Thermal response measurement of building insulating materials by infrared thermography

The existing building stock requires substantial interventions to meet the energy performance criteria imposed by the current standards. The installation of a new insulating layer into the building envelope is the most common energy retrofit measure. This strategy is usually focused only on steady state thermal conditions while it influences also the transient thermal behavior. However the on - site characterization of the building dynamic behavior is partially or totally neglected, due to the lack of a feasible investigation procedure. This may lead to a negative thermal performance of the building, paving the way to litigations between the contractor and the tenants. A novel measurement technique, based on infrared thermography, is proposed to investigate the dynamic behavior of the wall. Several wall samples are tested in laboratory with an experimental layout that resembled an outdoor installation, where a sinusoidal thermal stimulus is imposed on the back of the specimen. The surface temperature evolution over time is recorded with an infrared camera both on the front and on the back surfaces of the specimen, in order to measure the time-shift on a broad wall area. A key aspect of the proposed experimental procedure is that it could be applied to the on-site building survey, significantly improving the evaluation of the actual energy performance of the building. The obtained results are compared with a mathematical model showing good agreement.