It says, “Length limitation: Factory-made flexible air ducts and connectors should not be more than 5 feet ... Hart & Cooley Inc., a manufacturer of flexible ductwork and other HVAC accessories based ...

Q We had to put a new furnace in our home and they put in a flexible tube from the outside to the furnace. It was to supply fresh air for the furnace, but it seems to me like having an open window ...