Carbon-neutral design focuses on buildings that reduce or eliminate carbon dioxide emissions throughout its life cycle. A high-performance building integrates and optimizes, on a life-cycle basis all major high-performance attributes, including energy conservation, environment, safety, security, durability, accessibility, cost–benefit, productivity, sustainability, functionality, and operational considerations. Building energy performance simulation describes the process and tools that permit architects and engineers to analyze the effects of certain building properties, such as form, size, orientation, and mechanical systems on variables such as energy consumption and daylight. Performance simulation has typically been seen as a very complicated and technical process that only an engineer is able to perform. The building simulation discipline is evolving and maturing and improvements are continually being made to add more robustness and fidelity. To improve building performance and reduce carbon emissions, both digital and analogue tools should be integrated in the design process.