Thermal insulation of a flour mill to improve effectiveness of the heat treatment for insect pest control

One of the major problems that occur in flour mills, and more generally in industries for food storage and processing concerns the control of insect pests. Insects can multiply under favorable conditions and become responsible for contamination that can determine the non-conformity of productions to the norms and regulations of food quality. An alternative to chemical treatments for the control of insect pests in flour mills is represented by methods based on heat treatment of the indoor environment. The heat treatment consists in raising the temperatures of the surface where the insects live by increasing the air temperature inside the building. The optimum air temperature for heat treatment effectiveness ranges between 45°C and 55°C and has to be maintained for a period of 36-48 h in order to eliminate all life stages of insect pests for both dehydration and irreversible alterations in lipid and protein levels. The most widely used system for heat treatment in flour mills is based on heaters powered by electrical energy which are usually integrated with fans to ensure a uniform air temperature inside the buildings. The objective of this research was to analyze the heat transfer of a number of building elements of a flour mill located in Eastern Sicily (Italy) in order to highlight weaknesses in building thermal behavior. The analysis of building materials and components (e.g., floors, external walls, windows, pillars and beams) and the monitoring of the microclimatic parameters inside and outside the building before and during the heat treatment revealed that relevant heat losses occurred across thermal bridges. On the one hand, thermal bridges represented a weakness of the thermal treatment since insects found refuge in areas of the building where the surface temperatures are lower; on the other hand they caused a huge expenditure of electrical energy in order to maintain indoor air temperature within the optimal range. Therefore, the building components which determine the thermal bridges were analyzed with the aim of studying the contributions of different insulation materials on heat loss. Simulations were carried out by analyzing different insulation solutions to quantify heat loss reduction and possible solutions were proposed in this paper.