Faber KOLDING Installationsvorschrift Seite 50

EN
The vent system and the opening must conform to local codes.
This is a closed device in a framed-in space, a device without a fan
and with a chimney loss of more than 17% (not condensed).
The natural draught makes it necessary that the intake and exhaust
are at the same pressure. This requirement is automatically satisfied
when you use the Multi-Vent system.
EN 4