Velux GGU INTEGRA Manual de usuario descargar pdf (Pagina 98)

Building physics

98 VELUX

Underfelt

The underfelt protects the roof construction against harmful water

penetration, primarily from leakages in the rooﬁng material. These

leakages mean that wind driven rain and snow may penetrate the

rooﬁng material. Especially driving snow may cause problems if

there is no underfelt. Large amounts of snow may accumulate over

time and suddenly melt when the temperature rises.

Water that runs down the underfelt ends in the gutter. If the under-

felt is interrupted by eg a roof window, the water must be drained

o to the sides of the window by installing a drainage gutter. The

drainage gutter drains o the water to the adjoining roof section

(between two trusses) where it can continue down the underfelt.

As a result of eg small leakages in the vapour barrier small amounts

of moisture may enter the roof construction from the inside of the

building. This moisture must be removed in order to avoid moisture

problems with subsequent rot and dry rot.

Depending on the means to removing the moisture, underfelts are

divided into ventilated and unventilated underfelts.

1 2 ... 93 94 95 96 97 98 99 100 101 102 103 ... 151 152

Sin comentarios

Velux GGU INTEGRA Manual de usuario Pagina 98