Indoor lap pool

The applicable standard prescribes a maximum residence time of the pool water, depending on pool type: swimmer pools 4 h turnover, non-swimmer/paddling 1-2 h. This sets the minimum filter flow rate. For a 242 m³ lap pool at 4 h turnover that is 60.5 m³/h of filter capacity. Filter backwash once per day or above 0.5 bar differential pressure. Backwash water is warm (pool temperature − 3-5 K) and therefore a valuable heat-pump source.

Basis: the applicable national standard

Evaporation from the water surface is the dominant heat loss in an indoor pool (60-80 %). Smith/Löf variant of the Carrier formula: m_evap [kg/h] = β × A [m²] × (p_w_pool − p_w_hall) [kPa]. β-coefficient per the pool energy guideline (evaporation and ventilation) Tab. 4: 0.013 unused pool (covered), 0.040 normal use, 0.080 wave/diving pool. Evaporation enthalpy at 30 °C: 0.694 kWh/kg. Pool saturation vapour pressure via the Magnus formula: 611.2 × exp(17.62 × t / (243.12 + t)) Pa.

Basis: the applicable national standard

The applicable standard requires a minimum fresh-water make-up of 30 litres per visitor per day, independent of filter performance. This make-up dilutes metabolic products, urea and other substances introduced by bathers. At 1,500 visitors/week × 52 weeks that is 2,340 m³/a, which has to be heated from drinking-water temperature (~10 °C) to pool set-point (22-32 °C). At a 28 °C pool set-point this is roughly 50 MWh/a of heating energy for fresh water alone.

Basis: the applicable national standard

The applicable standard defines the target hall climate: air temperature 30 °C ± 2 K, relative humidity 55 % ± 5 %. Outdoor-air rate at least 30 m³/h per person at full occupancy, at least 4 L/(s·m² of water surface) in base mode. For a hall with 355 m² water surface: 4 × 355 × 3.6 = 5,112 m³/h minimum; in practice The applicable standard recommends ~16,000 m³/h for comfort and pollutant removal (trihalomethanes). Heat recovery via plate exchanger at 65-75 % efficiency is standard.

Basis: the applicable national standard

The national buildings energy act the national buildings energy act 2024 treats pools as non-residential buildings. Mandatory air-conditioning inspection every 4 years (ventilation > 12 kW). On change of ownership or major refurbishment, tighter envelope U-values apply (external wall U ≤ 0.24 W/(m²·K)). A demand-based energy certificate is required above 250 m² of heated floor area. A hall pool with 1,800 m² of envelope at U=0.8 does not meet new-build standards — so grant funding for envelope refurbishment (up to 35 % rate) is available.

Basis: the national buildings energy act 2024 (the national buildings energy act)