Investigation of a novel method of using wall cavities to preheat ventilation air using both solar energy and heat recovery.

This paper describes the analysis and practical testing of a novel method of pre-heating ventilation air for buildings by sucking the air from the cavity space in an external wall. The fresh air introduced into the building is pre-heated partly by recovery of the heat escaping through the inner leaf of the wall and partly by collection of some of the solar energy incident on the outer leaf of the wall. A classroom at Napier University in which the system was installed was monitored to assess the energy and comfort benefits. Consideration was also given to noise levels and the optimum control strategy. It is concluded that the "cavity-breather" method of pre-heating ventilation air is both energy-efficient and practical.