HVAC: documenting ASHRAE 62.1 compliance
Standard 62.1 specifies minimum ventilation rates and other measures intended to provide IAQ to building occupants.
J. Patrick Banse, PE, Smith Seckman Reid Inc., Houston
ANSI/ASHRAE Standard 62.1-2010, Ventilation for Acceptable Indoor Air Quality, including normative Appendix A and approved addenda a, c, d, and e contained in the 2011 Supplement, form the current version of the standard. The standard is noted by ANSI as a consensus standard, meaning it was developed and approved by concurrence of more than a simple majority that reached a substantial agreement by directly and materially affected interest categories. The standard also contains Appendixes B, C, D, E, F, G, H, I, and J, which are termed informative and are not part of the standard. However, these appendixes contain valuable information regarding methods of compliance and documentation required by the standard. As with any code or standard, it must be read in its entirety to determine the applicability to the specific project or task at hand.
The standard by itself is not a code nor is it enforceable, unless it has been adopted by reference by an authority having jurisdiction (AHJ). Portions of this standard, such as ventilation rate tables and formulas, have already been incorporated into some of the model building codes. As with any code or standard incorporated by reference, it is incumbent upon the designer to discuss the requirements and applicability with the AHJ.
The purpose of the standard is to “specify minimum ventilation rates and other measures intended to provide indoor air quality (IAQ) that is acceptable to human occupants and that minimizes adverse health effects.” It applies to most all occupancy and use types of new buildings, additions to existing buildings, and changes to existing buildings as identified in the standard. It defines requirements and air-cleaning system design, installation, and operation and maintenance (O&M). Other codes and standards may have ventilation requirements that should also be considered.
Documentation of all aspects of the project ventilation is required as it is defined within the standard. The documentation is required to be formal and is specifically listed in Sections 4 (Outdoor Air Quality), 5 (Systems and Equipment), 6 (Procedures: Ventilation Rate Procedure; IAQ Procedure; Natural Ventilation Procedure); and 7 (Construction and Startup).
Section 4 requires that the outdoor air quality be investigated by the designer and both the regional air quality (geographic) and the local air quality (building site) be documented and discussed with the building owner or representative. Conclusions regarding the discussion and acceptability should remain in the project file.
Section 5 relates to the systems and equipment in the project and requires the design documents to specify minimum requirements for air balance and testing. Design assumptions with respect to ventilation rates and air distribution and effectiveness (clarified by Addendum a) must be clearly stated within the design documentation. A personal preference is to show these design criteria on the mechanical project cover sheet. Additionally, mechanical ventilation system controls (clarified in Addendum e) and sequences must clearly show that minimum outdoor airflow is provided at all times as required by Section 6 under any load conditions.
Air cleaning, outdoor air intake locations, minimization of rain intrusion, exfiltration (building pressurization) clarified in Addendum c, drain pans, access for cleaning and maintenance, air distribution systems, air classification as noted in the ventilation standard tables, and the supply, return, and exhaust systems and construction requirements must be clearly shown and documented. When required, a summary of each HVAC system may be necessary to show compliance.
There are three ventilation procedures described in Section 6: the Ventilation Rate Procedure (VRP), the IAQ Procedure, and the Natural Ventilation Procedure. Any of these procedures may be used to satisfy the ventilation required as each have specific requirements and are viewed as being a valid basis of design as long as they are properly documented. In each case, the exhaust requirements of section 6.5 (clarified in Addendum d) must be met. The VRP is a prescriptive method based on minimum ventilation rates in the breathing zone based on occupancy type, number of occupants, quality of outdoor air, distribution effectiveness, and class of air. Formulas in the standard are used to determine the breathing zone ventilation air of each space and occupancy density. Table H-3 in the Appendix identifies a clear way to document the ventilation airflow for each space. Documentation for this method by the designer requires that a written description of the equipment, methods, control sequences, setpoints, and the intended operational function shall be provided. A table showing minimum and maximum outdoor air intake airflow for each system shall also be provided.
Documentation for the IAQ procedure requires the design documents to include: contaminants of concern considered, sources and emission rates, concentration limits and exposure periods, and the analytical approach used to determine ventilation rates and air cleaning. Contaminant monitoring and evaluation plans must also be included. The IAQ procedure may be combined with the VRP and documented as to how the ventilation rates and air-cleaning were achieved. Table H-4 in the Appendix may be used to properly show the IAQ procedure with the requirements of Section 6.3.
The Natural Ventilation Procedure is required to be designed in accordance with proper opening sizes and locations as well as to the minimum ventilation rates required by Section 6.2 and/or 6.3 of the standard. The documentation for this procedure must include all design criteria and assumptions as well as system operation requirements to achieve the required outdoor airflow.
Section 7 identifies requirements during the construction and system start-up phases of the project. Items included in this section are protective measures, cleanliness, air filters, HVAC test and balance, and drain pan testing. The contractor is required to provide this documentation to the building owner or representative that consists of O&M manuals, HVAC control system description with schematics and sequences, air balance report, construction drawings, and design criteria and assumptions. Section 8 of the standard is concerned with O&M and the requirements apply to buildings and their ventilation systems and components constructed or renovated after adoption of this section. The engineer and facility manager should discuss these requirements with the AHJ to determine if and how compliance with this section may be required.
Inclusion of this standard through reference by an AHJ will require both the designer and contractor to provide detailed information both on the design drawings and after installation is complete to show not only compliance, but methods used to achieve and maintain the requirements during building operation. Rethinking how information is presented on drawings and what additional information is required post-construction may reduce the potential anxiety of 62.1-2010 compliance.
Banse has more than 35 years of experience in the consulting engineering field with the past 30 years in healthcare design and engineering. He is a member of Consulting-Specifying Engineer's Editorial Advisory Board.