Urban climate control strategies and buildings’ retrofitting: a simulation study in the UNESCO heritage site of Valparaiso, Chile

Climate neutrality is a concept that envisages, in addition to the drastic reduction of greenhouse gas emissions, also the generation of climatically acceptable urban conditions. In this sense, any intervention in the building sector must consider not only the mitigation of global warming, but also the adaptation to ongoing climate change. The urgency is to carefully evaluate the consequences of each construction process, as well as the retrofit of existing buildings. In particular, the redevelopment interventions of the building stock must no longer only consider energy efficiency and the transition towards renewable energy, but also adequate strategies for improving the climatic conditions outside the buildings. The use of climate simulations as a tool for choosing design strategies has become widespread in recent years as a working methodology. Yet, in heritage contexts, there is still a certain reticence to consider scientific data as a valid resource for determining design criteria, favoring rather historical readings and formal analyzes of buildings as constraints to be respected even at the expense of energy and environmental improvements. This work proposes the search for a fair compromise between the valorization of the built heritage and climate neutrality, understood here as the restoration of conditions of habitability and comfort of open spaces, or at least, the reduction of harmful urban microclimatic phenomena.

The research uses the Envi-Met software to simulate the microclimate and estimate the potential for reducing the intensity of the urban heat island phenomenon in the “El Almendral” sector, located in the urban heritage context of Valparaiso, Chile. Different intervention proposals are compared, considering urban greenery, evaporative cooling solutions and changes in the materials of pavements, facades and roofs of the buildings in the sector under analysis. The results show that the reduction in urban heat island intensity is greater in the case of green interventions, compared to blue and gray ones. In particular, with the combination of tree planting and incorporation of green-roofs and green-façades, reductions in the average temperature of the sector of the order of 0.5-0.75 degrees centigrade are achieved depending on the time of day. The second strategy is the one that considers cool materials for pavements, followed by cool materials for facades. The use of water bodies, in this specific case, is relegated to last position in terms of effectiveness as a cooling strategy for the sector.