Covered Roof Whirly Bird
If you have whirly birds like this on your roof,
it's a good idea to cover them in the wintertime, to prevent heat loss.
This keeps your attic warm and helps lower heating costs in the winter.
If you leave them uncovered, they will continue doing their job and that's moving hot air out of the attic.
The only problem is, that you need to remove the covering in the summertime.. Don't forget.
These whirly birds are used for attic ventilation and are relatively easy and inexpensive to install.
Whirly birds have been around for years, even though I don't see very many of them installed anymore.
I have seen these leak during heavy rains.