Breathable and water tightness are decisive factors to attain living comfort. Nevertheless other aspects call for great attention: VENTILATION. We report here a short introduction about ventilation, as defined by the NORM U32035110/9.3.1 (REVISION OF LAW UNI 9460/1989) – UPDATING JUNE 2002, EXTRACT:

On a ventilated roof we have either a free and garret or a proper cavity along the pitch, suitable to generate upward motions due to the expansion of the heated air (see UNI 9460/13.4 picture beside).

When a cavity at constant thickness along the pitch is to be adopted, the thickness itself and thus the flow section depends on the roofing type, on the pitch length, on its slope, on the type of cavity (in communication with the below-tile area or not), on the shape of the incoming and outgoing sections, on external weather conditions (wind, sun irradiation...).

Generally, the flow section of cavities able to reduce thermal flow in summer climate, in case of usual slope of roofs in Italy (17° 20°) and usual pitch length (maximum 7 m), is at least 550 cm2 large for each meter of pitch width, below the fillet in case that the cavity is in communication with the fillet itself. Such prescriptions must be followed even in case of a cavity bounded by two flat parallel layers (double planking, panel...). On the roof there must be a proper section for the incoming air along the gutter line and another section for the outgoing air on the ridge. This section is obtained through continuous or discontinuous cracks (the entrance of insects and birds is stopped) or openings that limit as much as possible the obstruction. On the top, the water and snow seal must be assured.

1) External protection
2) Ventilation layer
3) Breathable underlay
4) Insulation layer
5) Vapour control layer
6) Bearing element

Main features of ventilation are:

- in the warm season: to reduce heat underneath the bent tiles tanks to upward motions. This makes the habitability of the garret comfortable;

- in the cold season: to avoid stagnation of humidity underneath the clay tiles, with consequent condensations that damage the insulating material and other structures of the roof.

It is always placed underneath the clay tiles (better if in contact with them) and upon the thermoinsulating element. Recommended size: smallest cmq/ml 400 - biggest cmq/ml 800 (v. UNI9460/13.4 - U32035110/9.3.1).

VAPOUR CONTROL LAYER It limits the passing of steam in order to prevent condensation inside the roof system.It improves living comfort and reduces the humidity percentage in the interiors. It protects from rain the beneath structure during construction . In case of penetrations from the upper layers, the vapour control layer is a further protection.

It is also defined as air-tight layer: it lets vapour go out gradually, but it holds back the air in the living area. In this way it helps the energetic control according to the D.L. 311. The VCL (Vapour Control Layer) is placed on a wood board or on a concrete roof and below insulation.

BREATHABLE UNDERLAY

Its main function is to protect the roof and the beneath building from possible leaks of the main protection. At the same time it allows vapour to go out as quickly as possible, without damaging the structure and insulation. Breathable underlays also protect insulation from undesired air movements that make insulation uneffective.

RE.PACK offers high-quality Vapour Control Layers and Breathable Underlays, 10-year guarantee, with high features and strictly CE-branded.

Here we list products offered by RE.PACK to meet these requirements.