Colloquially, the term "ventilated roof" is usually used for roofs that have a rear ventilation level under the roof covering. According to DIN 4108-3, however, ventilated roofs only include those that have a ventilation layer directly above the thermal insulation. If the ventilation layer is missing or is too small according to DIN 4108-3, it is called an unventilated roof, even if a rear ventilation level is still arranged in the further structure. The common roof structure with a rear ventilation level between the underlay and the roof covering is referred to as a rear-ventilated roof covering.
Source: bauwion
