This paper studies the energy behavior of several public heated swimming pools with semi-transparent covers located in southeastern Spain with high consumption of their air-conditioning installations. The scientific novelty of the work is to determine the influence of solar radiation on the energy performance of this type of building and to demonstrate that the use of passive systems such as natural ventilation and solar control enhance the energy efficiency in glazed heated swimming pools in a warm semi-arid climate. The methodology used consisted of on-site measurements of current hygrometric behaviour and a study of alternative solutions by simulation of virtual models with improved hygrothermal conditions. In the on-site measurements, thermographic images were used to analyse the thermal envelope and hot-wire probe measurements to determine the temperature distribution and air velocity inside the pool enclosure. For the study of alternative solutions, simulations were carried out, including an analysis of incident solar radiation and different natural ventilation and solar control solutions. The results obtained showed that the current hygrothermal behaviour of the interior spaces does not comply with the regulations on the thermal quality of the indoor environment. The results show that the proposed natural ventilation and solar control solutions substantially improved the hygrothermal properties and energy savings of the pools analysed. This work offers an alternative solution that avoids the implementation of costly air conditioning systems and the energy consumption of installations, promoting more sustainable renovations that contribute to improving the indoor comfort of users with interventions that are compatible with existing buildings.