Abstract: Flat boards are elements used in dry construction, especially in building systems such as the Light Steel Frame (LSF). In Brazil, boards made of Portland cement and synthetic fibers are extensively applied. However, they have an unsatisfactory hygrothermal behavior, low dimensional stability, and high thermal conductivity. Therefore, this study analyzed, as an alternative, magnesium boards that have greater dimensional stability and lower thermal conductivity, although such magnesium oxide (MgO) boards are not currently made in Brazil. Comparative analyses and measurements of thermal performance were carried out by Spectrophotometer tests to calculate solar absorptance, by infrared thermography to obtain surface temperatures of LSF Panels, and by evaluation of external (Te) and internal (Ti) dry bulb temperatures with data loggers and prototype instrumentation. Results demonstrated that the magnesium-based boards can contribute to better thermal performance of the built environment Ver menos