Condensation in external walls.

Despite energy efficiency in buildings advancing significantly and providing huge benefits for a sustainable future, it has also come with its challenges, especially concerning condensation within external walls. Homeowners and industry professionals are all too familiar with the unpleasant surprise of internal dampness, peeling paint or worse yet, the emergence of mould – a narrative far from the dream home or perfectly executed architectural project.

To understand why this occurs we need to understand what the causes are and strategies to prevent them. Condensation occurs when humid air contacts a cooler surface, transforming moisture in the air into water droplets. In the context of external walls, the humid internal air comes in contact with the cooler surface of the cladding and causes condensation to form on the back surface of the cladding.

In older homes without insulation, there is plenty of air circulating within the wall to carry the moisture away and stop it from creating issues. As insulation has been added to create more consistent internal temperatures, this has created a problem where the water cannot move or dry out, so it pools on the structure and slowly rots the timber and also forms mould within the wall. As we can see in the below diagram.

However, through knowledge and understanding there always comes solutions, and vented cavities within external walls offer a promising answer to this ever-present issue.

A ventilated cavity acts as a breathing space between the external cladding and the inner elements of a wall. This small expanse allows for continuous air flow, which carries moisture away before it settles and creates problems. Think of it like a shield—and a rather intelligent one—defending interior spaces from the relentless humidity assault. In the below diagram we can see the benefits the cavity provides and space where moisture can be carried away.

Here's why a ventilated cavity can be particularly effective:

Improved Airflow: Deliberate gaps at the top and bottom of walls create convection currents, fostering an environment where air circulates naturally.

Moisture Escape Route: Instead of trapping moisture, the cavity provides a passageway for it to exit, keeping the internal wall dry.

Enhanced Insulation Efficiency: By maintaining a drier environment, insulation performance is optimized since wet insulation loses thermal resistance.

This trifecta of benefits shows that ventilated cavities not only tackle the symptoms of condensation but gets right to the heart of moisture management.

Wall condensation is no minor inconvenience; it's a risk to both the longevity of Australia’s homes and the well-being of their inhabitants. As the evidence stacks up, the case for ventilated cavities becomes irrefutable. They’re more than just a preventative measure—they're an integral feature of forward-thinking design, echoing the importance of adaptability in modern architecture and construction.

Sap Architecture includes wall details in all of our projects and always detail a ventilated cavity to alleviate condensation issues. Speak to your builder, designer, or architect to confirm if this approach is being adopted to ensure your home is being built to last and provides the healthy living environment that should be expected.