Pioneering Work Towards Low Energy Swimming Pools by Gale & Snowden Architects with Exeter University

Gale & Snowden Architects and Engineers has recently completed design work for the UK’s first Passivhaus Certified public swimming pool and leisure complex for Exeter City Council with funding from the Technology Strategy Board under the Design for Future Climate programme. As part of this work Gale & Snowden is pleased to publish a joint academic building physics paper with Exeter University entitled ‘Modelling Low Energy Swimming Pools adapted to Climate Change’.

The results show that the key energy loads for the building are heating the pool water to maintain temperature and heating fresh water followed by heating the pool hall to maintain a high air temperature. Simulations show that the pool hall will require heating throughout the year even under a 2080s climate change scenario. The energy load for this space heating outweighs the loads for cooling and dehumidification even in future climates. Therefore the overall strategy should be to minimise the pool evaporation and heating load where possible, this can be achieved by:

• Maximising solar gain to the building throughout the year by orientating to the south with optimum glazing ratios.
• Minimising heat loss from the building by including high insulation and high airtightness standards such as those recommended by the Passivhaus standard.
• Maintaining relative humidity levels of around 65% and fresh air rates of 0.5 ac/h for normal use are the optimum in terms of minimising energy loads, using variable speed fans to alter fresh air supply rate to balance humidity and water evaporation with occupancy will result in lower energy use.
• Including shading devices has a detrimental effect on the energy requirements for the buildings, as it will reduce the solar gain that can contribute to the heating load and therefore increase the overall energy loan.
• Significantly increasing the glazing levels will result in a neutral energy effect, as although the heating energy load will be reduced across the climate change scenarios, it will increase the cooling loads by an equal amount in 2050 and a greater amount by 2080. This study is useful if glazing areas are required to increase daylight levels or views out.
• The use of efficient mechanical processes and heat recovery (sensible and latent where possible) will become even more prevalent in future swimming pool buildings in particular at reducing dehumidification loads and heating colder incoming fresh air load.
• Finally, lowering the pool water temperature will decrease evaporation and reduce water-heating requirements. The fresh air supply rate may also be reduced to maintain relative humidity.

We have devised a methodology for the incorporation of swimming pools into thermal modelling software. We have presented proof of concept by modelling an example swimming pool and examining heat loads for different levels of ventilation and humidity. The method accounts for latent and sensible heat losses from the pool water and the required energy to heat water and maintain humidity in the pool hall. This methodology has been used to assess the impact of different design scenarios on the energy loads of the pool building in the current climate and under estimates of climate change over this century.