Low-Cost Procedure for Evaluating the Thermal Resistance of Building Materials

The use of unconventional building materials locally produced through an artisan process, as well as the upcycling of materials and components, is severely limited by the lack of technical information and product specifications enabling their use in building design and construction. In many cases, nonstructural building elements with relevant insulating properties cannot be employed due to missing information on their thermal properties. On the other hand, standard certification procedures are so complex, expensive, and time-consuming to be fully out of reach for do-it-yourself (DIY) builders.To address this problem, a simplified, low-cost test procedure was developed at Politecnico di Milano to be used by students, as well as for a first thermal performance evaluation of building materials in research projects, where accuracy is not strictly regulated. A cube test box with a side of 600 mm was built using a certified insulating material, with known third-party product specifications (extruded polystyrene insulation—XPS), leaving an open side for accommodating the sample to be tested. An incandescent lamp was placed inside the box to heat its interior up to a stable temperature, while an infrared optical pyrometer was used to measure the external surface temperature of the testing sample.Assuming a direct relationship between temperature difference and variation of thermal conductivity, it was possible to estimate the R-value of the sample material with a precision higher than 94%. Certified materials with known thermal conductivity were also measured using the same procedure, in order to validate the proposed simplified testing method.The testing equipment, which is extremely cheap and easy to build, proved effective to perform a preliminary assessment of thermal properties of building material samples, achieving results with acceptable accuracy for initial research stages. This simplified testing method could also be easily employed in developing countries as an aid for DIY construction practice—when thermal property specifications of local building materials may not be available.