Improving the durability of flat roof constructions

Flat roof constructions are mainly used on commercial, institutional and industrial buildings, where insulation is placed on top of the load-bearing deck and then covered with a roof membrane. Through time, there is a risk that the membrane will allow water passage as holes might form due to weathering effects or physical loads.

Water will then enter the insulation, and as a vapor retarder is normally found below the insulation thus trapping the water in the insulation, the leak can remain undetected for a long period. When the leak is finally discovered, the insulation has to be discharged as there is no easy method of drying it.

To be able to dry the insulation, and thereby regain the functional requirements of the roofing system, two new solutions for insulating flat roofs with existing materials are proposed for high density mineral wool and expanded polystyrene. Monitoring equipment are part of the system, thereby making it easier to detect leaks faster.

When a leak is detected, the membrane is repaired locally. In order to remove water which has already entered the insulation, an air gap or a system of air channels between the deck and the insulation is subjected to forced ventilation with outdoor air. When the water is removed, the ventilation is stopped, and the roofing construction can continue to function as intended.Roofing systems where trapped moisture can be removed are cost-effective compared to traditional roofing insulation systems, and as leakage can be treated, they have a longer life span reducing the overall cost.

Furthermore systems, where moisture can be removed, offer a high probability that the thermal conductivity remains at its designed value through the entire life of the roofing system. If the roofing membrane should fail, the insulation can be dried and the thermal conductivity will return to its original value instead of a much higher value found in traditionally insulated constructions.