4. Double fac¸ade
Numerical investigation was performed into the potential of using buoyancy-induced flow in a double fac¸ade for natural ventilation of a four-storey building with a total height of 12 m (Fig. 12). The double fac¸ade was simplified as an empty cavity, neglecting possible blinds for shading and walkway at each floor level for servicing, etc. Again, the length of cavity was assumed much larger than the cavity width so that flow was two-dimensional. Predictions were performed for the facade with cavity widths ranging from 0.4 to 1 m and three configurations of inlet openings. The three configurations
were: (i) single inlet at the bottom of the cavity (facade ventilation), (ii) four inlets on the inner skin, one on each floor of the building with a fixed size (0.2 m high) (room ventilation) and (iii) same as (ii) but with an opening size varied with cavity width such that the total area of four inlets for the four floors was the same as the outlet area. In addition, the effect of integrating PV into the outer skin was investigated. Heat fluxes were used as thermal boundary conditions for the two skins. Heat gains by inner and outer skins were estimated from the