Building energy consumption accounts for a large proportion of a country's total energy consumption. One approach to achieving the goals of energy conservation and greenhouse gas (GHG) reduction in the building sector is to use good thermal insulating materials in the building envelope. The thermal transmittance (U-value) of the building envelope plays a key role in the evaluation of the thermal performance of a building. Recently, many countries have been increasingly approving the planning, design, and construction of net zero energy buildings. In a net zero energy building, the energy demand from the operation of the building is met by renewable energy generated on site. The application of a renewable energy system to produce electricity is necessary for a ZEB. In particular, Building Integrated Photovoltaic (BIPV) systems are a promising strategy to integrate PV systems with building materials to reduce construction costs and add aesthetic features. BIPV systems that generate electricity can also play an important role in achieving zero energy balance in buildings. In this study, we referred to ISO 12567-1 and CNS 10523 A3197 to set up the insulating performance testing equipment and to investigate the U Value of various types of building integrated photovoltaic (BIPV) panel. The experimental results indicated that the thermal conductivity of insulation material and thickness of the BIPV system are the major factors affecting U value. Five types of photovoltaic panel selected in this study have little difference in U value. However, the insulating material inside BIPV system has a significant effect on the U value of a BIPV panel.