|Abstract||The building sector is one of the main sectors in Qatar; however, it consumes a huge portion of primary energy sources. Today, there is a worldwide trend to utilize renewable sources of energy to cover buildings’ energetic needs using local climate conditions. The common source of energy, the sun, can be efficiently utilized in covering energetic supplies of buildings. To be able to consume energy of the sun, various components and materials are designed. This thesis is focused on the preparation and complex physical characterization of heat absorbers based on Phase Change Materials Heat Absorbers (PCM-HA). The materials are designed based on recycled high-density polyethylene (W-HDPE) obtained directly from a local industrial company in Qatar, paraffin wax and expanded graphite (EG) which can all be used together as the main components in improving the passive heating or cooling of buildings. Thus, this work is directly related to environmental protection and energy conservation in buildings. A big attention is given to the long term stability of the PCM-HA. The materials were artificially aged at selected conditions (temperature, UV irradiation, humidity) to characterize their long term behavior. This type of characterization was rarely reported in literature. Thus, the obtained results conveyed valuable benefits. This long-term experimentation confirmed the significant reduction in paraffin leakage from the thermal system up to 9.83%. Thus, this also confirms the high ability of the materials to absorb and release reaching 70 J/g of heat energy. Samples mixed with EG did not lose their mechanical integrity and compactness even after 100 days of accelerated artificial aging. Adding to this, various PCMs are applicable not only in building sectors, but also in thermal protection of electronic devices. For this reason, the dielectric behavior of the developed materials are explored and results confirmed an increase in electrical conductivity due to addition of EG to the materials.