LED Parking Garage Lighting lowers your cost of ownership. It tremendously reduces maintenance, and reduces
energy consumption which lowers CO2 production.
Perhaps more importantly, proper lighting can improve safety and reduce claims. Parking lot and garage lighting is not for the motorist or the vehicle; it is for the pedestrian.
Quality lighting is essential to seeing irregular surfaces or curb lines, slippery or wet areas, concrete wheel stops, pole bases and bollards, vehicle conflict, and feeling safety from facial recognition.
Table-1 below shows illuminance figures recommended by IESNA, the NPA and required by DOE/GSA. Some fixtures can't possibly comply with RP-20, but how do you know? Some fixtures may require several together in order to comply. Now there is a tool to solve the mystery. Verify IES files or see an output sample here Sample IES Output RP-20 Besides saving your bottom line, LEDs can help ensure compliance to ANSI/ASHRAE/IESNA Standard 90.1 and help with LEED Building certification for energy and tax credits. They are required for Commercial Building Energy Alliances LED Parking Lot and Parking Structure Lighting. This Payback Calculator will calculate original and new Lighting Power Density to help ensure compliance. It also lets you calculate interest cost of the money to see if on your ROI is favorable. This guide highlights some key lighting levels of existing standards and shows a few examples of luminaire placement for common parking garage layouts. See the CBEA Parking Structure Spec. PDF for conformance criteria. Here is a preview of proposed changes to RP-20. See more layout information here
Table 1
Bold text & yellow-background are areas that can be achieved with properly designed LED luminaires. *Facing the drive aisle 5' above the parking surface at points of lowest horizontal illuminance. (LM-64-01) Red text & orange-background represents a problem area for common downlight fixtures, however, not a problem for properly designed garage fixtures. † This illuminance requires higher power luminaire. †† Vertical illuminance values are to produce a uniformity ratio of no more than 4:1 horizontal illuminance. IESNA LM-64-01 is a measurement procedure for parking garage lighting to the RP-20-98 Standard. (Vertical illuminance is measured with the light meter placed against the wall facing the light source.) Note the US Department of Energy Building Energy Codes Program ANSI/ASHRAE/IESNA Standard 90.1-2007 sets a maximum LPD of 0.225 W/ft2 while meeting RP-20 illuminance criteria. (See link below for overview slides.) Rensselaer Polytechnic Institute's Lighting Research Center (LRC) developed a S/P unified system of photometry to recommend when and how to use a scotopic multiplier. The program recommends that luminance requirements of 0.6 cd/m2 and higher should be used directly without scotopic multipliers. Simply stated, all RP-20 horizontal illuminance criteria exceeds this threshold, therefore parking garage fixtures should be selected directly according to IES photometric files with NO scotopic multipliers. See more about scotopic here. Up-light is not required in either RP-20-98 or NPA parking garage Standard, however, it improves ambiance in most enclosed structures. Vertical footcandles are specified in RP-20 and LM-64. A properly designed LED parking garage light will provide illumination for vertical walls with less waste and glare in other areas. Some LED 'downlights' are promoted as parking garage fixtures. However, since they are not specifically designed for this application, they rely upon floor reflectivity to achieve the RP-20 required vertical footcandles. Downlights that rely upon floor reflectivity may conveniently meet the LM-64 criteria since that suggests measuring illuminance during periods of minimal vehicle occupancy. In this case, vertical footcandle levels will be diminished during actual garage activity, but that's when vertical illuminance is most necessary. The lighting designer is cautioned to verify vertical illuminance without the need of floor reflectivity. A downlight will usually create a hot spot and not adequately illuminate the far ends of a parking stall. Since the RP-20 horizontal uniformity Max/Min ratio is 10:1, meeting its horizontal illuminance criteria with typical downlights may require additional fixtures. Increasing the power of a Type 5 or a downlight fixture in a double row application will increase glare before it conforms to RP-20. These graphs illustrate what to look for in IES photometric files for parking garage luminaires.
 
Cutoff is essential on the motorist approach side to prevent blinding the driver.
