Dark-fired tobacco growers in western KY and TN spend an estimated $4 million annually on materials for firing the crop. Design of newly constructed dark-fired tobacco barns in this region are generally cross-tier, 32 to 36 ft. wide, 3 to 4 tiers high, with house wrap insulation on the walls and the roof of the barn. These barns are much more efficient for fire curing than the older barns that were not insulated as well. The objective of this research was to determine if additional curing efficiencies could be seen if insulation was also added in the floor of the barn. A layer of foil-back double bubble insulation was added in the entire floor of a newly constructed dark-fired tobacco barn near Hickory KY in 2017. Insulation was back filled with six inches of topsoil. During installation, four thermocouples were installed in the floor of the barn to measure ground temperature during curing. An adjacent barn of similar design but with no floor insulation was used for comparison. Data loggers were placed in the bottom tier of both barns to monitor air temperature and relative humidity during curing. Both barns were filled simultaneously with the same tobacco and fired four times using the same firing method. Data loggers showed that the barn with floor insulation got 4% hotter and had 8% lower relative humidity on average during the cure than the barn with no floor insulation. There were no statistical differences in tobacco-specific nitrosamines (TSNAs) or benzo-[α]-pyrene (BaP) between the two barns. However, some uncured (fat) midribs were found in tobacco along the perimeter of the barn without floor insulation that were not found in the floor-insulated barn, suggesting that the barn with no floor insulation could have been fired a fifth time. (Reprinted with permission)