Alex Cook
ENTS Senior Capstone Project
Spring 2003

This project is an attempt to gauge the system of existing exterior lights on the Carleton campus and in Northfield to identify what has been done well and to address ways to improve outdoor lighting in these areas. It stems from my personal interest in energy efficiency and astronomy and my love of the stars and the night sky.

There are numerous stakeholders in the issue of exterior lighting: those concerned with safety and security, astronomers and stargazers, and engineers from Facilities and Maintenance concerned with energy usage and aesthetics. In discussing the issue of exterior lighting, there are often disputes between these different stakeholders, but I argue that the interests of each of these stakeholders are not mutually exclusive and can indeed be reconciled. In many ways, those lights good for security are also good for astronomy and can be energy-efficient, too. This point will be made clear throughout the project.

Currently, a general set of guidelines for exterior lighting (published for and used by the University of Iowa) are used by Facilities in making decisions concerning changes in exterior lighting. Among others, their guidelines call for a foot-candle minimum on footpaths, which is what our Facilities staff uses as a general rule. The goal is soft, continuous light because it minimizes the extreme light and dark spots associated with discontinuous lighting. Facilities does its best to balance the interests of safety & security, aesthetics, energy usage, and darkness. In order to achieve this end, several different types of exterior lights are used. Of these, four are used specifically for footpaths & parking lots: Bollards, globes, old boxes and new boxes. These all produce different kinds of light and lighting patterns, and thus are used for differing purposes. Bollards are waist-high, low level lights especially found near Goodsell Observatory. Globes are globe-shaped on poles and are concentrated around Sayles and the walkways around the Bald Spot. Old boxes produce a circular-shaped lighting pattern, whereas new boxes produce a more oval-shaped pattern, and can thus be used more effectively on footpaths. Both old and new boxes can also be found in parking lots around campus. No new globes are being purchased and will be replaced by new box lighting as they burn out. Old boxes are also being phased out as the new boxes provide light that can be more focused on a given area.

Energy efficiency and usage is an extremely important aspect of the debate surrounding exterior lighting issues. Unfortunately, the structure of Carleton's energy measurement system makes an accurate assessment of the amount of energy used by any given light impossible, let alone that of the entire exterior lighting system. Carleton's energy meters sometimes measure the energy usage of numerous buildings, and there are also several meters for one building in some cases. However, despite these measurement difficulties, the amount of energy used by our exterior lights is probably about 10-15% of our total energy usage - this is consistent with many other institutions that are able to accurately measure their exterior lights.

With these basic facts in mind, I set out to investigate what I saw as seven areas where exterior lighting is particularly important. These seven areas are: the different types of lighting and their placement around campus, especially in different areas (footpaths, parking lots, etc.), the area surrounding the Observatory, the hockey lights on the Bald Spot in winter, the Recreation Center, the LDC & Myers (which affect the Observatory due to their proximity), the illumination of buildings and doorway entrances (using wall packs), and the town of Northfield.

Before investigating the other areas of campus, I wanted to get an insight into the overall campus lighting system, especially regarding footpaths and parking lots (doorways and building entrances will be investigated below). All four of the types of lighting mentioned earlier are used for footpaths somewhere on campus. Bollard lights are concentrated near Goodsell (for obvious reasons), while globes are concentrated near Sayles and the walkways around the Bald Spot. Parking lots on campus, conversely, use old and new boxes exclusively, with a continual shift toward the new boxes. Again, soft, continuous light is the goal for the parking lots. Finally, nearly all of the doorways on campus have wall packs of some sort, but those currently used are very ineffective (further discussed below).

Overall Campus Lighting System

Based on the facts about our campus lighting system, I began with an investigation of the Goodsell Observatory and its immediate surrounding area. The Observatory is very dark relative to the rest of campus, for obvious reasons, and is affected most by exterior lights nearby (cf Inverse square law of brightness). This means that ambient light from the Rec Center, Bald Spot, LDC, and Myers will interfere much more with observing in Goodsell than any light from Northfield or the Twin Cities. Bollard lights are used around the Observatory to minimize this kind of interference. Also, the Astronomy department has control over many of the nearby lights (Bald Spot hockey lights, Olin) in order to retain the best observing conditions possible. Thus, this area of campus is relatively well positioned to maintain a sufficient amount of light. If any changes were being considered, my recommendation would be to ensure that the Astronomy department is included in the discussion.

Hockey Lights

The next area I investigated was the hockey lights that grace the Bald Spot during winter term each year. These lights, while essential to play on the rinks, also produce significant light pollution that can be seen from miles away. The lamps themselves are 1000 W metal halide and were installed in the mid-1990s. The goal for these lights, like the rest of campus, was to retain uniformity of light; this is especially important with rinks because a fast-moving puck can be hidden by any shadows. The lights were angled outward to provide a blending of light across the rinks, and deflectors were added after installation to curb light pollution. Currently, the lights are administered by Security, the broomball czars, and are able to be turned off by the Astronomy department in preparation for observing sessions. Unfortunately, the lights cause excessive light pollution which bothers neighbors, and the high albedo of the snow surrounding the lights means that any light that escapes is directed upward. Thus, my recommendations are to either add more deflectors or to tilt the lights at a steeper angle (currently about 35¡). Furthermore, the hockey lights are rather old and could be replaced with more energy-efficient ones; this should be done as the current bulbs burn out. Finally, the amount of time the lights are on should be minimized to avoid many of the aforementioned problems.

