Since energy consumed in buildings accounts for approximately 40% of the total energy consumption of industrial countries, the adaptation of solutions for zero-energy buildings (ZEB) to existing structures is an important field of investigation. Historically significant buildings can serve as exemplary models if joint strategies for sustainable design and historic preservation are carefully developed and preservation-related conflicts in the application of highly visible sustainable measures are thoroughly addressed. Based on the project of retrofitting the historic monument of the Republic of Cyprus Presidential Palace in Nicosia, this paper addresses the challenge of upgrading existing, historically valuable structures toward ZEB. A series of energy-efficient technologies and measures for the Presidential Building are proposed. Material and technical systems modifications are integrated with architectural inquiries concerning the aesthetic impact of adding passive and active systems. The proposals were combined in different scenarios and analyzed with respect to efficiency and visual impact. The paper illustrates that ZEB necessitates a holistic understanding and planning of all energy consuming and producing aspects - environmental context, materials, structure, mechanical equipment, user behavior, among others. Discussing and comparing the engineers' and architects' approaches, this paper argues for the necessity of an integrative design process in retrofitting architecturally and historically significant structures toward ZEB.