Why is recirculation with filtration considered beneficial for IAQ under 62.1?

• A. It is never recommended due to energy concerns.
• B. It reduces airflow to save energy but does not affect air quality.
• C. It can improve energy efficiency while still filtering contaminants; must meet IAQ criteria.
• D. It is required in all new buildings.

Answer: (C)

The idea being tested is balancing energy use with IAQ when you filter recirculated air. Reusing indoor air and passing it through filters before it re-enters the occupied spaces lets you reduce the amount of outdoor air that must be conditioned. Conditioning outdoor air is energy-intensive, so recirculation with effective filtration can lower energy use while still removing contaminants from the air. Of course, you must verify that the overall IAQ remains within the criteria set by ASHRAE 62.1 for the given system and occupancy, meaning the filtration level and ventilation rate together keep pollutant levels acceptable. So this approach can improve energy efficiency while still filtering contaminants, provided IAQ criteria are met.