The validity of daylight calculations in rights to light cases

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 aim of this research was to discover whether it is possible to justify an alternative level of sufficiency. It has however been established that any substitute methodology would need to be able to produce results which are capable of being used in both negotiation of compensation and advice to the court By testing the validity of the original research, comparing this with alternative methods of measurement and a mathematical analysis of available illuminance using site and model measurements for triangulation, a new standard has been developed which more accurately represents the value of daylight in a room and leads to a better assessment model. Further research and experimentation would test and confirm the levels of illuminance required for sufficiency. It is proposed, therefore, that the daylight calculation should be undertaken, in future, using a CIE overcast sky model, accounting for Lambert’s formula and that the readings should be taken at work surface level (approximately 762 mm in most cases) rather than the current level of 850 mm. It is further proposed that the level of illuminance required should be equivalent to at least 25 Lux (0.5% Sky Factor) over at least half of the area of the room rather than the 1 foot-candle (10 Lux or 0.2% Sky Factor), which is currently used. Using this new methodology, the practitioner will be better able to advise both the client and the court, where the degree of loss might be actionable.