A new passive heating design on the basis of phase change materials tailored to residential buildings

Space heating in residential buildings, particularly in cold climates, consumes substantial energy. Passive solar heating strategies reduce heating demand by utilizing solar energy. However, their effectiveness is limited during daytime. Phase change materials (PCMs) offer a solution by storing heat during the day and releasing it at night. To maximize PCM effectiveness, optimizing PCM placement, melting temperature, and thickness is essential. This study designs and evaluates a passive heating system for two room cases in a residential building in Seoul: a single-exposed (one exposed wall) and a corner-exposed room (two exposed walls). EnergyPlus simulations assess various interior placements, melting temperatures (21 °C–29 °C), and thicknesses (5 mm–40 mm). Results showed that placing PCM on the floor, where solar irradiance is the highest, achieved the greatest total load reduction—15.2 % in the single-exposed room and 11 % in the corner-exposed room. However, in the presence of a radiant floor heating system, west-wall placement avoided heat interference with the radiant system, reducing total energy supply by 12 % and 10 %, respectively. The optimal PCM thickness for heating load reduction was 17.5 mm and 20 mm, while total load reduction plateaued at 17.5 mm for both rooms. During intermittent seasons, overheating increased in the single-exposed room but decreased in the corner-exposed room, highlighting the influence of room placement on PCM performance. The proposed PCM-based passive heating system demonstrated significant potential for energy savings and thermal regulation, supporting its effectiveness in improving heating efficiency across indoor conditions.