WATERPROOFING AND VAPOUR DIFFUSION SYSTEM

APPLICATION AND BENEFITS OF THE PERFORATED VENTILATION LAYER

With the application of the perforated asphalt membrane and the installation of suitable ventilation (surface and depth), we ensure:

1. The evaporation-dispersion of the water vapour which exist and moving inside the waterproofing we are going to apply to the external environment, through water vapour diffusion layer we create.
2. The application of the main waterproofing layer in a semi-independent manner on its substrate (the bitumen is applied to the holes of the perforated membrane), as required by the relevant technical specification ELOT 1501. (Hellenic Organization for Standardization S.A.)

The application of the bituminous waterproofing membrane (5kg or 6kg) should ideally be applied in a semi-independent manner.

In order to achieve this semi-independence, the perforated ventilation membrane is laid as the 1st layer where it has holes in its surface. After that we apply the tar paper as a 2nd layer by using a flame cutter over as much surface area as the holes of the first layer allow.

In this way we ensure:

• Adhesion of approximately, 30% of the substrate.
• In the remaining 70% of the perforated ventilation layer, without the holes, the waterproofing membrane is not adhered, allowing semi-independence to the substrate as well as the combination of transpiration 
  - dehumidification with the surface and depth ventilators as the water vapour due to temperature increase (in a roof the temperature increase is up to 80oC per year) rises through the perforated ventilation layer with expansion to the environment - atmosphere.
• The dispersive movements of the waterproofing layer are autonomous and natural due to its semi-independent installation, which gives it a longer life expectancy. That comes in contrast to the total installation of the bituminous waterproofing layer (Without the placement of the perforated ventilating layer as the 1st layer) where necessarily and based on the aforementioned it would follow the contractions - expansions of the substrate and of course with a shorter life expectancy especially in asphalt membranes <5kg.
• The protection of the final asphalt waterproofing layer, since the movements of plate expansion and contraction are absorbed by the first layer of the perforated ventilation layer. 

See here