In this paper we describe a new methodology for optimising building and urban geometric forms for the utilisation of solar irradiation, whether by passive or active means. For this we use a new evolutionary algorithm(a hybrid CMA-ES/HDE algorithm) to search the user-defined parameter space, within defined constraints. The fitness function, solar irradiation, is predicted using the backwards ray tracing program RADIANCE in conjunction with a cumulative sky model for fast computation. Application of this technique to three very different scenarios suggest that the new method consistently converges towards an optimal solution. Furthermore, with respect to configurations subjectively chosen to be intuitively well performing, annual irradiation is increased by up to 20%; sometimes yielding highly non-intuitive but architecturally interesting forms.