Phase change materials (PCM) can be outfitted in building envelopes to not only provide thermal comfort for occupants but also trim heating, ventilation and air conditioning (HVAC) loads. However, the efficacy of PCMs depends highly on its thermo-physical properties and climatic condition. In this regard, a multi-objective optimization technique is adopted to unearth the optimal type and location of PCM that can minimize heating and cooling loads considering five cities of Iran namely Tehran, Tabriz, Bandar Abas, Shiraz and Yazd with distinctive climates. Then, the optimal PCMs are environmentally and economically assessed. The study showed that the PCM with a melting temperature of 25 degrees C outperforms in terms of cooling load while the PCM with a melting temperature of 21 degrees C favors the heating performance. Moreover, the utilization of PCM results in electricity saving of 4.5-5.5% for all the climates. On average, the annual carbon footprint is reduced by 1297 kg, 1420 kg, 2040 kg, 1027 kg, and 1248 kg for Tehran, Tabriz, Bandar Abas, Shiraz, and Yazd, respectively. The payback period was found to be more than 70 years for all the cities considering current economic conditions. However, the energy subsidies are projected to fall in the near future that may make PCM integration economically feasible.