Answer: | TRUE - Kitchen down draft or exhaust systems cannot use flexible ducts. Downdraft exhaust systems, like standard updraft systems, must employ rigid metal ductwork that terminates outside the envelope of the home. That means the termination point must be through the roof or out of the crawlspace. [Additionally - flexible dryer hose CANNOT be used in gas appliance (water heaters and furnaces). Gas fired appliances require a rigid "rated" product that is specifically approved for the exhaust of combustible exhaust.] Why can't flexible duct be used and why does it need to terminate outside the envelope of the structure? Because of fire hazard. Flexible duct can trap combustible contaminates and flexible duct is not rated to meet the potential heat requirements. And, as far as the necessity of an exterior point of termination - think about it - if a fire develops in the exhaust duct and the duct terminates in the attic or within the crawlspace the fire could engulf the house before anyone would see the flames. |
