Whirly Bird Attic Vent
The whirly bird attic vent is a great way for
removing hot air from the attic.
These attic fans have been around for quite a while now and seem to do a pretty good job for most people.
I installed two of them in one of my houses and realistically could not feel much of a difference in the attic temperature .
While standing on the roof, on a warm day, you could feel a steady stream of heat flowing from the whirly birds though and they seem to be doing their job.
I also installed attic fans and these seemed to work pretty good, when I say pretty good, I lived in an area where 90° to 100° temperatures were not uncommon in the summer, and it seemed like I was replacing hot air with warm air and it never made much sense to me, so I eventually removed the fans from the attic.
It's a good idea to cover the whirly birds up in the wintertime, this keeps the warm air in the attic and helps keep the rest of your house warm.