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A preliminary investigation has been carried out to determine the potential for using ultra-wideband (UWB) radar to determine the moisture level within building envelopes. Radio waves are affected by moisture content because their reflection from the surface of a material depends upon the dielectric constant of that material, a property with a strong dependence on the moisture content. UWB radar holds the potential for gaining greater information from a wall than can be obtained by conventional radar because of the large frequency range covered by emitted signals. Tests on small samples of oriented strand board (OSB), pine, and gypsum board have shown that the energy reflected from the samples increases with increasing moisture content. Further investigations were carried out on a simulated wall consisting of panels of gypsum board, insulation, and OSB sheathing that were conditioned to varying moisture contents. Algorithms have been utilized that enable the user to separately identify the moisture levels of the individual layers in the wall. The last part of the study joined the radar unit with mapping software to create three-dimensional images of the moisture condition of a wall. These results may lead to a new technique to nondestructively map the hygrothermal state of the building envelope.

Units: Dual

Citation: ASHRAE Transactions, vol. 110, pt. 2