The least duct thickness is defined by regardless of what code jurisdiction which the task is located in. Below are two code references connected to the needed thickness and product style for grease ducts. Condensate Canopies: Made for kitchens with significant condensation ranges, these canopies accumulate and drain excessive humidity. https://grease-tight-extract-duct23445.full-design.com/commercial-kitchen-extract-systems-for-dummies-79210289