Hello:

Have never really thought about this much, but we have a whole-house attic
fan in the gable end of our attic.
It has metal flaps that close off the louvred opening when the fan is not
running.
When it is running, they open (automatically) due to the air flow.

Also have a louvred opening in the opposite gable end (no automatic flaps)
that is open all the time.

Wouldn't I, perhaps, be better off if without these automatic-closing flaps
?

e.g., I would think that in summer it would be better to have cross flow
air due to wind, etc., even if the fan was off ?

Same argument, I would think, even in the winter.

So, why do they use these automatic closing metal flaps on gable louvres ?
(are they only used when there is an exhaust fan located there ?)

What advantage and usefulness are they ?

BTW: do most folks use screens over these gable louvred ends ?

Thanks,
Bob