Kingspan Insulation has introduced a new guide that provides better understanding of building fabric condensation and its damaging consequences.

The new Kingspan Insulation guide addresses the growing concern in the Australian building industry that improving the energy performance of new buildings may also lead to structural damage from rot or corrosion arising out of increased condensation if appropriate considerations to insulation are not made.

With the nationwide focus on energy efficiency, buildings are increasing airtightness and insulation but also risking potentially destructive condensation, according to Kingspan Insulation. A world leader in thermal insulation innovation, Kingspan Insulation manufactures both ultra-thin flexible insulation and high performance rigid insulation products.

For better understanding within the building industry, Kingspan Insulation has developed a guide to clarify building fabric condensation, also known as interstitial condensation, and to offer management recommendations.

Most building materials have some water permeability and a difference in water vapour pressure on either side of the structure will draw vapour through. Rot, corrosion or mould from persistent condensation can cause structural damage.

Buildings in Australia’s coolest and most warm/humid zones face maximum risk from these conditions. In Tasmania and alpine regions, vapour from inside a building may cause condensation inside cladding, while condensation is most likely to happen on the back of plasterboard in far north Queensland and the Northern Territory.

To manage moisture and minimise condensation it’s necessary to lower water vapour pressure within the building fabric cavities using ventilation or restricting moisture entrance, or both.

Kingspan Insulation’s guide recommends sealing building fabric gaps on the warmer side to limit air movement into the structure. Additionally, high vapour resistant/low thermal resistant materials should be used on the warm side, with low vapour resistant/high thermal resistant materials or ventilated cavities on the cold side.

Where condensation is predicted to be harmful, moisture should be limited from reaching the colder elements of the building structure by using layers to control or resist vapour or by including a ventilated air space between the insulation and outer elements.

Generally vapour barriers should be used on a structure’s warm side, behind the plasterboard lining in a cold climate or behind the cladding in a warm climate. Vapour permeable membranes are used to lower vapour pressure build-up within cavities and to allow the vapour to pass through to spaces where it can condense and drain harmlessly to the outside of the building. Vapour pressure within building cavities can also be effectively managed through appropriate ventilation.

Interstitial condensation can also be controlled through surface temperature management within the structure by distributing insulation to minimise temperature change. For example, using roof as well as ceiling insulation will help prevent condensation under the roof. 

In cold climates, controlling a building’s internal humidity will limit the movement of vapour from living spaces into the structural fabric, reducing the risk of interstitial condensation. With a trend to more airtight buildings, air-conditioning or living area ventilation will reduce internal vapour pressure.