JohnMo Posted December 30, 2022 Share Posted December 30, 2022 The other tack would be go direct to your MP, if that fails direct to the press and social media. State the clauses are impossible to reach and effectively your local council is banning ASHPs, then state all the environmental reason why the government says we must all install heat pumps to save the planet. Name and shame the council. 1 Link to comment Share on other sites More sharing options...
JamesPa Posted December 30, 2022 Author Share Posted December 30, 2022 29 minutes ago, JohnMo said: The other tack would be go direct to your MP, if that fails direct to the press and social media. Good idea in principle, but one I'm sure won't work. The LPA is pretty insulated against external criticism. To be honest it has to be given the government imposed housing targets which it has to uphold against fierce, repeated and loud criticism from the local nimbys. Unfortunately our LPA has severe trouble recruiting planners because they can't afford to pay enough. Most of the staff are therefore quite junior and I thus doubt that they understand this area well enough to make an informed holistic judgement. Link to comment Share on other sites More sharing options...
Alan Ambrose Posted December 30, 2022 Share Posted December 30, 2022 (edited) >>> The rating level of noise emitted from the air source heat pump (ASHP) system hereby approved shall not exceed 10dB below the existing background noise level as measured or calculated at 1 metre from the façade of the nearest noise sensitive property. The measurement and assessment shall be made according to BS 4142:2014+A1:2019 'Methods for rating and assessing industrial and commercial sound' at the nearest and / or most affected noise sensitive premises, with the ASHP system operating at maximum capacity and be inclusive of any penalty for tonal, impulsive or other distinctive acoustic characteristics. I'm not so sure it wouldn't pass the regs they have cited. It should be easy for an acoustics person to figure out from: + the actual noise of the unit (which should be in the manufacturer's spec).. + the actual level of background noise. + the distance to the neighbour's place. + any intermediate barriers. Or you can just try putting a fake noise source with the right noise level in the right place (maybe a phone with a recording with or without a USB speaker) and hotfooting it over to the neighbour's place with (in the first instance) a phone app or a cheap dB meter. Then measure the noise level with and without the noise source on. Voila, a first cut estimate. That'll tell you whether you're easily within / way over / or on the borderline. While you're at it you can even ask the neighbours to do a mark one earhole test. If they're not happy, you can chat about noise screening measures. Some more facts would be useful e.g. the answers to the points above. Edited December 30, 2022 by Alan Ambrose Link to comment Share on other sites More sharing options...
JohnMo Posted December 30, 2022 Share Posted December 30, 2022 Re reading this, they have given permission to install with a noise clause. Have they actually asked you to demonstrate that you comply with the clause, or is it accepted, if you install you comply? If you don't have to demonstrate or prove anything, and really they need to ask for that explicitly, just install. Then take it the clause is the council just playing, let's cover our arse, just in case there are complaints. Link to comment Share on other sites More sharing options...
Temp Posted December 30, 2022 Share Posted December 30, 2022 20 hours ago, JamesPa said: It's a retrofit so, in extremis, I could go for meeting the conditions for deemed consent, but then I have to pay the MCS premium and (ironically) install the louder and uglier of the two alternative units I am considering. In that case perhaps you can appeal that the condition doesn't meet the 6 tests in the NPPF. Necessary, reasonable etc It might be worth telling the planners you could install one under deemed consent and see if they will amend the condition to the 42db test in MCS020 to avoid the cost of an appeal. Link to comment Share on other sites More sharing options...
JamesPa Posted December 30, 2022 Author Share Posted December 30, 2022 2 hours ago, Alan Ambrose said: the actual noise of the unit (which should be in the manufacturer's spec).. + the actual level of background noise. + the distance to the neighbour's place. + any intermediate barriers. 59dbA (or 60dBA if I go for the MCS option): Mitsubishi 11.2kW or Samsung 12kW (the new 'quiet' one) 30- 35dbA 6m to the neighbours wall, 7m to the nearest window none respectively. 1 reflective surface within 1m Meets MCS specs (roughly speaking 3dB below an assumed ambient of 40dbA) but not LPA spec (25 dBA ie 10 dB below actual ambient) Would need another 12-17dB attenuation plus to meet the LPA specs. No chance. 1 hour ago, Temp said: 1 Link to comment Share on other sites More sharing options...
