Abstract:
Nowadays, humanity is consuming unsustainably the planet’s resources. In the scope of energy resource consumption, e.g., the
intense use of fossil fuels has contributed to the acceleration of climate changes on the planet, and the overriding need to increase
energy efficiency in all sectors is now widely recognized, aiming to reduce greenhouse gases (GHG) emissions by 69% in 2030.
Largely due to climate changes,water has also become a critical resource on the planet and hydric stress risk will rise significantly
in the coming decades. Accordingly, several countries will have to apply measures to increase water efficiency in all sectors,
including at the building level. These measures, in addition to reducing water consumption, will contribute to the increase of
energy efficiency and to the decrease of GHG emissions, especially of CO2. Therefore, the nexus water energy in buildings is
relevant because the application of water efficiency measures can result in a significant contribution to improve buildings’ energy
efficiency and the urban water cycle (namely in abstraction, treatment, and pumping). For Mediterranean climate, there are few
studies to assess the extent and impact of this nexus. This study presents the assessment of water-energy nexus performed in a
university building located in a mainland Portugal central region. The main goals are to present the results of the water and energy
efficiency measures implemented and to assess the consequent reduction of water, above 37%, and energy (30%) consumption,
obtained because of the application of water-efficient devices and highly efficient light systems in the building. The water
efficiency increase at the building level represents at the urban level an energy saving in the water supply system of 406 kWh/
year, nearly 0.5% of the building energy consumption, with a consequent increase in the energy efficiency and in the reduction of
GHG emissions. Complementarily, other energy-efficient measures were implemented to reduce the energy consumption. As the
building under study has a small demand of domestic hot water with no hydro pressure pumps and has a small water-energy
nexus, it was concluded that the significant reduction of the building energy consumption did not influence the indoor comfort.