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In 1995, a joint research project 1 with the Institute for Research in Construction was initiated to assess the in situ thermal performance of a number of insulation products used as exterior basement insulation in contact with the ground. Sixteen insulation specimens measuring 610 mm and 1220 mm wide were installed on the exterior basement walls of an experimental building, test hut no. 1, located on NRC campus in Ottawa. These specimens were instrumented prior to backfilling and their thermal performance was monitored over two full years. Soil temperatures and moisture content were monitored concurrently. Weather events were recorded daily. This paper focuses on the performance of the two spray polyurethane foam (SPF) specimens assessed in this experiment. Through analysis of the surface temperatures of the specimens, water movement was detected at the insulation/soil interface through various periods of heavy rain and major thaws throughout the two-year period. Over the same period, the surface of the concrete on the inside of the insulation showed no evidence of water penetration through the SPF layer. The insulation specimens were retrieved after 31 months of exposure in the soil. Good and continuous surface adhesion was also noted on removal. Samples were taken from these exposed specimens. When tested in the lab, after recovery and drying of the specimens, the compressive strengths of the SPF samples were slightly higher than those tested at the beginning of the experiment. For the conditions recorded over two years of monitoring, the thermal performance of each insulation specimen was found to be stable through the heating season. The thermal performance appeared not to be significantly affected by water movement at the exterior face of the insulation. One SPF specimen showed steady thermal performance through two heating seasons while the other actually improved in the second year. It was concluded that the key performance factors of the 76 mm thick SPF specimens sprayed on the exterior surfaces of the concrete basement wall all remained at a very good level, i.e., the in situ thermal resistance, the compressive strength, and the moisture contents of the specimens.