This is the 3004th most frequent German word.
außen
"Außen" means "outside" or "external" in English.
Here, "außen" is used as an adverb referring to the outer part or surface of the door.
Die Tür ist außen bemalt.
The door is painted on the outside.
In this sentence, "außen" indicates a spatial position outside of a specified area.
Außen ist es kälter als innen.
Outside, it is colder than inside.
"Außen" here is describing the exterior aspect of the facade in comparison to the interior.