The lattice Boltzmann method (LBM) is an innovative approach in computational fluid dynamics (CFD). Due to the underlying lattice structure, the LBM is inherently parallel and therefore well suited for high performance computing. Emerging many-core devices, such as graphic processing units (GPUs), nowadays allow to run very large scale simulations on rather inexpensive hardware. In this contribution, we present some simulation results obtained using our multi-GPU LBM solver. For validation purpose, we study the flow around a wall-mounted cube and show good agreement with previously published results. Furthermore, we discuss larger scale flow simulations involving nine cubes which demonstrate the practicability of CFD simulations in building aeraulics.