Abstract
An important aspect of longwave radiation exchange within urban canopies is the degree to which the sky is obscured by surrounding buildings, a concept which may be described by the sky view-factor (ψs). Hitherto, expressions for sky view-factors in the urban context have been derived for symmetrical urban canyons of infinite length. In this paper an analytical expression is presented which permits the determination of sky view-factors for the more realistic case of urban canyons in which buildings are irregularly aligned and of finite length.