Sound transmission and ventilation
MALCOLM TAYLOR
| Posted in General Questions on
From a practical perspective the ideal ventilation system might be a fan (or HRV) connected by several very short runs to the rooms it serves.
Is there a point where the runs are too short and form a path for sound transmission between the rooms? Do the small ducts used by systems such as the Zender work better at preserving acoustical privacy? should the ducts be configured so they all enter the fan or core so that there is no shortcut for sound transmission?
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Replies
Malcolm,
Here is a quote from Zehnder:
“Supply and extract air ducts are fitted with attenuators to keep air distribution as quiet as possible.
Because each air vent is individually connected to the manifold, noise transmission from room to room is not possible.
This guarantees almost noiseless air distribution to the separate rooms.”
Thanks Steve. That answers one question fairly comprehensively. Most other HRVs and fans only have one input and outlet. I guess moving the junction of ducts as close as possible, rather than using a tree and branch approach would help, but that's just speculation on my part.
Malcolm: If you stand right under our ceiling mounted Zehnder HRV unit you can hear it, but there is no sound at all at the supply outlets.
Stephen,
i'm more concerned with the ducts creating a flanking path between rooms for household sounds to carry. I take it you don't see that in your place?
Malcolm: I don't, but all of the ducts are in a utility chase that extends the entire width of the building. None of them run in any room walls or ceilings.
Just a clarification for you, Malcolm, in the Zehnder system the supply and return 3" poly or fabric ducts are connected to supply and return acoustical manifolds that effectively attenuate the sound transmission from the entering ducts. The fabric ducts are also less likely to transmit sound than the smooth interior "Clinside" poly ducts. I have no detectable room to room sound transmission through the HRV ductwork. I used all Zehnder fabric ducts, manifolds and vent boxes, but mated that system effectively to a Broan (Venmar) ECM (Electronically Commutated Motor) HRV. ECM costs a bit more than the PSC motors, but uses far less electricity. Cheaper to run by far in the long run.
Thanks for the replies. I'd be interested in some thoughts on the non-Zendher systems which use conventional ducting that constitute the vast majority of installations.