Impact of roof geometry on cross-ventilation in vaulted buildings: a CFD study

Abstract

The roof geometry is an important parameter in determining the natural cross-ventilation in buildings. Although many studies have been performed on natural ventilation, the impact of the large set of vaulted roofs on the building cross-ventilation remains to be addressed. In this paper, high-fidelity computational fluid dynamics (CFD) simulations, validated with experimental data, are performed on five naturally ventilated buildings with two opposing windows, each with a specific type of vaulted roof and otherwise identical, in 0° incident flow angle, to assess the impact of vaulted roof geometry on the building cross-ventilation performance. The following vault geometries are investigated and compared against a flat-roof building with the same specifications: (i) segmental, (ii) low-rise pointed, (iii) mid-rise catenary (iv) high-rise pointed and (v) high-rise catenary. The results show that compared to the flat-roof building, the vaulted roofs cause a <5% decrease in volume flow rate and 16-29% increase in the average mean velocity magnitude at the occupants’ level. In vaulted buildings, the low-velocity regions of the flow are moved further away from the occupied zone towards the ceiling, thus providing a fresher air to the occupants. The results clarify the high potential of vaulted roofs for natural ventilation and sustainable design.