The success to an inaudible MVHR system lies in a well engineered MVHR units, a good design and sufficient attenuates or otherwise called silencers.
Target values for bedrooms and habitable rooms are 20 dB(A) (A-weighted noise pressure level of the unit) and 35 dB(A) for the installation room.
We recommend for every project to have sufficient silencers at the supply and extract outlet of the MVHR unit installed. Silencers at the exhaust and sometimes the intake are at times necessary when the surrounding area is very noisy or sensible to noise.
Depending on the kind of ducting, we also recommend cross-talk silencers between the bedrooms, study and other rooms which need to be extra quiet. Due to the nature of semi-flexible systems, where all ducts come together in distribution boxes, these cross-talk silencers are normally not necessary.
What does the dB(A) mean?
| dB(A) | Sound | Example |
| 10 | Almost inaudible | Breathing, a pin dropping |
| 15 | A whisper at 2m distance | |
| 20 | Faint Audible | Quiet natural area with no wind, rustling of autumn leaves |
| 25 | Breathing at 1m distance | |
| 30 | Very quiet | Whispering |
| 35 | Very quiet room fan at low speed at 1 m distance | |
| 40 | Distraction when learning possible | Living room, quiet class room |
| 45 | Noise of normal living or radio in the background | |
| 50 | Audible | Conversation at home, refrigerator working |
| 60 | Conversation at 1m distance, e.g. in restaurant | |
| 70 | Irritating | TV set on loud, vacuum cleaner |
| 80 | Unpleasant | Dishwasher |
What does the dB(A) values for attenuators mean?
| dB drop | Reduction in noise | How much noise passes through |
| 1 dB | 21% | 79% |
| 3 dB | 50% | 50% |
| 6 dB | 75% | 25% |
| 9 dB | 87.5% | 12.5% |
| 10 dB | 90% | 10% |
| 15 dB | 96.9% | 3.1% |
| 20 dB | 99% | 1% |
| 30 dB | 99.9% | 0.1% |
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Sustainable Homes Scotland Ltd
t/a PAUL Heat Recovery
Unit D, Pitreavie Business Park
Pitreavie Crescent, Dunfermline
KY11 8PU Scotland
Registered in Scotland – CRN: SC331209
Directors: Stefan Huber, Allan McEwan, Garrie Glasgow
