Reflecting on rights of light

A right of light is an easement. Interference with a right of light gives rise to a claim in nuisance in the same way that an interference with a right of way or any other easement is a nuisance. In the context of a right of way, the law is clear that not any impediment to exercising the right will be a nuisance. Rather, to be actionable, and therefore to entitle the claimant to damages or an injunction, the interference must be “substantial”. The position relating to an interference with a right of light is exactly the same. The law reports are full of cases about whether or not interferences with rights of way are sufficiently substantial to be actionable, so why not rights of light? The Waldram effect  The credit (or blame) for this can largely be given to Percy Waldram. In the 1920s, Waldram devised a method for measuring light and (more importantly) loss of light to a room. The Waldram method proceeds on the basis that 10 lumens of light per square metre (or lux) is a sufficient amount of light (equivalent to the illumination which would be received from a candle one foot away). A typical overcast sky without any obstruction of light has an illumination value of 5,000 lux and therefore 10 lux = 0.2% of this, referred to as a sky factor of 0.2%. Waldram concluded that if at least 50% of a room at desk height had a sky factor of at least 0.2% then the room could be considered sufficiently well-lit. This approach has become known as the 50/50 rule and, as a matter of practice, rights of light surveyors have generally proceeded on the basis that an interference with light will be substantial and therefore actionable where it results in less than 50% of the room enjoying a sky factor of at least 0.2% and will not be actionable where at least 50% of the room remains “well-lit”. While this approach has the advantage of certainty, the results can be startling: if a room goes from 80% to 55% well-lit this will not be a substantial interference but a change from 53% to 46% will be. The Waldram approach can also be criticised for what it does not take into account. A Waldram analysis will not take account of the impact of artificial light, for example. Case law seems to indicate that, for now at least, that is probably the correct approach. However, of more significance is the exclusion of reflected light. In reality, only a limited part of the light which we perceive comes directly from the sky. A significant element is by way of reflected light off surfaces (including light reflected off of the new development itself). The Waldram approach fails to take account of this additional source of light, thereby over-emphasising the impact of the interference. The courts have long since recognised that the Waldram approach and the 50/50 rule are not definitive and should not be treated as more than a “rule of thumb”. However, all too often, Waldram is treated as being conclusive and, in practice, the analysis of the extent of the interference is rarely taken beyond the Waldram analysis. As such, the question of whether or not there is in fact an actionable interference is one which is rarely in dispute, meaning that the court’s opportunity to depart from the “rule of thumb” has been very limited.    Commercial parties value certainty and there is undoubtedly something to be said for the fact that applying the 50/50 rule does provide an objectively certain outcome and means that the parties know where they stand. However, developers (and adjoining owners) should not lose sight of the fact that Waldram is not the final word on the matter and that, ultimately, the adjoining owner must demonstrate that the development will cause a substantial interference with its access to light. Alternatives to Waldram How else might a substantial interference be assessed? Asking the judge to simply imagine for him or herself how much light will be lost if the development is built is challenging to say the least. In the 1920s, the options available for measuring light were primitive – Waldram’s method is based on the level of light needed to comfortably read a newspaper by candle light. However, technological advances in the use of virtual reality and CGI mean that it is now possible to measure light in different ways and to demonstrate the impact that the development will actually have on the human perception of light. The use of this technology exposes some of the anomalous outcomes that can arise from an unwavering adherence to the Waldram method. Take, for example, the contour diagram below. This shows the impact that (applying the conventional Waldram method) a hypothetical proposed development would have on a neighbouring room. The diagram shows that before the proposed development, some 91% of the room enjoyed a sky factor of at least 0.2% (the green contours) whereas after the development, this will reduce to 40% (with the hatched area behind the red contour, no longer enjoying a sky factor of at least 0.2%). The loss of light appears dramatic and, applying the Waldram methodology and the 50/50 rule, the conclusion that there is a substantial and actionable interference seems irresistible. But what if alternative methods of measuring the loss of light are used? The outcome of three alternative measurements is considered below. Right of light The purpose of a right of light is to protect enjoyment of light. The task for the court in any given case is to determine whether or not an interference with that enjoyment is sufficiently substantial to merit protection from the court. The Waldram analysis is undoubtedly an important tool in that exercise. However, it is not the only tool and developers should consider whether conclusions reached on the basis of a Waldram analysis might be open to challenge based on alternative methods of measurement. Holistic approach The proper approach to assessing whether or not an infringement is substantial ought to be a holistic one, taking account of all available evidence and, perhaps most importantly, applying a commonsense approach. If a reduction in light can only be demonstrated by technical measurement and does not ultimately have any material impact on human perception or enjoyment it is very difficult to see why it should be regarded as substantial and actionable. Waldram revolutionised the practice relating to measurement of light but is it time for a new revolution? Moving away from Waldram Daylight factors [caption id="attachment_921150" align="aligncenter" width="847"] Daylight factor existing[/caption] [caption id="attachment_921151" align="aligncenter" width="847"] Daylight factor proposed[/caption] Daylight Factor (DF) is a measurement of the diffused daylight in a room. The measurement takes account of the size and location of the window and the room as a whole and, importantly, the impact of light being reflected off of the walls, ceiling and floor. The impact of our hypothetical development on the DF is much less severe. Illuminance [caption id="attachment_921154" align="aligncenter" width="847"] Illuminance existing[/caption] [caption id="attachment_921152" align="aligncenter" width="847"] Illuminance proposed[/caption] Alternatively, measuring illuminance can be used. This is the approach regularly adopted by engineers when designing a lighting strategy (natural or artificial) for a given use in a room and involves measuring the amount of light which hits the surfaces within the room. Again, the impact of our hypothetical development on the level of illuminance in the room is minimal. Luminance [caption id="attachment_921155" align="aligncenter" width="847"] Luminance existing[/caption] [caption id="attachment_921156" align="aligncenter" width="847"] Luminance proposed[/caption] Finally, what of the impact of the development on luminance? Luminance (not to be confused with illuminance) is intended to show the power of the light that will actually be detected by the human eye when looking at any given surface. It therefore takes account of both internally and externally reflected light and provides a good gauge of how the light in the room would actually be perceived by an occupier. What the Waldram method would show as a clear actionable interference is much less significant in terms of luminance.  Oliver Law is a rights of light surveyor and the founding director of Chancery Group. Paul Tonkin is a senior associate in the real estate disputes team at Hogan Lovells International LLP