The architecture, engineering and construction (AEC) sector has great potential and responsibility for reducing its considerable resource consumption and high share of global emissions. However, economic factors are often cited as barriers to more environmentally friendly solutions in building design. Hence, environmental and economic life cycle assessment (LCA and LCC) are of utmost importance in building design. They serve as the base methodologies for what we call the “Eco2” framework. In this context, monetary valuation of multiple environmental impacts allows to integrate the results as a basis for design decisions. A case study representative of small-scale office buildings in Germany illustrates the Eco2 framework and shows the influence of temporal parameters (discount rates and price changes), as well as of differing monetary valuation, on the ranking of design options. Varying the temporal parameters affects the ranking of different solutions for the structure and finishes of the case study building but not for its mechanical, electrical and plumbing (MEP) systems and operation. However, the ratio of environmental life cycle cost (eLCC) to financial life cycle cost (fLCC) is significantly higher for MEP systems and operation than for the structure and finishes. This investigation shows that it is possible to achieve simultaneous emission and cost savings, whereas temporal factors can decisively influence decision making in design processes.