Used to have mould ceiling that we got to get mould removal company to come in 3 times to clear and repaint mbr bathroom ceiling, we have just installed window mount exhaust fan. Should we close door to speed up the drying process and to allow better flow of air out of the fan? I only have one window in the bathroom which already installed the fan. It’s quite strange that after we installed the fan, bathroom floor still need at least 7 hrs to be dry (used to take 14 hrs before install fan). 

Hi, I know this is a rather old post - not sure if you have found the answer, but how big is the bathroom, and what model of exhaust fan are you using? The exhaust fan might be too small for the bathroom - MBR bathroom is quite big and might need a more powerful fan to dry.