Assessing water, energy and emissions reduction from water conservation measures in buildings: a methodological approach

Water-energy nexus is a cornerstone in modern societies, with significant impacts at social, environmental, and economic levels. In addition to the issue of water scarcity that several regions of the world already face or are forecasted to face in the near future due to demand increase and availability reduction (e.g. pollution, climate changes), water consumption in buildings entails substantial energy consumption. In most cases, part of this energy is produced from non-renewable sources, encompassing greenhouse gas emissions. The present research effort presents a generic methodology to assess the cascade impact of water efficiency measures in buildings in terms of water, energy and emissions reduction. The methodology is applied to the Mediterranean climate zone context for two different types of non-residential buildings: university buildings and hotels, with very distinct water end use and consumption patterns. Lastly, are performed sensitivity analyses between the proposed methodology and simplified approaches. Is observed that assuming a linear relationship between flow rate and water consumption can lead to overestimations of up to 64% in water savings. Is also explored the relevance of the water consumption and energy mix seasonality typical of climates with marked dry and wet seasons, such as the Mediterranean region. The importance of the seasonality is discussed in terms of the time scale considered to apply the methodology, revealing that adopting a simplified (annual) approach, instead of the proposed approach, can lead to relative differences between - 62 and 233% in the presented case studies.