Abstract The topic of low-energy buildings received a widespread and growing interest in last years, thanks to energy saving policies of developed countries. The design of a low-energy building is addressed with energy saving measures and renewable energy generation, but the correct assessment of phenomena occurring in a building usually requires to perform dynamic simulations and to analyze multiple scenarios to attain the optimal solution. The optimality of a technical solution may be subject to contrasting constraints and objectives. For this reason, designers may employ mathematical optimization techniques, a non-familiar topic to most of building designers. In this paper, a review on optimization of low-energy buildings design is provided, in order to collect the results of previous works and to guide new designers. The topic received an increasing interest in last years, with multi-objective optimization and genetic algorithms being the most popular. The most common objective functions are the costs and the operating energy consumption, while the environmental aspects are often neglected. As low-energy buildings should reduce the global energy demand, their design may benefit enormously from the assessment of energy consumption and environmental impacts in the whole life cycle, even in a simplified way.