October 1, 2010
By Barry Justus
Generally, pools are constructed with little, if any, regard for energy conservation; however, with a little effort from the contractor and an intelligent investment by the client, this situation can be remedied.
Poolscape, for example, was approached by a client in the small community of Georgetown in Halton Hills, Ont., who wanted a unique project; the idea was to build a luxury indoor pool that was extremely energy efficient. The first step was similar to any other pool installation—configuring its design. However, where it differed from most typical pool installations was the importance of balancing the needs for conservation, efficiency, esthetics, functionality, budget and economics, which can be quite challenging.
There are a number of key elements and variables that must be controlled to achieve maximum energy efficiency, including:
The combination of these design elements, available technology and project management will result in significant savings for the client over the life of the project. In this case, the overall goal was to add a 186-m2 (2,000-sf) addition to the home as well as a fully tiled lap pool, chill pool, stand up hot spa, steam room and 111-m2 (1,200-sf) underground bunker, all without increasing the client’s energy costs.
To achieve this goal, a combination of proven methods were implemented; however, there is a fine line between achieving maximum energy efficiency and maximum economic efficiency.
This particular project was located in an area with no natural gas, a short summer season and an influx of black flies in the spring. The design process spread over eight months allowing for proper site investigation and exploration of various options.
An outdoor pool was quickly ruled out. After much debate and research, it was decided the most energy-efficient solution was to combine all of the best elements of an indoor and outdoor pool.
The pool location and environment are in constant battle with a project’s overall energy efficiency. Outdoor pools lose much of their energy via evaporation and conduction, while indoor pools are even less efficient, as indoor air quality must be maintained in a narrow range of temperature and relative humidity so the environment remains comfortable for the client. On top of this, pool water constantly evaporates in an indoor pool setting, which takes heat and moisture from the pool and places it into the surrounding air. This air must then be conditioned to reduce moisture content.
In an ideal world, the most efficient pool is one that is shut off and contained in a Thermos-style bottle. This insulated, isolated body of water does not evaporate or lose heat, and has maximum hydraulic efficiency. This is the level of efficiency the design team hoped to achieve when the pool was not being used.
In the real world, people swim in the pool, water evaporates, pumps are moving water, water features are operating, hot spas are heated and chill pools are chilled. To achieve maximum design efficiency, a balance needed to be struck between the needs of the ideal environment and reality.
The project design comprised a luxury pool that could be enjoyed year round in a pleasant, yet energy-efficient environment. A number of design methods and elements were used to achieve this goal, including:
An indoor pool requires the use of dehumidification equipment to maintain air quality. There is a constant battle between evaporating pool water and maintaining a tolerable level of humidity in the enclosed building. One solution is to turn off dehumidification equipment and open the enclosure, which allows the pool to be operated like an outdoor pool. In this case, the unique glass enclosure has automated, motorized roof panels that open and sliding doors in the vertical walls, which enable air to flow freely. On the hottest summer days, natural convection currents draw the hot air out of the enclosure and up through the roof. This particular pool enclosure is equipped with automated rain sensors, which close the roof panels during inclement weather. In the winter months, solar gain during the day is captured by the geothermal system and held for use during cold, dark nights.
In the spring and fall, the building is opened during the day and closed in the evening. This allows solar heat to be captured during daylight hours, while preventing the rapid nighttime cooling effect. There is a net gain in energy efficiency by the intelligent use of the flexible pool enclosure.
The overall esthetics of allowing in natural light, keeping out insects and providing an open air concept, while maintaining the ability to enjoy the pool any time of the year, are an added bonus for the client.
The most important item to add to a pool with regard to energy efficiency is an automated pool cover. Constructing an indoor pool without a cover will result in increased energy costs throughout the pool’s life. Various studies indicate upwards of 70 per cent of a swimming pool’s heat loss can be saved simply by installing an automated pool cover. In an indoor pool setting, this heat loss is further compounded, as evaporated water must be removed from the air by the heating, ventilating and air conditioning (HVAC) system. It is critical to keep the pool, chill pool and spa covered when not in use to maintain maximum efficiency and the ‘Thermos effect.’ For this project, the automated cover was installed in the underground bunker.
Ground temperature, a mere 1.2 m (3 ft) below the earth’s surface, is generally around 13 C (55 F) degrees. For this installation, the goal was to maintain the pool at 28 C (82 F), the chill pool at 14 C (58 F) and the hot spa at 39 C (102 F). To do this, rigid foam insulation was used beneath the building’s foundation, the full depth of the pool bunker’s interior walls, and the entire shell of the pool, chill pool and hot spa. It was also decided against using closed-cell spray foam on the bunker walls and pool shell for esthetic reasons, as it is unattractive compared to the clean, crisp lines of rigid foam insulation. (Note: Some building codes require insulation to be covered with drywall in an indoor environment when connected to a living space.) In this case, the insulation in the change and steam rooms, as well as the bathroom were covered with tile. Self-closing steel doors separate the mechanical room from the living space. As with all insulation, there is a diminishing return on investment (ROI). For example, twice the amount of insulation does not double energy efficiency results.
In addition to the foundation, shell and bunker walls, all of the plumbing lines were insulated, both inside and outside the concrete shell. All geothermal and water supply lines inside the building were also insulated. There was no compromise in energy efficiency by not insulating the project’s waste and drain lines.
