Courtyard buildings in desert climates: are they energy efficient when air-conditioned?

Courtyard buildings are typically recommended as a passive solution for compact desert architecture. However, an increasing number of desert buildings are becoming air-conditioned and isolated nowadays. In these cases, the performance of such a form becomes a matter of question, as the prospected goal becomes minimisation of energy consumption as means for achieving thermal comfort. This paper questions the validity of using courtyard building shapes when air-conditioned in the desert environment. The performance of courtyard buildings is compared to that of other solid building forms. Also, the effect of form, proportions and orientation on energy consumption in the moderate and extreme hot desert conditions is detected. The paper also addresses the climatic conditions in which courtyard buildings likely to be recommended. A base case of a two-storey squared residential building was simulated using the Energy-Plus software in three cities: Jeddah, Cairo and Alexandria. To this base case, three courtyard buildings of 1:1, 1:2 and 1:5 courtyard aspect ratios were compared. Solid rectangular forms having the same built area and nearly the same proportions as the courtyard buildings were also compared. The forms were tested under three cases of urban fabric: free-standing buildings, linear fabric and compact fabric. For comparison with a contrasting colder climate, all cases were also simulated under the temperate climate of Berlin. Results showed that a free-standing courtyard building was not a preferred building form, as it resulted in the lowest energy efficiency in all tested cities. A better performance occurred when arranged in a linear pattern, nevertheless, it consumed more energy in comparison to solid building forms. When set in a compact urban pattern it proved to be more efficient than the solid building forms of the same fabric only in the moderate climates, while still less efficient in the extreme hot or cold climates. However, even when located in a compact fabric, air-conditioned courtyard buildings could not be recommended as they achieved less energy savings than solid rectangular forms set in a linear fabric.