Author Topic: STC-61 soundproof enclosure for tankless water heaters  (Read 3876 times)


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STC-61 soundproof enclosure for tankless water heaters
« on: February 21, 2009, 04:57:08 PM »
I'm considering the purchase of some tankless hot water heaters for a remodel project, but the added noise versus tanked is making me hesitate.  One of the applications would be for hydronic heating, and so I'm concerned about the noise that would be emitted at night, causing sleep disturbance.  However, if I can solve the noise issue, tankless would offer advantages for my situation. 

To keep this simple, I'll assume the tankless units are zero clearance closed combustion.  So, the main sorce of noise is the ignition sequence at startup plus the blower motor noise whenever the units are operating. 

I looked at the three wall generator enclosure design that's posted as a generic solution on this website, but a tankless water heater has:
1.  Air intake and exhaust pipes that need to be routed through the roof.  These can conduct noise.
2.  The water pipes themselves could conduct noise.

Does it matter?  I don't want to go to the bother of making a soundproof enclosure if it's defeated by something as obvious as this.

The ideal place to put the tankless units would be in a wood framed attic.  Can it be sufficiently sound isolated there, or would I be hugely better off from kicking it downstairs and mounting it on/in a structure in the garage?

In the extreme--and I'll admit it seems extreme, even to me--I'm prepared to build a drystacked enclosure outdoors, "just to be sure".  I say "just to be sure", because the combined cost of later redoing a failed attempt will be significantly more than just doing it right the first time.  For a "just to be sure" drystacked outdoor enclosure, Endura Block offers STC-61, which is the best I've found.  If it works as advertised, I expect it would also be "good enough".  I would put the outdoor enclosure on its own isolated concrete slab.  Then, the only point of contact would be the water pipes running in and out of the house.  For this scenario, what should the roof of the enclosure be?  I don't think I can use drystacked for that, although I could possibly use IFC.  Is there anything better/cheaper I should consider for the roof of the enclosure?  No sense in building great walls if the sound will just pour out of the roof. 

Lastly, I assume PEX would transfer less noise than copper?  Would it make any difference?

I welcome any advice.