Soundproofing a heat-pump's external unit

[Garald]

As lots of people here already know, I am getting a heat-pump - and do not have much of a choice but to install it on a shared courtyard that, while long, is not very wide (about 4m on the narrower end). While the other owners are very receptive to the idea, I want to avoid future trouble (with the neighbors, and also for myself - the external unit will have to be close to my home-office/guest room downstairs) by getting one of the quieter heat-pumps, e.g., Saunier-Duval:

https://www.saunierduval.fr/france/download/genia-air-1/geniaset-split/saunier-duval-geniaset-split-brochure-gp-202103-2041667.pdf

or, less perfectionistically by a couple of decibels, https://www.hitachiaircon.com/uk/ranges/heating/yutaki-s-combi

Then I also want to put a sound-reduction box around the external unit. Look, for instance, at this heavy-duty device:

https://solflex.eu/en/hcsschalldaemmgehaeuse14db/?lang=2

- the manufacturer claims it (a) reduces noise by 14dB, (b) will not reduce the efficiency of an air-pump installed within.

 

Is this really possible? Is such an outcome likely? (The smallest model here would be suitable for the 7kW Saunier Duval; the Hitachi external unit is probably too small for this sound-reduction box - I'd have to find some other one.)

From the moment the air flow is being limited in anyway, I would imagine performance would be affected. Or is there no significant effect in this case?

 

[Moonshine]

It is perfectly feasible to put a ASHP in an acoustic enclosure and not have a detrimental effect on it performance, as long as the space outside isn't too tight. However it has significant cost implication.

 

One recent project I was looking at costings of the acoustic enclosure at around £4.5k.

 

There are plenty of acoustic enclosure manufacturers, just give them a call and tell them what unit you are putting in and they will be able to provide quotes at different levels of noise reduction 

 

For permitted development you need to limited the noise from the ASHP to 42 dB at the nearest boundary.

 

The unit you have selected is quiet but you describe the Location its going into as a tight space. You need to factor in noise reflections from hard services (the noise data presented in the data sheets don't include this.

[Bonner]

These look very bulky and expensive for something which should not be necessary IMO. A heat pump will be no more noisey than a passing car or the wind on a breezy day. In the summer, you might want to time it to come on at specific times to avoid disturbing people enjoying the courtyard. Suggest you plan to add one later if it really is a problem.

[nod]

1 hour ago, Bonner said:

These look very bulky and expensive for something which should not be necessary IMO. A heat pump will be no more noisey than a passing car or the wind on a breezy day. In the summer, you might want to time it to come on at specific times to avoid disturbing people enjoying the courtyard. Suggest you plan to add one later if it really is a problem.

Plus 1

 

Our friends have a Mitsubishi HP and noise was a big concern to them also As it’s virtually under the bedroom window But it’s no more noisy than our gas boiler 

[Ralph]

Have you actually stood beside a a unit while it's on? We live out in the country and it's very quiet so any noise is very noticeable. Our Daikin is supposed to run at 38 dBA and I never notice it and it's below our bedroom window. 
 

 

 

[Conor]

They are nowhere near as loud as you think. And it's a white/ continuous noise so not anyway annoting. Fit it as is, of there are issues down the line, then address them. 

Edited December 7, 2022 by Conor

[JamesPa]

MCS set out a methodology for calculating the noise level taking into account reflective surfaces, obstructed views etc and provide a spreadsheet which does it here https://mcscertified.com/wp-content/uploads/2021/04/MCS-Heat-Pump-Calculator-Version-1.10-locked.xlsm  The methodology and the meaning of the various terms is described here https://mcscertified.com/wp-content/uploads/2021/10/MCS-020.pdf

 

I suggest you start with this and put in the relevant factors.  When I did mine I found that it was better (and indeed necessary to meet the condition for permitted development) to move the unit nearer to the neighbouring property, but as a result away from a reflecting wall, than the position I had originally intended.

 

Note especially the difference between sound power level and sound pressure level, both of which are quoted in dB.  Manufacturers like to quote the latter, often at 5m or 3m distance without telling you the assumptions made) because its a lower figure.  Ignore it when comparing models or doing calculations as the figure can all too easily be manipulated by the marketing men (or women). 

 

You need to start with the sound power level (which is the total energy per unit time emitted in the form of sound from the unit).  This is not dependent on the location etc. and cannot easily be manipulated  From that figure you can (using the MCS spreadsheet) calculate a sound pressure level (which is the intensity experienced at a particular point in space) relevant to your particular circumstance.

 

MCS explains it quite well, its worth the read. 

[jack]

2 hours ago, Moonshine said:

For permitted development you need to limited the noise from the ASHP to 42 dB at the nearest boundary.

 

I seem to recall that OP is in France.

 

[Garald]

44 minutes ago, jack said:

 

I seem to recall that OP is in France.

