The results of the building optimisation presented in this article come from the author’s entry project in the Design Optimisation Competition 2014. Simulations were conducted to help to design an office building and to minimise its costs and impact on the environment. Ultimately, the building’s construction costs were reduced to £2,294,216 and annual CO2 production to 136,169.3 kg, while maintaining discomfort hours below 200 hours per year and daylight floor area above threshold on the level of 60.0 %.