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Answered: American Society of Heating, refrigeration and Air-conditioning Engineers (ASHRAE) standard

American Society of Heating, refrigeration and Air-conditioning Engineers (ASHRAE) is a worldwide professional association that seeks to advance design and construction of heating, ventilation, air conditioning and refrigeration (HVAC&R) systems. ASHRAE was founded in 1894. ASHRAE members are in excess of 50,000 globally- composed of architects, engineers, mechanical contractors, equipment manufacturers, building services engineers, and others concerned in design and construction of HVAC&R building systems. Even though ASHRAE bears ‘American’ in its name, it is a global organization. ASHRAE publishes a set of standards and guidelines that relate to issues and systems of HVAC that are often used as references in building codes. The standards are of invaluable use to consulting engineers, architects, mechanical contractors, and government agencies. Some of the standards published by ASHRAE include; Standard 34 – that provides designation and safety classification of refrigerants, Standard 55 – that provides thermal environmental conditions for human occupancy, Standard 62.1 – concerning ventilation for acceptable indoor air quality, Standard 62.2 – concerning ventilation and acceptable indoor air quality in low rise residential buildings, Standard 90.1 – concerning energy standard for buildings except low rise residential buildings, Standard 135 – a data communication protocol for building automation and control networks, and Standard 189.1 – which provides for the design of high performance, green buildings except low rise residential buildings

In this paper, focus is on ASHRAE Standard 62.1. The latest edition being ASHRAE Standard 62.1-2013 that Superseded ANSI/ASHRAE Standard 62.1-2010. The standard includes ANSI/ASHRAE addenda listed in Appendix. It deals with Ventilation for Acceptable Indoor Air Quality in commercial and high rise buildings residential buildings. For low rise residential buildings, the ventilation requirements are covered in ASHRAE Standard 62.2.

Purpose of ASHRAE Standard 62.1-13

The ASHRAE standard 62.1 serves three fundamental purposes. The first one being that it provides guidelines on the minimum ventilation rates and on other measures with an intent to provide acceptable indoor air quality to human occupants in a building/space and to minimize adverse health effects. Secondly, the standard acts as a regulatory measure. This means that the guidelines covered within its scope must be adhered to in new buildings, where additions are made to existing buildings, and where changes are made to existing buildings. Lastly, the standard is intended to be used as a guide to improving indoor air quality of existing buildings.

Circumstances that led to the development of the code

            Development of ventilation requirements has been through reviews over the years. Lavoisier in the 18th century suggested that “bad air” indoors was caused by buildup of carbon dioxide gas rather than by the depletion of oxygen gas through inhalation. Pettenkofer in about one hundred years later idealized that biological contaminants was the cause of “bad air” indoors thereby disputing Lavoisier’s suggestion.

Billings together with his colleagues in early 20th century suggested minimum ventilation rates of 15 l/s per person which was based on hygienic concerns resulting from occupants’ organic exhalations. Many states in the United States adopted Billings’s rates. The rates were also included in a model law by American Society of Heating and Ventilating Engineers, (ASH&VE) the society that was the predecessor of ASHRAE. In 1913, New York State Ventilation Commission was formed. It was tasked to study ventilation requirements in public buildings like schools. They reported that there was no justification for the requirement of 15 L/s per person. Instead they reported that ventilation ranging between 5 L/s and 7.5 L/s per person was adequate for classrooms. In 1930s, chamber experiments were conducted by Lehmberg, Yaglou and their colleagues whereby body odor levels were treated as a function of ventilation rates. Their work showed that body odors would be maintained to non-objectionable levels to persons entering the space from clean air environments by about 8 L/s per person ventilation rates.

In 1946, American Standards Association released a standard that focused on lighting and ventilation through use of windows in all habitable rooms. The standard lacked ventilation requirements. However, it contained an appendix with recommendations for ventilation rates where mechanical ventilation was employed in addition to use of windows. The rates were 2.5 L/s per m2 in office spaces and 7.6 L/s per m2 in public buildings such as schools. These rates translated to 50 L/s and 22 L/s per person in office spaces and classrooms respectively based on occupancy densities described in ASHRAE 62.1-2013. From 1946, the next phase of ventilation and IAQ standards development was marked by publication of ASHRAE Standard 62-73 in 1973. This standard covered natural and mechanical ventilation. 

