Developing building projects with low environmental impacts is a real challenge, yet a problem faced every day by designers. To that end, in the design process, iteration between propositions and objectives have been used that are complex and time consumption. The impact targets leading to low-carbon buildings have the potential to simplify this complexity and saving time in the building design process. This study introduces a methodology for the definition of impact targets for components and systems of buildings. The definition of impact targets has been envisaged as a two-step process combining top-down and bottom-up approaches. The desired impact target of building is defined by a top-down approach and the targets for components and systems by a bottom-up approach. Impact targets for the Swiss context are defined applying the methodology to the smart living building that aim at reaching the 2050 goals of the 2000-watt society vision. Through this approach, we were able to set up impact targets on the components and systems level for global warming potential indicator. Impact targets can be used as guidelines in the design process for developing component or system one by one without analysing the whole building, which is guided toward low carbon objectives.