In Construction, un' vacuum sanitaire' is a space nonaccessible from a few tens of centimêtres of top located between the ground and the first floor of the Bâtiment and being used as insulation between this one and the ground. The increase of Humidité since the ground are eliminated out of the building by the natural ventilation of the vacuum obtained with the peripheral air vents. They have a netting to prevent that the insects and larger animals place there.