Permitted Development Rights review - phase 3: consultation

2. Domestic Renewables

2.1 Domestic solar energy equipment

Current PDR for domestic solar equipment

2.1.1 Various PDR already allow the installation of domestic solar panels in several contexts, including:

• Solar panels attached to a dwellinghouse (class 2B).
• Solar panels attached to a building containing flats (class 4A).
• Solar panels attached to buildings (e.g., sheds, garages, outbuildings) within the curtilage of a dwellinghouse (class 3A).
• Free-standing panels within the curtilage of a dwellinghouse (class 3B).

2.1.2 Class 2B permits the improvement, addition or other alteration to the external appearance of a dwellinghouse. Class 4A permits the improvement or alteration to the external appearance of a dwelling situated within a building containing one or more flats.

2.1.3 Classes 2B and 4A are both general PDR which allow a variety of works to the exterior of houses and flats – including solar panels and associated mountings – provided that they do not protrude more than 1 metre from the outer surface of the wall or roof. For that reason, these provisions are sometimes referred to as the "1 metre bubble". Neither class applies within a conservation area. Although class 2B and 4A PDR do apply to listed buildings, listed building consent would still be required for any installation of solar panels on a listed building (see paragraph 1.3.7).

2.1.4 Class 3A permits the provision, alteration, maintenance or improvement of certain buildings within the curtilage of a dwellinghouse. This class is subject to various restrictions. In particular, it does not allow development in either the front curtilage or side curtilage that fronts onto a road – and buildings developed or altered under this class may not exceed 4m in height (or have eaves exceeding 3m). Furthermore, no part of the building developed or altered under class 3A within 1m of the curtilage boundary can exceed 2.5m in height. Under class 3A, it is possible to install solar panels on a garage, shed or other outbuilding provided these restrictions are complied with.

2.1.5 Class 3B permits certain building, engineering, installation or other operations within the curtilage of a dwellinghouse. The class does not allow development in either the front curtilage or a side curtilage that fronts onto a road – and structures provided under this class may not exceed 3m in height. This PDR does not apply where, as a result of the development, more than 50% of the rear or front curtilage would be developed (excluding the original dwellinghouse and any hard surface or decking). Class 3B does not apply in conservation areas or within the curtilage of a listed building. Subject to these restrictions, this class would cover the installation of free-standing solar panels.

2.1.6 There are currently no PDR that would allow the installation of free-standing solar panels within the curtilage of a building containing flats.

Context for change: domestic solar equipment

2.1.7 As paragraphs 2.1.1 to 2.1.6 underline, current PDR already allow for the installation of solar panels on domestic properties with relatively few restrictions. The notable exception is houses and flats in conservation areas. The Scottish Government's Draft Energy Strategy envisages a significant increase in domestic renewables output by 2030. As such, and having regard to the cost-of-living and climate crises, we think it is reasonable to consider whether those living in conservation areas could be given greater flexibility to install solar panels.

2.1.8 Heritage protection remains an important consideration, and we recognise that the role of a conservation area is to protect that location's character and the features which contribute to its character. Where proposed installations could have significant impacts on the appearance of buildings or land within conservation areas, it is right that a planning application continues to be required.

2.1.9 In light of these considerations, we propose to extend PDR to allow the installation of solar panels on domestic properties in conservation areas in some – but not all – circumstances. Specifically, we are minded to allow solar panels attached to the rear elevation^[1] of a property, or side elevation provided it does not front a road. In proposing this change, our intention is to strike a balance between climate and heritage considerations.

2.1.10 As regards solar panels within the curtilage of domestic properties, classes 3A and 3B allow householders to utilise their garden space while recognising the potential impacts on the street scene and/or neighbours. Although class 3A allows solar panels to be attached to domestic outbuildings, this is only the case where the combined height of the building and panels does not exceed the restrictions (2.5m within 1m of the curtilage boundary or 4m otherwise). This limits the applicability of these PDR to more substantial outbuildings such as garages. We are minded to extend PDR to allow for solar panels to be installed on a wider range of outbuildings within the curtilage of a dwellinghouse. This would give additional flexibility to homeowners to consider siting panels in the most appropriate position. We are not minded to amend class 3B (free-standing solar panels).

