Cooling demand in the building sector is growing rapidly; thermal energy storage systems using phase change materials (PCM) can be a very useful way to improve the building thermal performance. The right use of PCM in the envelope can minimize peak cooling loads, allow the use of smaller HVAC technical equipment for cooling, and has the capability to keep the indoor temperature within the comfort range due to smaller indoor temperature fluctuations. This article presents an overview of different PCM applications in buildings for reducing cooling loads under different climate conditions, and the factors affecting the successful and the effective use of the PCM. Many drawbacks have been found in PCM applications, mainly the intense impact of summer weather conditions over the PCM performance, which prohibits its complete solidification during night, and thus, limiting its effectiveness during the day. Proposed solutions are reviewed in this article. Finally, a topology diagram is presented to summarize the steps leading to an effective use of PCM in building applications.