I need to replace my bathroom ventilation fan. I am in 2nd floor condominium. My bathroom dimensions are 60 square feet and ceiling height is 8'2".
As per formula I found for CFM (height × length × width × 0.13) ,I need fan with around 62.4 CFM.
I can only find 50 and 80 CFM fans, can't find anything between. Should I go with 80 CFM fan ? There is around 10' to 12' of duct work before it opens outside on the wall.
I have attached picture of the flexible white duct which is connected to solid metal duct as you can see in the far end of the picture.
Can I replace flexible duct with solid duct to get more smooth air flow ?
Do I need to buy insulated duct ?
My building is around 34 years old. Not sure if there are specific code requirements for my case.