JamesPa Posted December 30, 2022 Author Share Posted December 30, 2022 1 hour ago, Temp said: 21 hours ago, JamesPa said: It's a retrofit so, in extremis, I could go for meeting the conditions for deemed consent, but then I have to pay the MCS premium and (ironically) install the louder and uglier of the two alternative units I am considering. In that case perhaps you can appeal that the condition doesn't 1 hour ago, Temp said: In that case perhaps you can appeal that the condition doesn't meet the 6 tests in the NPPF. Necessary, reasonable etc It might be worth telling the planners you could install one under deemed consent and see if they will amend the condition to the 42db test in MCS020 to avoid the cost of an appeal. I think that's pretty much my plan! Link to comment Share on other sites More sharing options...
JamesPa Posted December 30, 2022 Author Share Posted December 30, 2022 2 hours ago, JohnMo said: Re reading this, they have given permission to install with a noise clause. Have they actually asked you to demonstrate that you comply with the clause, or is it accepted, if you install you comply? If you don't have to demonstrate or prove anything, and really they need to ask for that explicitly, just install. Then take it the clause is the council just playing, let's cover our arse, just in case there are complaints. I think you are spot on with the arse covering. Problem is, once it's it it's in and is a lot of hassle to remove if anyone did complain (at which point council would be forced to take enforcement action). Link to comment Share on other sites More sharing options...
JamesPa Posted December 31, 2022 Author Share Posted December 31, 2022 Just a note to thank everyone who has responded to my planning consent issue. Its given me lots of ammunition to fight the LPA. Today it was windy and the traffic was busy. Background noise (measured on my phone, so not very accurate) was 47dBA. 10dB below that, as currently required by my LPA, is achievable, about the same as MCS in fact. On a quiet windless day a few weeks ago, measured with the same phone, the background noise was 35dBA. Both are likely to be inaccurate, but the difference is probably quite accurate which frankly makes a mockery of specifying (as the LPA has) that the noise from the heat pump should be 10dB below background. It also makes me wonder if noise consultants working for developers deliberately pick noisy times of day/noisy days to make measurements (why wouldn't you?). Hopefully the LPA will see sense when I feed them some of the pitfalls. I fear, however, they may be reluctant to back down and its headed for an appeal, or caving into installing having an MCS registered installer install the noisier and uglier of the two possible options so I can get it in under permitted development. Either way thanks for the ideas! Link to comment Share on other sites More sharing options...
Temp Posted December 31, 2022 Share Posted December 31, 2022 Normally the background is averaged over a long period. I would suggest a week minimum. For bigger developments a month or more. I was involved with a wind farm planning application and they had monitors at about a dozen sites around the area for a few months. 9 minutes ago, JamesPa said: It also makes me wonder if noise consultants working for developers deliberately pick noisy times of day/noisy days to make measurements (why wouldn't you?). Indeed. Not all of the home owners that volunteered to have noise meters were made aware that the should notify the company when there were unusual noisy activities such as temporary building work or crop harvesting next door. One owner was told by the consultant collecting the data that it was very quiet when the wind was blowing from the north or west. The company chose to dispense with that companies services when it came to the appeal, meaning residents couldn't challenge the expert on that statement. The expert just said it wasn't something he had looked at. Residents asked repeatedly for the noise data but the company delayed providing it until it was close to the appeal. This despite statements by the government they should do do. Residents couldn't afford their own noise expert to process the data anyway. Link to comment Share on other sites More sharing options...
Nickfromwales Posted December 31, 2022 Share Posted December 31, 2022 On 30/12/2022 at 19:06, JamesPa said: 1 reflective surface within 1m You can install acoustic baffles, such as angled timber sections ( al-la louvred door type design ) which have gaps between the 'blades', and even clad those with faux or living greenery to further absorb / dissipate the sound. FYI, a Panasonic HP, which I installed for clients living in a tightly-packed urban setting, was very quiet indeed. With the next door neighbour stood less than 1m away from it, whilst it was gong full wallop ( 47oC flow at that time as I was commissioning it ), she stated that it simply could not be heard running / operating. The only obvious sound ( not noise ) was from the fan, which could only be heard when stood directly in front of the unit, and at less than 5m away from it. This was in a very low energy requirement dwelling, and if the heat load had been much higher the results would have been different. You'd need to fully understand these variables to ascertain the resultant sound emission, as the operational conditions will be a huge influence on the outcome. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 1, 2023 Share Posted January 1, 2023 13 hours ago, Temp said: Residents asked repeatedly for the noise data but the company delayed providing it until it was close to the appeal. This despite statements by the government they should do do. Residents couldn't afford their own noise expert to process the data anyway. Was that the RES farce that was on telly a few years back? Link to comment Share on other sites More sharing options...
