18 July 2023
In 2022, BRE Guidance – Site Layout Planning for Daylight “A guide to good practice” was updated. The update gives consideration to the changes in the new British Standard on daylighting in buildings BS EN 17037 – Daylight in buildings. These recent guidance updates change how internal daylight and sunlight levels are assessed in proposed dwellings.
Over the past 8 months, our team have provided a range of CPD sessions for clients to give an overview of the changes, providing guidance to navigate this.
Now almost a year into this new guidance, our team have a wider understanding of the impact they are having on clients and projects in which the team are working on. So, to further support our clients, the team have produced an easy-to-digest Q&A, to help navigate what these changes mean and why they should be given more significant consideration.
Assessing and optimising the presence of daylight and sunlight in proposed buildings has become more intricate and demanding. Now, the orientation of buildings, arrangement of rooms, and positioning of windows necessitate greater consideration of the sun's path and the need to infuse homes and buildings with an abundance of invigorating natural light.
Previous methods of assessing daylight and sunlight in proposed dwellings are superseded. However, achieving internal levels of daylight and sunlight will be more challenging. There will be a transition period during which the old assessment methodologies may still be accepted by Local Planning Authorities (LPAs), especially since many Urban Development Plans (UDPs) reference the old BRE Guidelines. Nevertheless, it is more likely that Councils will now request updated assessments to ensure a comprehensive officers report before presenting it to planning committees. This approach helps to minimise the risk of Judicial Review (JR).
In light of these changes, the orientation of buildings, room locations, and the height and placement of windows will require careful consideration concerning the sun path. For example, south-facing living rooms and kitchens should be prioritised to ensure the comfort and well-being of residents.
The changes have aimed to increase the overall amount of daylight and sunlight a proposed building will achieve; there are various reasons for this, including sustainability issues such as the increased pressure on energy prices. By reducing the need for electric lighting in the daytime through good building design can improve sustainability. Moreover, studies have shown that exposure to natural light, especially in the morning, positively impacts mental and physical health.
There are several instances where conducting a daylight, sunlight, and overshadowing assessment becomes essential. It is crucial to address these factors early in the design process to minimise the risk of major redesigns during the later stages of development due to significant daylight impacts on surrounding properties. A comprehensive evaluation of daylight, sunlight, and overshadowing is necessary for various projects. For instance, when considering office conversion under permitted development or converting a barn into residential properties, it is important to ensure that the prospective occupants will receive an adequate level of daylight amenity. Similarly, a daylight assessment becomes imperative when planning to add extensions to existing properties that are adjacent to neighbours’ windows or gardens. Additionally, it is worth noting that different local authorities include daylight assessments in their validation checklists, often using the following criterion:
Any application where there is potential adverse impact upon the current levels of sunlight/daylight within the habitable rooms of adjacent residential buildings and those of the proposed building(s) (Birmingham City Council Validation List 2021)
As mentioned above, depending on the size of the development, yes, a daylight sunlight and overshadowing assessment is required for planning, particularly in densely populated areas. Our team are on hand to determine if your project would require an assessment.
To meet the guidelines for proposed properties, some mitigation measures include adjusting the head of the window to increase the level of daylight reaching further into the rooms. Additionally, incorporating dual-aspect rooms is an ideal solution, providing two sources of daylight within an apartment/kitchen living room unit. It is recommended to have south-facing kitchens, living rooms, and north-facing bedrooms to optimise room orientation for maximum daylight and sunlight exposure in the proposed unit.
While increasing window size may seem like the best approach, it can lead to challenges such as overheating in summer, energy loss in winter, higher construction costs, and potential overlooking issues during the planning stage.
In recent times, there has been a noticeable decrease in the success rate of projects when compared to those that followed older guidance. This decline can be attributed to the fact that a more comprehensive and expansive understanding of daylight distribution throughout the building is necessary.
At M-EC we use the latest technologies and expert analysis to provide feedback on design feedback at all stages of the process. Our trained lighting team understands the importance of achieving optimal levels of daylight and sunlight in dwellings to support planning applications. With a strategic approach, we achieve the best outcomes for your project whilst keeping costs reasonable and within budget.
To find out more about our lighting and daylighting services, click here.
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