This paper describes the measurement of ground and internal wall temperatures, local surface heat fluxes on the basement walls and floor, and overall heat losses for a concrete wall basement. The heat fluxes were measured with heat flux meters and mimic boxes. Daily and seasonal measured performances are displayed. A portion of the walls was covered with additional insulation. This allowed comparison of insulated and non-insulated basements and showed that a modest amount of insulation could reduce the annual heat loss by approximately 50%. The local fluxes are shown to vary significantly with depth and the insulation was most effective when applied to the upper wall surface which communicated with the ambient air through a relatively short path through the earth near grade level. Temperature stratification effects are shown to be important, especially with respect to floor heat fluxes.