Proposals: domestic solar equipment

2.1.11 We propose to introduce new PDR which enable solar panels to be attached to dwellinghouses and buildings containing flats which are located in conservation areas – subject to the following conditions:

• Solar panels installed under this PDR are not permitted:
  • On a principal elevation or a side elevation where that side elevation fronts a road.
  • If any part of the solar panel, including associated mountings, protrude more than 1 metre from the outer surface of the wall or roof.
  • Within the curtilage of a listed building.
• Solar panels are to be removed as soon as is practical should they become inoperative, or are no longer in use.

2.1.12 We propose to introduce additional PDR for the installation of solar panels on outbuildings ancillary to, and within the curtilage of, a dwellinghouse – subject to the following conditions:

• Solar panels installed under this PDR may not protrude more than 200mm from a wall or pitched roof of an outbuilding, or more than 500mm from the surface of a flat roof.
• The PDR would only apply to outbuildings that are located:
  • Within the rear curtilage or side curtilage not facing a road.
  • Within the rear curtilage in a conservation area.

2.1.13 The intention is that this specific PDR for solar panels attached to domestic outbuildings would provide greater flexibility than is currently offered by class 3A.

Question 1: Do you agree with the proposed PDR for solar panels attached to domestic properties in conservation areas?

Please add any comment in support of your answer

Question 2: Do you agree with the proposed PDR for the installation of solar panels on outbuildings ancillary to, and within the curtilage of, a dwellinghouse?

Please add any comment in support of your answer

2.2 Domestic Air Source Heat Pumps

Current PDR for domestic air source heat pumps

2.2.1 Class 6H permits the installation, alteration or replacement of an air source heat pump ("ASHP") on a dwelling or within the curtilage of a dwelling. The class does not differentiate between dwellinghouses or buildings containing flats: it is applicable to both. There are a number of restrictions on development under class 6H, the key ones being:

• No more than one ASHP is permitted on, or within the curtilage of, any building (containing a dwelling).
• If the ASHP is attached to a dwelling, no part of the ASHP (including housing etc.) can protrude more than 1m from the surface of any external wall or roof. Within a conservation area the ASHP must also be at ground floor level and on the rear elevation of the dwelling.
• If the ASHP is within the curtilage of a dwelling ( including those within a conservation area), it cannot be forward of the front elevation or side elevation where that elevation fronts a road. Nor can the ASHP and associated equipment or housing exceed 3m in height.
• The class does not apply in a World Heritage Site or within the curtilage of a listed building.

2.2.2 Class 6H provides that any ASHP installed under the PDR must comply with MCS-020.pdf">Microgeneration Certification Scheme MCS 020 planning standards or equivalent. MCS 020 covers the installation of ASHPs and, among other things, stipulates that noise levels for an ASHP must stay at or below 42 decibels from a 1m distance from any habitable room^[2].

Context for change: domestic air source heat pumps

2.2.3 The Scottish Government published its Heat in Buildings Strategy in October 2021, which aims to see all buildings reach a good level of energy efficiency (which for homes is at least equivalent to an energy performance certificate band C) by 2033 and use zero emissions heating and cooling systems by 2045. Heat pumps are a key zero direct greenhouse gas emissions technology, and a very efficient way of using electricity to provide heat. We will consult in detail on proposals for a Heat in Buildings Bill later this year which will include further detail on how we propose to introduce regulations by 2025.

2.2.4 The current limitation which provides that only one ASHP per building is permitted under class 6H can be restrictive, for example where a building contains flats. Situations may arise where one owner can install an ASHP under the PDR but subsequent dwellings within the same building cannot. This situation could become problematic given the anticipated future uptake of ASHPs as set out int the Heat in Buildings Strategy.

