The influence of urban microclimate on building energy needs and hygrothermal performance

A vast literature describes how much urban heat islands impact the energy needs of urban buildings. Often, cities show nighttime air temperatures higher by 3-4 °C than adjacent non-urban areas. This yields to cooling loads in average higher by 13% for urban buildings. However, few studies assess the building energy performance over a long period, and none includes heat and mass transport, which is also relevant in determining the energy uses and the comfort conditions for the end user. Herein we assess the hygrothermal performance and the energy needs of a reference building representative of the Italian stock of the 1970s. We compare its performance calculated with hourly urban weather data with that got with a rural dataset, from 2000 to 2008. The achieved results point out that, in addition to building energy needs, also hygrothermal risk and heat and mass transport in general are different in urban areas. This might yield to a different design concept for urban buildings with respect to non-urban ones, even though they are, nominally, in the same climate zone.