This study investigates a possible alternative reuse of spent coffee grounds (SCG), the major residue of the brewing process, to manufacture green geopolymeric materials for innovative building applications in energy-saving construction, in line with the European Green Deal towards zero-energy building. Specimens were prepared by a combination of biomass fly ash from the Kraft paper-pulp process, as raw material (70 wt%), and SCG (up to 17.5 %), as filler. The high amount of reused bio-wastes makes the material fit the requirements for the Minimum Environmental Criteria (MEC) certification, in light of the Circular Economy (CE) approach. Sustainability is also boosted by the manufacturing process that completely occurred at ambient conditions (20 °C, 65 % RH). Materials engineering performance is evaluated to predict possible applications in construction and promote an integrated architectural design process to propose a “coffee-house” equipped with an innovative energy structure and envelope. For the scope, different technological solutions are designed and virtual energy modelling is implemented to simulate the performance of a building model in different climatic conditions and estimate the possible real efficacy of the proposed solutions in relation to building efficiency and cost management, as envisaged by the EU 2018/844 on the buildings’ energy performance. The major result is that the developed material represents an optimum candidate to substitute traditional construction and building materials with a great manufacturing financial saving, up to 37 % for the 17.5 % SCG, and an energy improvement up to about 19 % per year, leading further saving in the yearly building management.