Building physics

Condensation of vapour against the backside of a zinc-titanium construction, for example against the backside of roof- or facadebays and gutters, can cause serious corrosion if certain conditions are not met. Thus it must be ensured that the backside of the zinc surface is ventilated sufficient if no measurements are taken to prevent condensation.

For non-insulated roofs it is sufficient to support the zinc with a wooden roof deck, consisting of rafters and timber boarding. The boarding is placed with 5 mm gap between them. To decrease the capillary sensitive contact with the board, these can best be applied unplaned. If, however, for example a plywood decking is used to support the zinc covering, a layer of natural glass fibre is advised between the plywood and the zinc to prevent corrosion.

For insulated roofs and facades the risk of internal condensation is even bigger, because the difference between temperature internal and external is on average larger than for non-insulated constructions. To prevent condensation in these cases a vapour barrier in combination with a ventilated cavity is necessary.

When a warm roof construction is chosen, i.e. an insulated construction without ventilated cavity, a Puren-M insulation system can be used for a quick and easy application. This so called 100% vapour tight system will prevent condensation problems.