Normal plasterboard panels in the bathroom ceiling

Hello,

we installed standard gypsum plasterboards (GKB) from Knauf on the bathroom ceiling.

Now, after everything is done (filled, holes for the spotlights) and the painter is in the house, he pointed out to us that it would have been better to use the green, impregnated boards (GKBI).

Inquiry with the drywall contractor who installed them: He said he had asked Knauf again and that these boards can also be used for "moderately damp rooms, such as bathrooms." Apparently, he already knew that, which is why he installed them.

The painter, however (who also works in drywall), thinks it would have been better not to do that, because at some point yellow stains would appear due to the humidity after showering.

Opinions on the internet also differ. Some say the green boards are just a money-making scheme, some say it doesn’t matter on the ceiling because it is only important for splash water, others say it is especially important on the ceiling (to use impregnated boards).

The technical data of both boards are the same, especially the "water vapor diffusion resistance number," if that plays any role here. Only the water absorption capacity is lower in the impregnated boards.

What is your opinion on this?

I can't tell you either, but what color does your painter use in the bathroom? Can't this be solved right away with an appropriate coating that also won't discolor later?

He is supposed to paint the ceiling with latex, and that's fine. It's not a swimming pool after all.

If there is no permanent whirlpool and/or steam sauna in the bathroom, it is not so bad. It is still standard to use the green boards in damp rooms, which is incomprehensible...

I think there are at least 2 or 3 prefabricated house builders who standardly do everything in grey

A single-family house usually does not have a genuine "wet room" either