Jérôme Diot
Directeur technique développement durable et énergie
Published on June 20, 2019

Reading time : 4 min

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Bioclimatic swimming pools to reduce energy bills

Swimming pools, which are among the biggest energy consuming constructions, weigh heavily on the energy bills of local authorities. According to the French energy and environment agency ADEME, they account for 40% on average of the energy consumption attributed to sports facilities, which in turn are second in the list of energy consuming public buildings, after schools. Nevertheless, thanks to technical innovation implemented from their design phase, this expense can be significantly lowered.

© Egis

A low consumption geo solar swimming pool at Château-Renault

To design the Château-Renault swimming pool, we sought to minimise requirements thanks to a dynamic heat simulation study following which we attempted to fulfil them as far as possible using renewable energy installations: geothermal heat pumps and solar panels.

The building has been oriented in such a way so as to receive maximum solar heat and sunlight on the south, west and east facades. The glazing selected offers high transmission values for solar heat and outdoor light. A horizontal awning and high sunshades prevent glare during the summer, but allow heat from the sun and light through during winter months.

To avoid thermal bridging leading to condensation which could weaken the building, the walls were insulated externally. The roof is also planted.

Geothermally heated pools

In Château-Renault, water resources are in abundance: at the end of the 19th century, they contributed to the development of a world-renowned tannery, which no longer exists today.

Having obtained confirmation of promising geothermal potential next to the pool complex, two 37 m boreholes were drilled to allow for water to be sourced and returned. The water, at a temperature of 10 to 15°C, is fed into a 60 kW heat pump, emerging at 45°C to heat the pools to 32°C. Additional and back-up heating is performed by a gas boiler.

Furthermore, the air is heated by a thermodynamic air handling unit (AHU) which also dehumidifies the air. During the summer, excess heat in the air is collected by the AHU to heat the pools.

Innovative solar cells

The domestic hot water (DHW), preheated thanks to a heat exchanger using the smoke of the gas boiler, comes from 80 m² of solar panels on the roof. As the Bâtiments de France architect refused to authorise sloping panels due to their proximity to the château, we used a Swiss technology that uses flat-laid cells.

The technology comprises a stainless-steel exchanger and a selective black chrome layer to absorb the heat energy of solar radiation whilst considerably reducing radiation loss. Irrigation is perfect, since 98% of the surface area of the panel is in contact with the fluid.

Their performance remains lower than that of classic cells, since the absence of a glass pane means that the greenhouse effect cannot be created, but this lower yield is compensated by laying them flat, allowing us to install more solar panel surface area. In addition, these cells offer the advantage of being cheaper, very robust (hail-proof and even walkable) and, more importantly still, they can self-regulate in the event of high temperatures. This eliminates any risk of the cells cracking due to the evaporation of the heat transfer fluid. Solar power accounts for 40% of domestic hot water required by the pool.

Laying the cells flat prevents panels from casting shadows onto one another - © Egis

Water efficient operations

The design of the facility limits the consumption of drinking water to approximately 60 litres per bather. Instead of sand, the AFM technology, using crushed recycled glass, was selected to treat pool water.

It offers higher performances and delivers savings in energy, water and chlorine. It can be noted that this chlorine is in gas form, which is much more effective.

All of these technologies help to deliver excellent quality pool water.


The Amboise (37) pool complex offers a full range of innovations!

Egis is responsible for managing the construction of this 2,200 m² pool complex designed by the firm Coste Architectures. It comprises a pool hall (1,153 m²), a sports pool (375 m²) with six lanes, a beginner’s pool (125 m²) with one to two 12-metre lanes, and several related facilities: reception, changing rooms, toilets, showers, sickbay, staff and technical facilities.

The project has received an enthusiastic welcome due to its aims to reduce consumption costs, optimise and recover energy and reduce its carbon footprint.

Here again, the building has a bioclimatic design with healthy and sustainable materials (wooden structure and cork floor covering). It is fitted with biological filtration (chlorine-free) to treat the water.

The complex draws substantially on renewable energy and energy recovery, in particular using hybrid photovoltaic panels. Water consumption will be significantly reduced thanks to the use of high efficiency filtration for pools, water saving devices for sanitary appliances and harvested rainwater for cleaning. In addition, the pool complex also has energy recovery devices on grey water, on the combustion smoke of boilers and on the thermodynamic unit in the swimming pool hall.

© Agence Coste Architectures

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