[AIVC, Air infiltration and ventilation glossary, 1992]:the degree of protection from wind offered to a building by upstream obstacles. These may be windbreaks, shelter belts, or other buildings.

[EN 12792-2003, 325]:obstacle in the neighbourhood of the dwelling by which the infiltration or ventilation is influenced.

[EN 12792-2003, 327]:direct extraction of supply air before it contributes to the treatment of the space.