Solving natatorium air dispersion and condensation challenges
Indoor pools are challenging environments for design engineers, especially when considering indoor air quality and the longevity of exposed metal components. A natatorium’s corrosion-potential environment of high humidity, gaseous pool chemicals, and condensation is a recipe for disaster for metal heating, ventilation, and air conditioning ductwork. The toxic mix slowly disintegrates metal air distribution systems in natatoriums.
Billy Farr
Engineering Sales Manager, North America
US
The condensation that forms on metal ducts and other metallic materials expedites the disintegration.
Unlike metal, the fabric doesn’t allow condensation to form because of the properties inherent in its technology. Fabric duct can be specified as permeable, which allows air to pass through the fabric weave. This airflow through the entire duct surface prevents condensation on the material. The fabric duct also does not require special coatings to protect against corrosion or rust. The polyester fabric used in natatoriums should be UL-2518 classified, which among other qualities ensures that the fabric does not propagate biological growth. Fabric ducts also can be specified with additional antimicrobial treatment for extra protection against mold and other microbial growths.
Fabric can outperform metal diffusers in air dispersion performance because the fabric duct’s construction is unique in that it incorporates a variety of factory-designed, integrated vents or nozzles that span the duct length in a linear fashion and are specified at no extra charge. The linear design allows for uniform dispersion of the mechanical system’s dry, conditioned air across windows, ceilings, and walls to prevent condensation.
Fabric duct is manufactured with multiple linear vents and orifice diameters engineered to provide desired throws specified by the consulting engineer. For example, a duct run with the wall on the right side might have the following linear vent configuration and percentage of distribution: 10 o’clock for the ceiling (30%); 2 o’clock and 5 o’clock for the upper and lower wall or windows (60% combined); and the 7:30 mark for the pool surface (10%). Each vent is designed to achieve the desired throws.
Metal is often misconceived as less expensive than fabric. However, in the end, the required extras drive up the price of the metal. Fabric duct is designed as a complete system with all the extras, such as suspension hardware and dispersion vents. Metal ducts rarely are priced to include the required extras.
Finally, Fabric duct installs 40-70% faster than metal, reducing labor costs that can shave weeks off the ductwork installation, allowing other trades to complete their work sooner.
Additional Information
FAQ
Warm, saturated air meets a cold surface — a window, a steel truss, an unheated wall — and drops its moisture there. Natatoriums produce far more water vapor than a typical building, so any dead air pocket near a cold surface becomes a condensation point.
Related terms: dew point, saturated air, cold surface, water vapor, dead air pocket
Learn more about eliminating hot spots, cold spots, and drafts in FabricAir blog article Rethinking Air Distribution.
It resists the corrosion that chlorinated, humid air causes in galvanized metal ductwork, and its dispersion pattern is engineered to keep air moving across the full pool hall rather than short-circuiting near the diffuser — which is what prevents the cold-surface pockets that cause condensation in the first place.
Related terms: corrosion resistance, chlorinated air, air dispersion pattern, pool hall airflow, diffuser short-circuiting
Learn more about corrosion risk in humid environments in FabricAir blog article Mitigating Corrosion in Humid Environments.
By directing conditioned air along the building envelope — walls, windows, roof deck — the airflow keeps those surfaces above the dew point instead of leaving them exposed to still, saturated air.
Related terms: building envelope, dew point, roof deck, window condensation, conditioned air
Chlorine off-gassing attacks galvanized steel and its fasteners over time, leading to rust and eventual duct failure. Fabric duct systems have no exposed metal fasteners in the airstream, which removes that failure mode entirely.
Related terms: chlorine off-gassing, galvanized steel, duct fasteners, rust, fabric duct system
Learn more in FabricAir blog article Mitigating Corrosion in Humid Environments.
Get valuable content first
Enter your email and be among the first to get tips and articles from our experts about HVAC industry topics.