Evaluating non-intrusive energy retrofits for the built heritage of the historic centre of Oporto

Abstract

Traditional building materials and techniques should be preserved when selecting retrofit strategies. The most recurrent energy retrofit strategies proposed for the historic centre of Oporto are mainly focused on achieving, or even overlapping, the reference U-values established for the external envelope on national energy regulations, although historic sites are not obliged to comply with it. On the other hand, national cultural heritage preservation policies, by allowing alterations on these historic buildings interior, validate the adding of thermal insulation materials on internal walls. Nevertheless, these inteventions may put to risk architectural patrimonial values, hence, sustainable ones. A more opportune intervention could be the enhancement of the windows performance, due to its most common bad state of conservation. This article analyses the performance of two non-intrusive retrofit strategies, in a representative model of these buildings: the enhancement of ventilation and the substitution of the single glazed windows for double glazed ones, and the two combined. On a first approach, using as a reference the heating loads limits established in the energy regulation of 2013 and the normative methodology, it is calculated the corresponding number of hours of daily heating use, in order to stand below these limits. The results obtained showed that this is attainable, in comfortable conditions of heating use. In order to achieve more accurate results and conclusions a dynamic simulation was performed using energy models, for the heating and cooling season. The enhancement of ventilation proved to be the most effective retrofit strategy.