Wet insulation in flat roofs: what should you do?

wet insulation


Have you detected that the insulation beneath the flat roof of your home has become damp? Then it’s best to sort it out as quickly as possible. Wet insulation makes homes damper, leading to uninhibited mould growth. Fortunately, you can solve this and even prevent it.

What causes wet insulation?

If you detect that the insulation in your home is wet, it is crucial to find out where it comes from. There are two ways moisture problems can occur in flat roofs: by infiltration or condensation. (Of course, the insulation can also get wet before it is laid, but this can easily be avoided if the material is properly stored).
The first thing to always check is the recent weather. Condensation problems primarily occur during hot or cold spells, not rainy weather. If there is a leak or if the vapour barrier has not been properly fitted, the warm indoor air comes into contact with the cold surface of the waterproofing. Then the water vapour turns to water again, condensation forms against the waterproofing, and the insulation gets wet.
Infiltration problems occur when it rains, due to gaps in the roof structure. Then there’s only one thing to do: check all possible infiltration routes. Visual inspections and measuring the moisture can help you detect the source of the moisture.

Do you need to replace wet insulation?

Most insulation will lose its insulating capacity if it gets wet. That’s why it is essential to replace the material if it cannot dry sufficiently. If you do manage to get the insulation layer completely dry, then you don’t need to replace it.

How can you prevent wet insulation?

Of course, ‘prevention is better than cure’ is also the rule here. As such, make sure you have a well-installed vapour barrier. This layer of foil protects the insulation against moisture. Make sure that the vapour barrier is airtight and that there is an overlap of about ten centimetres between the different strips. For underneath the vapour barrier, it is best to choose an insulation material such as XPS. Not only is this material moisture-resistant and rot-proof, but also pressure-resistant and dimensionally stable.

Would you like more information about XPS insulation or our vapour barriers? Then don’t hesitate to contact us. We will be happy to help, with no obligation.