Natural swimming pool in Eckermannpark

The town of Winsen (Luhe) in Lower Saxony is planning the construction of a new outdoor swimming pool on the grounds of Eckermannpark. In connection with the new construction of the bath, a gastronomy and bathing building as well as a small pavilion for the bathing supervision are being built; the planning of the functional buildings is the responsibility of D:4 Architektur. The entire project is energy self-sufficient, inclusive and not only environmentally but also animal friendly. The natural pool with biological water treatment is the first CO2-neutral operated outdoor pool in Germany. General planner as well as responsible for the design and technical execution of the bath is the experienced company Polyplan Kreikenbaum. The filigree functional buildings being constructed on the site are also characterized by the idea of sustainability. The natural pool in Eckermannpark is scheduled to open for the 2024 summer season.

In total, the site contains an open area of 19,500 m² and a water area of approx. 3,600 m². The open-air pool is to be integrated into the open space in a natural way. Thus, the spacious pool, which, by the way, is not connected to the Luhe River but to the existing park water body Weiherbogen, will have an organic shape. The water will be treated entirely without chemicals, namely purely biologically through plant filters. The open space will include playgrounds, sunbathing areas, picnic areas, and a water playground, as well as boules courts and a beach volleyball court. Outdoor showers and changing snails are also placed near the pool. Two buildings will house the pool attendant and first-aid room, as well as barrier-free sanitary facilities such as toilets and hot water showers, an information point and catering facilities.

The natural swimming pool
Designed and laid out by Polyplan Kreikenbaum, the natural-looking swimming pool will have sandy beaches and many shallow water accesses, a shallow water zone with a water depth of 30 cm, but also water depths of up to three meters, a slide and climbing wall, and five 25-meter lanes. Neptune filters, hydrobotanics and phosphate absorbers ensure unadulterated bathing pleasure without chemical additives such as chlorine. The treatment and purification of the pool water is carried out in accordance with the guidelines for the planning, construction, maintenance and operation of outdoor pools with biological water treatment - swimming and bathing ponds (in short: FLL guidelines). The water is subjected to a biological and mechanical cleaning process in planted substrate filters before it is fed back into the pool in bathing water quality.

The wooden pavilions
The entire bathing area is supervised: on the west bank there is a small building with panoramic windows for the bathing supervision. It is to be built according to a design by D:4 in wooden construction and will house two rooms on 40 m²: one for the bathing supervision and one sanitary room. The second building - also a design by D:4 Architecture - on the site is much larger at 400 m² and centrally located between the entrance and the pool: It offers covered space for the info point of the natural bath, sanitary facilities, changing rooms as well as rooms for the year-round gastronomy. These three essential functional units are united under one round roof.

Building concept
The single-story pavilion is round, seemingly floating and filigree. The building rises on a concrete slab, with the floor approximately 0.5 m above ground level. The new building is also accessible via ramps and stairs. As a circular building, the pavilion, which was planned using Building Information Modeling (BIM), looks vivid and open from all directions of the park.

The wooden roof with a span of around 13 m rests on round galvanized steel supports. At the highest point, it rises a good 6 m. The almost floating flat roof with a slight incline consists of a supporting structure of glulam trusses and an overlying board stack ceiling. It has an extensive green roof and also supports almost 200 photovoltaic panels, which are used for power supply.

Underneath is set a round wooden structure that forms the actual rooms - structurally independent of the PV system supporting roof. The timber frame building with its own flat roof is 4.20 m high. The wood-frame walls are clad with back-ventilated larch sheathing; numerous glazed areas and openings allow plenty of natural light to enter and contribute to a transparent, light effect. All thermal insulation is in accordance with the GEG.

In particular, the south-facing facade is extensively glazed: this is where the guest room is located, offering a wide view over the entire natural pool. In front of it is a terrace of around 150 m², which can be reached directly via three exterior doors. Furthermore, two windows with counters offer the guests a snack sale accessible from the outside. Oriented in a westerly direction towards the main entrance to the pool, the information point is located next to the 270 m² catering area as a central point of contact. Connected to this is the staff area for employees of the pool operation. In the eastern part of the pavilion, in the direction of the pool, the sanitary facilities and four hot showers in connection with individual changing cubicles are directly accessible from the outside. There are separate entrances to the various functional areas inside.

Regenerative energy concept
The power supply and building heating are provided exclusively by regenerative energy. 184 x 360 watt photovoltaic modules with 66.24 kWp are installed on the elevated flat roof of the main building. Electricity will be generated by the photovoltaic system on the roof. In addition, electricity will also be generated by wind power at a later date: It is planned to retrofit a small wind turbine, which will be placed as a vertical rotor between the parking spaces and the building.

Heat is generated via a water-to-water heat pump with approx. 45 kW. The heat is generated in summer via absorber plates on the roof below the PV system. In winter outside the bathing season, the heat from the pool water is used. The individual rooms are heated via underfloor heating. The rainwater drainage of the pavilion is done by discharging the rainwater locally into the pond arch. Due to this energy concept, a climate-neutral operation of the natural pool is possible.

More information:

www.winsen.de > Citizen participation

www.youtube.com > Information event preliminary design for a natural swimming pool in Eckermannpark

www.abendblatt.de > Bathing paradise in Eckermannpark // Article in Hamburger Abendblatt (2022)