Evaluating deep retrofit strategies for buildings in urban waterfronts

The renovation and requalification of existing building stock and the exploitation of renewable energy sources are considered key actions in the European Energy Roadmap to 2050. In this scope, a noticeable potential application is represented by urban constrained built heritage, whose rehabilitation can be considered both as a strategy for its conservation and an enhancement of competitiveness for a sustainable city. The proposed research evaluates the potential of scalable retrofit strategies in existing buildings through the exploitation of on-site renewable energy sources available in urban waterfront. The methodology starts with the collection of data concerning environmental and climate conditions, predictable building energy demand for heating and cooling services, and timescales of available on-site renewable energy sources. The approach has been tested by the development of a detailed building energy model (BEM) for a constrained building in the urban waterfront of Trieste, in Northeastern Italy; the building construction dates back to the early 1980s and it is located in a valuable historical and cultural context. According to the preliminary rehabilitation proposal by Trieste Municipality, a baseline energetic model has been carried out to evaluate and optimize retrofit strategies for building envelope and energy systems, including renewable energy source exploitation. The study considers particularly hydrothermal energy stored in sea basin that could play a significant role in urban waterfronts contexts. The main results show that the most effective adaptation strategies are characterized by key factors such as envelope thermal inertia in reducing heating and cooling demand in middle seasons, thermal effects of roof greening, and the combination of plants that exploit several discontinuous renewable sources and accumulation systems, such as photovoltaic systems and sea hydrothermal energy. This paper looks at a strategic vision that focuses the need to manage plant systems through advanced commissioning or by developing an integrated smart thermal grid. This research is embedded in a pilot project concerning the development of a low-temperature thermal grid in the waterfront of the old town of Trieste.