanical ventilation systems. The changes in this...
ASHRAE STD 62.2
February 1, 2020
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
Background: Since 2007, Section 4.1 (Ventilation Rate) of ASHRAE Standard 62.2 has stated that “each dwelling unit” is to be provided with “outdoor air” at the rate specified. This rate is...
June 22, 2019
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Addendum t removes the potential for people to claim they would have installed a balanced system to avoid installing an unbalanced system. It also aligns the maximum airflow requirement...
June 22, 2019
Ventilation and Acceptable Indoor Air Quality Residential Buildings
A description is not available for this item.
June 22, 2019
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Addendum c aims to minimize the potential for formulating variable ventilation control strategies that could result in substantial underventilation for noticeable periods of time. Note: In...
January 13, 2019
Ventilation and Acceptable Indoor Air Quality Residential Buildings
Background: The scope states that Standard 62.2 will not necessarily achieve acceptable indoor air quality if the system is not operated as designed. Operations (and maintenance) are not required by...
January 1, 2019
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
March 9, 2018
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
April 27, 2017
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
January 1, 2017
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
FOREWORD Addendum b modifies the language regarding controls for on-demand ventilation systems to better accommodate cases where the on-demand fan is also used toward the wholedwelling ventilation...
November 4, 2016
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
October 7, 2016
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
September 26, 2016
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
June 9, 2016
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
May 24, 2016
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
March 29, 2016
Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A description is not available for this item.
January 23, 2016
Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings
FOREWORD The intent of Section 7.2.2, “Demand-Controlled Local Exhaust Fans,” is to require fans to have at least one speed setting meeting the minimum required exhaust airflow rate where the...
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