Article: It's Easy Being Green

It’s Not Easy to Be Green

Kermit the Frog of Sesame Street fame may have had a point at one time when he sang his ballad “It's Not Easy Being Green”. This may have also been true with indoor pools not many years ago as designers, developers and managers wrestled with how to operate and maintain comfort conditions for their patrons during all types of outdoor conditions and doing it cost effectively. The good news is it’s become increasingly easier to do this with improvements in equipment, structural design and advanced operating techniques.

Green with regards to indoor pools may have many different shades! Green is certainly saving energy through recycling energy, but it is also utilizing dehumidification equipment that operates most efficiently under all conditions. Green is also maintaining the health and welfare of the pool occupants from chemical and even structural problems. And less we forget the sustainability issues of green 410A refrigerant that does not harm the ozone layer or the limiting of trash heaps from equipment that failed to reach its projected life.

Consider Your Location When Selecting Dehumidification Equipment

The choice of dehumidification equipment is probably the most critical decision when developing an efficient indoor pool facility. When evaluating different brands of dehumidifiers, compare the components used. You may be surprised to find not all are built for the long haul.

First, only consider a dehumidifier designed for the indoor pool environment. Standard air handlers work well in HVAC applications but quickly deteriorate in a corrosive pool environment. Dehumidification units with a rated life of 15 years under non-pool conditions can self destruct in only a few years of pool operation.

Think about your geographic location when considering your equipment for best results. Pools in cold, dry locations require heating a majority of the time so energy recycling is critical for energy savings. Air-to-air heat recovery will also reduce heating needs by capturing energy in the ventilation air steam.

The use of non-refrigerant based ventilation equipment can save energy because it takes advantage of the fact that for most of the year the air outside is drier than the poolroom and can be utilized for humidity control. Heat recovery systems such as heat pipes or plate-type heat exchangers recover waste heat from the exhaust air stream and reclaim it into the outside air stream.  Ventilation-based dehumidification units maintain reasonably good summer conditions while not as accurate as mechanical dehumidification.

In hot, moist environments, mechanical dehumidification equipment is almost always required to maintain low RH and to cool during the long, hot season. Here it’s important to have a unit with an efficient refrigeration system that allows compressor cycling, and air mixing control.

In areas with long hot seasons and low humidity, dehumidification through ventilation or mechanical dehumidification can be used. Cooling can be maintained using chilled water (ventilation-type) or by refrigeration (mechanical dehumidification) during peak heat times. As the temperature decreases, compressors can be shut down to save energy while maintaining the desired RH level.

Smart Equipment Design and High Efficiency

There’s efficient dehumidification equipment and then there’s exceptionally efficient dehumidification equipment. The difference being efficient units may have low energy-using components while exceptionally efficient units include operational strategies that save even more energy.

Just in the past few years, some manufacturers have increased their unit’s efficiency nearly 16% with efficiency measured as the moisture removal capacity per compressor kW input.

First and foremost, a mechanical pool dehumidification system must have the ability to recycle the energy removed during the dehumidification process back to the pool water and air. A majority of the indoor pools, regardless of geographic location, require heating 70% to 90% of the year. Selecting a system with a high thermal COP can satisfy dehumidification and heating while almost eliminating fossil fuels for auxiliary heaters.

Quite often outside conditions are such that space heating, cooling and dehumidification can be handled through 100% economizer operation. Dehumidification systems with an integral economizer and smart control package will continually monitor outside conditions and select the most economical operation during occupied time. This not only maintains maximum occupant comfort, it reduces energy requirements and natural resource use.

All new refrigeration-based systems must now include refrigerants such as R134a that are chlorine-free.  R-410A refrigerant also produces more cooling and dehumidifying capacity per kW thereby increasing system efficiency. Unfortunately, older systems using refrigerants like R-22 have little choice because this cannot be upgraded.

Large dehumidification equipment used for commercial operation and natatoriums must have ample cooling capacity to deliver moisture control as well as seasonal cooling. Efficient refrigeration systems operate using multiple compressors to manage the load and allow multi-stage modulating to manage the load. This feature yields maximum system efficiency and life while assuring the best quality space and pool water conditions at the lowest cost.

