ᐅ Is the fresh air intake or the exhaust air louder in a mechanical ventilation system?

Hello,

can you tell me if the supply air or the exhaust air is louder at the outdoor ventilation grilles? There must be differences.

Best regards
Sabine

At the same distance from the ventilation unit and with the same size of the ventilation grilles, the exhaust air is generally louder outside, partly caused by flow separation at the edges of the ventilation grilles.
With very short ventilation ducts, the humming of the fans can also be heard outside on the supply air side, because the silencers are only installed on the interior side of the building.
The noise level can be transferred and amplified on the building structure depending on the type of duct material used and how the ducts are fastened.

AOLNCM schrieb:

With very short ventilation ducts, you can also hear the fan humming on the supply air from outside because the silencers are only installed on the interior side of the house.

Is there a recommendation on the minimum length the ventilation duct should have?

Best regards
Sabine

It largely depends on the design of the system... my fresh air intake is 50cm (20 inches) long and practically silent outside even at the highest setting...

Exhaust air, on the other hand, is always audible... in this case, it is due to the airflow noise caused by the grilles mentioned.