Photovoltaic thermal (PVT) solar collectors generate heat and electricity. Building Integrated (BI) facade collectors are suited to high rise buildings. Ulster University researches novel Integrated Collector-Storage Solar Water Heaters (ICSSWH). This study investigates Planar Liquid-Vapour Thermal Diode (PLVTD) heat transfer and characterises performance of a BIPVT-PLVTD-ICSSWH prototype. A thermal resistance network representing evaporation, vapour transfer, condensation, fluid conduction and convection, plate-to plate radiation, and solid conduction is established and evaluated using Stefan-Boltzmann and Fourier laws together with Rayleigh/Reynolds-Nusselt and Rohsenow correlations.