Membrane roofs are widely used building materials, and their solar radiation coefficients significantly affect the
thermal environment of the steel structures below them. In this study, the solar radiation coefficients of common
membrane roof materials, namely, ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE),
polyvinylidene fluoride (PVDF), thermoplastic olefin (TPO), and polyethylene (PE), were obtained from systematic
specimen tests. The temperatures of steel plates below different types of membrane roofs were measured
during summer under solar radiation. A numerical simulation method was presented and verified. The following
conclusions were drawn from the results of the test and numerical analyses. 1) The ETFE and PE membranes have
a high solar radiation transmittance of up to 0.8, which can be effectively modified by printing silver dots and by
increasing thickness. 2) The PTFE, PVDF, and TPO membranes have a relatively low solar radiation transmittance
below 0.25. 3) The temperature of steel structures below the ETFE and PE membranes is over 61.7 °C during summer,
which is at least 27.7 °C higher than ambient air temperature. 4) The temperature of steel structures below
the PTFE, PVDF, and TPO membranes is over 41.2 °C during summer, which is at least 7.2 °C higher than ambient
air temperature.