Robotic implementation of the slide method for measurement of the thermal emissivity of building elements

• Thermal emissivity, or emittance, is a key property for heat transfer of building surfaces.
• For accurate assessment of building performance, it must be known by measurement.
• The most used measurement method with low thermal conductivity materials is the ‘slide method’ modification of ASTM C1371.
• The slide operation, performed by hand, may be time-consuming and affected by the operator.
• A robotized version of the slide method has been developed to eliminate the man in the loop.

A significant interest exists in measuring the thermal emissivity of building surfaces since high values combined with high solar reflectance allow rejecting solar energy absorbed by irradiated surfaces, whereas intermediate or low values permit to limit condensation of humidity, heat loss to the sky, or heat transfer through airspaces. The most used measurement method is probably that described by the ASTM C1371 Standard, which correlates the thermal emissivity to the radiative heat flux exchanged in the infrared between the sample surface, kept at ambient temperature, and the bottom surface of a hot emissometer head. With samples showing a low thermal conductivity, the ‘slide method’ modification is generally used: the hot head is allowed to slide above the sample in order to prevent this from warming up. The slide movement, however, is carried out by hand and time is needed to achieve a stabilized output, therefore the measurement may be time-consuming and also affected by the operator. In order to solve both problems, an automated approach is proposed here, in which the head is moved by the arm of a robot. This manages either the slide movement or the calibration with reference samples, interacting with a computerized data acquisition system that monitors the emissometer output.