Velux GGU INTEGRA Uživatelský manuál stáhnout pdf (Strana 109)

Building physics

VELUX 109

Snow and ice around VELUX roof windows

In prolonged cold periods with heavy snowfall considerable

amounts of snow may accumulate on the roof and a VELUX roof

window could become covered.

When the temperature rises the window will often be the ﬁrst

place where the snow starts melting because of the small extra

heat loss on and around the window. Melt water will run down the

window and freeze once it reaches the colder, better insulated roof

surface below the window.

In such cases a bank of ice can form below the window damming

newly melted water and thus causing water ingress around the

window. Neither the window nor the roof surface is designed to

resist this.

To avoid such problems, make sure that water can always

drain o from the bottom section and along the sides of the

window.

Banks of snow and ice should therefore be removed from the area

around the window in the same way as leaves and other debris

should be removed from ﬂashing and gutters to allow rainwater to

ﬂow freely.

Note! When installing windows in areas with severe weather condi-

tions, extra measures should be taken:

• Always include underfelt and ensure a tight connection to the

window. Rooﬁng materials are not designed to resist dammed up

water.

• Avoid thermal bridges by insulating carefully around the window.

• Pay extra attention to the vapour barrier to avoid moisture

penetration around the window.

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Velux GGU INTEGRA Uživatelský manuál Strana 109