Process Checklist

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Design Checklist

A helpful 9-point natatorium
design checklist

Online Design Manual

Process Checklist

  • Key Design Concerns for Traditional* Pools
  • Step 1: Operating Conditions
  • Step 2: Supply Air
  • Step 3: Outdoor Ventilation Air per Standard 62-2004
  • Step 4: Exhaust Air
  • Step 5: Load Calculations
  • Step 6: Condensation and Vapor Migration
  • Step 7: Energy & LEEDs Considerations
  • Outdoor Ventilation Air
  • Condensate Reclaim
  • Refrigerant Reduction

Printable Design Checklist Bookmark and Share

A printable design checklist has been created for your convenience to summarize the details below.

Process Checklist

At the core of every successful natatorium design is a system that provides the operator the year round conditions they expected while meeting ASHRAE design standards, satisfying local codes and being as energy efficient as possible.

This design guide has covered many important aspects to consider and putting it all together properly can become a daunting task. The Seresco team has worked on thousands of indoor pools and developed a helpful checklist to help ensure all vital aspects are considered during the design process. Seresco understands also that product flexibility is essential to allow the designer to work around all the project-specific issues while not compromising their design, and offers the most flexible product line in the industry. The overall performance of a Natatorium will be directly impacted by the number of deviations and compromises taken in its design.

Once all the design parameters have been established, the only remaining decisions will be: what would they like incorporated into their Seresco dehumidifier and what they want provided externally. Unit mounted heating coils, exhaust fans, heat recovery packages, weatherproof outdoor cabinets and heat rejection to cooling towers/dry-coolers/outdoor condensers are some of the configurations available from Seresco. The project specific details generally dictate what is the most appropriate.

Key Design Concerns for Traditional* Pools

The back cover of this manual is a handy checklist that covers the Key Design Considerations.

* Please contact factory for Waterparks and pools heavy with water features. Design standards have been established for ‘traditional’ bodies of water and do not adequately address the special needs of these facilities.

Step 1: Operating Conditions

Do not guess. Get the desired pool water temperature, room temperature and relative humidity in writing from the owner.

Operating conditions have a tremendous impact on the entire design and cannot be changed by a large degree after the fact. It is critical that the designer educate the customer on the implications of their operating temperature choices. Maintaining the room air temperature 2°F - 4°F above the pool water temperature will help reduce evaporation – but the temperature must still be comfortable to the patrons. Reduced evaporation in turn reduces the pool water heating requirement.

Step 2: Supply Air

Calculate the supply air requirement of the space based on the room volume. Your target air change rate per ASHRAE is 4-6 volumetric air changes per hour, with a 6-8 air change rate in spectator areas. This is a calculation and sets up the entire air handling systems.

  • Supply air must get down into the Breathing Zone. It is critical for comfort and good IAQ that the treated supply air get down to the pool deck and occupants.
  • Ensure the return duct location compliments the supply air duct location and promotes a good air pattern. In a large natatorium, several return air grilles might be required to achieve a good air pattern is the space.
  • Be careful to avoid air short circuiting or placing supply diffusers too close to the return duct opening. This can ruin the effectiveness of the supply air and give any return duct mounted sensors false readings.

Step 3: Outdoor Ventilation Air per Standard 62-2004

Most localities have adopted Standard 62 as their local code. The baseline outdoor ventilation air requirement is:

  • 0.48 CFM/ft² of water surface area and wet deck for regular pool. Wet Deck is a maximum 6-8 foot perimeter around the pool.
  • If you have a spectators seating area, add 7.5 CFM per spectator during swim meets.

Introducing more outdoor air than codes is not recommended. In winter it will increase space heating and pool water heating costs significantly. Too much outdoor air in winter can also lower the relative humidity levels to uncomfortable levels for the patrons.

  • Outdoor air must be filtered.
  • Ensure the airflow is balanced when the system is commissioned.
  • Seresco’s glycol heat recovery loop taking heat out of the energy rich minimum exhaust air stream and preheating the minimum outdoor air is an effective means of reducing outdoor air heating costs and generally has a very attractive payback.
  • Thermally insulate the exterior of the outside air duct.

Step 4: Exhaust Air

The room should have a slight negative pressure. ASHRAE recommends 0.05 to 0.15 inches of water column. A good rule of thumb is to exhaust 110% of the outdoor air CFM. A well located exhaust fan can significantly improve the air quality in the space. If the space has a spa or whirlpool, the exhaust air intake grille should be located directly above it. This source captures and extracts the most contaminant-laden air before it can diffuse into the space and negatively impact the room air quality.

