External Ducts fall away from MVHR - mitigating mould risk

[sheeners]

Hi 

 

our MVHR unit will be in a tight space where external ducting for exhaust and fresh air intake need to dip down below a rafter before reaching the roof vent. I've read that the fall of the ducting should be towards to unit so that any condensation can run through the unit drain. That's not going to be possible.

 

It's a warm loft and I'm planning on insulating the pipes. Possibly also have an enthalpy exchanger.

 

Question: what is the condensation risk inside the external ducts and what mitigation options do I have? I have read about inline drainage in the ducting at the lowest point. However, I cannot find any such material to buy. 

 

Thank you for sharing your thoughts.

 

Edited 5 hours ago by sheeners

[markc]

Generally you don’t want any “pooling” points in ductwork, but if air is always moving then any condensation that does form should be quickly moved as it evaporates again.

[JohnMo]

If you read the manufacturers instructions, they will mist likely tell you to add a condensate drain at any low points. If not I pretty sure building regs will.

 

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