2.2.5 We recognise that this could increase the potential for noise associated with the operation of ASHPs to affect neighbouring properties, particularly where the cumulative impact of several ASHPs is considered. The current PDR rely on the standards set out in MCS-020, including maximum noise levels, an approach we believe is effective. However, where more than one ASHP is installed on a building containing multiple dwellings, it may be appropriate to also specify restrictions on the size of the individual ASHPs and/or a minimum separation distance from other dwellings within the building (horizontally or vertically). This would be in addition to the requirement to comply with MCS-020 standards, which we are minded to retain.

2.2.6 Additionally, the UK Government has commissioned independent research on noise emissions from heat pumps, which will inform consideration of whether the equivalent PDR in England are fit for purpose and reflective of advances in heat pump technology. Findings will be published in the Summer. We will take account of the findings of that research, in addition to the feedback from this consultation, in finalising any amendments to the current PDR for domestic heat pumps in Scotland. Subject to the findings of the UK Government's review, we understand that the Microgeneration Certification Scheme will also consider the need to update MCS-020. Amendments to these standards would apply to Scotland.

2.2.7 Within conservation areas, the current PDR only allow installation of heat pumps if they are at the rear of a property and at ground level. We consider that the restriction limiting installations to rear elevations remains appropriate in terms of reducing visual impact on local amenity. However, in the interests of providing additional flexibility there may be scope to remove the restriction requiring installation at ground level.

Proposals: domestic air source heat pumps

2.2.8 We propose to amend the class 6H PDR for domestic ASHPs by:

• Providing that one ASHP per dwelling is permitted under the PDR, rather than the current restriction of one per building.
• Providing that where an ASHP is installed on a building containing flats:
  • the outdoor compressor unit must not exceed 1.5 cubic metres.
  • the external parts of the ASHP (including any housing etc.) must not be within 1 metre of any window of a habitable room, or door, of another flat in the same building.
• Remove the requirement that an ASHP installation in a conservation area must be at ground level.

Question 3: Do you agree with the proposed amendments to PDR for ASHPs?

Please add any comment in support of your answer

2.3 Domestic Ground Source and Water Source Heat Pumps

Current PDR for domestic ground and water source heat pumps

2.3.1 Class 6D and class 6E permit the installation, alteration or replacement of a ground source heat pump (class 6D) or a water source heat pump (class 6E) within the curtilage of a dwellinghouse or a building containing a flat.

2.3.2 There are no other restrictions in either class regarding location or positioning of the pump relative to the building. Nor are there any restrictions preventing installation within a conservation area or other designated area.

Context for change: domestic ground and water source heat pumps

2.3.3 Essentially both types of pump consist of a heat exchanger drawing heat from liquid circulating in a system of underground pipes; the pump itself can often be installed within the property. However, classes 6D and 6E refer specifically to the pump, with no reference to associated pipes. This contrasts with the PDR for non-domestic ground source and water source heat pumps (see section 3.4), which do refer to underground pipes. This could potentially cast doubt on the scope of the PDR for domestic pumps under classes 6D and 6E. We consider that it would be appropriate to address this in the interests of providing greater certainty.

Proposals: domestic ground and water source heat pumps

2.3.4 We propose to amend classes 6D and 6E to clarify that, in addition to the ground/water source pump itself, the PDR also cover the associated underground pipework and any above-ground connections to the pump. The pipework would need to be wholly within the curtilage of the dwellinghouse or flatted building.

Question 4: Do you agree that classes 6D and 6E should be amended to include reference to the installation etc. of pipework and associated connections required to operate a ground or water source heat pump?

