When the system boundary is scaled up from a single building to urban buildings, the overall system
performance is not equal to the simple aggregation of individual performance because of the system
interactions. One interaction is between a building and other buildings, typographies or obstructions.
These obstructions considerably influence the solar radiation on building rooftops, and also impact on
building energy since solar radiation plays an important role in building energy uses [17]. Building energy
use is also sensitive to the microclimate that can be altered by another system interaction, e.g. local air
temperature and wind are modified by urban form through the increased thermal storage within buildings
and impervious surfaces, and urban canyon effect, etc., known as the “Urban Heat Island Effect” [18].
Occupant density and behavioral pattern, which reflects the interaction between buildings and social and