Buildings are made completely of materials. Hence, in this book, the characteristics of materials used in green buildings is elaborated on, including for green roofs and green facades. For the purpose of energy structural reduction and saving, a strategy designed by the authors is explained as well. The last two chapters explore phase change energy materials and their related technologies. The chapters introduce newly developed experimental characterisation technique and numerical simulation method for PCMs (phase change microcapsules), as well as microPCMS, which have drawn great interest due to their high heat capacity and easy manipulating and operating, and thus are potentially applicable in various industries.