The paper presents results from a wider study into providing displacement ventilationin 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 thatventilation airflows can be induced using gravity chillers and heaters in conditionswhere this type of installation would otherwise fail. The paper also describes initialexperiments undertaken to see how far the same equipment can be used in heatrecovery.One test installation is modelled using a proprietary zonal model. Experimental resultsare also compared to the results which could be inferred from CIBSE data. Theauthors argue that both the zonal model and the CIBSE data are very conservativetools for predicting low speed gravity driven airflows and suggest that more accuratemethods of modelling airflows would enhance the take-up of this type of technology.