# Adjust an Air Cavity

An air cavity is the space between two layers in a building element, like walls, roofs or windows. While it might seem like just a gap, it plays a key role in how a building manages heat and moisture. That’s why air cavities are a critical part of building energy simulations.

How the cavity performs depends on how much air moves through it. The more ventilated it is, the less it helps with insulation. But increased airflow can be useful for reducing condensation risk. Getting the balance right is essential to maximise overall performance.

## Ventilation Strategy

To adjust an air cavity's ventilation level, hover over the air cavity material on the left-hand side of your screen. Click the material icon in the top-left corner. A dropdown menu will appear where you can choose the ventilation strategy, select from 'Unventilated', 'Slightly Ventilated' or 'Well Ventilated'.

<figure><img src="/files/yIILOqhfuDKviGUJT0Hk" alt=""><figcaption></figcaption></figure>

## Ventilation Exposure

Most ventilation strategies in wall systems assume that air enters from the external side. If that’s not the case, you can change the airflow direction using the 'Ventilation Exposure' setting. Simply switch it to 'To Internal' if the cavity is ventilated from the inside. Not sure which to choose? It’s best to leave it set to 'To External' by default for outer cavities past the water control layer amd 'To Internal' for inner cavities interior to the thermal control layer.&#x20;

<figure><img src="/files/jacXWFbODbaZngj2bRVq" alt=""><figcaption></figcaption></figure>


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