At indoor waterpark resorts, swimming is no longer an activity relegated to the summer.

However, maintaining a constant pool environment requires year-round attention, especially as outside and inside variables change season to season.

It’s a given that outside temperatures directly affect the inside heat loss/gain. For a majority of indoor pools, water and space heating are required 70 percent to 90 percent of the year, so when weather turns cold, it’s critical to carefully manage the humidity, and air and water temperatures in the pool environment to avoid escalating energy costs.

The key is to maintain summer-like conditions on the inside regardless of the weather outside. By adequately monitoring and maintaining humidity, you can do that cost-effectively.

For starters, ideal water temperature is around 82 degrees Fahrenheit, with the air temperature slightly higher. To maintain those optimal set points, controlling humidity is essential. The desirable humidity range is generally 50 percent to 60 percent. Humidity greater than 60 percent creates a sticky feeling and/or difficult breathing. Low humidity results in evaporative cooling on the bather’s skin, causing a chill.

During winter months, the moisture content of the outside air is generally lower, making it suitable for dehumidification. However, the outside air temperature is much colder and requires constant heating to maintain comfort within the facility. If left unchecked, the heated air will be constantly exhausted while the incoming air will have to be heated, escalating operational costs. That’s where efficient dehumidification equipment comes in.

Dehumidification systems utilizing refrigeration are considered some of the most precise in terms of overall control of dehumidification and temperature. The technology uses electricity as the primary energy source and offers a reclaim mechanism in the form of a heat pump cycle, which adds the heat back into the air and water.

Mechanical dehumidifiers recover more of the latent heat from pool water evaporation than passive heat exchangers. They also have sophisticated control systems that can constantly monitor inside and outside temperatures and humidity settings, choosing the least costly method to control the set point conditions.

Some operators have outside-air-based dehumidification equipment. These packaged dehumidification units use ventilation to remove moisture, and feature sophisticated mechanics and software to minimize operational costs. To be practical for winter operation, OA systems should be equipped with heat exchangers within the exhaust circuits. Cost savings can be significant, with improvements up to 50 percent compared with units lacking heat exchangers.

No matter what kind of system you have, here are a few additional strategies for wintertime operation that can help lower HVAC costs:

  • Reduce the ventilation rate during off-peak hours. Humidity set points generally are established to maintain desirable levels during peak operational times, when the rate of evaporation is high. Lowering the amount of ventilation to meet the lower evaporation rate during off-peak hours reduces fan operation, as well as the heating requirements. Savings generally are significant (up to 50 percent) compared with constant operation day and night.
  • Install temperature sensors. Monitoring temperatures of exterior walls, windows and roofing can save energy and prevent damaging condensation. Mount cold-temperature sensors on the coldest surfaces. When connected to the HVAC control system, they check the surface temperature, and systems can automatically lower the dew point when required.
  • Don’t deactivate your dehumidification system during off-hours. It’s not uncommon for the space temperature to drop 10 to 15 degrees at night during colder seasons. This greatly increases the rate of evaporation due to the large difference in vapor pressure. With air distribution systems off, moisture rapidly rises vertically to the cold ceiling, condenses and drops back into the pool, resulting in cosmetic and structural damage. Instead, dehumidify at the minimum level and maintain proper air temperatures to minimize evaporation.
  • Use a thermal blanket or cover on unoccupied pool surfaces. This is perhaps the simplest energy-saving strategy. Covers eliminate water-to-air interaction by providing an impermeable membrane over pool surfaces. With covers in place, a temperature setback can be implemented during off- hours, saving energy on space heating.
  • Manage pool water agitation. Another factor when managing water evaporation is water agitation. It creates more surface area, resulting in increased evaporation. Agitation can be as simple as swimmers splashing or spray from various amenities,
  • Careful management of peak-load dehumidification along with shutting off unused waterfeatures can help eliminate unnecessary pool water agitation. Also avoid the use of absorbent deck coverings such as carpet, and limit wet deck areas by installing adequate drainage and/or reducing deck overspray.