Committee of experts compose white paper with key information for HVAC industry

FALLS CHURCH, Va. – In a new white paper, “Return Ductwork Requirement for Airborne Pathogens Through the Airstream,” experts discuss the reduction of pathogen transmission using a building’s original mechanical design, original installation, design intent and proper maintenance by a skilled, trained and certified technician. Two approaches a building engineer has at their disposal to reduce pathogen transmission are pressure barriers and airflow distribution.

The white paper discusses the pros and cons of using the cavity above a finished ceiling as a return air plenum combined with supply air to the air handler as a proper ventilation technique.

Considerations include how ventilation systems affect the health and well-being of building occupants as well as HVAC workers. For instance, while a ceiling plenum provides some fan-specific energy efficiency and a reduction in material and labor costs, it could put occupants and workers at risk and result in unintended energy losses.

With a negative ceiling plenum, negative pressurized architectural plenums can draw in untreated and humid outside air through the building’s skin or roof or unconditioned air from untreated spaces. That untreated air must then be treated at a cost of energy.

A ducted return system allows a testing, adjusting and balancing (TAB) professional to alter room pressures and airflow patterns to accommodate a change in use or mitigate pathogen transmission during a pandemic. There also are additional safety concerns regarding daily maintenance tasks, source control and the introduction of additional airborne particulates that may compromise indoor air quality. An open ceiling plenum is difficult to clean and disinfect while ductwork can be easily cleaned.

Authors of the white paper include members of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Technical Committee 5.2 Duct Design, which has officially approved the document. Members of the technical committee who worked on the document include John Constantinide, Florida-licensed mechanical engineer and vice chair of the technical committee; Chris Ruch, director of training for the National Energy Management Institute; John Hamilton, chief operating officer of the Testing, Adjusting and Balancing Bureau; Bob Reid, Spiral Pipe of Texas, business development/engineering; Walter Robison, design engineer for ATCO Rubber Products; Randy Young, Joint Committee on Energy and Environmental Policy and member of Sheet Metal Workers Local 104; and Chris Van Rite, MiTek and committee chair.

Founded in 1894, ASHRAE is a global society advancing human well-being through sustainable technology for the built environment. It and its members focus on building systems, energy efficiency, indoor air quality, refrigeration and sustainability in the industry. Through research standards, writing, publishing and continuing education, ASHRAE shapes tomorrow’s built environment today. More information can be found at

The National Energy Management Institute (NEMI) is a not-for-profit organization jointly funded and managed by the Sheet Metal and Air Conditioning Contractors’ National Association (SMACNA) and the International Association of Sheet Metal, Air, Rail and Transportation (SMART) workers. It provides valuable education on emerging markets, new technology and advances in manufacturing and construction processes to the sheet metal industry. Additional information can be found at or by calling 703-299-5646.

Originally posted on Eye on Sheet Metal.