Recreation Center

A third area I investigated was the Recreation Center and its effects on the Observatory. The Rec Center's size and proximity to Goodsell means that it undoubtedly creates some amount of interference, despite measures that have been taken to reduce this impact. For example, K-wal (a translucent material) was installed on the rim, but only partially prevents light from escaping. Also, blinds have been installed on the side facing campus to prevent further light from escaping. However, in addition to light escaping from both these areas, exterior lights ring the outside which allow more light to escape.These problems are unfortunately very large and would be prohibitively expensive to alleviate. Ideally, the K-wal would be replaced with something less translucent, and the outer ring lights would be reduced.

The LDC & Myers

The LDC and Myers are also areas that need improvement. Due to their proximity to Goodsell, any light that escapes from these buildings potentially interferes with observing. There are numerous problems with both exterior lighting and interior lighting that escapes to the outside from these buildings. While the LDC's exterior lights are well-shielded and direct light downwards, the interior lights from the dining hall are rarely turned off and shine directly outside. Conversely, while there is not a big problem with light from Myers' interior escaping, its exterior lights are bulbs which protrude. These kinds of lights cause glare (and are thus much less secure than they seem) and cause light pollution which interferes with observing. Improving the lighting of these areas is thus quite simple. In the LDC, ensure that the interior lights are turned off immediately after clean-up to minimize the escape of light, and in Myers, the exterior lights should be replaced with box lights whose bulbs are indented.

Illumination of Buildings & Entrances: Wall Packs

Our campus is saturated with wall packs, lights used to make entrances to buildings and doorways more secure. Unfortunately, the vast majority of wall packs on our campus are inefficient and do not achieve this purpose. Most of them have bulbs that protrude and illuminate the building more than the sidewalk or doorway below. Thus, the use of wall packs is an issue of architectural preference versus security: some people like that they shine on the buildings, but do not realize that they, then, are in the shadows. Though admittedly sometimes the illumination of buildings is aesthetically pleasing, for our purposes it is useless: security interests should override those of aesthetics. The wall packs that are currently used cause glare (thus making the shadows next to buildings seem even darker) and do not illuminate the sidewalk. Furthermore, most of them have incandescent bulbs, which are not as energy efficient as fluorescents. These kinds of wall packs should be replaced, either immediately, or else as they burn out. In both cases, Facilities should refrain from purchasing further wall packs of this structure and with incandescent bulbs.

Northfield

Finally, I wanted to investigate exterior lighting in the town of Northfield itself and how its lighting stacked up against that of the College. Predictably, Northfield's lighting has more light pollution and is not quite as efficient as that of Carleton. The overall emphasis on aesthetics rather than energy efficiency is quite evident. Downtown is notably well done, and results in very little energy lost. The major problem areas of Northfield are "the Strip" (Hwy 3) and certain large businesses. In addition to the lighting itself, the overall layout of many of the businesses and facilities necessitates a much higher degree of exterior lighting than would be required had a different construction plan been used. Furthermore, Northfield actually has an exterior lighting ordinance which restricts the amount of light pollution from any one light source or business, but this regulation is rarely, if ever, enforced. To achieve greater efficiency and less light pollution, this ordinance must be clearly reiterated to lawmakers and law enforcement personnel and be actively enforced. Also, I recommend that we ask large businesses and facilities to alter their policy to include concerns about light pollution, security, and energy efficiency. Many southwestern cities (notably Tucson, AZ) have already implemented such measures with great success.

Overall, then, a few major conclusions can be drawn about this issue. First, there are numerous stakeholders in this issue, and these parties must come to a consensus in deciding on a standard for the Carleton campus and Northfield. While Facilities has set a general guideline of a foot-candle illumination of footpaths, we must decide if that standard should apply to all of campus (do parking lots need to be that lit up?) and if not, what standard should be used for other areas. This standard will also likely need to be set lower for the area around the Observatory.

In light of these investigations and conclusions, I will sum up a few of my recommendations. First, continue to replace all of the globes on campus as they wear out. Old boxes should continue to be replaced by new boxes, as Facilities is already doing. Problematic wall packs on campus (especially those closest to Goodsell) should be replaced with box lights, either immediately or as the old ones burn out. Involvement with Northfield on lighting issues is crucial, as is a continuing dialogue with students concerned about security and safety issues. Through these types of discussions and dialogue, it is possible to balance the interests of those concerned about security, energy efficiency, and aesthetics and of those who wish to preserve the night sky for its own sake. Lighting that is good for security, that is, which shines downward and onto what really needs to be illuminated, is also good for astronomy and can also be energy efficient.

Special thanks to Professor Joel Weisberg (Astronomy & Physics), Richard Strong (Director of Facilities), Dennis Easley (Superintendent of Grounds), and Wayne Beierman (Chief Engineer) for their help with this project.