History of evolution of the ASHRAE Standard 62.1

The standard was first published in 1973 as Standard 62. The latest version being ANSI/ASHRAE standard 62.1-2013. This latest version is a combination of Standard 62.1-2010 and the ten addenda to the 2010 edition that were approved and published. The standard undergoes regular updates that are based on ASHRAE’s continuous maintenance procedures. Through the set procedures, continuous revisions of Standard 62.1 is conducted by addenda that are publicly reviewed, approved by ASHRAE and ANSI, and published. Publishing is done in a supplement usually about eighteen months after each new edition of the standard. The addenda are also published when a completely new edition is published which happens after every three years.

The standard has been subject to multiple changes over the years since it was first published. These changes are a true reflection of the increasingly expanding body of knowledge, experience, and research concerning ventilation and air quality. However, the purpose of the standard has remained consistent throughout even though the means of achieving it has evolved. The first edition of the standard adopted a prescriptive approach to ventilation. It specified both minimum and recommended rates of outdoor air flows that helped to obtain acceptable indoor air quality for a variety of indoor spaces. In the 1981 edition, minimum rates of outdoor airflow was reduced. The prescriptive approach was laid off and a performance based approach was adopted. This procedure dubbed indoor air quality procedure (IAQP) facilitated the calculation of outdoor air amount that was necessary to maintain the indoor air contaminants levels below recommended limits. The current edition of the standard consists three ventilation design procedures which are IAQ procedure, ventilation rate procedure VRP, and natural ventilation procedure.

In 1989, a new edition was published in response to an increasing number of buildings with apparent indoor air quality problems. The new edition increased the minimum outdoor rates of airflow significantly. It also introduced a necessity for finding air intake flow requirements from outdoor for multiple-zone recirculating systems. Subsequent editions of 1999 and 2001 only made several minor changes and clarifications that barely impacted minimum specified rates of outdoor airflow. In 2004, a new edition was published that revised the entire standard. In this revised edition, IAQ procedure was modified to enhance enforceability. Also Ventilation Rate Procedure was modified by changing both minimum outdoor airflow rates and procedures for determining zone-level and system-level rates of outdoor airflow. Subsequent editions of years 2007 and 2010 of the standard only provided a few significant updates. These updates focused on enhancing utility and clarity of the standard.

Recent changes in the standard and their implications

The ASHRAE Standard 62.1-2013 edition has been revised and improved in various ways. Changes have been made to enhance clarity and get rid of identified inconsistencies. Some of the significant changes that have been made to this latest edition are described below.

The Table 6.2.2.2 on “Zone Air Distribution Effectiveness,” has been modified. This increases effectiveness of underfloor air distribution systems that meet some specified criteria. In the 2010 edition, floor supply of cool air and ceiling return provided that the 150 fpm (0.8 m/s) supply jet reaches 4.5 ft (1.4 m) or more above the floor. However, in the 2013 edition, floor supply of cool air and ceiling return, provided that the vertical throw is greater than 50 fpm (0.25 m/s) at a height of 4.5 ft (1.4 m) or more above the floor

In humidification systems, the requirements for quality of water that need to be used has been clarified and modified.

The requirements for building pressurization level were clarified and a clarification on the definition of “exfiltration” added.

An alternative performance concerning prescriptive exhaust rates was added. In this alternative approach, the concentration of contaminants of interest is monitored and the information obtained acts as a basis for control of exhaust flow rates. This approach differs from the usual IAQP whereby the amount of outdoor air needed to maintain indoor air contaminants concentration to below certain recommended limits.

A change that states that as far as toilet air is cleaned to Class 1 may be recirculated. Class 1 air maybe recirculated or transferred to any space as per ASHRAE 62.1-13 clause 5.16.3.1.

Some changes were also made concerning ventilation rates and space types in Table 6.2.2.1. The changes added refrigerated warehouses and changed the ventilation rates of sports-related spaces to include a per-occupant component which allows use of demand controlled ventilation in these spaces. This is illustrated below by extracts from both ASHRAE 62.1-2010 and ASHRAE 62.1-2013.

