How does draft (wind thingy inside the house) happen ? Why does it usually work when you open two windows/doors ?
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If you open a door, air can flow in *or* it can flow in. If it did both, you’d just have a little bit of a breeze *just* inside of the door and nothing elsewhere in the house.
If you open *two* doors, it can flow in through one and out through the other, and has to travel the full distance between them through the inside.
Its a pressure difference.
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The air is flowing to equalize the pressure. the low pressure area can be caused by things like an external wind (which can overpressure the facing side and create a low pressure area in a buildings wind shadow) or a temperature difference (where thicker cold air seeks to replace thin warm air).
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the opening of several doors or windows creates both a connected area big enough to have those pressure differences, and creates a bottleneck that increases the flow (and pressure) as it tries to squeeze thought that bottleneck.