A full-depth engineered underground concrete bunker was constructed surrounding the entire pool, offering a number of energy efficient aspects. For example, the bunker space located under the pool deck allowed all the plumbing, walls and floor space to be insulated. It also acts as a barrier that separates the various bodies of water from direct contact with the surrounding cold earth.
All of the pool’s mechanical, electrical, automation, HVAC, irrigation, lighting and geothermal equipment was housed in the bunker. This allowed the duct work to be installed in an insulated air space, rather than in the ground, as in a standard indoor pool installation. It also minimized plumbing runs by allowing the equipment (e.g. pumps, heaters, etc.) to be installed as close as possible to the aquatic features.
When all was said and done, there was even enough space left over to create storage, change, shower and steam room facilities, toilet and sink amenities and a large work space.
The seamless integration built into the equipment and plumbing systems was designed to maximize efficiency, resulting in substantial energy savings. For example, the variable-speed pumps run at 600 revolutions per minute (rpm) to provide the minimum water flow required to operate most project components. Full-speed operation (3,450 rpm) is limited to cleaning cycles and maximum hydrotherapy on spa jets.
Each aquatic feature (e.g. pool, chill pool and hot spa) was designed to operate on its own dedicated circulation system, with each having its own cartridge filter and variable-speed pump.
Suction lines are 76 or 101 mm (3 or 4 in.) as required, and pressure lines are 51, 63.5 and 76 mm (2, 2.5 and 3 in.). The system was designed for suction velocities of 1.37 metres per second (mps) (4.5 feet per second [fps]), and pressure velocities of 1.98 mps (6.5 fps). Using the proper size of pipe, along with minimizing fittings and pipe lengths, the hydraulic system’s efficiency and safety can be maintained.
The pools are interconnected through an in-floor cleaning system, which allows the three pools to share the same salt water sanitizing system. Distributing water through the floor of the pools also prevents thermoclines from developing. The in-floor warm water returns distribute clean water from the bottom of the pool, allowing natural convection currents to distribute the heat evenly throughout the pool. This process is reversed in the chill pool.
The equipment used for this project includes:
A 32-zone automation system was installed to allow maximum control on energy efficiency. With this system, the client can manage all functions from a touch pad in their kitchen, or by remote in the pool room.
The pump run cycles were automated to maintain the minimum flow necessary to achieve proper water chemistry and turnovers; cleaning cycles were programmed to operate at night to take advantage of lower electricity rates. Where possible, the heating and chilling cycles were also timed to run during the night for the same advantages. All lighting features (both outdoor landscape and indoor) are controlled by the automation system to maintain ambiance and minimize consumption. All of the lighting is LED or low-voltage. For safety reasons, the automated pool cover was not connected to the automation system, as it uses a turnkey operation for opening/closing.
All blowers and jet pumps have built-in timers, which turn off the equipment after a certain period of time, while a series of automated valves control filter, vacuum and chemical distribution cycles. Temperature controls for each body of water are also fully automated and connected to the geothermal system. Waste water collected from dehumidification is also automatically recycled back to the pool.
The client’s home had an inefficient propane heating system, as well as an electric air conditioning system. To improve heating/cooling efficiencies for the home, and the project, a shared-energy geothermal system was installed.
To comfortably heat the indoor pool environment, as well as the pool and hot spa water, radiant in-floor heating was installed in the pool deck [bunker ceiling]) and throughout the pool floor. The system uses spare heat from the geothermal house heating system to heat the pool. Water in the chill pool is also cooled via the geothermal system.
Further efficiencies are achieved by taking the waste heat from the chill pool and adding it to the hot spa, and vice versa. Combining the home and pool systems saves large amounts of energy.
Engineering the HVAC system for the project was quiet challenging. The pool enclosure comprises mainly glass, except for its aluminum structural frame, and had to be completely enveloped in a curtain of warm dry air to prevent water vapour from condensing on the windows.
Massive amounts of large-scale duct work penetrate the concrete bunker roof (pool deck) in 158 sleeves. It is more efficient to sleeve supply air vents in the concrete deck rather than core drilling after the concrete has been poured. A central spine of return air keeps the glass free of humidity. In the winter, the HVAC system enables a bather to stand near a window and still feel warm.
Every aspect of this project was engineered to achieve the goal of constructing a long-lasting, minimal-maintenance, energy-efficient environment. An engineered concrete design ensured the pool shell, bunker and building walls were constructed in a methodical and interconnected manner.
Common sense has to prevail on a project of this nature, as it can be easily argued that a simple inflatable children’s pool is more ‘green’ than a luxury indoor pool. However, by utilizing technology, along with efficient building practices, such as keeping construction waste to a minimum and recycling on site, the project goal was realized.
Many of these techniques can be utilized on other projects to dramatically lessen the industry’s carbon footprint, while also providing the client with a lifetime of reduced energy costs, which will pay for themselves many times over.
Author note: A number of industry experts consulted on and contributed to this project, including: Gary Scott (Zodiac Pool Systems Canada Inc.), Fred Breen (Colbree Enterprises), Jake Hamoen (JTH Best Engineering Inc.), Steve Hamoen (Zonelife Inc.), and Mark Albertine and Bruce Marsh (OpenAire Inc.).
Barry Justus is the owner of Poolscape Inc., a landscape contractor and pool designing and building company based in Burlington, Ont. He can be reached at firstname.lastname@example.org or by visiting www.poolscape.com.
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