 

 

Right - regulations are actually not so different, but one has to be careful; the acceptable value at someone's doorstep is defined in France in terms of what the ambient value would have been without the heat-pump - it should not exceed it by more than 5dB during the day and 3dB during the night. This is a quiet courtyard, at least when the kids in the neighbouring elementary school aren't having recess. Moreover, one can also be called to task if the legal level is not surpassed overall but is in fact surpassed in certain frequency bands.

 

As other people have pointed out, there are also echos in a small courtyard. Thank you very much for

46 minutes ago, JamesPa said:

MCS set out a methodology for calculating the noise level taking into account reflective surfaces, obstructed views etc and provide a spreadsheet which does it here https://mcscertified.com/wp-content/uploads/2021/04/MCS-Heat-Pump-Calculator-Version-1.10-locked.xlsm  The methodology and the meaning of the various terms is described here https://mcscertified.com/wp-content/uploads/2021/10/MCS-020.pdf

 

I suggest you start with this and put in the relevant factors.  When I did mine I found that it was better (and indeed necessary to meet the condition for permitted development) to move the unit nearer to the neighbouring property, but as a result away from a reflecting wall, than the position I had originally intended.

- I'll do this after teach class.

 

46 minutes ago, JamesPa said:

 

Note especially the difference between sound power level and sound pressure level, both of which are quoted in dB.  Manufacturers like to quote the latter, often at 5m or 3m distance without telling you the assumptions made) because its a lower figure.  Ignore it when comparing models or doing calculations as the figure can all too easily be manipulated by the marketing men (or women). 

 

Right; Saunier-Duval, in particular, seems to sell a good product a little too eagerly.

Even if you go by their estimates, if we need to get the 10kW model (the next one down is 7kW, which could be very tight, considering the unit also needs to produce DHW - the heating needs are around 6kW), then we are at 43dB at 3 meters (without counting the echo). So, we are not really talking *whether* to have some soundproofing, but *what* kind of soundproofing to have - something that reduces the noise by 5dB (say), costs hundreds, is relatively slim and improves the unit's appearance while also protecting it, or something that reduces the noise by 14dB, costs 2000eur+installation costs (optimistically speaking) and is bulky and ugly. Or something in between.

 

 

Here is the floorplan. Courette = little courtyard, R+1+C = place where I live (a GP occupies most of the ground-floor, and I now own the rest; the heat-pump would be in front of my main staircase, close to the room that will be my guest-room/girlfriend's home office/in-law apartment that can hypothetically be rented out but will probably be mainly used for my actual parents; other people live in the building labelled RDC+C. The total width of the courtyard is a bit under 4m at its narrowest point, if I remember correctly.

 

Edited December 7, 2022 by Garald

[Garald]

On 07/12/2022 at 07:47, Moonshine said:

There are plenty of acoustic enclosure manufacturers, just give them a call and tell them what unit you are putting in and they will be able to provide quotes at different levels of noise reduction 

 

Can you recommend some?

 

[Garald]

(If I can get one that looks like a handsome wooden rubbish bin, that would be ideal. There's actually rubbish bins right around where the unit will be located, and I'm thinking of providing some wooden camouflage for them as a visual favor to myself and others.)

[Garald]

Additional reason for getting an enclosure: what if someone feels like playing football in that courtyard?

[SteamyTea]

5 hours ago, Garald said:

Additional reason for getting an enclosure: what if someone feels like playing football in that courtyard?

They are perfect for putting bicycles against.

And every Frenchman has at least 2.

 

[TonyT]

Your handsome bin cover over your external unit will no doubt block air flow.

 

Spray the covers to match the surrounding and leave at that 

[Bob77]

I was worried our Daikin outdoor unit might be noisy but unless you stand right next to it you can't even hear it. It's mounted on the front of the house under the kitchen window. When it's very quiet in the house you can just about here a tiny bit of vibration coming through the house wall when you are indoors and it is running full tilt, but outdoors the only noise really is a slight air movement.

[Garald]

2 hours ago, TonyT said:

Your handsome bin cover over your external unit will no doubt block air flow.

Right, if I made it myself. Does nobody (competent) make one?

[Moonshine]

10 hours ago, Garald said:

Can you recommend some?

 

Not a specific one but....

 

http://eec.co.uk/

https://www.environ.co.uk/

https://caice.co.uk/

https://www.soundplanning.co.uk/acoustic-enclosures/

https://acousticenclosuresltd.co.uk/

[Garald]

4 hours ago, Moonshine said:

 

Not a specific one but....

 

http://eec.co.uk/

https://www.environ.co.uk/

https://caice.co.uk/

https://www.soundplanning.co.uk/acoustic-enclosures/

https://acousticenclosuresltd.co.uk/

PS. Some sources in France or at least in the continent would be helpful (unless these deliver, but then there's also customs).

[Moonshine]

37 minutes ago, Garald said:

PS. Some sources in France or at least in the continent would be helpful (unless these deliver, but then there's also customs).

 

i don't work in France so don't know but i am sure www.google.fr will help.

[Garald]

22 minutes ago, Moonshine said:

 

i don't work in France so don't know but i am sure www.google.fr will help.

I have tried. The Dalek influence is surprisingly strong on this side.