Permitted Development Rights review - phase 3: consultation

4. Thermal Efficiency: Domestic and Non-Domestic Buildings

4.1 Overview

4.1.1 Chapters 2 and 3 of this consultation look at various technologies providing renewable heat and power. However, the increased use of such technologies is one part of the wider drive to reduce emissions associated with powering and heating buildings. Improving buildings' thermal efficiency has an important role to play too. That is the focus of this Chapter.

4.1.2 In many cases, improving the thermal performance of a building will involve internal works, such as loft or wall insulation, draught-proofing, secondary glazing and the use of shutters or lined curtains. Under planning legislation^[8], works which affect only the interior of a building – or which do not materially affect the external appearance of a building – do not constitute 'development' for planning purposes, and so do not require planning permission.

4.1.3 Notable examples of thermal efficiency improvements which could affect the exterior of a building, and therefore might require planning permission, include the installation of replacement windows (section 4.2) and external cladding (section 4.3). This Chapter outlines the current position and seeks views on proposals for change in respect of such works.

4.2 Replacement Windows

4.2.1 The installation of like-for-like replacement windows (i.e., where the building's external appearance is not materially affected) does not require planning permission. That is because such works do not involve development (see paragraph 4.1.2).

4.2.2 Even where the replacement of windows would affect the external appearance of a building, planning permission is in many cases granted by existing PDR and so a planning application is not needed. Whether or not a planning application is required depends on the type and location of the building, as explained below.

4.2.3 Irrespective of whether planning permission is required, listed building consent must be obtained where the building in question is listed.

Current PDR for replacement windows in domestic buildings

4.2.4 Existing PDR allow for the alteration or improvement of dwellinghouses (class 2B) and buildings containing flats (class 4A), outwith conservation areas, as long as the works do not extend beyond the so-called "1 metre bubble" (see also paragraphs 2.1.1 to 2.1.3). These provisions cover the replacement of windows, with no constraints on the design of the new windows installed.

4.2.5 Classes 2B and 4A do not apply in conservation areas or, under Class 4A, within the curtilage of a listed building. As such, replacing the windows of domestic buildings which are located in a conservation area will generally require an application for planning permission – unless the replacements are exact replicas of what is being replaced and the external appearance of the building is not materially affected.

Current PDR for replacement windows in non-domestic buildings

4.2.6 As with domestic properties, there is no specific PDR for the replacement of windows in non-domestic buildings. Rather, replacement windows are permitted by general PDR classes which provide for the alteration of certain types of non-domestic building:

• Class 9A: extension or alteration of shops, financial and professional service establishments falling within class 1A of the use classes order^[9]
• Class 9C: extension or alteration of schools, colleges, university or hospital buildings, nursing homes and other buildings used for the provision of care.
• Class 9D: extension or alteration of office buildings.

4.2.7 Clearly, not all types of non-domestic building are covered by these classes (e.g., hotels, cafes and restaurants). Furthermore, the list of designated areas within which classes 9A, 9C and 9D do not apply is more extensive than the equivalent classes providing for the alteration of domestic buildings (i.e., classes 2B and 4A). Specifically, 9A, 9C and 9D are disapplied within: sites of archaeological interest, National Scenic Areas, historic gardens or designed landscapes, historic battlefields, conservation areas, National Parks and World Heritage Sites.

Context for change: replacement windows

4.2.8 We are interested in the potential to extend PDR for replacement windows so that they cover houses and flats within conservation areas. Doing so could help provide greater certainty to households who are looking to install more thermally efficient windows in their properties, and save them the time and expense of submitting a planning application. Depending on how it is taken forward (in terms of what it permits and any conditions it is subject to), a PDR could also offer further savings by enabling households to utilise more cost-effective materials.

4.2.9 Making it simpler and quicker to replace windows in conservation areas may also help to facilitate the on-going upkeep and maintenance of our historic buildings and ensure that they can meet the challenges of our changing climate. By reducing the number of planning applications handled by authorities, PDR could also lessen burdens on planning departments.

4.2.10 We nevertheless recognise that a conservation area's special architectural or historic interest may in part derive from the design and appearance of buildings' windows – and that they can make an important contribution to the area's character or appearance. It follows that if planning controls on the replacement of windows within conservation areas were lifted entirely – and this enabled the installation of replacements with no constraint on their design at all – this could have an adverse impact on their overall character or appearance.

4.2.11 For these reasons, we envisage that a PDR for the replacement of windows in conservation areas – if taken forward – would not take the "blanket" approach that currently applies outwith conservation areas (class 2B and 4A). We consider that a more nuanced approach would be required within conservation areas – one which strikes an appropriate balance between: supporting households to improve the thermal efficiency of their properties on the one hand, and protecting the historic environment on the other.

