Suppliers often recommend zip ties for securing ducts to fan housings, but that is not enough.
Using insulated duct is important to help prevent condensation from forming inside the duct, where it may collect or drip into a room through the fan body. To connect insulated flex duct, the author first secures the inner plastic sleeve with a high-quality foil tape ...
... He then pulls up the insulation and secures it with the zip tie.
It’s usually easier to secure the duct to the fan first and then install the fan in the ceiling.