Towards Climate-Resilient Dwellings: A Comparative Analysis of Passive and Active Retrofit Solutions in Aging Central European Housing Stock

This article evaluates the effectiveness of various energy retrofit solutions—both passive and active—for reducing energy demand and improving indoor thermal conditions in apartments of typical multifamily buildings in Central Europe, considering current and future climate conditions. This study combines computer-based co-simulations (EnergyPlus and CONTAM) with in situ thermal measurements to identify challenges in maintaining indoor thermal conditions and to support model validation. Key indicators include the number of thermal discomfort hours and heating and cooling demand. The evaluated strategies include passive measures (wall insulation, green or reflective roofs, roller blinds, solar protective glazing) and active solutions such as mechanical cooling. The comfort operative temperature range of the adaptive model is adopted as a measure of thermal comfort and the energy demand in individual apartments as a measure of energy efficiency. The simulation results showed that solar protective glazing combined with a reflective roof reduced thermal discomfort hours by up to 95%, while modern windows alone decreased them by 90% and lowered heating demand by 18%. In contrast, typical passive solutions such as internal blinds or balconies were significantly less effective, reducing discomfort hours by only 11–42%. These findings highlight that, while no single retrofit measure is universally optimal, well-selected passive or hybrid strategies can substantially improve summer comfort, maintain winter efficiency, and reduce long-term reliance on energy-intensive cooling systems in aging multifamily housing.