Please add any comment in support of your answer

2.4 Free-standing domestic wind turbines

Current PDR for free-standing domestic wind turbines

2.4.1 Class 6G permits the installation of a free-standing wind turbine within the curtilage of a dwelling. For the purposes of these PDR, a dwelling refers to a dwellinghouse, a building containing one or more flats or a flat contained within such a building. The class is subject to a number of restrictions, which stipulate that:

• Only one wind turbine is permitted in the curtilage of any dwelling.
• The turbine must be situated no less than 100m from the curtilage of another dwelling.
• The turbine must, as far as is reasonably practical, be sited so as to minimise its effect on the amenity of the area.
• The turbine must be used for domestic microgeneration only.
• The turbine must be removed, as soon as is practical, if it is no longer needed or operating.
• The turbine cannot be located within a conservation area, the curtilage of a listed building, a World Heritage Site, a Site of Special Scientific Interest or a site of archaeological interest.

2.4.2 The current PDR do not include any restriction on turbine height. They are, however, subject to a prior notification and approval process. This means that, prior to the turbine being installed, the developer must notify the relevant planning authority, providing a description of the proposed development, the design and size of the turbine and a location plan. The planning authority may, as they consider it appropriate, decide that the proposal is acceptable and can proceed or that further consideration of the siting and appearance of the turbine is required.

2.4.3 This further consideration allows the planning authority opportunity to require changes to the location and/or appearance before the development can proceed. However, the current provisions are complex and apply differently to different aspects of the proposed development with approval being required for the design and size of the turbine, and separately, a prior notification and approval process for the siting and external appearance of the turbine.

Context for change: free-standing domestic wind turbines

2.4.4 Wind turbines can have a significant visual impact on the surrounding area, and have additional potential to affect the amenity of neighbouring properties (e.g., noise impacts). There are also safety considerations with a potential risk of injury or damage in the event of a turbine collapsing. These considerations are reflected in the restrictions class 6G is subject to – notably the 100m separation distance and the prior notification process.

2.4.5 While free-standing domestic wind turbines may be appropriate in more rural locations, the potential to affect neighbouring properties and uses in more urban settings is likely to be more significant. Nevertheless, the current requirement to locate the turbine at least 100m from the curtilage boundary may be overly restrictive, even in rural areas. We are therefore considering whether it would be appropriate to introduce a more flexible approach, under which separation distance is related to the height of the proposed turbine.

2.4.6 As noted in paragraph 2.2.2, the current PDR for domestic ASHPs are subject to a condition requiring compliance with Microgeneration Certification Scheme (MCS) planning standards – MCS 020. These standards, which cover a range of matters such as noise levels, apply to domestic wind turbines as well as ASHPs. In view of potential amenity impacts, we are minded to require that turbines installed under class 6G comply with these standards.

Proposals: free-standing domestic wind turbines

2.4.7 We propose to amend the class 6G PDR for free-standing wind turbines by:

• Introducing a maximum turbine height of 15m, measured to the tip of the wing blades.
• Providing that the distance between the lowest part of the turbine blade and the ground must be at least 5m.
• Replacing the separation 100m distance between the turbine and curtilage boundary with a calculation of the turbine height plus a specified safety factor (e.g., height + 10%).
• Adding a requirement to comply with the MCS 020 planning standards.
• Simplifying the prior notification and approval process so that a single procedure covers all aspects of design and siting.
• Providing that the turbine and blades must be painted a uniform neutral colour and not bear any advertising.

2.4.8 We propose to retain other elements of the current class, including the requirement for prior notification and approval, to ensure that planning authorities can exercise some degree of control where a particular proposed development could have potentially unacceptable impact on amenity.

Question 5: Do you agree with the proposed amendments to PDR for free-standing domestic wind turbines?

Please add any comment in support of your answer

Question 6: Do you agree with the current list of designated areas where the PDR do not apply, noting that the list does not currently include national parks or National Scenic Areas?

Please add any comment in support of your answer

2.5 Domestic wind turbines attached to a dwelling

Current PDR for wind turbines attached to dwellings

2.5.1 At present there are no PDR for the installation of a wind turbine mounted on a domestic property.

Context for change: wind turbines attached to dwellings

2.5.2 Wall- or roof-mounted wind turbines tend to be smaller and have lower energy output than free-standing turbines. We nevertheless recognise that installing a small turbine on a domestic property could make a valuable contribution to renewable electricity generation, including providing power to other equipment such as a heat pump. As with free-standing turbines, the potential impacts on amenity and safety are important considerations. Accordingly, any new PDR for domestic turbines fixed to a dwelling would need to be subject to a number of restrictions.

