Ground frost or hoar frost.
Increase the vent to 4" as hoar frost will not over lap a 4"opening
rime, hoar
ice
Hoar, rime
Frost is frozen dew. It can also be called rime or hoar.
The basic meaning of hoar is to be greyish white in color. There is no such animal by the name of hoar, however, a wild boar is a wild pig.
Frost, hoarfrost, hoar, rime, snow
Yes if you happen to be walking on a vent terminal
This type of frost gets its name from the word "hoar," which means "ancient," because it resembles an old man's bushy, white beard. It happens when water vapor freezes instantly after coming into contact with a very cold surface.
The closing up of a vent terminal do to warm moist vapors touching the sides of a colder surface
Hoarfrost is another name for frost. It is a deposit of ice crystals that form on objects when the temperature drops below freezing and atmospheric moisture condenses directly on surfaces.