ASHP noise assessment

Here is the graphical output from our noise modelling software for the 1st of these (multiple) ASHPs.
This is based on the noise level we measured on Friday just gone, which was 50dBA @ 1m (just off-axis so as to avoid turbulent air noise).
The resulting level at the nearest neighbour is 32.5dBA, they will of course have their own ASHP unit which will be noisier than this.
The noise limit that MCC have imposed here is effectively 31dBA at night, even though that would effectively be “unmeasurable”. Hence this situation exceeds the MCC target in this instance by 1.5dB.
So we are seeking clarification from MCC to see what exactly is meant by their noise limits and what to do to comply with them.

I got this from our assessment which would imply MCC are making up their own standards?
“Background noise level. For the purposes of the
MCS Planning Standard for air source heat pumps 40 dB(A) the background noise level is assumed to be 40 dB(A)”

I think the council can ignore national guidelines if they want but they have to be able to justify them in court if an aggrieved party decides that they want to contest it. What they can’t do is claim that their version is the national standard, so they can’t claim that their own rules are MCS or a version of MCS.

@Jonathan_Keenan @Tim_Gilbert
Information for developers | Manchester City Council
The council (like several other local planning authorities) have their own planning and noise advice / conditions. In this case they are largely basing their guidance on BS4142 " Methods for rating and assessing industrial and commercial sound". So when an ASHP cannot be assessed under the MCS / permitted development rights then it will fall under local planning application rules. Yes conditions such as these can be appealed but as I understand it that would be an expensive process for a householder to do.
NB I am not saying that the current MCC planning and noise guidance is fully appropriate. Rather I am just saying that is the current state of play with this in Manchester and quite a few other local authority areas.

It isn’t realistic for a householder to go to court. It is more a tool for developers or landlords of multiple dwellings.

OK this is just weird.
I live in Manchester as well, and on enquiry to eeh planning office was sent a detailed list of when a ASHP fell under permitted development and NOWHERE did it say anything about noise levels. I queried this and was told categorically that noise levels were not part of it. The main requirement is that it is not within 1m of the boundary. MCS have rules about noise levels from ASHPs, But Manchester planning tell me they do not…

That is extremely odd. Octopus advised me to apply for planning as their MCS 020 assessment resulted in a ‘fail’ so requiring permission. I assume the MCS 020 is based on national not local permitted development rules. Once planning permission was requested MCC seem to be applying noise level limits, perhaps because they can once permission is applied for?
That would be a strange approach but wouldn’t entirely surprise me.

The solution may be to withdraw your application and stick to the permitted development rules as closely as possible.

Your new neighbours, if they ever move in, can’t really complain about noise that existed before they moved in.

Edit: Your proposed heat pump is for heating only, so when working hardest your neighbours would have the windows closed most of the time and when they ventilate in summer your heat pump will be silent. Planning rules don’t take such simple facts into account.

Here is vebatim the text of the email I was sent:


Further to our conversation, the installation of an air source heat pumps on domestic premises is permitted development, not requiring planning permission provided that:

-The development would result in the presence of more than 1 air source heat pump on the same building or within the curtilage of the building;

-In the case of the installation of an air source heat pump, a wind turbine is installed on the same building or within the curtilage of the dwellinghouse;

-In the case of the installation of an air source heat pump, a stand-alone wind turbine is installed within the curtilage of the dwellinghouse;

-The volume of the air source heat pump’s outdoor compressor unit (including any housing) would exceed 0.6 cubic metres;

-Any part of the air source heat pump would be installed within 1 metre of the boundary of the curtilage of the dwellinghouse;

-The air source heat pump would be installed on a pitched roof;

-The air source heat pump would be installed on a flat roof where it would be within 1 metre of the external edge of that roof;

-In the case of land within a conservation area the air source heat pump— (i) would be installed on a wall or a roof which fronts a highway; or (ii) would be installed so that it is nearer to any highway which bounds the curtilage than the part of the dwellinghouse or block of flats which is nearest to that highway;

-The air source heat pump would be installed on any part of that wall which is above the level of the ground floor storey.

Development is permitted subject to the following conditions— (a) the air source heat pump is used solely for heating purposes; (b) the air source heat pump is, so far as practicable, sited so as to minimise its effect on the external appearance of the building; (c) the air source heat pump is, so far as practicable, sited so as to minimise its effect on the amenity of the area; and (d) the air source heat pump is removed as soon as reasonably practicable when no longer needed.

I trust this is of assistance."

I then replied:
"Thank you so much for this detailed response.

Reading this, there is no statement about proximity to a neighbour’s windows (other than the 1m from a boundary statement) or anything about noise levels (not that I intend to get a noisy heat pump!!), both of which I have read on the internet as issues. So am I correct in assuming that neither of these are planning issues or anything else?

Thank you,"

And got the reply:
“That’s correct. There is no requirement in relation to neighbouring windows, other than the 1 metre distance to the common boundary.”

This seems to be at complete odds with what you have been told.
I can only think of 2 possible explanations:
(a) if the ASHP falls within the permitted development then they can say nothing about noise, but if it needs planning permission then they can and do OR
(b) at least one of the people we have been in contact with does not know their own department’s regulations…

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Thanks. This is very interesting. Could you say when this correspondence took place (in case the rules have since changed)?
My current thinking is to withdraw the application as it would seem to me that we fall within permitted development. We come close to, but within the 1m rule.

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Hi Jonathan,
It was on the 13th March this year (ie 3 weeks ago). The first thing the guy said to me was “Let me get back to you as the regs have very recently changed” and half an hour later sent me what I quoted above. I kind of assumed that it was national regs but I suppose they could be local Manchester regs.
Note also that whatever Manchester say, the noise calcs are a requirement from MCS. If you fail those then no reputable installer will install a heat pump there, you won’t get MCS accreditation and hence you won’t get the government £7,500 grant…

Ah. There’s the problem then. Mine fails the MCS by 3db (or 1db if I put in the correct distance to the neighbours window). I can do under permitted development but the MCS says I need planning which planning have made far too expensive to contemplate. I need MCS as I cannot do the instal without the grant. Catch 22

I’ve looked at MCC planning page on their web site and it just point to the national planning portal. This reflects everything you wrote with the addition of the need to comply with NCS which is the catch all.
I’m looking at adding a small 0.3m tall fence to the top of the boundary wall placing the ASHP out of line of sight which would gain me 10db on the NCS and result in a pass for permitted development. Not sure if/how that would do the job…

Any structure would do. And then remove it after the HP is fitted.

Yep, I was thinking of whatever would be the simplest and cheapest option as it just has to hide the unit from the nearest window to get the desired reduction in db.

OK we seem to have bottomed this :grinning:

Planning permission isn’t the issue - it is meeting the MCS noise requirement. Either you need to find some way of meeting that where the unit is or you need to site the heat pump somewhere different. Once you solve that problem, then all the planning issues should go away as it will be under permitted development.

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Or as previously suggested, get a quieter unit.

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I tried my own MCS for various options and for the size unit they have calculated there isn’t one quiet enough. If I recalculate the heat loss (I tried rule of thumb and Heatpunk) to what is possibly a more realistic smaller ASHP it is still not enough to get past the MCS and I don’t want to go too far as ours is a fairly big house. I’m waiting to see is Octopus will proceed on the basis that I put up the fence to sneak the whole thing into permitted development.

I certainly think it’s worth finding a smaller unit. I’m surprised there isn’t one that meets MCS requirements.

An alternative to a superstructure to the wall is to build a baffle next to the heat pump. The baffle could be something useful, like a garden storage box.