Even though the walls of the house are damp, she assured me that they won't go mouldy, and she was right. Why?

Question

The house did not have any ventilation and the walls were white. But even though it had damp it did not go mouldy.

Answer 1

Because it was built under water.

Answer 2

Without out more information I would guess due to proper ventilation.

Answer 3

The material used to construct the walls may have been pre-treated. The only thing that I question is why one wouldn't remedy the ventilation issue.