Solar radiation properties of common membrane roofs used in building structures

• Ethylene tetrafluoroethylene and polyethylene membranes have a high solar radiation transmittance of up to 0.8.
• Solar transmittance of Polytetrafluoroethylene, polyvinylidene fluoride, and thermoplastic olefin membranes is below 0.25.
• Silver printing dots and air cushion can effectively reduce the transmittance of the ethylene tetrafluoroethylene membranes.
• The temperature of steel structures under ethylene tetrafluoroethylene membranes is at least 27.7°C above ambient air temperature during summer.
• The temperature of steel structures under polytetrafluoroethylene membranes is at least 7.2°C above ambient air temperature during summer.

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.

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