4.2.12 If it is to balance these twin objectives, we anticipate that a PDR of this nature would need to be subject to conditions and limitations relating to particular elements of a window's design. For example, conditions could require that the replacement window matches the current one in respect of:

• Its opening mechanism (e.g., sash and case).
• The dimensions and colour of its frame and astragals^[10].
• The number, orientation and colour of panes.

4.2.13 A condition could potentially also require that the replacement window matches the existing one in respect of materials. This would mean that if the current window is, for example, timber-framed then the replacement would also need to be. However, this type of approach could significantly reduce flexibility to install materials which are more thermally efficient and/or more sympathetic in design terms. Furthermore, conditions relating to matching materials may be unnecessary (from the perspective of safeguarding visual amenity) if the matters listed in paragraph 4.2.12 are controlled by conditions. In other words, if the PDR required that the opening mechanism, frame dimensions and panes of the replacement window match those of the current window, then this may ensure that visual amenity is sufficiently protected without needing to explicitly refer to materials. We would welcome views on these points.

4.2.14 Furthermore, it may be that conditions could vary depending on the elevation of the building. For example, the PDR could be more restrictive in respect of windows on principal elevations (and side elevations fronting a road) on the basis that these are more sensitive to alterations than rear elevations. A further consideration is whether the PDR, if taken forward, should apply in World Heritage Sites. In practice, if a PDR for replacement windows did not apply in World Heritage Sites, this would principally affect Edinburgh Old Town and New Town.

4.2.15 We would also welcome views on what "matching" would mean in practice. If this were to be taken as an exact replica or like-for-like replacement, then arguably a PDR would be unnecessary because works would not be development for planning purposes (see paragraphs 4.1.2 and 4.2.1). As regards frame dimensions, for example, it may be necessary to allow a reasonable degree of tolerance.

4.2.16 For non-domestic properties, it is not considered proportionate that only buildings in a relatively narrow range of uses (i.e., those covered by classes 9A, 9C and 9D PDR) can install replacement windows without a planning application. It is reasonable to expect that a wider range of occupiers might wish to improve the thermal efficiency of their premises by replacing the windows – and it is not clear why only those buildings covered by classes 9A, 9C and 9D should be able to do so under PDR.

4.2.17 As such, we are minded to bring non-domestic buildings into line with domestic buildings as regards PDR for replacement windows. In other words, amend the GPDO so it is possible to replace the windows of all non-domestic buildings without a planning application, unless the building is located within a conservation area. Listed building consent would continue to be required to replace the windows of any listed building.

4.2.18 Should new PDR be taken forward for the replacement of windows in houses and flats within conservation areas, subject to conditions, it would seem logical to take a similar approach to non-domestic buildings in conservation areas.

4.2.19 If new PDR for replacement windows were introduced, planning authorities would retain powers to prepare an article 4 direction (see paragraph 1.3.8) which, subject to the approval of the Scottish Ministers, can be used to restrict PDR in certain locations.

Proposals: replacement windows

4.2.20 For domestic properties (houses and flats), we propose to introduce PDR for the replacement of windows of buildings within conservation areas – subject to conditions or limitations specifying that:

• The PDR does not apply in World Heritage Sites.
• For windows situated on the front elevation of the building, or side elevation fronting a road, the PDR would only apply if the replacement window matches the existing window with respect to:
  • Its opening mechanism.
  • The dimensions and colour of its frame and astragals.
  • The number, orientation and colour of panes.

4.2.21 For non-domestic properties, we propose to align PDR with domestic properties, as regards the replacement of windows.

Question 17: Do you agree with the proposed PDR for replacement windows of domestic buildings located in conservation areas?

Please comment in support of your answer

Question 18: Do you have any comments on the conditions that we propose the PDR for replacement windows would be subject to?

Please add any comment in support of your answer

Question 19: Do you agree with the proposal to align non-domestic buildings with domestic buildings, as regards PDR for replacement windows? Are there any types of non-domestic building that should be excluded?

Please add any comment in support of your answer

4.3 External cladding

4.3.1 As with replacement windows, the "1 metre bubble" provisions for domestic alterations (classes 2B and 4A) would currently cover the installation of external cladding in many cases. However, these PDR do not apply in conservation areas.

4.3.2 Given the potentially substantial impact that the installation of external cladding could have on a building's visual appearance, and the impact this could have on the character of an area, we do not intend to provide for such works to be carried out under PDR in a conservation area. It is considered that such works should continue to require a planning application if located within a conservation area.