Venting a Skillion Steel Roof
The ventilation of a low pitched roof is critical, commonly referred to as a flat roof, when it comes to the incidence of water precipitation during frost conditions (absence of natural air movement)
This is the reason why smoke pots are employed in vineyards an orchards around the world to create some movement however slight to offset the damage to pants and fruit as may occur when subjected to these conditions
Without air movement natural ventilation is not possible.
To avoid the occurrence of water precipitation to the underside of steel, glass in a building, the surface(s) need to be isolated from any air volume as may exist.
To illustrate the point using a case study consisting of a building of approx 100 s/m, rectangular in shape, walls well insulated with R2.5 and internally lined in cement fibre sheeting, situated in the Adelaide hills
The roof was of a steel cladding, pitched at 4 degrees, and flashings extremely well sealed
The ceiling lining, consisting of compressed wood and cement tiles was installed approx 150mm under the roof and R3 Insulation was located above the ceiling tiles.
A well insulated area by any standard…..nevertheless…. toward the end of every winter season the white ceiling tiles showed signs of discoloration due to presence of moisture
No matter what means were employed the only one remedy worked, when the roof was removed and foil was placed in direct contact with the underside of the roofing material….a simple foil vapour membrane.
In roof ventilation, and or with any situation, treating the symptom is never as successful as stopping the problem.
Whether insulation is used or not, the foil membrane, insulated or not, against the underside of the steel roofing is critical.