Properly selected and installed, outdoors fixtures should not put light directly up into the sky (uplight), nor on other people’s property (spill light) in objectionable levels and certainly not into their homes. (IESNA G-1-03 – 3.2)

As little as one lux has been shown to interfere with the normal hormonal response to the diurnal cycle of night and day. JF Duffy and CA Czeisler, “Effect of light on human circadian physiology”, Sleep Med Clin. 2009 June: 4(2): 165-177.

So pouring light into someones bedroom is not a small matter. However, light can be an irritant anywhere it is unwanted. People should not have to go through a daily process of covering and uncovering their windows – each night and day – because someone else is careless with their outdoors lighting.


The Obtrusive Lighting Committee of the Illumination Engineering Society of North America, performed a study of this question in which a collection of volunteers were asked to rate a number of lighting scenarios, (IESNA TM-11-00). While, predictably there was a range of responses among the participants, the committee established guidelines for objectionable spill lighting based on levels that the average participant found to be “Very objectionable” – level 4 on a five point scale.

What is deemed objectionable naturally depends, in part, on the ambient lighting level of the setting. Accordingly, guidelines were set for four different conditions ranging from intrinsically dark landscapes, such as national park (E1) through to dense urban areas with commercial activity and high levels of night time activity (E4). Between these extremes, low ambient light levels such as one might find in rural and suburban areas were classified as (E2) and medium levels, such as urban residential areas (E3).

It is a simple matter to determine whether this guideline is being exceeded, by taking a reading at the property line using a suitable light meter.


Environmental Zone Pre-Curfew Limitations Post-Curfew Limitations
E1 1.0(0.10)    0.0(0.00)**
E2 3.0(0.30) 1.0(0.10)
E3 8.0(0.80) 3.0(0.30)
E4 15(1.50) 6.0(0.60)


*Lux (footcandles) values on a plane perpendicular to the line of sight to the Luminaire(s)

**Where safety and security are issues, nighttime lighting is needed. Such lighting should meet IESNA recommendations for the particular property being lighted. Lighting should be designed, however, to minimize light trespass.




ht trespass please let us know by subscribing to our trespass victims list. Growing this list will help us move public policy to address this problem. We may also be able to help. Next thing to do is bring the issue up with your neighbor. Tell them your concern and suggest a reasonable solution. Usually just installing a shield will do, though sometimes a new fixture or relocation of a fixture is required. You might refer them to the companion webpage to this one – a Good Lighting Neighbor.

If discussions don’t work, in a civilized urban setting there will be an ordinance that precludes such offenses and you can lodge a complaint with the code enforcement office. However, in most instances, in this state, there will be no such ordinance. In that case, you should first write your city counsel representative and mayor to complain about the lack of an ordinance to protection people from lighting abuse.

Beyond making a complaint about the lack of an ordinance, you will need to decide how important the problem is to you, weighted against the relationship you have with your neighbor. If a voluntary solution was not reached, the later is probably not much of a consideration since it is hard to maintain a good relationship with a bad neighbor. In any event, at that juncture the only practical course forward, for most people, is to take he matter to Judge Judy, which is to say file a claim in small claims court.

An ordinance is obviously the better solution, but unless people complain we can’t realistically make that happen.