2.5.3 If a new PDR for wall- or roof-mounted wind turbines is taken forward, we are not minded to make it subject to prior notification and approval. We consider that limitations on the size, location and appearance will be sufficient to minimise potential adverse impacts on neighbouring properties.

Proposals: wind turbines attached to dwellings

2.5.4 We propose to introduce a new class of PDR for the installation, alteration or replacement of wind turbines mounted on the wall or roof of a dwellinghouse, subject to the following restrictions. A turbine installed under the PDR would only be permitted if:

• Mounted on a detached dwellinghouse.
• It is the only turbine on the same dwellinghouse.
• It complies with MCS 020 planning standards.
• No part of the turbine, including blade, would protrude more than 3m above the highest part of the roof.
• No part of the turbine, including blade tips, would be less than 5m from the ground.
• Located at least 5m from any curtilage boundary.
• The swept area of the turbine is no more than 4 square metres.
• It is a uniform neutral colour with no advertising or other designs.
• It is not located in a conservation area, National Park, National Scenic Area, Site of Special Scientific Interest, World Heritage Site or within the curtilage of listed building.
• The turbine is removed as soon as is reasonably practical should it no longer be required or cease generating electricity.

2.5.5 The proposed PDR would not extend to wall- or roof-mounted turbines attached to outbuildings or structures that do not form part of the dwellinghouse itself.

Question 7: Do you agree with the proposed new PDR for wall or roof-mounted wind turbines attached to a dwellinghouse?

Please add any comment in support of your answer

2.6 Flues for certain domestic heating systems

Current PDR for domestic flues

2.6.1 Planning legislation provides that planning permission is required for 'development', the definition of which^[3] excludes works which affect only the interior of a building or do not materially alter its external appearance. In most cases the equipment for wood burning stoves, biomass boilers and biomass heating systems, other than the flue, is installed within a building, and so it does not require planning permission. Installing, altering or replacing a flue on a dwelling may not require planning permission if it does not materially alter the external appearance of the building. In the event a flue does require planning permission, it is often granted by PDR.

2.6.2 The GPDO contains specific PDR for the installation, alteration or replacement of domestic flues for biomass heating systems (class 6C) and combined heat and power ("CHP") systems (class 6F), which includes CHP fuelled by biomass sources. The term domestic in this context refers to existing dwellinghouses (terraced/semi-detached and detached) and existing buildings containing one or more flats. These PDR are subject to various limitations, which provide that a flue:

• must not extend more than 1m above the highest part of the roof (excluding any chimney) to which it is fixed.
• must not be located on the principal elevation of the dwellinghouse or building containing a flat in a World heritage Site or conservation area.
• must not be within an Air Quality Management Area (for Class 6F, this only relates to CHP fuelled by biomass).

2.6.3 While classes 6C and 6F PDR are specific to particular types of flue, the majority of domestic flues are permitted under general PDR, which allow improvements, additions or alterations to the exterior of dwellinghouses (class 2B) and buildings containing flats (class 4A) within a "1 metre bubble" (see paragraphs 2.1.1 to 2.1.3). The limitations on these general householder PDR classes do not relate specifically to flues, but would nevertheless restrict the installation of a flue under PDR if:

• It would protrude more than one metre form the outer surface of an external wall, roof plane, roof ridge or chimney;
• It would be located in a conservation area or, in the case of a building containing flats, within the curtilage of a listed building; or
• It would be permitted development under class 6C or 6F.

Context for change: domestic flues

2.6.4 The Cleaner Air for Scotland 2 (CAFS2)^[4] strategy has an action point for the Scottish Government to "consider with local government what changes are needed to the current PDR for flues for woodburning stoves and biomass boilers". This relates to the PDR for flues for biomass heating systems (class 6C) and householder PDR in class 2B and class 4A that may grant permission for flues for wood burning stoves^[5].

