Revised Lighting Code Recommendation
City of Rockwall, Texas
Why do we need a modern residential & commercial lighting
There are numerous reasons to enact a modern commercial – residential lighting code. A
few reasons are:
; To reduce energy consumption by using directed lower wattage fully shielded
lighting fixtures with reflective interior surfaces
; To increase property and street safety by reducing glare from unshielded
; To eliminate exterior lighting glare a safety hazard especially for older
; To prevent light trespass onto neighboring properties
; To retain and recover our Texas heritage of clear dark skies
What is a SHIELDED light fixture
“A lighting fixture constructed in such a manner that all light emitted by the fixture,
either directly from the lamp or a diffusing element, or indirectly by reflection or
refraction from any part of the fixture, is projected below the horizontal as determined
by photometric test or certified by the manufacturer. Any structural part of the light
fixture providing this shielding must be permanently affixed. ―
In plain English - No light shines above the horizontal, from any part of the fixture; and the bulb is not directly visible.
Unshielded lighting wastes up to 50% of its energy out in the wrong direction! Examples of several shielded and unshielded fixtures are shown on the next pages:
The bottom light is the same light, retrofitted with a ―Hubbell Sky Cap‖ reflective
aluminum shield, to reflect the light toward the ground. The top light loses 45 percent of its light horizontally or skyward. The bottom light puts twice as much light on the
ground up to 45 feet distance horizontally from the light when the light is mounted at least 25 feet above the ground.
Among the advantages of shielded lighting are better visibility, less glare and more energy efficiency. Standard lighting fixtures can waste 50 percent or more of their light. The light may travel horizontally above the ground, or up into the sky. Glare from the bright light makes it hard to see at night creating a safety hazard.
A typical dusk-to-dawn light with a standard prismatic shield wastes 45 percent of its
light skyward. That means your unshielded light is wasting 45 cents of every dollar to spend to power it. A shield, such as a ―Hubbell Sky Cap‖, redirects this stray light back to
the ground. This kind of reflective shielding improves the efficiency of this kind of light fixture to the point where you can replace the 100-watt high-pressure sodium vapor bulb with a 70-watt bulb and get nearly the same amount of light on the ground. With two shielded 70-watt high pressure sodium vapor bulbs, mounted at a height of 30 feet, you could light an area the size of a football field. With low-pressure sodium fixtures, you could light the same area with far less electricity. However, low pressure sodium may have higher maintenance costs which are offset by reduced energy consumption vs high pressure sodium fixtures. (Yielding similar total operating costs)
Won't this increase the likelihood of more crime and burglaries?
This is completely untrue. By eliminating the glare and uneven lighting associated with unshielded lighting, and directing the lighting toward the building or ground, shadows and other dark areas where criminals may hide, are eliminated. See this example below:
Notice the two unshielded lights on each side, compared to the shielded light in the center. The glare from the unshielded fixtures blinds your night adapted eyes and prevents you from seeing into the shadow areas. It also creates a driving safety issue.
Unshielded light fixture with a visible bulb
Shielded Light Fixtures with directed light- the light fixture bulb is not visible
Shielded landscape lighting in a public park or residential property
Excellent shielded streetlights illuminating the road notice how the ―cobra‖ head is
recessed and cutoff below the edge of the fixture
Cheap very inefficient flood light wasting 50%+ energy toward other adjoining property and into the sky-- producing a bright blinding glare to drivers
The same unshielded halogen lamp as above at night, notice the GLARE and dark shadows it creates—they WILL blind you while driving at night!
Light trespass- unshielded lights across the street force this resident to install heavy shades on windows
Efficient shielded exterior lighting- full cutoff- many business locations in Rockwall already have this type of lighting- for example the Wal Mart Neighborhood Store
Typical glaring unshielded fixture- terribly inefficient lighting
Sports field with full cutoff shielded lighting- notice how few lights are needed
How much will this cost the city?
Probably NOTHING! The average life of an exterior fixture is about 8 years before the ballasts and bulbs need replacement. By grandfathering current fixtures for 8 years the City and its residents can replace street, building, and residential lighting as they need new ballasts, bulbs, or full replacement. However we would recommend that new residential and commercial construction comply immediately with the new Code. The ―model‖ lighting code and Excel Spreadsheet, which are attached, discuss
this in more detail.
However the energy saving COSTS should be considered. Several cities have already replaced all street and city building fixtures with fully shielded lighting and paid for the change with reduced energy usage in as little as 3 years! You have a spreadsheet attached which shows how energy cost savings INCREASE over time.
Because fully shielded luminaires cast all their light on their target, and none into the sky, they can provide the same illumination with only 70% of the electricity used by a "fish bowl" luminary. Hence, a 250 W bulb on a fish-bowl street light can be replaced with a 150 W bulb, and a 150 W bulb can be replaced with a 100 W bulb. This reduction in wattage will produce the following operational savings assuming 4000 street lights:
Years to Wattage Savings per Calculation: recover Reduction: year: cost:
(100 W reduction per street light) * (4,000 = From 250 W street lights) * (10 hours/day) * (365 2.8 years $211,700/year to 150 W: days/year) * $0.145/KWH
(50 W reduction per street light) * (4,000 = From 150 W street lights) * (10 hours/day) * (365 5.7 years $105,850/year to 100 W: days/year) * $0.145/KWH
Calculations are for street lights only and do not include city building lighting nor do
they take into account the INCREASING cost of electric power- see the spreadsheet
Where has this been done before?
The list of cities is very extensive! Plano, TX, El Paso, TX, Vail, CO, Boulder, CO,
Maui, HA, Aspen, CO, Redmond, WA, Broken Arrow, Ok, Seattle, WA, Tucson, AZ,
Austin, TX, Flagstaff, AZ, San Bernadino, CA, Tyler, TX, McKinney, TX------ and
numerous other small and large cities. If you Google ―shielded lighting code‖ you
will get hundreds of examples! Rockwall should be on the forefront of this trend
and not the last to implement a modern shielded, reduced energy, lighting code.
SEE SAMPLE LIGHTING CODE HANDOUT-------- for your review and
Why is the
except on the road!
Conclusions and Next Steps
We would recommend that the Rockwall City Council direct The Planning and
Zoning Department to immediately begin an investigation of residential and
commercial shielded Lighting Codes and present to the Rockwall City Council their
recommendation for a revised Commercial and Residential Lighting Code. Key
factors for Zoning Department consideration are:
A. To reduce Rockwall’s total yearly lighting energy expenses
B. To eliminate glare from unshielded exterior lighting fixtures
C. To establish a common sense lighting code for future growth
D. To protect our Texas heritage of clear dark skies
E. To eliminate light trespass onto adjacent properties
F. To improve the nighttime esthetics of the City using shielded fixtures
G. To implement this Zoning Change with minimal transition costs to the City
and its citizens, and to work with TXU and TXDOT, on the lighting they may
control within the City limits of Rockwall to achieve compliance uniformity.
Calculations for energy savings should be conducted assuming that all street and exterior government buildings were converted over a period of 8 years. Retrofit shielding for street lighting should be considered. However, the maximum energy savings will result from a REPLACEMENT with a fully shielded reflective light fixture at reduced
wattage. Low pressure sodium should be considered for certain applications wherever color rendition is not important.
Additionally, we would suggest that the Rockwall City Council and the Planning and Zoning Commission refer all technical lighting questions to the IESNA- Illuminating
Engineering Society of North America.
Thank you for your kind consideration of this zoning proposal.
123 Highview Lane
Rockwall, Texas 75087