All dehumidification equipment requires blower systems to circulate conditioned air and ventilation throughout the facility. But not all blower motors are built alike, and some can be very expensive to operate. Select dehumidification equipment that utilize NEMA/TEFC Premium Efficiency Motors because they require less energy for equal loads and have longer service life. NEMA Premium Efficiency Motors are superior to EPAC high-efficiency rated units.

Even the fans designs can affect efficiency. Backward Inclined Airfoil-Type Fans (BIAF), as an example, move air more efficiently, resulting inreduced energy requirements.

The discussion about dehumidification units would not be complete without touching on the overall construction of the equipment. The pool environment is highly corrosive due to the chloramine off-gassing that attacks metallic surfaces of all types. These units should be built to withstand the corrosive indoor pool environment through the use of high performance coatings, copper construction of critical parts and quality components to ensure long life. Longer life reduces the demand on natural resources and reduces the impact on disposal.

Environmentally conscious equipment providers also use powder coatings on the sheet metal sections that meet or exceeds the highest US and European standards for minimum VOC (Volatile Organic Compounds) air pollution emissions. Powder paint coating is the most environmentally friendly commercial painting technology in use today, and it scores highest in protection against the corrosive effects of highly concentrated chemical and humidity laden air from the pool rooms.

Additionally, critical components like compressors should not be located in the corrosive air stream because it decreases their life expectancy, decreases reliability and uses more natural resources.

It’s a little known fact that a properly operating dehumidification system can remove an entire swimming pool worth of water from the poolroom air in a year. Look for dehumidification systems that can recycle this water back into the pool, saving water and reducing the load on utility infrastructures.

Control Strategies Make the Difference

As mentioned earlier, dehumidification equipment manufacturers overall have made great strides in improving operation by using high efficiency components. But there are additional efficiencies to reap by taking advantage of a solid equipment design along with a sophisticated control system!

Since pools are rarely occupied 24 hours a day, dehumidification is still required during the unoccupied mode to maintain the space conditions but ventilation requirements are not necessary. The unit’s control system should include an occupied/unoccupied mode to shut down outside air and exhaust air fans, saving on both blower operations as well as conditioning the outside air.

Condensation formation may seem more of an appearance issue but it leads to structural component determination and inefficient use of energy and equipment. A wall condensate prevention system constantly monitors the outside conditions via a sensor on the coldest inside wall. As the outside temperature lowers (along with the wall temperature) a Smart control system will lower the space dew point as needed. This feature prevents condensation on the cold surface, unnecessary over-sizing of the dehumidifier and excessive compressor operation.

Maintaining ideal and precise environmental conditions has a fairly high cost of operation with water and space conditioning required most of the year. Depending on your geographic location and the low percentage of times cooling is required, waste heat removal is still necessary. By utilizing the huge thermal mass of an indoor pool, a smartly engineered system can redirect the waste heat to the pool with little affect on water temperature, eliminating the need for an external condenser. Energy savings are achieved by minimizing compressor operation and eliminating condenser motor operation while reducing the impact on global resources for the unnecessary equipment.

In addition to traditional economizer operation, there is a variation called “Smart Economizer” that supplements water and space heating using outside air. As hot, moist air travels over the evaporation coil to cool and dehumidify, the smart control system compares it to the outside conditions. If the outside air is warmer and dryer than the conditioned air, it is used and the conditioned air is exhausted. The Smart Economizer will add another 15% to 20% energy savings over dehumidifiers without an economizer.

Ventilation is mandated in all commercial buildings and indoor pools are no exception. However ventilation becomes more costly in colder climates where the make-up air must be heated to maintain desired space conditions. By installing a passive air-side heat recovery system you can capture heat energy normally exhausted during space ventilation to preheat the incoming air, saving considerably on fossil fuel requirements.

Another way to reduce ventilation requirements, especially during swim meets or limited occupancy is CO₂ Demand-based ventilation. Many dehumidification systems have preset ventilation volume based on average occupancy. Controllers equipped to monitor CO₂ levels can adjust the amount of ventilation to meet the occupancy requirements while not over ventilating. Overall operating costs can be reduced quite significantly by reducing heating and cooling loads.

