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Roof System

Double ventilation roof system

In a building, the roof is an essential and delicate component. It is continuously exposed to multiple weather events, including severe ones, which is why every component of the roof system must meet the highest quality requirements.

Among the roof systems is the ‘cold roof’ with double ventilation, which expels vapour and cools down through two ventilation cavities. The flow of water vapour is slowed or stopped below the insulation and then released through the ventilation cavity, thanks to the placement of our vapour barrier (or retarder) below the insulation and our highly breathable membrane above. An additional highly breathable or breathable Silcart membrane will be placed above the outer deck to expel any residual vapour and as an additional waterproof layer to the roof covering.


Vapour check are defined as those impermeable, airtight elements whose function is to reduce the passage of vapour to minimise condensation inside the roofing system.

The undertile vapour barrier membrane is entirely composed of three polypropylene layers. Ultrasonic welding makes the material completely recyclable. It avoids unwanted moisture infiltration by regulating its flow into the roofspace. It’s UV-stabilised and anti-slip.


As the first layer of protection installed on the first deck, Silcart offers a vapour barrier that reduces the passage of moisture from inside the house to the outside environment, passing through the insulating layer; at the same time it protects the deck from the stresses caused by operators during the laying of the roof.


Vapour barriers are defined as bituminous impermeable, airtight elements whose function is to significantly reduce the passage of vapour to minimise condensation inside the roofing system.

The lightweight bituminous undertile membrane is composed of a polyester core saturated with special bituminous compounds with a polypropylene non-woven fabric finish. It ensures complete watertightness. The membrane is characterised by excellent mechanical properties. It’s UV-stabilised and anti-slip.


The vapour barrier is suitable for various applications.

Placed above the first deck, and below the insulating layer, a low-weight barrier can be used, which is easy to lay and shape; it is a vapour barrier option for those who prefer a product with higher mechanical performance compared to synthetic sheeting, while limiting the passage of vapour.

In the case of a double-ventilation roof system, on the second deck we recommend using a vapour barrier with a higher weight, which has a higher performance. This is because it is the layer most exposed to the weather and where mechanical fixings often present the largest cross-sections. This facilitates the quick and safe channelling of rainwater and its discharge into the eave line. The higher weight makes it an ideal product in locations characterised by a harsh climate or high temperature fluctuations.


Breathable synthetic underlays are defined as those elements that are water- and wind-proof and whose function is to let vapour through from confined spaces under the roof by means of diffusion.

The highly breathable undertile membrane is made entirely of three polypropylene layers welded with ultrasound technology. The absence of glues and other polymers makes the product highly recyclable and breathable. It’s UV-stabilised and anti-slip.


The synthetic membrane placed above the insulation allows for rapid dissipation of excess vapour through undertile ventilation, helping to maintain the thermal properties of the insulation layer.


Flexible underlays and membranes for pitched roofs with discontinuous covering where mechanical fixing is required.


We provide our expertise and experience for customised advice on products and processes.

We support designers and technicians in choosing the most suitable and efficient materials and solutions for the successful implementation of the project.

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