Please Help: What Is Happening To My Room?

Hi Ooduarere and Engineers.
Good morning.
this structure was built in December 2019.
I noticed the room is always moisty,
When the room windows and door is shut… The glass sweat from inside.
Now it’s the roofing(decking), just this part of the decking.
The room is well ventilated but since no occupant the windows and doors are always shut.

Above the decking is completely tiled and two brand new water tanks are sitting untop.

What could this imply?