The luminaire should be available with cutoff specified, or it should be field adjustable.
The required cutoff angle will depend on the application and mounting height.
The 75° angle is required to illuminate the far end of a parking module, as in IESNA RP-20. | |||||||||||||||||||||||||||||||||||
| Standardized Parking Stall Layout | ||
Conceptually we may consider a Parking Module as six parking stalls within an area approximately
28-ft. x 60-ft. This helps us define and organize the space, and predict the lighting requirements.
There are multiples of these modules, end to end, or side to side. Beam spacing is typically 18 to 22 ft. |
|
But parking modules don't always fit according to the beams, and the structure may have only eight feet of clearance.
The larger luminaires must sometimes fit between beams.
Lighting manufacturers have provided for two commonly known lighting layouts: "single row" and "double row" designs. Of course variations arise because every floor plan has its unique drive aisles and turns, signage locations, corners, windows and stall walls. |
| Standardized Lighting Layout | |||||
Single row lighting is illustrated below for a covered structure.
Luminaires are centered above each drive aisle to light the far walls of parking modules. The curved-in shape represents cutoff toward the driver approach to reduce disability glare.
Single row layouts were popular with HID light sources, and will nearly always have a uniformity Max/Min ratio exceeding the 10:1 IESNA limit.
This floor plan uses eight luminaires.
|
|
Double row lighting is illustrated below for a covered structure. Two rows of luminaires are shown with a row along each side of the drive aisle.
These fixtures may usually be about half the Wattage of a single row fixture, and the double row layout may sometimes require a few more. However, the lighting will be much more
uniform and the disability glare toward the drive aisle will be much easier to control.
This floor plan uses 11 luminaires.
 | |||
| |||||
Reflectance adds to the room illumination, and is a function of surface condition. White light against a smooth gray surface will reflect approximately 50%. In commercial settings with white light, wall reflectance is often estimated at 50%, ceilings 80% and floors 20%, or, that's the amount we use in calculations.
Smooth gray concrete walls can naturally have a 50% reflectance value. White paint on ceilings will easily boost those to 80% reflectance. Ceilings should always be painted if possible. Floor reflectance is typically low, and using that in calculations is misleading because a full garage will have most of the floor covered with vehicles. Its light enhancing benefit will change with garage activity and maintenance. Walls and ceilings usually contribute to better lighting as they enhance and smooth the total room illumination.
Clean, reflective surfaces can improve the overall Average to Minimum Illumination Ratio, and when surface treatment and painting is designed in from the project start, more energy can be saved. Proper painting of the walls can boost reflectance by over 20%, and could allow reduction by that much in energy usage with no reduction in illumination quality.
LED Payback Calculator (Assumes that original lighting complied with IESNA RP-20)
Photometric Viewer Download: Acuity Photometric Viewer 3.3
Visit IESNA for RP-20-98 & LM-64-01 and visit National Parking Association for Standards.
Download the DOE/GSA Specification.
LEED (Leadership in Energy and Environmental Design)
ANSI/ASHRAE/IESNA regulations Standard 90.1-2007 (1Meg PDF slide).
ANSI/ASHRAE/IESNA Standard 90.1-2004 Page Reader Only
The lighting system design must account for each interior surface having either light reflectivity or light absorption. When a surface isn't present, that border must be considered an opening through which light will escape. Open areas or windows require cutoff luminaires to avoid waste and avoid sending light pollution elsewhere. Given the vertical illumination that standards suggest, light energy can go right out the window. Outward-facing luminaires must have sharp downward cutoff, or, they must be wall mounted and shine back into the area. Windows or open back-to-back parking bays require more attention to layout.
Painting of interior surfaces is not essential, however, this Program is about conserving energy. Some manufacturer's paint and surface treatments not only boost reflectance, they repel typical garage dirt and hydrocarbon buildup to maintain that reflectance over long periods of time.
The low profile allows LED luminaires to mount either on the beams or suspend between the beams, when HID and Induction luminaires are too bulky.