DIN 4108-3 specifies the free ventilation cross-sections for ventilated roofs. Although these apply to the room above the insulation, they have also proven themselves in practice for ventilation under the roof covering and are recommended by the ZVDH. For roofs with a roof pitch of 5° or more, the following cross-sections are required:
- Free ventilation cross-section in the roof area with a height of ≥ 2 cm.
- Free ventilation cross-section at the end of the eaves and lect ≥ 2 ‰ of the corresponding sloping roof surface, but at least 200 cm²/m.
- Free ventilation cross-section at ridge and ridge ≥ 0.5 ‰ of the associated sloping roof area, but at least 50 cm²/m.
- Blocking value (Sd value) of the component layers below the ventilation layer ≥ 2 m.
Source: bauwion