2.6.5 The concerns here relate to the adequate dispersal of pollutants to the air, without causing nuisance to neighbours, but also the effects from cumulative emissions from these technologies, at least regarding urban areas.

2.6.6 The main pollutant of concern in this regard is fine particulate matter, for which there is no known safe threshold. Larger biomass systems, including most CHP systems, are generally more efficient in terms of emissions than smaller ones, such as wood burning stoves and biomass boilers. That, and the wide range of these smaller systems (with corresponding variability in quality and performance) are why the CAFS2 action point focusses specifically on the PDR for flues associated with wood burning stoves and biomass boilers.

2.6.7 It is important to acknowledge that there are limits to how far amending PDR can, in isolation, address concerns about the dispersal of pollutants from these specific technologies and the cumulative impacts of emissions in urban areas. Changes to PDR could, however, form part of a wider package of measures aimed at tackling these issues.

2.6.8 With regard to adequate dispersal of pollutants, CAFS2 indicates the relevant solutions tend to be unique to the circumstances of a case. Because PDR conditions and limitations apply universally, it is difficult to see how this could be addressed with sufficient granularity in the GPDO. As to cumulative impacts on urban areas, the GPDO does not distinguish between 'urban' and 'rural' locations – such terms being too vague to provide the basis for effective restrictions. There is no obvious proxy designation, with clearly defined boundaries, which would map a distinction between urban and rural areas for these purposes.

2.6.9 Whilst the class 6C and 6F PDR do not apply in Air Quality Management Areas ("AQMAs"), individual AQMAs have been, and may increasingly be, revoked as the related legal requirements are met. As there is no known safe threshold as regards fine particulate matter, the legal objectives regarding AQMAs can be met without necessarily addressing concerns about such matter. In addition, many of the complaints about emissions arise outside AQMAs.

2.6.10 In light of these points, our view is that any changes to (or removal of) PDR for certain flues as part of an attempt to control cumulative emissions would need to apply more generally, rather than targeted to 'urban areas' or AQMAs. Removal of PDR could help to address the issue of pollutant dispersal, at least as far as the lack of requirements to address this in the current PDR is part of the concern.

2.6.11 Any PDR changes would not be retrospective and so would not affect emissions from existing flues or chimneys. As noted at paragraph 2.6.1, the installation of a new flue may not necessarily require planning permission; hence it is does not necessarily follow that removing PDR would automatically result in planning applications in all instances. Furthermore, where planning applications for flues were submitted, planning authorities would need an appropriate policy basis for decision making as regards concerns about the cumulative emissions. In light of these limitations, amending PDR for flues should not be regarded as a panacea. However, as noted at paragraph 2.6.7, we are interested in views on the role of such changes as part of a wider set of measures aimed at reducing issues associated with air pollution.

Proposals: domestic flues

2.6.12 In the context of concerns about the adequate dispersal of pollutants and the impact of cumulative emissions on air quality, we would welcome views on the removal of PDR for flues for wood burning stoves and biomass boilers. Specifically, we are interested in feedback on:

• Removing class 6C PDR (flues for biomass heating systems); and
• Amending class 2B and class 4A PDR for dwelling to exclude flues for biomass heating systems and wood burning stoves.

2.6.13 It should be noted that as well as the installation of flues on dwellings, the PDR cover the alteration or replacement of flues on dwellings. We would welcome views on whether PDR for alteration and replacement of flues should be retained, even if the installation element of the PDR is removed.

Question 8: Do you have any comments on the potential removal of PDR for flues for wood burning stoves (including wood burners and log burners), biomass boilers and biomass heating systems?

Please add any comment in support of your answer

Question 9: Noting that current PDR cover the installation, alteration or replacement of flues, should any removal of these PDR be limited to installation of new flues, or also prevent existing flues being altered or replaced under PDR?

Please add any comment in support of your answer