Economic analysis of foundation heat gain for refrigerated warehouses

A set of recommendations on the optimal R-values for thermal insulation to be placed underneath the foundation of refrigerated warehouses is presented. The analysis is based on results from a simplified tool for calculating foundation heat gain for refrigerated warehouses. Three insulation configurations are considered: horizontal uniform insulation, horizontal perimeter insulation, and vertical perimeter insulation (placed along the foundation walls). The recommendations are based on a detailed economic analysis using the life-cycle cost (LCC) method. Moreover, the effects of insulation type, location, slab size, and soil thermal conductivity on the optimal insulation R-value are discussed. The efficiency of the refrigerating system and the electricity cost are also accounted for in the economic analysis. It was found that the horizontal uniform insulation configuration is required for freezers in all U.S. climates. The cost-effective R-value for this insulation typically increases as the slab size decreases and as the soil thermal conductivity increases. Moreover, it was found that adding insulation to chilled coolers and coolers may not always be cost-effective in cold climates.