We have a low rise (4 story) multifamily residential project considering LEED v4 BD+C in Boston. The ventilation system is a constant-volume dedicated outdoor air system with heat recovery, which provides all outdoor air supply and exhausts all air from the apartments, with the exception of a dedicated dryer exhaust.
The Minimum Indoor Air Quality Prerequisite contains a requirement that “Gas ranges must have hoods that exhaust air directly to the outdoors.” In Boston, vented hoods are not required for domestic gas ranges, but there are strict requirements for such hoods IF they are present. Per the International Mechanical Code, a domestic kitchen hood exhaust system must have its own dedicated exhaust risers, may not interact with any other system, and the exhaust fans must be on emergency power. Providing a dedicated kitchen exhaust system would severely increase the cost of the project and would effectively rule out heat recovery.
Our project proposes to meet the intent of the requirement by providing recirculating kitchen hoods above the gas ranges along with general exhaust drawn from the kitchen near the recirculating hood. In this way, kitchen exhaust can pass through the general exhaust system and therefore the heat recovery system. This design will provide equivalent indoor air quality with a lower energy footprint and lower first cost for the owner.
(Note: we are aware that this could be avoided by using electric ranges rather than gas. The owner has a stated preference for gas ranges, and we are evaluating options to accommodate this preference.)