Venting For Island Cooktops

A cooktop built into a kitchen island is a bold design statement that brings the room’s cooking area into the spotlight — but properly venting a cooktop in this prominent location is not easy. Local building codes may vary in terms of specific requirements for cooktop venting; most requirements, however, fall in line with a few simple vent design guidelines.

Options

Because an island cooktop sits in the middle of the kitchen, venting it with an overhead range hood is more challenging than installing a hood over a cooktop that sits against a wall. Free-hanging hoods are typically much more costly than wall-mounted hoods — a wall-mounted hood can usually be installed for less than $1,000, while a free-hanging hood may cost well over $10,000. A less expensive option is a downdraft vent that pulls the cooktop’s exhaust down into the island cabinet rather than venting through the ceiling.

Requirements

The minimum amount of ventilation airflow required by a gas cooktop varies depending on the BTU output of the cooktop. A general guideline is to divide the total BTU output by 100 to determine the flow rate of the ventilation system in cubic feet per minute. For example, a cooktop with an output of 70,000 BTU would require a ventilation system rated at 700 cubic feet per minute. Electric cooktops require 200 cubic feet per minute of airflow for each foot of the cooktop’s width; for most electric cooktops, 400 cubic feet per minute does the job.

Ducting

Local building codes may require that cooktop hoods deliver their exhaust outside the house through ducts rather than simply recirculating the exhaust back into the kitchen. Codes may also specify the materials used to construct the duct work. Typical specified materials include stainless steel, galvanized steel or copper. Always check with your local building authority to find out the requirements in your area before you install a cooktop or ventilation system.