Design Right to Ensure Spa Air Quality
By Harry Topikian
Spa area patron complaints can run the gamut from chemical odors, uncomfortable rainforest-like conditions, visible mold and mildew to building deteriorations and foamy, unsanitary spa water. Most of these problems typically stem from improper building and ventilation design or poor installation and maintenance.
There are no statistics to draw from, but based on calls to mechanical equipment manufacturers concerning spa room problems, it's estimated that at least half of all spa rooms never operated correctly right from the ribbon cutting, or have degraded into inoperable conditions due to poor maintenance. The end result is that many spa management companies are exposing their customers to uncomfortable or unhealthy conditions that eventually will affect patronization.
A common problem in spa room building construction is the absence, poor positioning or breach of a vapor retarder, which is a plastic sheet, foil-backed or extruded plastic sheet, or vapor retardant paint/coating that envelops the entire room. The architect or engineer might specify a seamless vapor retarder, but they are at the mercy of the contractor whether it's installed properly without any leaking. A breach, such as an unsealed seam, can lead to building deterioration from condensation infiltration or worse yet, mold and mildew inside walls.
Another common design problem is the improper positioning of the return air grille within 20 feet of the spa. Since the 100°F to 105°F heat of spas, in comparison to 80°F pools for example, tend to leach more human body oils and other organic solids, it doesn't take long for this residue to coat the grille, the ductwork interior and the HVAC unit parts when the return grille is positioned too closely. A return air design with slightly more cubic feet of measurement (cfm) airflow than the supply air is important for keeping the room under negative pressure. This prevents spa and chemical odors from infiltrating the non-aquatic areas of the facility. Since some of the return air must be exhausted in order to bring in a code-compliant percentage of outdoor air, the best design solution is to put a dedicated grille directly over or near the spa to exhaust the contaminants directly outdoors. Then the mandatory return air grille for the HVAC equipment can be positioned elsewhere in the room.
As for maintenance, spa water should be tested three times daily in addition to draining and refilling after every 40 users. The combination of high heat, excessive evaporation rates due to jet agitation, high counts of human body organic compounds and other factors exclusive to spas makes water chemistry 10 times more critical than a swimming pool. A spa with excellent water balance in the morning can quickly turn into a cesspool by 1 p.m.
Air distribution into the space is also critical, especially for exterior windows, skylights and walls. Condensation will appear on glass and walls when air distribution is insufficient or poorly diffused. Some equipment manufacturers offer computational fluid dynamics (CFD) computer-aided modeling to analyze problematic spa and pool spaces to correct air distribution.
Another key is dehumidification. Conventional air conditioning can dehumidify somewhat, but it can't handle the huge humidity loads of spa rooms where dozens or maybe hundreds of pounds of moisture per hour must be removed. Mechanical dehumidification equipment is the only method that can maintain the indoor air comfort of 50 percent relative humidity (RH).
A good spa role model that accomplishes the spa area design, construction and maintenance considerations is the Fontainebleau Miami Beach. The 56-year-old hotel recently completed a $1.1-billion renovation/expansion, which includes the new 40,000-square-foot Lapis Spa, a wonderland of spas, steam rooms, therapy pools and some other humidity-producing features such as a 35-foot-long rain corridor, colored mists and a curtain of falling water.
Taming the humidity in these areas is the mechanical design of Lawrin Ellis, P.E., LEED-AP, CxA, mechanical project engineer with TLC Engineering for Architecture (TLC), Ft. Myers, Fla., and Matthew Wiechart, P.E., LEED-AP, CxA, senior mechanical engineer with TLC, Orlando, Fla. The design maintains humidity to a comfortable 50 percent and makes this indoor aquatic playground possible.
The Lapis Spa has seven main areas, and one factor in TLC's success is the use of four dehumidifiers, each of which remove a total capacity of 90 pounds per hour of moisture in the four humid environments. Four separate units provide more individual control for areas where temperature, humidity and occupancy vary greatly. The four aquatic areas are:
- Men's Spa (2,000 square feet with a 162-square-foot whirlpool spa)
- Women's Spa (2,000 square feet with one large 261-square-foot whirlpool spa and two smaller individual pools and a steam room)
- Rain Shower/Co-ed Pool (3,200 square feet with a 505-square foot, 82°F lap pool and a 47-square foot, 102°F rain shower water feature)
- Wet Treatment Area (an area with a 130-square-foot whirlpool spa and a 58-square-foot spa)
Particularly challenging for TLC was the wet treatment area, which has several smaller suites where guests spend entire days receiving massages, spa treatments and other services. To supplement the preferential treatments, each personal room has individual temperature and humidity control with a variable air volume (VAV) box. VAV boxes are individual controls for rooms that are normally supplied by variable speed air handlers, however in this instance, dehumidification was a key issue.
Another design challenge is condensation prevention on a wall of windows that allows patrons to view the Fontainebleau's breathtaking ocean views. On winter days when Miami's temperature can momentarily dip below 40°F, the dehumidifiers are integral in keeping the glass free of condensation, which is a typical problem when windows separate two vastly different temperature environments.
Indoor air comfort is as important as the spa services. All the diffusers, ductwork and other air distribution components were specified and positioned to deliver a gentle 40-feet/minute air velocity at six feet above the floor to eliminate uncomfortable chilling effects on the spa occupants, according to Ellis.
Even well-designed spas with the all-important negative building pressure still typically produce many types of odors from massage oils, sanitizing chemicals, perspiration, etc. Therefore, TLC also specified a scent dispersion system.
The new Fontainebleau Miami Beach still retains its 1950s charm that made it a world-famous destination of yesteryear, but it's the state-of-the-art equipment and design innovation of today's engineers and architects that pamper today's guests with five-star luxury and style.
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