ABSTRACT— The residential buildings sector in Egypt represents the largest sector that consumes energy, with a rate of 40.5%. The Trombe wall is a passive design technique that contributes to reducing energy consumption in buildings.The objective of this research is to improve the heating capacity of the Trombe wall by embedding a phase change material (PCM), i.e. Paraffin wax, in the wall. A test room was built in the new city of Beni-Suef, Egypt, to evaluate the performance of the modified Trombe wall, which is integrated with a PCM. The dimensions of the Trombe wall are 2 m × 2.7m, and is painted black, and a single pane of glass of thickness 6 mm is installed outside the wall, leaving an air gap of 30 cm. The indoor air temperature of the test room in the winter of 2023 was measured and compared in cases of (a) traditional wall, (b) traditional wall with PCM and (c) a Trombe wall integrated with PCM. It has been found that the maximum temperature difference between the indoors and outdoors temperatures in cases (a) and (b) were 4oC and 5.2oC, respectively, however, using a Trombe wall integrated with PCM, increased the temperature difference to 7.1oC. The period during which the room temperature was higher than the outside temperature in case of the Trombe wall was 20.5 h. It can be concluded that integrating a PCM in the Trombe wall resulted in a more stable and comfortable indoor climate.