inside vent covers

Vent covers also work well during the hot summer to help when the air conditioner is operating. Vents are cold in the winter and hot in the summer.

They are insulating covers. They will help keep down condensation and drafts from the vents. Most vents are just one layer of material as a result there is a lot of cold air intrusion.

Fantastic fan has double walled vents that help.

Cold weather camping. Some folks stuff insulation in the opening.