When spacing for MVHR ducts is tight, a combined intake-exhaust grille may be the solution

Building Regulations requires that an MVHR’s intake grille (bringing fresh air into the property) and the MVHR’s exhaust grille (exhausting air from the property) should be 1.5 metres apart from each other. This is to prevent the system from sucking in the warm, humid exhaust air back into the property, also known as “cross-contamination”.

The MVHR intake supply grille should also be two metres from the boiler flue, and far from the chimney, etc. It should also be at least 300mm from any windows – although noise from an MVHR isn’t normally significant given the very low airflow rates.

When space limitations cannot allow for a 1.5 metre gap between the MVHR intake and exhaust grille (especially in smaller properties), it is possible to use a specially-made combined intake-exhaust grille, such as a MAICO KWH, pictured:

MAICO KWH Combined Intake-Exhaust grille for MVHR systems

This diverts warm air up and away from the property, and allows cold supply air to be fed into the MVHR from below, preventing any possibility of cross-contamination of air supplies.

That means fresh, filtered cold air into the home, in a neat and tidy external grille that’s weatherproof and easy to clean.

Patrick

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