This work studies the effect on Embodied Energy (EE) of concrete when Ordinary Portland Cement (OPC) is partially substituted with natural Pozzolanic Volcanic Ash (VA) at the material and the building scale. The work aims to demonstrate potential improvements to the EE of buildings by comparing the EE of the cement mix with VA replacement to that of baseline case of traditional concrete. Embodied Energy Coefficients (EEC) express the EE of each building product in Mega Joules (MJ) per kg of material. Hardened cement paste made with up to 50% of the OPC replaced by volcanic ash with a mean particle size of either 17 mm or 6 mm is considered. Replacement of OPC with volcanic ash decreases the EEC, however the mix design must be engineered considering the volcanic ash composition to maintain the optimum mechanical strength. Grinding the volcanic ash from 17mm to 6mm led to increased compressive strength when replacing up to 40% of OPC with 6 mm sized volcanic ash. An average of 16% decrease in EEC values can be achieved when 40% OPC was replaced with VA. On a building scale, the initial EE is the energy consumed related to the extraction, production, and transportation of materials. For buildings with an average Structural Material Quantities (SMQ, expressed in mass of material per area) value of approximately 2000 kg/m2, a 16% decrease in EE value was observed among a sample set of 26 residential and commercial buildings when 50% of OPC is replaced with VA. The demonstrated reduction in EE values were calculated when natural supplementary cementitious materials (SCM) such as volcanic ash are used as a partial replacement to OPC, and it can be adapted to design and build energy-efficient systems tailored for structural and non-structural applications.