The word "sauna" refers to a special kind of cleansing, relaxing, dry-heat bath and to the room in which it is taken. Sauna rooms must be built to withstand temperatures in the 170 to 200°F range, plus exposure to sweat, splashed water, and frequent pulses of humidity. The explosive growth of health clubs during the past decade has introduced an increasing number of Americans to sauna bathing. For convenience and privacy, more affluent Americans are bringing the sauna and exercise rooms into their homes. Proper design and installation of saunas require planning, the right selection of building products, and quality finish work. Costs vary and can be a bit steep, often $75 to $100 per square foot of floor area.