BRE BR209 PDF

INTRODUCTION

People expect good natural lighting in their homes and in a wide range of non-domestic buildings. Daylight makes an interior look more attractive and interesting as well as providing light to work or read by. Access to skylight and sunlight helps make a building energy efficient; effective daylighting will reduce the need for electric light, while winter solar gain can meet some of the heating requirements.

The quality and quantity of natural light in an interior depend on two main factors. The design of the interior environment is important: the size and position of windows, the depth and shape of rooms, and the colours of internal surfaces. But the design of the external environment also plays a major role: eg if obstructing buildings are so tall that they make adequate daylighting impossible, or if they block sunlight for much of the year.

This guide gives advice on site layout planning to achieve good daylighting and sunlighting, within buildings and in the open spaces between them. It is intended to be used in conjunction with the interior daylighting recommendations in BS 8206-2 Code of practice for daylighting^[1], and in the CIBSE publication Lighting guide: daylighting and window design[2]. This guide, Site layout planning for daylight and sunlight: a guide to good practice, complements them by providing advice on the planning of the external environment. If these guidelines on site layout are followed, along with the detailed window design guidance in BS 8206-2 and Lighting guide: daylighting and window design, there is the potential to achieve good daylighting in new buildings, and retain it in existing buildings nearby.

Other sections in the guide give guidance on site layout for solar energy, on the sunlighting of gardens and amenity areas, and briefly review issues like privacy, enclosure, microclimate, road layout and security. The appendices contain methods to quantify access to sunlight and daylight within a layout.

This guide supersedes the 1991 edition which is now withdrawn. However, the main aim is the same to help ensure good conditions in the local environment considered broadly, with enough sunlight and daylight on or between the buildings for good interior and exterior conditions.

The guide is intended for building designers and their clients, consultants and planning officials. The advice given here is not mandatory and the guide should not be seen as an instrument of planning policy; its aim is to help rather than constrain the designer. Although it gives numerical guidelines, these should be interpreted flexibly since natural lighting is only one of many factors in site layout design (see Section 5). In special circumstances the developer or planning authority may wish to use different target values. For example, in a historic city centre, or in an area with modern high rise buildings, a higher degree of obstruction may be unavoidable if new developments are to match the height and proportions of existing buildings. Alternatively, where natural light is of special importance in a building, less obstruction and hence more sunlight and daylight may be deemed necessary. The calculation methods in Appendices A, B and G are entirely flexible in this respect. Appendix F gives advice on how to develop a consistent set of target values for skylight under such circumstances, and Appendix C shows how to relate these to interior daylighting requirements.

The guidance here is intended for use in the UK and the Republic of Ireland, although many of the principles outlined will apply to other temperate climates. More specific guidance for other locations and climate types is given in a BRE Report Environmental site layout planning^[3].