Rights of light: Waldram's conundrum

Purpose – Over the last few years it has been established that there is a need to re-evaluate the basis of assessment of the sufficiency of daylight, in rights to light cases, where the loss of daylight after obstruction might lead to injunction and/or damages. The purpose of this paper is to further examine whether the methodology used by surveyors, whereby the effect of glazing, window frames and internal reflectance are ignored, is valid and whether theoretical values can be translated into real values obtained through practical experimentation. Design/methodology/approach – Modern methods of assessment of daylighting, for design purposes, calculate a whole room average as a percentage of available daylight from a Commission Internationale de l’Eclairage (CIE) sky whereas Waldram's methodology, in rights to light cases, results in a contour line marking the series of points in a room where the task lighting, from a uniform sky, would be insufficient for normal use. These two methods appear incompatible and the conundrum is that whilst the courts are seeking to determine adequacy of daylighting to a room, the practitioners need to be able to measure the reduction in a way that has real meaning and can be valued. Findings – By comparing theoretical results using the Waldram methodology with those obtained using the Building Research Establishment (BRE) methodology and with physical measurements on site and in an artificial sky dome, it can be demonstrated that results using the Waldram Diagram, or the proposed CIEL Diagram, can be translated into real values of daylighting for a room and that these values are more realistic than those obtained through the BRE methodology. Originality/value – This research (which is ongoing) will be useful to practitioners and the courts in determining rights to light cases and is a significant contribution to the debate initiated in this journal by Michael Pitts some 12 years ago.