Basic principles
Without any flow
hot air rises/cold air falls, that's how you get frost on a clear night, no clouds to keep hot air in or cold air out
Gasses in the atmosphere have different densities
air being a gas is denser than gas from the dropping of your pigeon so it will rise or sit above the air, hence bad designed lofts have foul air in the apex even if you left your door open all year
With the correct flow you bring fresh or more air in the bottom pushing the lighter gas from your pigeon droppins out the top, a nice steady flow is better as it will push the gas out the highest point, rather than too much it will waft about and could linger longer in pockets
Britains position is that when we get
south westerly winds from atlantic bringing rain as it cools over the north sea.
south easterly winds bring the hot dryer air from huge land mass of europe
north westerly winds bring cold air fom the artic mixing with damp air from the atlantic giving us sleet/snow
north easterly winds bring cold air from iceland and norway giving us cold bitter but dryer air
High pressure over us keeps it all away and low pressure lets it all in
So if you can why not try and use these basic principles when siting, building or designing your loft
Try sitting in a south facing conservatory on a summers day, try sitting in a north facing conservatory on a winters day and visa versa
This may seem like a lot of bull to some but it is used in designing in all walks of life, I can give you hundreds of examples, why not try it for your pigeons