The proportion of Energy consumption in the building industry is great, as well as the amount of cooling and heating system. Scholars have been working on energy conservation of Heating, ventilation, and air-conditioning and other systems in buildings. The application of occupant behavior data for building energy optimization has started gaining attention from scholars. However, occupant behavior data concerns many aspects of occupants privacy. Different types of occupant behavior data contain occupants private information to different levels. It is crucial to conduct privacy protection of occupant behavior data when using occupant behavior for energy conservation. This paper presents the aspects of privacy issue when using occupant behavior data, and methods to protect data privacy with blockchain technology. Both two options of using blockchain for privacy protection, sending data records as transactions and storing files on the blockchain, are explained and evaluated with temperature records from an open access paper. Sending data as transactions can be used between sensors and local building management system. While storing files on blockchain can be used for collaboration of different building management systems. Advantages, drawbacks, and potentials of using blockchain for data and file transfer are discussed. The results should be helpful for using occupant behavior data for building energy optimization.