Also well worth mentioning was the plenum system used to heat the building. Whether by accident or design, this system, in which heated air is passed through the building by convection via ducts built into the fabric, owes its origins to the Roman hypocaust. It was a system ideal for use in the saturated atmospheres of swimming pools because it encouraged ventilation. It created much comment at the time and featured in contemporary textbooks. The original building is now protected as a category A listed building.