I live in Poland with my wife and daughter, and we just got the keys to our new apartment, which, unlike in the US, is given in what’s called “developer’s state” – meaning it is a concrete shell inside that has to be renovated for living.
Question:
What exactly is Natural/passive/gravity ventilation and how does it work?
I (kind of) know that if you keep everything shut tight, it can cause “reverse ventilation(?)” where instead of pushing air out it actually sucks more cold air into your living space(?)
In: Engineering
A closed box won’t have any air moving in or out. However, if you punch holes along the bottom edge, and along the top edge, two things happen:
* Hot air rises. This means slightly higher pressure at the top, so air will go out the holes at the top, and to replace it, colder air from outside will go in through the holes at the bottom. This is called the [chimney effect](https://en.wikipedia.org/wiki/Stack_effect); smoke naturally goes UP in the chimney because hot air / smoke rises.
* Wind can push air around. If you put your box with holes in front of a fan, some of that fan air will get through the holes (top and bottom) on the side of the box that’s facing the fan, and flow through the box, and come out the holes on the opposite face.
So you want to have windows on basically all sides of the apartment, so you can open them in the summer and let the wind pass through your house.
And for heating in the winter, you can put some heating elements close to the floor, where the coldest air will be, and as they warm up the air it will go upwards and more cold air will be sucked into the heating elements. Basically put your heating elements at the ground level, not at the ceiling level.
Otherwise, [gravity vents](https://en.wikipedia.org/wiki/Passive_ventilation) means you have some vents (that you can open in the summer and close in the winter) at floor level, and you have other vents and ducts at the ceiling level to take air out. Use the chimney effect to suck cold air from outside and push it out through the (chimney) vent at the top.
You can see in that wiki article that they sometimes pass the air through pipes in the ground, cause the ground stones are usually cold, before getting it into the house. But mostly it’s about wind direction vs. where your windows are, and the chimney effect.
You can also “enhance” this “natural” ventilation with fans to suck air in or push air out. That’s “mechanical” ventilation.
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