eli5: How does draft happen


How does draft (wind thingy inside the house) happen ? Why does it usually work when you open two windows/doors ?

In: 0

Its a pressure difference.


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).


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.

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.