The same theory applies to the dehumidification unit’s poolwater pumping system, which is separate from the pool’s pump and filtering system. Most dehumidification systems are designed to heat either the air or water using energy recovered through the dehumidification process. By using a Smart Pool Water Pump Control as part of your control system, the unit’s pump is turned off when the system is in the air priority mode. Savings can add up to $3,000 per year by using the pump approximately 50% of the time.

The Building Design Will Affect Efficiency

As can be seen, there are many ways to a Green pool environment based on the type of dehumidification equipment chosen and the features available. But even the best equipment will only do a mediocre job if the facility is designed incorrectly and/or has inadequate air distribution

Basic building design considerations should include protection against air migration. Vapor barriers should be installed immediately behind the interior wall surface to prevent moisture within the pool room from migrating into the wall where it will reach dew point much quicker because of the colder air temperature. If not installed or installed improperly, the dew point will be reached within the wall and the moisture will impregnate the insulation, decreasing its R value.

Good thermal performance doors and windows limit heat migration and condensation formation Glass doors and windows that are exposed to outside air should have good thermal performance. Double and triple glass panels are best, and they should be insulated or sealed in metal or vinyl clad frames wherever possible. Window frames must have thermal breaks and be sealed to adjacent walls and insulated with a non-porous insulating material.

Pool facilities with open sunlit atriums and windowed walls are candidates for high cooling loads. This greenhouse effect can be offset by increasing ventilation rates during peak periods or simply opening doors and windows.

Water attractions such as slides, fountains and cannons have gained in popularity, but higher costs are associated with their operation due to an increase in the evaporation rate. Dehumidification systems must work harder and longer to maintain a desired 50% to 60% RH within the facility.

Surface areas that collect water from the pool create an additional load on the dehumidification equipment. Avoid the use of absorbent deck coverings such as carpet within the pool area, and limit wet deck areas by installing adequate drainage and/or reducing deck over spray.

Good Airflow Design Maintains Comfort, Reduces Operation Cost

Efficient dehumidification will take place if the air distribution system is designed properly. The objective of an air distribution system within the pool enclosure is to maximize air flow of warm, dry supply air over any surface that is prone to condensing temperatures, including all walls, windows and skylights.

Careful consideration must be given to the location of supply air ducts and the location of the air return grill. 80% of the supply air should be directed at the walls with the remaining 20% directed along the ceiling to break up any stratifications and stagnation occurring near the ceiling. A wall washing technique should be used to reduce the incidence of cool, dead air spaces that may form around windows or walls and migrate to the pools edge.

Position ceiling supply ducts near windows and preferably close enough to sufficiently wash the cold glass with an even blanket of air. The supply air should be ducted below grade around the inside perimeter of the enclosure using linear slot diffusers for low set windows and sliding glass doors.

Returns must be positioned so that all of the moist, warm air flows efficiently back to the dehumidification system, eliminating dead areas where air stagnation can occur. While typical heights are 10 to 15 feet above the floor to capture the rising warm, moist air, recent studies show positioning returns nearer the surface lightly draws off the chloramine air layer that may settle over the pool’s surface. This technique also draws off the moist air while not over-affecting evaporation rate or creating uncomfortable air currents.

Never position ducts in a way that will result in short cycling of the supply air. Short cycling is caused when the location of the return duct is too close to, or directly in line with, the supply duct causing the warm, dry supply air to recycle prematurely.

Maintain a slight negative pressure of 0.05 to 0.15 in. of water in the pool area relative to surrounding spaces to prevent moisture and chlorine odors from being pushed into other areas of the building.

Conclusion

Whether replacing an existing environmental control system of designing a new pool facility, it is important to know you can deliver excellent bathing conditions while not draining the bank dry through high operating costs. Today’s high efficiency dehumidification equipment is good for you and good for the environment.

Remember not all dehumidification equipment is designed and built the same. Because of the special nature of an aquatic facility, choose a manufacturer with experience in this area and you will enjoy many years of uninterrupted operation.

# # #