Dobbins JLUS IMP Public Draft Light Pollution Study | Page 124

lamp), to limit glare and trespass off-site, and to simplify interpretation for users and code
enforcement.
S ection 4.2 Total Outdoor Light Output Standards.
Figures: 50,000/100,000/150,000 lumens/acre (total nonresidential lumen budget)
Type: technical
The majority of lighting needed on nonresidential properties is for basic area lighting, such as
lighting for automobile and pedestrian areas including parking lots and walkways. Other
lighting is often used for decorative purposes such as landscape lighting and building
floodlighting.
For area lighting needs, basic recommendations of the lighting industry are for an illumination
level of 0.2 footcandle (fc) at the dimmest point on the parking lot (IESNA, 1998). Assuming
typical lighting technical parameters such as fixture efficiencies, light loss factors, and application
efficiencies (see table below), between 50,000 lumens/acre (lm/ac) and 100,000 lm/ac are
adequate to meet these needs. With typical design efficiencies, 100,000 lm/ac allows a
substantial amount of lighting for nonessential uses such as ornamental lighting, while 50,000
lm/ac has much less room for such uses. A limit of 150,000 lm/ac allows a substantial amount
of light for nonessential uses, or for less efficient designs. 50,000 lm/ac can also meet the basic
area lighting needs but will require in many cases designs that are more efficient than average
but achievable with good lighting design.
Lighting technical parameters
lm/ac
50000 50000* 100000 150000 150000*
application CU
0.5
0.7
0.5
0.5
0.7
LLF
0.65
0.65
0.65
0.65
0.65
fixture CU
0.65
0.65
0.65
0.65
0.65
parcel illuminated fraction
0.65
0.65
0.65
0.65
0.65
0.4
0.5
0.7
1.1
1.6
average illuminance (fc)
ave/min illuminance
2.1
2.9
3
3
3
minimum illuminance (fc)
0.2
0.2
0.2
0.4
0.5
* efficient design
CU= coefficient of utilization; LLF = light loss factor
Figures: 5,000/10,000 lm/ac (total nonresidential unshielded lumen budget)
Type: technical
Research shows that unshielded lighting has a dramatically increased impact on dark skies
compared to the same amount of shielded lighting. A 10,000 lumen unshielded light has a 2-
10x greater impact on dark skies than a 10,000 lumen fully shielded light (Luginbuhl, Walker
and Wainscoat, 2009).
increased impact on dark skies, the POLC allows as a compromise some unshielded lighting,
though with tight limits on the total amount. Though there is no particular lighting design or
application that dictates the figures of 5 000 lm/ac or 10,000 lm/ac , these values have been
found to be a practical compromise that provides flexibility with reasonable impacts on night
skies.
Figures: 20,000 lm/residence (total residential lumen allowance); 5,000 lm/residence (total
residential unshielded lumen allowance); 5,500 lm/residence (total residential unshielded
allowance minimum)
Type: technical
Lighting needs and desires on residential properties are highly variable and subject to individual
tastes. The figures listed in the POLC are liberal, allowing as many as ten 100 W or eighteen
75 W incandescent lamps. As many as 5,000 lm/residence may be unshielded, equivalent to
about five 60 watt incandescent lamps.
Section 4.3 Lamp CCT Standard.
Figures: 4300/3000 K CCT
Type: technical
Standards for lower correlated color temperatures (CCT) limit light emissions with
wavelengths shorter (bluer) than about 500 nm (blue-green to the human eye). Light
emissions below 500nm wavelength contribute very little to vision, but have larger
demonstrated or potential negative impacts such as sky glow, glare and circadian rhythm and
health disruption (IDA, 2010). Thus, lower CCT diminishes these negative effects with
minimal impacts on efficiency, while still allowing a wide variety of available products and
design approaches to outdoor lighting. The specific figures chosen ( 4300 K and 3000 K ) are
selected to include the majority of LED products ( 4300 K ), and to specify "warm white" or
lower CCT ( 3000 K ) in residential areas.
Section 4.5 “House Side” Shield Standard.
Figures: 10,000 lumens/50 feet
Type: technical
When residential properties are located adjacent to commercial properties, the potential for
the high intensity lighting commonly used on commercial properties to intrude on residential
properties requires particular attention. The POLC requires that brighter lights ( 10,000 lm
and greater) mounted within 50 feet of a residential property line must have an additional
shield, called a "house side shield," to limit trespass. The particular figures chosen are guided
by a general principle of requiring the additional expense of special shielding only when the
potential for light trespass is greatest.
Though there are no critical lighting needs, and very few lighting needs of any kind, which
require unshielded lighting, in some applications unshielded lighting is commonly used (for
example building façade lighting, landscape lighting, flag lighting). Despite the dramatic
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Appendix A:
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