This paper presents results from a wider study into providing displacement ventilation in urban areas by taking air into buildings from the top without the use of fans. Results from large scale experimental work are given. These results indicate that ventilation airflows can be induced using gravity chillers and heaters in conditions where this type of installation would otherwise fail. The paper also describes initial experiments undertaken to see how far the same equipment can be used for heat recovery. One test installation was modelled using a proprietary zonal model. A further zonal model was created to compare an assisted gravity system with a partially fan-driven system. This system failed on numerous occasions during a hot summer. However, fans are shown to be advantageous in winter heat recovery. A hybrid system is suggested for use under UK conditions.