Moonshine Posted January 1, 2023 Share Posted January 1, 2023 15 hours ago, JamesPa said: Just a note to thank everyone who has responded to my planning consent issue. Its given me lots of ammunition to fight the LPA. Today it was windy and the traffic was busy. Background noise (measured on my phone, so not very accurate) was 47dBA. 10dB below that, as currently required by my LPA, is achievable, about the same as MCS in fact. On a quiet windless day a few weeks ago, measured with the same phone, the background noise was 35dBA. Both are likely to be inaccurate, but the difference is probably quite accurate which frankly makes a mockery of specifying (as the LPA has) that the noise from the heat pump should be 10dB below background. It also makes me wonder if noise consultants working for developers deliberately pick noisy times of day/noisy days to make measurements (why wouldn't you?). Hopefully the LPA will see sense when I feed them some of the pitfalls. I fear, however, they may be reluctant to back down and its headed for an appeal, or caving into installing having an MCS registered installer install the noisier and uglier of the two possible options so I can get it in under permitted development. Either way thanks for the ideas! There is specific guidance than data should not be collected during prolonged wet conditions as wet roads elevate background noise levels. Also data should be used with caution if wind speeds are over 5 m/s. Background noise data needs to analysed to determine what are the typical background levels during the operational period of the unit. The thing with ASHP's is they operate during the night when background noise levels are lower. 10 dB below background is stringent and depends on the LPA. Link to comment Share on other sites More sharing options...
JamesPa Posted January 1, 2023 Author Share Posted January 1, 2023 25 minutes ago, Moonshine said: The thing with ASHP's is they operate during the night when background noise levels are lower. yes but: They would normally be operating below maximum at night because the target flow temp is set back They only operate at maximum when the outside temp is at its coldest, at which time occupiers of adjacent properties will, for the most part, be indoors with the windows closed. If exterior background is quite low, the noise experienced by anyone indoors even with the windows open, will be dominated by the internal background not the external background (the latter will most likely be inaudible). 10dB below background may be reasonable in a dense urban environment (where background is high enough to be relevant) but not so in the 'suburbs.' where the background is itself so low as to be inaudible to those who would be affected when a heat pumps is operating at its maximum. I guess that's, at least in part, the thinking behind MCS 020. 34 minutes ago, Moonshine said: There is specific guidance than data should not be collected during prolonged wet conditions as wet roads elevate background noise levels. Also data should be used with caution if wind speeds are over 5 m/s. Noted, I bet developers ignore this! Link to comment Share on other sites More sharing options...
Moonshine Posted January 1, 2023 Share Posted January 1, 2023 6 minutes ago, JamesPa said: Noted, I bet developers ignore this! Tbh they don't get the chance, well the developers I work for dont. I have never had the end client wanting to force technical details like these, as this is my expertise they are paying me for. I choose when and where to survey, as everything I stick in a report has to defendable. The condition your LPA has set is interesting as it doesn't look it has to be discharged, is it stated as a pre commencement condition? The 10 dB below figure is used by mainly London authorities, and is based on the guidance of bs4142:1997. There were big changes that came about with the 2014 version of 4142. One of these is now there is emphasis on context of impact, and your point about night time impacts with people indoors is valid but can usually be addressed on the context of the impact (bs8233:2014) Unfortunately the way the condition is worded the 10 dB below figure is stated as an absolute value. A recent assessment I did was for two ASHPs and condenser units in a residential development had to go in an enclosure, as it was a London LPA that wanted 10 dB below the minimum background. Other authorities are more flexible, and will allow up to +5 dB depending on context. For my own ASHP, I chatted with the EHO and it was agreed to do the noise assessment on my planning app to the mcs method even though it wasn't going in as permitted development. Also note assessing to BS4142 you may have to apply corrections for tonality or itermitancy. BS 4142 is more stringent than the mcs method. 1 Link to comment Share on other sites More sharing options...
