Development of optical fibre humidity sensors for assessing the quality of housing insulation materials

A fibre optic-based relative humidity (RH) sensing system has been developed for assessing the qualities of housing insulation materials, based on a Polyimide (PI)-coated Fibre Bragg Grating (FBG) device. This forms the key moisture sensitive element, allowing a carefully-designed and packaged sensor system to be fabricated, evaluated and calibrated, creating the robustness and reusability needed. Following calibration, the system performance evaluated on a range of commercial housing insulation materials shows excellent performance in establishing the key moisture-transport parameters of the materials routinely used by structural engineers. Cross-sensitivity issues are addressed allowing the RH sensor system to operate over a wide range of RH level experienced normally in this application. A sensitivity of 1.1 pm/%RH, with low hysteresis from a ruggedized sensor, is observed.