Façade-integrated ventilation units with heat recovery - energy efficiency and indoor air quality

This contribution reports on investigations about the performance of decentralised ventilation units with heat recovery. Such units can be easily installed in individual rooms and therefore offer an interesting alternative to central ventilation units. Nevertheless these units exhibit some problems. Experimental examinations of two commercial decentralised units showed that the real effectiveness of heat recovery was always below 50 % and that considerable leakage between the air ducts can result in poor indoor air quality. Additional investigations have been performed to measure air flow patterns and local age of air within a test chamber. The obtained measurements have been compared with CFD simulations and showed rather good agreement. This verification of simulation results allows for further numerical studies of indoor air quality under several conditions.