JamesPa Posted January 1, 2023 Author Share Posted January 1, 2023 5 minutes ago, Moonshine said: One of these is now there is emphasis on context of impact, and your point about night time impacts with people indoors is valid but can usually be addressed on the context of the impact (bs8233:2014) Unfortunately the way the condition is worded the 10 dB below figure is stated as an absolute value. 5 minutes ago, Moonshine said: For my own ASHP, I chatted with the EHO and it was agreed to do the noise assessment on my planning app to the mcs method even though it wasn't going in as permitted development. Thanks for this, it helps. I have a sneaking suspicion that the condition imposed by the LPA was chosen without particularly careful consideration. Its probably the default one they apply to industrial developments or commercial air conditioning near a residential environment. If it were applied uniformly across the District (which is predominantly suburban/rural) there are very few places where domestic ASHP would be practical! Its not stated as a pre commencement condition and as you say quite likely does not need to be expressly discharged (just met). Practically speaking however one would want to know it could be met before commencing the installation otherwise its a lot of cost for nothing. As well as it being stringent, unreasonably and unnecessarily so having regard to the practical way ashps are used for heating, the burden of proving it is also out of proportion, to my mind, to the scale of development (essentially replacing a gas boiler). Presumably this is another part of the thinking behind MCS, which is a mechanical calculation that almost anyone can do. 13 minutes ago, Moonshine said: Tbh they don't get the chance [to manipulate the results], well the developers I work for dont. pleased to hear that! Link to comment Share on other sites More sharing options...
Moonshine Posted January 1, 2023 Share Posted January 1, 2023 21 minutes ago, JamesPa said: I have a sneaking suspicion that the condition imposed by the LPA was chosen without particularly careful consideration. Its probably the default one they apply to industrial developments or commercial air conditioning near a residential environment Presumably this is another part of the thinking behind MCS, which is a mechanical calculation that almost anyone can do. It looks like a standard condition but can be applied to ashp (none mcs) and air condenser units in a residential setting serving a house. Again its down to the LPA what they want, though a decent consultant should be able to be a voice of reason. The issue here is that its a planning condition and set in stone unless you get a variation, or the lpa don't need something submitted The mcs calcs are simple and it's good for their intended use, but they assume a fair bit, especially that the background noise level at the receptor is 40 dB, when in reality it can be lower than this, some times much lower. Link to comment Share on other sites More sharing options...
JamesPa Posted January 1, 2023 Author Share Posted January 1, 2023 (edited) 33 minutes ago, Moonshine said: The mcs calcs are simple and it's good for their intended use, but they assume a fair bit, especially that the background noise level at the receptor is 40 dB, when in reality it can be lower than this, some times much lower. I've often wondered why they bother building this 'assumption' into the calculation. They could more simply say that the calculated sound pressure from the heat pump at the assessment point should not exceed 37dbA, which would lead to the same pass/fail outcome in all cases so far as I can see. As you say the background noise level may in practice be lower than 40dBA, but there is a level below which the background noise is irrelevant for this application, because its too low to be heard indoors (where it matters). Below this level only the sound from the heat pump matters because that's all you are going to hear (or not). MCS seems to take this into account rather well (much better than a background noise- relative condition in fact). So far as I can see MCS only fails (to deliver a sensible conclusion) where the background noise is so high as to drown out a heat pump. In my house (and therefore presumably also my neighbours house) I can barely hear the background noise if I stand 1m from an open window. So its totally irrelevant in the practical case of being indoors when its bitterly cold, windows are shut and the ASHP is working at maximum. What matters is the absolute value of the noise from the new source, which is what MCS effectively relies on. Edited January 1, 2023 by JamesPa Link to comment Share on other sites More sharing options...
Alan Ambrose Posted January 1, 2023 Share Posted January 1, 2023 Well I think this is a very good discussion as a bunch of us are likely to face similar hurdles. While I generally like to be squeaky clean, I think in this case the LPA/MCS/BSI systems are a bit stacked against you, so a bit of street smarts are required. How about these tactics: (1) Install + Inform the neighbours of your plans and tell them you'll taking great pains to observe the noise rules. + Install as planned. Have a backup plan for extra attenuation / screening if needed/desired. + Make some measurements yourself before/after installation along the MCS/BSI lines. I like the time graphs for their sciency look and feel, and that suggests a logging noise meter/app. + Tell the LPA the work is done as specified. If they ask you for the calcs/data, submit them. + Check with the neighbours after installation to make sure they're happy. (They're the only ones really who have the ability to spark up the LPA). That should be it. However, if, despite your careful handling of the neighbours they raise a complaint to the LPA: (2) Argue and remediate if necessary. + Submit and/or point the LPA to your calcs/data. + The neighbours/LPA will either have to put a consultant to work through your calcs/data or employ one of their own to make their own measurements. Bearing in mind the most LPA's are stretched right now and their general remit is to encourage energy efficiency (e.g. heat pumps) either of these IMO is very unlikely. + If the neighbours / LPA get the bit between their teeth. Then: (a) ask them to identify the errors in your calcs / methodology. (b) propose your back plan for attentuation. (c) if and only if that is accepted, implement your backup plan. That should be it, but if there are still objections: (3) Circle the waggons. + make updated measurements yourself and submit your updated data/calcs. + If either of the neighbours / LPA still have the bit between their teeth, then I suggest they'll need to prove non-compliance (and you've already demonstrated that you've done everything in your power to comply). + if they can prove non-compliance and you can't think of any other attenuation mechanisms, go to appeal. + plead (a) you have taken every possible step to comply, and (b) heat pumps are government recommended technology. + if you lose, take it to the papers and embarrass the LPA. It's BS that you even have to think this through, of course. I would be willing to bet that you'll easily stop at (1) above. In my view, LPAs are in an Alice in Wonderland state atm. How does that sound? 1 Link to comment Share on other sites More sharing options...
