= Natural ventilation
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<Natural ventilation> exchanges air through openings using pressure differences generated by wind or <buoyancy>. A warmer indoor column can have a different vertical <hydrostatic pressure> gradient from outdoor air; connected low and high openings then permit a circulation. Wind can instead create unequal external <pressures> on different sides of a building.
The resulting <volume flux> depends on opening areas, their discharge properties and the pressure differences that remain once flow is established. The <stack effect> and <cross ventilation> describe different driving geometries and can reinforce or oppose one another. Measuring indoor/outdoor <temperatures> alone does not determine the exchange rate without those geometric and flow conditions. A simple thermal budget combines the exchanged <enthalpy> with internal heating; a stratified room can require more than one representative <temperature>.
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