Vibration and sound dampening for bath fans and spot ERV’s
Kail_Z
| Posted in Mechanicals on
After receiving sound advice on this forum I have decided to run all insulated galvanized steel duct for my bath fans and spot ERV’s in the house I’m trying to build. I have read that installers like to use a small portion of flex to mitigate vibration noise in the metal duct. I really don’t want to run plastic flex duct for durability reasons, we are in the country and rodents are always a issue. can something else be used to limit vibration noise.? Is there any kind of coupler available for this? Thanks for any advice you might have?
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Replies
I think fantech makes silencers for various size ducts. I have not used one so I have no idea as to the effectiveness but it may be worth a look.
Kail, the key part of "a short portion of flex" when used as an acoustic decoupler is "short". Unless your place is crawling with rats (which I doubt), I'd stay with the standard recommendation. If you're feeding registers from ducts in a vented crawlspace open to vermin, you might have your HVAC contractor position the flex in a joist bay so any plastic components can be protected with cheap-and-cheerful sheetmetal blocking. But if you are worried about rodents eating flex duct, you should also worry about them eating insulation, wiring and plastic piping.
However, if short flex duct segments still seem unsuitable to you, consider using 1" insulation on the interior of sheetmetal ducts. Manville's Lincoustic insulation (and quite a few similar competing products) has excellent NRC properties you will not get from duct exterior insulation.
One other option is to have your ducts fabricated from rigid fiberglass duct board, which has good acoustic properties and is substantially self-insulating.