A cooktop assembled to your kitchen island is a bold design statement which brings the room’s cooking area into the spotlight — but properly putting a cooktop in this prominent location isn’t straightforward. Local building codes can change in terms of specific requirements for cooktop venting; many requirements, however, fall in line with a couple easy vent layout guidelines.
Since an island cooktop sits at the middle of the kitchen, venting it with an overhead range hood is harder than installing a hood over a cooktop that sits against a wall. Free-hanging hoods are typically much cheaper than wall-mounted hoods — a wall-mounted hood can usually be set up for less than $1,000, even though a free-hanging hood may cost over $10,000. A more affordable choice is a downdraft vent that pulls the cooktop’s exhaust down into the island cabinet rather than venting through the ground.
The minimum quantity of ventilation airflow demanded by a gas cooktop fluctuates dependent on the BTU output of the cooktop. A general guideline is to split the total BTU output by 100 to ascertain the flow rate of the ventilation system in cubic feet per minute. As an example, a cooktop with an output of 70,000 BTU would call for a ventilation system rated at 700 cubic feet per minute. Electric cooktops require 200 cubic feet per minute of airflow for every foot of the cooktop’s width; for many electric cooktops, 400 cubic feet per minute does the occupation.
At California, codes needs as laid out in the ASHRAE Standard 62.2 require that kitchens include a mechanical ventilation system which can move 100 cubic feet of air each minute if the system is operated intermittently. In the event of a continuously operated system, the system must achieve five air changes per hour. These requirements are minimum criteria, and when your installed cooktop demands more powerful ventilation, then the cooktop requirements supersede the code requirements.
Local building codes may require that cooktop hoods deliver their exhaust beyond the home through ducts rather than simply recirculating the exhaust back into the kitchen. Codes may also specify the materials used to build the duct work. Typical specified materials include stainless steel, galvanized steel or copper. Always check with the local building authority to find out the requirements in your area before you put in a cooktop or ventilation system.