[throwawayboise]

I don't see that it matters much which way the fan is blowing. What matters is the air exchange, which is about creating an airflow.

If you have a multistory house you can open windows at the top and bottom, the warm air will tend to flow out and pull cool air in the bottom. In that situation if you have a fan, it would make sense to have it blowing air in on the lower level, or out on the upper level.

If you have a single level, the fan will just create a slight pressure difference in one direction or the other. You just need to open several windows, preferably on opposite sides of the room, and if you use a fan to pull cool air in that creates a positive pressure inside the room, which will force the warm air to be exhausted through the other open windows. If the fan is blowing warm air out, then the room pressure will be negative relative to the outside, and cool air will be pulled in through the other open windows.

[eru]

Yes, it's best if you can create an airflow from bottom to top in a multi-story place.

Getting a draft through your entire place is also good.

What I suggest with the fan works, when you can't do either of the two above.

> I don't see that it matters much which way the fan is blowing. What matters is the air exchange, which is about creating an airflow.

The latter explains the former. A simple experiment: sit 2m in front of a running fan, then sit 2m behind a running fan. In front, you will feel lots of airflow, behind you will feel almost nothing.

That's because the fan 'pulls' air in a diffuse manner, but pushes it as a directed bundle.

It's probably equally as effective to put your fan outside the home and point it inwards, or to put it inwards the home and point it outwards. Alas, most people can only put the fan _inside_ their home, perhaps at the window at best. But that's less effective at exchanging air with the outside than pointing it outwards.

> If you have a single level, the fan will just create a slight pressure difference in one direction or the other. You just need to open several windows, preferably on opposite sides of the room, and if you use a fan to pull cool air in that creates a positive pressure inside the room, which will force the warm air to be exhausted through the other open windows. If the fan is blowing warm air out, then the room pressure will be negative relative to the outside, and cool air will be pulled in through the other open windows.

To use your terminology: the fan is better at pushing air in a concrete direction, than at pulling air from a specific direction.