Paul Francis Shurtleff Architect The ceiling system is not the reason the material isn't damaged by mold and humidity. A room with any large water feature requires a special de-humidication system. This pool has an automatic cover which prevents the moisture from damaging the wood surfaces (including the ceiling). A de-humidity system is just a slightly over-sized Air Conditioner. Without a cover over the pool its very difficult control mold and expensive to run the air system.