30 May 2023
The changes to study of daylight and sunlight brought about by the revised BRE Report (BR209) have highlighted the requirement for a holistic approach to building design and the planning process. The necessity for interaction between natural light studies, overheating studies, landscape design and sustainability studies has become apparent as the need to balance natural light amenity against the needs of Building Regulation compliance is brought into the design process.
As always, it is in urban environments that the balancing act becomes most difficult. Whilst the revised British Standards (BS(EN) 17037) and the BRE Report provide reduced targets via the UK Annex for ‘difficult to light properties’, there are still difficulties achieving full compliance within modern developments in a built-up area. These difficulties, predominantly driven by the proximity of neighbouring and proposed buildings and the prerequisite to provide private amenity spaces, typically taking the form of balconies above the main windows of the units below, are further compounded by overheating concerns.
It is often the case that rooms at the lowest levels of developments have non-openable windows for acoustic and/or security reasons. This leads to ventilation issues that in turn lead to overheating issues, as such, it is often necessary to reduce glazed areas to help counter the effects of heat gain in these rooms. These reductions in window sizes obviously lead to further daylight access issues. There is clearly a need to discuss these restrictions as part of the planning process to allow Planning Officers and Committee members to appreciate the balance required and draw pragmatic conclusions.
It is becoming apparent that the role of daylight and sunlight consultants and their reports needs to expand beyond simply undertaking technical analyses to informing the design process in conjunction with other technical specialists. There is a necessity for daylight and sunlight consultants to interact with other consultants within the design team. As natural light tests are often the first detailed assessments done on a new project, daylight and sunlight consultants increasingly need to lead discussions on where natural light access can be restricted and where there are potential issues that will need alternative mitigation methods to combat overheating and other concerns.
The new daylight tests, if applied correctly, provide a wealth of information regarding the ingress of natural light within a room. The tests allow the exploration of window design, room layout, balcony arrangements, internal facades, external facades and landscaping. With the Spatial Daylight Autonomy test, room orientation becomes another element that greatly impacts the results but again can lead to other issues.
The worked example shown below explores the impacts detailed internal and external material design can have on daylight conditions within a room. The room assessed remains of the same layout and dimensions, but the specification of lighter colours both internally and externally is altered under each option. These seemingly modest changes in material specification can significantly impact daylight penetration within a room.
The BRE Report discusses surface reflectance and provides that they should represent real conditions. The guidance goes further and states that “Where surface finishes have been specified or measured on site, they can be used in the calculations…”.
Intelligent use of daylight calculation methods and clear reporting can show that even where rooms do not meet the BRE Report/BS (EN) guidance, daylight and sunlight levels may still be considered appropriate in the sense implied by the NPPF and NPPG.
Lichfields’ Neighbourly Matters team has been using the revised daylight and sunlight calculations in our design advice since the changes to the British Standards. We are championing a front-loaded approach to daylight and sunlight analysis and closer interaction between relevant consultants on all of our major development projects.
For further information please contact Toby Rogan-Lyons.
Toby Rogan-Lyons & Ben Kelway
16 Mar 2023
The publication of the revised BRE Report (BR 209) in June 2022 caught most planning authorities by surprise and highlighted a need for guidance and training on daylight and sunlight matters amongst Planning Officers. Lichfields received requests for, and provided, CPD sessions to Planning Officers within Local Planning Authorities across the UK, the Greater London Authority and the Planning Inspectorate along, alongside requests from architects and developers. These sessions, particularly those with Planning Officers, created opportunities to discuss the practical application of the new guidance.
Outside of the need to understand the revisions, CPD sessions allowed officers to voice their frequent concerns regarding reliance on reports supporting developments. These concerns were in some instances drawn with reference to the ‘Rainbird’ ( EWHC 657) and ‘Guerry’ ( EWHC 2899) cases, where planning permission was quashed by the courts due to errors and misleading statements within the daylight and sunlight reporting. What was clear was a need to be able to provide clear and robust guidance for committee members that Planning Officers had confidence in presenting. Amongst Planning Officers and committee members there can be a distrust of daylight and sunlight reports, particularly where they contain little interpretation of data or discussion where transgressions are noted other than assurances that these are ‘typical’.
The revisions created significant confusion within a field that was already seen on the whole as a bit of a ‘dark art’. The realisation that the revisions did not impact on the tests applied to neighbouring properties was mostly treated with relief. However, the changes regarding how proposed dwellings should be tested emphasised the many misconceptions and preconceptions held by those required to draw conclusions from analysis undertaken by others. Discussions on the new methodologies highlighted the limitations vertical sky component and no sky line testing pose in judging perceived daylight within rooms with the general refrain being ‘but what does it mean?’
Discussions on the new assessment methods centred on which of the new daylight tests (Daylight Factor and Spatial Daylight Autonomy - Illuminance) is the preferred test and confusion over whether both are required. It was clear that, if presented correctly, the illuminance method was more relatable to personal experience than the daylight factor method. There were also concerns and misconceptions that the daylight factor method was the same as the average daylight factor method previously used.
The new guidance also introduces the UK Annex, a new testing metric for ‘hard to light’ dwellings. This element of BS EN 17037 introduces UK only daylight targets which are aimed at properties where daylight access is restricted due to location and external limiting factors such as existing tree cover or within basement rooms. There is confusion over the use of the UK Annex and the alternative targets given. The BRE Report states that the UK Annex gives minimum recommendations for habitable rooms in the UK but also states the targets are intended for ‘hard to light’ dwellings. As such, reliance on the UK annex targets was not considered to be appropriate in all cases - can rooms at the upper stories of proposed tall buildings really be considered as ‘hard to light’. Reliance on the UK Annex alone, without justification, was seen as another element that generated distrust of daylight and sunlight reports.
Looking back through discussion notes the received commentary can be summarised as follows:
Are the new standards harder to achieve?
Concern over manipulation of the results and how they are presented,
How do the new methodologies tally with ‘appropriate’ daylight and sunlight arguments?
What factors are in the control of officers to improve results?
Is the UK Annex an appropriate target?
The need to present all results clearly with supporting justification where necessary.
Overall, the changes, once understood, were welcomed. There is a need to ensure that all analysis is presented clearly and, where necessary, relevant justification for deviations is discussed. There is an element of distrust of daylight and sunlight reports and more planning authorities will be seeking third party reviews of submitted analysis. The Lichfields team is being approached far more frequently than previously by planning officers to undertake such reviews.
The revisions to the BRE Report present an opportunity to provide greater design input as schemes progress. There is an opportunity to tie assessments into other design concerns such as overheating and sustainability and a greater co-operation between consultants should become the norm. Again, the opportunity for early daylight and sunlight analysis to inform the design process and a more collaborative cross-disciplinary approach to natural light and other disciplines is to be welcomed.
It is also clear that, while the testing of impacts on neighbours has not changed, there needs to be greater clarity and justification when presenting effects to assist Planning Officers and Committee Members. Use of illuminance and the revised sunlighting testing provides analysis results and imagery that are more easily grasped by the lay person. They show that there needs to be an educational element to reports and liaison with officers if support for a scheme is to be obtained.
The Lichfields Neighbourly Matters team has become adept at running the new testing methods, informing the design process and presenting results in a clear and accessible manner. We strongly advocate early inclusion of daylight and sunlight testing in the design and pre-application processes to help de-risk projects. Taking design teams and Planning Officers through the testing journey, explaining the new guidance and interpreting daylight and sunlight results with clarity promotes assurance in the final design, secures trust from Officers and allows schemes to be presented confidently at committee.