Despite the impact of climate change on worsening summer severity in southern Europe, some regions will maintain rigorous winter seasons. This poses a challenge for the social housing sector, with a considerable portion built before the introduction of national or European thermal regulations. Thus, heating practices with active systems in these contexts are limited due to the phenomenon of energy poverty. The aim of this paper is to provide an understanding of the impact of constructive retrofit measures on improving the indoor thermal conditions of a social housing dwelling located in the Portuguese region of Beira Interior during the winter season. A set of dynamic thermal simulations were performed for different intervention scenarios from a previously calibrated numerical model, using current and future climate datasets. Indoor air temperature results were then assessed considering thresholds defined in the national thermal regulation. Results show that the buildings in their current state do not ensure proper indoor conditions to face current and future climate challenges. Regarding retrofit interventions, compliance with the requirements defined by thermal regulations is not sufficient without the use of heating active systems to achieve indoor temperatures within the recommended values for the entire season. Although increasing thermal insulation always presents better results, the benefits for indoor conditions without the use of heating active systems are more evident during less severe winters.