Ductwork Fixing and Condensate Management

750 mm

MVHR ductwork must be securely fixed at appropriate intervals to prevent sagging, typically no more than 750mm apart, or as per manufacturer guidelines

MVHR ductwork must be securely fixed at appropriate intervals to prevent sagging, typically no more than 750mm apart, or as per manufacturer guidelines. Horizontal duct runs should be installed to a slight fall towards a condensate outfall to prevent water accumulation, while external wall penetrations must slope downwards to prevent water ingress. Ductwork should also be isolated from building elements to minimise noise transfer.

Basis in regulation

Part F
Approved Document F
Read the source

How to check it on site

Verify ductwork is securely fixed at correct intervals, horizontal runs fall correctly for drainage, and penetrations slope outwards; check for isolation from surfaces.

Common failure

Insufficient fixing causes sagging, leading to condensate traps and air pressure loss, while direct contact with surfaces can transmit noise.

Last updated 23 August 2026. This is our editorial summary of publicly available regulation, not building control approval or a warranty determination.

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