JamesPa Posted January 1, 2023 Author Share Posted January 1, 2023 4 hours ago, Alan Ambrose said: How about these tactics:... Interesting thanks. I think I will first try to persuade the LPA to change the condition to the one in MCS020 (which, IMHO, is the only defensible one (other than in very loud neighbourhoods) given that it is the one applied to permitted development. I doubt they will agree, if only because it means admitting they were wrong. MCS020 is achievable, I designed the installation to meet this and submitted the calculations with my planning application, but it appears that they were ignored. If, as I fear, they do not agree, I remain minded to appeal the condition, and request as part of the appeal that it be modified to specify the MCS technical condition (but not that the condition include the requirement for an MCS installer). Appeals are FoC, its just the time factor which puts me off. The NPPF says 'planning conditions should not be used to restrict national permitted development rights unless there is clear justification to do so.' So clearly what the LPA are doing is against the spirit of the NPPF if not the actual letter. In parallel with the appeal I'm tempted to do broadly as you suggest. Depending on how hard the LPA appear to be fighting, I will take a view on the risk. Or I might just decide 'sod it' and have the louder and more ugly unit (of the two I was considering) installed by an MCS registered contractor if I can get a reasonable quote. The problem with a backup attenuation plan is that it involves a large box around the unit which, because its sited on a flat roof, will look rather odd. Its also not clear how much reduction is achievable. Daikin, for example, do a low sound cover with 3dB reduction (see link below) which, depending on how much the background noise assessment can be manipulated, may (or may not) be enough. I'm not ruling it out, but it would in principle need separate planning consent (in practice I wouldn't bother, its removable after all), there don't seem to be too many pre-fabricated examples and its not entirely predictable! Incidentally the MCS calculation says that a visual barrier reduces the level by 10dB. I wonder if that's true in reality. All in all a bit of a mess, I was hoping that, given the lack of objection to the application from the neighbours (who have their own ASHP for a swimming pool) and the largely positive comments from the LPAs Environmental health officer, this would have been straightforward. Its a real disincentive to being green (as if there weren't enough disincentives already). Link to comment Share on other sites More sharing options...
Moonshine Posted January 1, 2023 Share Posted January 1, 2023 1 hour ago, JamesPa said: The problem with a backup attenuation plan is that it involves a large box around the unit which, because its sited on a flat roof, will look rather odd. Its also not clear how much reduction is achievable. Daikin, for example, do a low sound cover with 3dB reduction (see link below) which, depending on how much the background noise assessment can be manipulated, may (or may not) be enough. I'm not ruling it out, but it would in principle need separate planning consent (in practice I wouldn't bother, its removable after all), there don't seem to be too many pre-fabricated examples and its not entirely predictable! Incidentally the MCS calculation says that a visual barrier reduces the level by 10dB. I wonder if that's true in reality. Try companies like these, have your unit spec to hand and they will be able to give you an idea of the costs, dimensions of the unit and acoustic reduction possible http://eec.co.uk/ https://www.environ.co.uk/ https://caice.co.uk/ https://www.soundplanning.co.uk/acoustic-enclosures/ https://acousticenclosuresltd.co.uk/ A 10-15 dB reduction is perfectly feasible, but be sat down when you get the costs!!! it being in a roof is an interesting one and would the roof take the extra weight. Also you could just put an acoustic screen up which would be a lot cheaper than an enclosure. That is if your not looking for a massive reduction. Link to comment Share on other sites More sharing options...
