The Pool On The Mountain
Visitors see a breathtaking mountain view from three walls of glass and an interior tongue-and-groove wood design by Jeff Beer, principal, Beer & Coleman Architects Associates (Warren, N.J.). However, keeping the glass clear of condensation and protecting the wood from excess humidity generated by the 15- by 45-foot concrete pool and an accompanying six-person spa was the challenge solved by engineer William E. Williams, owner of 24-year-old consulting-engineering firm Mechanical Electrical Design, Annandale, N.J.
Williams anchored his HVAC design around a Dry-O-TronÂ® DS-40 Series dehumidifier from Dectron Internationale, Roswell, Ga. Site limitations mandated the use of the home's existing mechanical room, which already contained furnaces and boilers for the home. Williams designed a 6-foot-high loft support for the dehumidifier in an 18- by 18-foot mechanical room to allow service access and more floor space for the pool support equipment.
Pool builder and general contractor Ken Beer, president of Estates Management Corp. (Pluckemin, N.J.) had the task of fitting in RayPak (Oxnard, Calif.) spa and pool heaters and Hayward Pool Products (Elizabeth, N.J.) pumps and filters, and other pool support equipment into the cramped space.
Uphill ChallengesIt didn't help that the structure had to be built on an extreme mountain grade.
Another challenge was air distribution. The American Society of Heating, Refrigerating, and air-Conditioning Engineers (ASHRAE) recommends underdeck natatorium (pool room) ductwork to supply dehumidified air evenly to the windows. With little or no deck space to work with, Williams was forced to locate the supply duct trunk line (70 linear feet of 22-inch-diameter schedule 40 PVC pipe) in a 3-foot-deep trench outside the three perimeter glass walls. Locating the ductwork outside and underground required 1-inch-thick foam insulation - and extreme caution when back-filling the trench with heavy machinery.
Besides installing the entire dehumidification system and underground PVC ductwork, mechanical contractor Bob Brauch, president of Norman Sheet Metal & Mechanical Corp., Fairfield, N.J. was responsible for running nine PVC takeoff fittings through the concrete foundation and into custom-fabricated stainless steel reinforced plenum boxes.
Airflow Design DetailsBrauch's company also fabricated stainless steel collars that connect the plenums to the room's corrosion-proof, stainless steel linear floor diffusers, manufactured by Tuttle and Bailey, (Richardson, Texas). The diffuser velocity Williams specified is enough to keep the windows dry and comfortably dehumidify the space without overhead ductwork hanging from the low, 10-foot-high ceiling.
Williams' 3,000-cfm airflow design calls for 600 cfm of outside air and an exhaust of 540 cfm to create positive pressure in the room and eliminate any infiltration of untreated outside air.
Sizing the dehumidifier was critical to the project's success. Philip Nicholson, sales manager at manufacturer's rep Sitllwell-Hansen Corp. (Edison, N.J.) helped calculate the dehumidification loads. He explained that although an automatic pool cover reduces pool evaporation significantly, he and Williams still sized the dehumidifier as if there were no cover.
"If the owners have the cover off during an all-day party and the dehumidifier is undersized, too much moisture will accumulate," Williams pointed out. "If that happens enough times, structural damage to the pool enclosure or mold/bacteria could result."
One tip Williams has for other engineers, architects, or contractors designing their first pool enclosure is to make sure there is a seamless vapor barrier encapsulating the entire room's walls, ceiling, and floor.
The natatorium's space conditions are monitored and controlled by the dehumidifier's onboard microprocessor controller. The pool and spa are controlled by a microprocessor (by Jandy, Petaluma, Calif.).
While glass and wood might not be the best materials to fight condensation or moisture penetration, the aesthetics of these materials are preserved with Williams' design and the facilitation of it by the architect, general contractor, and mechanical contractor.
Publication date: 03/07/2005