Abstract The flow and dispersion of gases emitted by point sources located near a U-shaped building were determined by the prognostic model FLUENT using the RNG κ−e turbulent closure approximation. Calculations are compared against wind-tunnel measurements about such a U-shaped building and several other prognostic and diagnostic numerical models. FLUENT gives a mixed image in terms of accuracy of predicted concentrations compared to the wind tunnel experiment. For identical boundary conditions higher as well as lower concentration values are calculated for different test cases. Ground level sources show higher discrepancies than situations where the tracer was emitted from the roof of the model building. A major error source was found to be the stationary solution procedure that was chosen for all simulations.