Condensation control for new homes
Condensation is defined as the process where water in the air transforms into liquid water when warm air comes into contact with a cold surface below the “dew point”. The dew point is a temperature which varies depending on the temperature and humidity of the warm air. A simple demonstration of this is the water droplets that form on the surface of a bottle of a cold drink on a hot day. The hot air hits the surface of the bottle which may be at around 6°C and the water in the air condensates on the bottle.
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Where condensation forms in your home
In an energy efficient airtight building with a conditioned internal environment, moisture is added to the air by the occupants who are showering, cooking and breathing (exhaled air has a relative humidity of 100%). This creates an internal environment with a higher vapour pressure than the outside environment which forces or ‘drives’ the water vapour in the air outward in every direction looking for equilibrium.
As this vapour ‘drive’ occurs and forces moisture toward the cold outer surfaces of the building structure, impermeable materials such as glass, steel, plastic and traditional aluminium sarking materials cannot allow it to escape. As a result, there is a risk that condensation can form on the inside of the building, just as mist or droplets of condensation form on the inside of a window on a cold night.
To minimise this risk, the Enviroseal membranes allow moisture to easily pass through the sarking with minimal resistance, allowing any condensation formation to occur on the outside of the building as shown in Figure 1.
