What this video covers
The clip is about specifying a bathroom so mold has nowhere easy to start.
Mold-resistant board is the first item, using green or purple board rather than standard drywall in the wet zone. It costs marginally more at the point of building and behaves completely differently when it gets damp.
The takeaway
Material choice at build or refit time is the cheapest mold prevention available. Standard drywall in a bathroom is a decision you pay for later.
Read the full written guide: How to Remove Mold from a Bathroom Ceiling.