Construction services

Roof slope ventilation

The method of ventilating the pitched roof is determined by the attic arrangement and the type of initial covering layers used

In the unused attic, the thermal insulation is placed on the ceiling of the upper floor. The natural ventilation space is created by the volume of the attic itself between the thermal insulation and the initial covering layer. This space should be provided with free air flow through air intake vents located under the eaves and exhaust openings in the roof ridge and in the upper part of the gable walls.

In the attic, the roof ventilation is limited to ventilation gaps located in the roof slopes.

In contemporary roof structures, there are two basic solutions for the ventilation of roof slopes:

• Two-channel ventilation – Used in constructions, in which the undercoat is made of waterproofing materials, laid on boarding or foil with low vapor permeability. Two ventilation slots are necessary for the proper functioning of the ventilation – the first one between the thermal insulation and the undercoat, the second between the undercoat and the top roofing. The lower ventilation gap dries the thermal insulation and the roof structure. The upper slot further enhances the operation of the lower slot, further ensuring that the moisture dries quickly, which can get under the roofing during precipitation combined with strong wind,

• Single-channel ventilation – The water vapor flowing through the roof surface is removed to the outside by the air flowing in one gap formed above the initial covering layer, between counter battens.

It is only possible to eliminate the lower ventilation gap when using a layer of initial covering made of a special highly vapor-permeable nonwoven.

Air intake openings for ventilation slots are located under the eaves of the roof. The exhaust openings are placed in the ridge. Linear ventilation can be additionally supported in points by using special ventilation tiles, It is recommended to place ventilation tiles in places where the continuity of the ventilation gap is interrupted, e.g.. at roof windows or dormer windows.

tmpf65-2Ventilation in the unused attic - air inlet at the eaves of the roof, outlet in the ridge of the roof and through ventilation openings in the gable walls.

tmpf65-3Ventilation of roof slopes with one ventilation gap between the initial covering, and the top covering, used in roofs without full formwork.

tmpf65-1Ventilation of roof slopes with one ventilation gap above the thermal insulation and the other between the rigid plank or plywood sheathing and the top covering.