$20 attic fan for summer heat---storage friendly

The rear face of the vent cover is louvered to stop the rain from blowing in. This means though that when wind hits from behind it also hits that louvred surface, this stops a lot of the direct flow of wind. Most vent covers are also sized such that when the vent is fully opened the lid just touches the cover, this stabilizes both the vent cover and the lid and eliminates rattling.