ALIPAI 75 Air Vent

There is always some moisture in roof structures for various reasons.

Moisture is generated by the diffusion of water vapour generated when the building is in use. Moisture within the structure is generated by convection.

Some moisture is transferred into the structures from the outdoor air. The moisture in structures after the building is completed is caused by faults in storage or protection of the building materials.

Water content in some building materials:

• concrete: ~80 kg/m3 • lightweight concrete: 80-180 kg/m3

• timber: 20 kg/m3 If the roof is not ventilated, moist air from inside the building rises to the roof and becomes condensed on the internal surface of the felt, causing moisture in the thermal insulation.

In winter, the moisture freezes and the thermal insulation loses its insulating properties, resulting in a significant rise in heating costs. In summer, bubbles and cracks appear in the roofing.

Excessive moisture promotes the growth of fungi, moulds and micro-organisms. Alipai ventilates the roof structures and ensures efficient removal of moisture.