Table 1: ASHRAE 62.1-10 extract

Table 6.2.2.1 Minimum Ventilation rates in breathing zone

People Outdoor Air Rate  

Rp

Area Outdoor Air Rate

Ra

Notes

Default values

Occupant density

Combined outdoor air rate

air class

category of occupancy

cfm/ person

L/s/ person

cfm/ft2

L/s/m2

#/1000ft2 or #/100m2

Cfm/ person

L/s/ person

Sports and Entertainment

Sports Arena (play area)

0.3

1.5

E

1

Gym, Stadium (play area)

0.3

1.5

30

2

 

Table 2: ASHRAE 62.1-13 extract

Table 6.2.2.1 Minimum Ventilation rates in breathing zone  

People Outdoor Air Rate Rp

Area Outdoor Air Rate Ra

Notes

Default values

Occupant density

Combined outdoor air rate

air class

category of occupancy

cfm/ person

L/s/ person

cfm/ft2

L/s/m2

#/1000ft2 or #/100m2

Cfm/ person

L/s/ person

Sports and Entertainment

Gym, Sports Arena (play area)

20

10

0.18

0.9

E

7

45

23

2

 

 

 

Table 3: ASHRAE 62.1-13 extract- addition on refrigeration

Table 6.2.2.1 Minimum Ventilation rates in breathing zone

People Outdoor Air Rate Rp

Area Outdoor Air Rate Ra

Notes

Default values

Occupant density

Combined outdoor air rate

air class

category of occupancy

cfm/ person

L/s/ person

cfm/ft2

L/s/m2

#/1000ft2 or #/100m2

Cfm/ person

L/s/ person

Freezer and Refrigerated spaces < 50 oF

10

5

0

0

E

0

0

0

2

 

The MERV rating was changed from 6 to 8. This was achieved through modification of the filter requirements that concern air entering wetted cooling coils. The change reduces the possibility for particulate deposition on the coils that could lead to contamination e.g. biological contamination.

Versions of the code being applied by local authorities

The current ASHRAE standard 62.1-2013 and standard 62.2-2016 are the ones being largely employed by local authorities especially for the purpose of regulation. The Standard 62.1-13 takes care of ventilation needs for commercial and high rise residential buildings. On the other hand, Standard 62.2-16 takes care of ventilation needs for low rise residential buildings. However, the use of these codes is supported by use of other codes such as the international mechanical code.

Comparison between ASHRAE 62.1-13 and the international mechanical code

            It would be prudent to describe ASHRAE Standard 62.1-13 as a subset of the international mechanical code. This is because of the coverage of the two standards. While ASHRAE standard 62.1-13 focusses entirely on ventilation for acceptable indoor air quality for commercial and high rise residential buildings, the international mechanical code only covers it as one of its chapters.

The two standards also show variability in their purpose. For ASHRAE’s 62.1-13, the primary purpose is to provide acceptable indoor air quality. However, the purpose of the international mechanical code is to provide minimum requirements that will ensure safeguard of life or limb, health, property, and public welfare. This purpose is achieved through regulation and control of design, construction, material qualities, installation, location, operation, and maintenance of mechanical systems. Thus the two are different in that one focuses on ventilation rates while the other focusses on how to achieve the stipulated ventilation rates.

            Lastly the two codes differ in their scope. For the ASHRAE Standard 62.1-13, it applies to those spaces that are intended to human occupancy. This with exceptions of the spaces within single-family houses, vehicles, and aircraft. On the other hand, the international mechanical code applies to regulations of design, installation, alterations, maintenance, and inspection of mechanical systems permanently incorporated within buildings to regulate indoor environmental conditions and other related processes.

Conclusion

Development of the ventilation and IAQ standards has continuously improved significantly from the time the first ventilation standard was published about 70 years ago. The ASHRAE standard recognizes that more work is required to make the standards more effective in facilitating provision of better indoor environments in buildings. Most of such improvements will need further research into issues concerning contaminant mixtures and health effects of contaminants, source strengths in buildings, performance of IAQ control technologies, and new design approaches. Ultimately, the standard recognizes the differences between buildings and its occupants to support design approaches that are more flexible, while still meeting needs of regulators, policymakers, building owners, and designers who strive to provide high-performance and sustainable buildings to the people that occupy them.

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