It is resistance of a material to the UV radiation. The factor is one of the key ones that decide about a roof membrane lifetime on the grounds of polymers used in the production process, which are sensitive to UV radiation.

The additives increasing the material resistance to UV radiation minimise the consequences of UV reaction. Nevertheless, excessively long exposing of a material without roof covering, so its constant exposure lead to its significant weakness or limit the product’s lifetime. The lack of stabilising substances might bring such consequences as physical degradation or quicker decrease of a roof membrane technical qualities.

In dependence of the exposure time and the radiation intensity, it is recommended to install the final roof covering on a roof in the time, not longer than 6 weeks from the moment of a roof membrane installation. Due to the additives applied, responsible for the UV resistance enhancement, it is a period which does not have any meaningful impact on the way of a product use value decline.

The UV radiation influence on the roof membranes are divided on the direct ones which have an impact on a membrane while installing it on a roof and the indirect ones that influence a membrane, e.g. as a result of the radiation’s penetration on an attic through roof windows, roof hatch or slits in the load-bearing structure of a roof covering. Therefore, it is important to enable the influence of daylight effect on a roof membrane through its complete covering or an attic obscuring. Otherwise, the penetrated UV radiation will effect the exposed roof membrane, then its influence can lead to physical changes in the material structure.