Close Sub-floor Airbricks

Background: Sub-floor air vents are integral to maintaining the health of a building’s structure, primarily by mitigating risks associated with moisture, such as rot and condensation. These vents are strategically placed above the damp proof course in sub-floor areas or cellars. Their primary function is to ensure adequate air circulation, which helps in preventing moisture build-up that could otherwise go unnoticed, particularly in the event of leaks or similar water ingress.

However, these vents can also be a source of significant heat loss within a property. In the pursuit of energy efficiency and environmental friendliness, an alternative approach has been developed. This involves the temporary sealing of these air bricks, for instance, using products like rubberised flood protection devices (e.g., FloodKit Airbrick Plate, available at FloodKit), and monitoring sub-floor relative humidity.

The key to this method’s effectiveness lies in the careful monitoring of the relative humidity (%RH) in the sub-floor area near these closed vents. If the RH consistently exceeds 85% over an extended period, this could indicate an underlying leak or moisture problem, necessitating further investigation and potentially reopening the air bricks to restore ventilation.

Closing sub-floor air bricks can markedly reduce heat loss, making it an attractive option for energy conservation. However, it is crucial to balance this benefit against the potential risks of unmonitored moisture accumulation. Regular weekly checks of the sub-floor humidity are recommended. In scenarios where such monitoring is not feasible – for example, during extended absences from the property – it is advisable to reopen the vents to ensure ongoing air circulation and moisture control. Also open the air vents up in summer, when heat loss is not a consideration.

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