By:Monte Leeper
Q. I'm in the middle of construction right now and need some advice on
what to do about my hot tub. The room addition in my back yard off the kitchen will be more of a summer porch, unheated. My contractor told me if I use the hot tub in cold weather, or without opening the windows, the room will mildew. So I have two questions. How do I prevent the mildew and what should I finish the room in to prevent mildew from forming?
A. The unheated room creates a series of issues that must be addressed.
First, understand that moisture in the room, from the tub, or from air
flowing in when you open the windows, will be at a different temperature than the outside air, temporarily, during weather extremes. That is, when it is warm out and the room has not yet warmed up, or when the tub is running with heated water and the sun is going down, cooling off the outside air, for instance. You will have a constantly varying condition and the extremes will create the atmosphere where mildew will grow. In order to combat this condition, the air must be dry and the surfaces must be easy to clean.
Second, due to the fact that the room will be unheated, you can only dry the room by means of either portable equipment, a vent fan, portable fan, or salts meant to absorb moisture. The salt process is one of placing a bucket of salt crystals, found at marine supply houses, in the room. This may not work well, since the room air is changing temperature rapidly, but it may help. Ventilation and warmed surfaces will help keep the room dry.
Third, the surfaces on the interior need to be durable and cleanable. My experience has taught that ordinary gypsum board, called sheetrock, is not a good choice for high moisture conditions.
It is best to use wood planking or masonry finishes, since they are more durable to mildew. Cedar, for example, is mildew resistant because it contains resins (sap) that living organisms cannot live on. Some woods, such as pine, actually provide a good home and nourishment for spores, so avoid soft woods or species that are not insect resistant.
If you use a masonry finish with wood framing, try applying a cement board called "wonder board" or "Durock," then coating with a plaster finish. It will be tough as nails and easy to clean. A mildew resistant paint, such as "Thoro-Seal" or a similar product from your local paint store, will lessen the possibility of mildew. In any case, you will need to clean the walls annually to keep the mildew from forming. Enjoy your hot tub, and remember, listen to the lifeguard when one blows the whistle. Safety first.
