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Ashrae Standard 62.1
The Standards for Ventilation and Indoor Air QualityANSI/ASHRAE Standards 62.1 and 62.2 are the recognized standards for ventilation system design and acceptable IAQ.
AbstractAmerican National Standards Institute (ANSI)/American Society of Heating and Refrigeration and Air-Conditioning Engineers, Inc. (ASHRAE) Standard 62.1-2004 is a short but often misunderstood document outlining ventilation requirements intended to provide acceptable indoor air quality (IAQ) 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 practical needs of reliable intake rate control and the risks of indirect controls. Design recommendations offered are intended to increase the potential for both predictable compliance and the flexibility to accommodate future changes while providing the greatest control reliability with the most energy-efficient methods. INTRODUCTIONThis is a summary of American Society of Heating and Refrigeration and Air-Conditioning Engineers, Inc. (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 for energy minimization when compliance with 62.1 and energy codes are simultaneous goals. This is not a condensed version and this does not cover all requirements of the Standard. Designers are strongly encouraged to read the entire 19-page document (a total of 44 pages with appendices). The Standard cannot be understood or properly applied without considering the relationships and interdependencies of requirements of the document.This American National Standards Institute (ANSI)-approved standard has been developed by a Standing Standards Project Committee (SSPC) of the 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 1989.1In 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 promised 62.1 User’s Manual was recently published in December 2005. Work continues on a Guideline 19P, which is intended to provide design guidance for methods that exceed the minimum requirements of the Standard. Both of these supplemental documents should assist the designer and the facility operator in their understanding of and compliance with the Standard.
ANALYSIS AND RECOMMENDATIONSOur discussion of Standard 62.1 will try to mimic the structure of the Standard, provide recommendations for compliance, and highlight methods and assumptions to avoid. Our objectives have determined the content.The Standard’s “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 productivity and health. The procedures allowed for compliance with our national standard on ventilation are prescriptive or performance-based. Their selection and application should be evaluated for IAQ risk by the design practitioner.
DefinitionsSection 3 addresses the definition of terms used within the Standard. Noteworthy is the Standard’s definition of “acceptable IAQ,” which is defined 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.1This means that 62.1, like all ASHRAE Standards, assumes that one out of five occupants (20%) might not be satisfied with the results of compliance and might express dissatisfaction with the IAQ, even if the Standard is followed perfectly. Many sources have concluded that the majority of Heating Ventilation Air Conditioning (HVAC) systems designed in the United States 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:1. Changes in wind or stack conditions on the intake 3 system,2.
Changes in filter loading, or3. 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 today’s HVAC systems are partially to blame for many design deficiencies observed.Unlike thermal comfort, the effect of IAQ is difficult to measure (The work item that caused the most controversy was an attempt to standardise 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 IAQ. 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.
Ashrae 62.1 2016 Ventilation Rates
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 Outdoor Air QualitySection 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 the 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 Section 6.2.1.
Outdoor air treatment involves the removal of the particulates and gases encountered that are in excess of the minimum standards cited by cognizant authorities in Section 4.1. Systems and Equipment Section 5 specifies the minimum systems and equipment required under Standard 62.1. Section 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.
Ashrae Standard 62.1 Pdf
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.1The Standard recognizes that changes in mixed air plenum pressure, up to 0.5 in. WG 125 Pa variation on VAV systems, can significantly influence outdoor air intake flow rates. However, it neglects the significant influence of external pressure variations on all systems that result from changes in wind and stack pressures, which often exceeds 0.5 in. Therefore, providing the minimum outdoor airflow defined in Section 6 ‘effectively’ requires a dynamic control alternative for compliance—possibly the use of permanent devices capable of maintaining outdoor airflow rates.Not mentioning airflow measurement is analogous to ignoring the requirement for temperature measuring devices to maintain continuous temperature control.
Ashrae Standard 62.1 -2010
Because many systems, especially VAV, have thermal load requirements that differ from their ventilation needs, the requirements of this section can be more sustainable if the multispace Eqs. 6-1 to 6-8 are calculated for the design supply flows to individual zones using the minimum outdoor air requirements to each zone. In order to achieve the industry “standard of care” in professional HVAC design, the mechanical engineer is required to determine which zones may become ‘critical’ and that the worst ‘critical zone’ is at its minimum supply airflow. Even with the average reduction potentials due to the new ventilation rate (Table 6-1), this could still impose a severe energy penalty to many VAV system designs.it is necessary to maintai Because of the requirements set forth in the Standard for compliance “under any load condition,” n a constant rate of outdoor airflow in dynamic systems.
Logically, Section 5 should require continuous airflow measurement at the intake of all air-handling units with automatic controls that function to provide a building or space with a constant rate of outdoor air, regardless of the system size or type. Doing so would alleviate several practical issues, clarify application and compliance questions in Section 6.2.7, Dynamic Reset; Section 7.2.2, Air Balancing; and Section 8.4.1.8, Outdoor Airflow Verification.