Any heavy moisture getting into regular drywall will pucker it .

Moisture Resistant. This type of drywall should however not be installed behind ceramic tiles. Use in high water areas like bathroom and kitchens.
Installing moisture resistant drywall in the bathroom can help prevent growth of mold.

Green board is intended for use for ordinary wall applications in areas that experience constant high humidity, such as bathrooms and basements, but it does not have the superior mold-resistance of newer products. Also you have to seal the joints with caulk. Mold-resistant board options include USG (MoldTough), National Gypsum (XP) and American Gypsum (M-Bloc).

If you are already using your finished attic, it could be exposed to mold growth at one time or another because of its proximity to the roof. When you’re repairing drywall or using green board to install a new wall, you’ll do it very similarly to how you would regular drywall: Analyze and measure the area you would like to add drywall to.
These are also … It's an acronym that stands for mold, mildew and moisture-resistant.

It is an older form of water-resistant drywall that is gradually being phased out in favor of products that combine both moisture resistance and mold resistance. Not absolutely necessary to have greenboard, if you use regular you should prime and then do a nice coat of enamel paint and avoid the latex paint. Also known as greenboard or cement board, moisture-resistant drywall sheets use paperless backing and a special coating to prevent moisture from being absorbed better than traditional drywall sheets. Score your drywall according to the measurements you took. It is moisture resistant. Big difference there.

Green drywall is not waterproof. DEAR JOHN: There seems to be a significant amount of confusion about drywall, water-resistant drywall, and wallboard that is 100-percent waterproof.