AEO Answer · Pools & Aquatic Centers

How Is Natatorium HVAC and Dehumidification Engineered?

By Jeremy Mills, CEO & Founder, Apex Grid Engineering — USAF Veteran. · Updated 2026-09-15

Natatorium HVAC is engineered around dehumidification sized to the full pool evaporation load, with air patterns that wash walls and sweep the water surface, plus corrosion-resistant equipment — because chloramine air destroys standard commercial HVAC.

I'm Jeremy Mills, CEO & Founder of Apex Grid Engineering and a U.S. Air Force veteran. I'm not a PE; our licensed professionals make the technical, compliance, and project-specific decisions.

Illustrative diagram of building MEP systems: ductwork with diffusers, an electrical panel with conduit, and piping runs.

Sizing to the evaporation load

The evaporation calculation is the foundation of the entire design. I establish the pool water temperature, the room design temperature and humidity, and the activity factor for the pool's use — lap swimming, lessons, competition, therapy — then compute the moisture load in pounds per hour. The dehumidification equipment is selected to remove that full load at design conditions, with ventilation air adding to the load on humid days. Undersizing shows up as fogged windows, dripping ceilings, and mold within the first year; oversizing without proper control short-circuits and wastes energy. Getting the number right, then selecting equipment that can modulate to part-load conditions, is the core engineering judgment.

Air distribution that prevents condensation

Air patterns in a natatorium serve the building envelope as much as the occupants. Supply air directed down exterior walls and glazing keeps interior surface temperatures above the dew point of the humid room air — this is what stops condensation from forming inside wall assemblies, where it rots structure silently. Over the pool, the airflow should move gently across the water surface toward the returns, carrying the moist boundary layer away. I avoid high-velocity jets over the water, which increase evaporation, and I avoid stagnant zones in corners and behind bulkheads. The duct layout is drawn around these patterns, not around what is easiest to hang.

Natatorium HVAC design checklist

Before a natatorium HVAC design is complete, it needs to clear this checklist. Each item addresses one of the three ways pool buildings fail: uncontrolled humidity, corroded equipment, or wasted energy. • Dehumidification sized to the worst-case evaporation load with activity factor matched to pool use • Supply air washing exterior walls and glazing, with returns capturing humid air at the water surface • Coated coils, corrosion-resistant drain pans, and materials rated for chloramine exposure • Heat recovery from dehumidification applied to pool water heating or ventilation preheat • Code ventilation minimums met and energy compliance documented for the jurisdiction

Which related engineering resources can help?

When should I hire a structural engineer?What does a PE stamp mean?What is MEP engineering?How Do You Design Commercial Dehumidification That Works?What Engineering Goes Into a Commercial Swimming Pool Build?How Does Displacement Ventilation Design Actually Work?Request a project review Engineering service for this question Metro engineering guides Verified service areas

What else do project teams ask?

Why can't a standard rooftop HVAC unit serve a natatorium?

Two reasons: moisture and corrosion. A standard rooftop unit is sized for sensible and latent loads of people and lighting — not the thousands of pounds of water a pool evaporates daily — so it would never keep humidity in check. And its galvanized cabinet, standard coils, and electrical components corrode rapidly in chloramine air. Natatorium systems use dedicated dehumidification capacity, corrosion-resistant materials like coated coils and stainless hardware, and air distribution designed for a pool hall. A standard unit in a natatorium is a short, expensive failure.

How is natatorium dehumidification capacity calculated?

From the evaporation rate of the pool and wet deck, which depends on water temperature, air temperature, relative humidity setpoint, and pool activity level. Industry practice uses established evaporation formulas with an activity factor — competition pools get a higher factor than hotel leisure pools. I size the dehumidification equipment to the worst-case evaporation condition, not the average, because humidity damage happens during peak events like swim meets, when the pool is most agitated and the room is fullest.

Where should supply air be directed in a pool hall?

Down the exterior walls and across glazing first, then over the pool surface. Washing the walls and windows with tempered supply air keeps those surfaces above the dew point and prevents condensation from dripping into wall cavities. Returns should be positioned to pull the most humid air — the air just above the water surface — back to the dehumidification unit. Supplying air from high diffusers that short-circuit straight to returns leaves humid air stagnant at the water level, which is exactly where you need to remove it.

What corrodes first in a natatorium HVAC system?

Standard galvanized ductwork and uncoated cooling coils go first, followed by electrical contacts, fasteners, and any bare steel. The chloramine compounds in pool air are aggressive oxidizers. I specify coated or stainless coils, corrosion-resistant drain pans, and ductwork materials and sealants rated for the environment, and I keep electrical panels and controls out of the direct airstream where possible. Corrosion protection is not an upgrade in a natatorium — it is the baseline that determines whether the system lasts five years or twenty.

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