Moonshine Posted January 1, 2023 Share Posted January 1, 2023 8 hours ago, JamesPa said: As you say the background noise level may in practice be lower than 40dBA, but there is a level below which the background noise is irrelevant for this application, because its too low to be heard indoors (where it matters). Below this level only the sound from the heat pump matters because that's all you are going to hear (or not). MCS seems to take this into account rather well (much better than a background noise- relative condition in fact). So far as I can see MCS only fails (to deliver a sensible conclusion) where the background noise is so high as to drown out a heat pump. The background noise is very relevant, but so is context. BS4142 assessments look at the initial noise impact on building facade locations and private amenity spaces. Once the impact is determined at these locations the initial impact is modified looking at the context. The context looks at many things but one is looking at internal noise levels inside noise sensitive rooms of other people's houses, assuming windows are ajar, which gives 10-15 dB noise reduction. Also co text can take into account the absolute noise levels, and if the noise from the ashp is low relative to the existing ambient level (LAeq) I don't know what the layout of your site is to the neighbours but you need to consider the impact on gardens as well as windows when ajar. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 1, 2023 Share Posted January 1, 2023 7 hours ago, Alan Ambrose said: How does that sound Sounds very good to me. When some wind farms were build in Australia, many residents complained about the noise. When the developers showed Thier operational data, a lot of the time the turbines were shut down. Transpired that farms in that area were virtually worthless and the owners were trying to get compensation. So log noise data as well as operational data, then see if it correlates with the times the neighbours say it disturbs them. You could actually tell them this is what you are doing, then they will know to take you seriously. Link to comment Share on other sites More sharing options...
Sparrowhawk Posted January 1, 2023 Share Posted January 1, 2023 On 31/12/2022 at 17:50, Temp said: I was involved with a wind farm planning application and they had monitors at about a dozen sites around the area for a few months. [...] Residents asked repeatedly for the noise data but the company delayed providing it until it was close to the appeal. This despite statements by the government they should do do. Residents couldn't afford their own noise expert to process the data anyway. Do you know how the residents found the noise after the wind farm was built? I have low noise tolerance and living with a motorway a mile away and in direct line of sight was distracting and painful. I have heard that people complain about the noise of wind farms but when I have walked near one I haven't noticed much sound. Link to comment Share on other sites More sharing options...
JamesPa Posted January 2, 2023 Author Share Posted January 2, 2023 13 hours ago, Moonshine said: it being in a roof is an interesting one and would the roof take the extra weight. The plan with the roof mount is to take the weight on the walls, thus circumventing the question and avoiding any possibility that the roof deck vibrates and acts as a megaphone. The unit will sit on a unistruct framework which will transfer the weight to the flank wall of the house at one end, and the outside wall of the garage (to which this is the flat roof) at the other. The feet at the garage end will sit on a part of the deck supported directly by a joist, to avoid deck sag; at the house end the plan is to attach the unistruct directly to the house wall with anchor bolts. Given the span (2.6m) it needs the back to back (P1001) channel to take the weight without so much deflection that it feels uncomfortable, but actually its well within the maximum permissible load. If the Unistruct framework itself starts vibrating, a pair of mid-span feet will be added and jacked up just enough to transfer a little weight to a part of the deck directly above a rafter, in order to damp it down. A sideways extension of the same framework will serve as the mount for two solar panels to be added at around the same time (see separate thread in the PV Forum), the ashp provding the weight to hold them down. Unfortunately the location of the solar panels (determined by the position of the sun) provides only minimal sound screening. It took me a while to work the arrangement out, and of course may run into some practical problems when its implemented, but that's the plan. 13 hours ago, Moonshine said: Also you could just put an acoustic screen up which would be a lot cheaper than an enclosure. That is if your not looking for a massive reduction. Really neat would be if an acoustic screen also provided the personal protection against roof falls when maintaining the unit. The location is just about right and it could be mounted on the 'end' of the unistruct framework. It would look a bit odd though (but perhaps the fact it also acts as personal protection would help 'resolve' it visually) The MCS calculation says that, if the assessment point is invisible from the unit (and 250mm either side of the unit) then it gives a 10dB attenuation. I find this implausibly high unless its very solid, but presumably the MCS figures do have some basis in fact. Having said that you implied a post or two back that a window ajar is worth 10dB-15dB, so perhaps 10dB for a visual barrier is not so unreasonable. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now