  • The exhaust fan can be installed remotely or within the Seresco unit.
  • Energy recovery from the energy rich exhaust air to outdoor air should be considered.  

Step 5: Load Calculations

The Natatorium needs to be heated, cooled and dehumidified. Accurate calculations need to be carried out to establish the requirements to accomplish each.

  • Latent load (Pool evaporation, Outdoor Air (summer) and Spectators)
  • Building envelope sensible cooling load that includes Outdoor Air.
  • Building envelope heating load that includes Outdoor Air.

A majority of designers prefer to place the space heating coil inside the dehumidifier. The coils in a Seresco unit are fully coated and suitable for a pool environment. Seresco offers a full range of unit mounted control valves as well.

Care must be taken when considering gas heating. If chlorine from the natatorium is allowed to mix with combustion gases, hydrochloric acid (HCl) forms and is very corrosive. All Seresco’s gas heat options have been engineered so that are fully protected from this ever happening.

Step 6: Condensation and Vapor Migration

Establish the space dew point temperature based on the owners desired space conditions. Once done, the designer must identify all potential condensation spots in the building. A typical pool design of 82°F 50-60% RH has a peak dew point of 67°F. Therefore, any surface with a temperature below 67°F will condense moisture.

A vapor retarder is a material that restricts the rate of water vapor diffusion through the ceilings and walls of a building when below dew point temperature occurs. Failure to install the vapor retarder in the proper location will result in condensation within the structure and lead to tragic structural failure. Always ensure the vapor retarder is sealed at all the seams.

  • The Vapor retarder must be on the warm side of the dew point temperature in all walls, ceilings and floors.
  • All exterior windows, doors and skylights must be fully blanketed with warm supply air. 3-5 CFM/ft² is recommended.

Step 7: Energy & LEEDs Considerations

The energy consumption and performance implications of the building type and operating conditions must be discussed with the owner.

Operating conditions

Operating conditions have a tremendous impact on operating costs. It is critical that the owner understand that at the same water temperature a pool in a room at 78°F 50% RH will evaporate almost 35% more than that exact same pool in an 85°F 50% RH room. The pool room should be kept as warm as possible but still be comfortable to the patrons. Reduced evaporation in turn reduces the dehumidifier size and runtime as well as reduces the pool water heating requirement.

Heat recovery pool water heating

The dehumidifier's pool water heating option should be considered. It is site recovered energy and has a very attractive payback period. This process has an impressive COP of close to 8! The use of the pool water heating option also satisfies ASHRAE Energy Standard 90.1.

If it is chosen ensure that the pool water circuit is designed to allow water to be delivered to the unit reliably.

  • Provide a separate circulating pump.
  • Use the controls provided by the Seresco unit to control the auxiliary water heater operation.
  • Install the auxiliary pool water heater downstream of the dehumidifier for backup heating.
  • Ensure the pool water chemicals are introduced downstream of the unit, auxiliary heaters and pumps.

Outdoor Ventilation Air

Outdoor ventilation air is essential for maintaining good IAQ in the pool and is a code requirement. The natatorium also needs to be maintained at a slight negative air pressure, so warm energy rich air needs to be exhausted. These two airstreams at vastly different conditions present a perfect opportunity for heat recovery.

Seresco provides unit mounted heat recovery between these two air streams using a glycol run-around loop. This approach to heat recovery offers the best performance and design flexibility while staying in the smallest possible cabinet. They are also easily sized to meet the specific requirements of your facility. The result is a compact, cost effective heat recovery option that actually fits into a mechanical room.

Adding the glycol run around loop heat recovery option to your Seresco unit in a northern installation will typically realize a one year payback on your investment!

  • The heat recovery device should be suitably protected from corrosion and freezing.

Condensate Reclaim

Verify with local codes whether condensate return to the pool is allowed. While condensate is generally considered gray water, this condensate is actually cleaner and if introduced upstream of the filters and chemical treatment can help realize considerable water savings on site.

  • If allowed by local codes, the condensate reclaim from your Seresco unit can be the equivalent of one pool fill annually!

Refrigerant Reduction

Seresco’s new Protocol design reduces the refrigerant system charge compared to a traditional compressorized direct expansion type unit by a whopping 75% There is no operation penalty to this new design and is quickly becoming the new industry standard.

  • The Protocol unit’s refrigerant charge is so low that no special ventilation may be required in the mechanical room!