| Transverse Coverage and Cutoff
In order to prevent blinding the driver, cutoff is essential on the motorist approach side.
The IntenCity luminaire can be ordered with standard or custom transverse cutoff.
The required cutoff angle will depend on the application and mounting height. A common configuration for parking garage mounting heights of 8 feet has 38° on the driver approach and 60° on the downstream side.
These angles allow luminaire mounting on 20 ft. centers and keep the driver's vision relatively clear of disability glare.
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Standardized Parking Garage Layout
The industry has conceptual standards for new structures, and defines a Parking Module as six parking stalls within approximately 28' x 60' as illustrated here.
Parking structures are often designed with multiples of these modules, and with typical overhead beam spacing of about 18 to 22 ft. centers where luminaires can mount on, or in between.
But parking modules don't always fit according to the beams, and here are two basic layouts.
The diagrams to the right are looking down through the beams. The first illustrates Beams Across a parking module. The second illustrates Beams Aligned with a parking module.
Often these beams have only eight feet of floor clearance, and the larger luminaires must fit between beams. In the case between, the lighted path must follow the 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.
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Windows, Walls, Ceilings and Reflections
Degree of reflectance is a function of surface condition and color, and color of the light itself. White light against a smooth gray surface will reflect approximately 50%. A whiter light may find more reflective surfaces than a lower color temperature or monochromatic light source (Sodium Light).
In commercial settings with white light, wall reflectance is often estimated at 50%, ceilings 80% and floors 20%, or, that's the amount of light that's presumed to reflect and help illuminate the target area.
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, its light enhancing benefit will change with garage activity and maintenance, but 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.
Using the dimensions of the following layout examples for a 120' x 80' garage,
proper painting of the walls can boost reflectance by over 20%, and could save that much in energy usage with no reduction in illumination quality.
Our research with the aid of
Porter Paints is enlightening.
Single row lighting is illustrated to the right for an enclosed floor plan. Luminaires are centered along each drive aisle to light the length of parking modules. Each luminaire is set to cutoff (the curved-in shape) to the drive aisle direction to reduce the disability glare toward the driver.
This floor plan requires eight GLF luminaires to adequately light the area to standards.
Note that one location has a luminaire facing directly into the drive aisle. A Hybrid GLF is used here to reduce glare toward the driver, while also providing uplight. The opposite wing fully illuminates the far corner walls of the parking module. This is one example of combining photometrics in one luminaire. The IntenCity could provide a streetlight-type output with uplight in one wing, and a standard parking garage GL series output in the other wing.
If the North or South sides had windows or were open, the IntenCity luminaire can be ordered with side ( transverse) cutoff down to 24° to limit trespass.
Also note that in this layout, if the center wall was not separating the inside border of parking modules, motorists entering the inside parking stalls would face directly into bright light from the opposite modules. In this case, the designer can specify the Hybrid cutoff model for an optimum solution.
Double row lighting is illustrated to the right, with a row of luminaires aligned along each side of each drive aisle. These luminaires are ordinarily the same as for single row, but rotated 90° and overlapped lengthwise according to structure spacing.
Side cutoff of the GL Series can be adjusted down to 24° to reduce wall illumination and possibly allow open walls or windows on these East and West sidewalls.
The floor plan shown will have vertical illumination at the North and South sides when using the GLF luminaire. If there are windows or no walls at North or South sides, the Hybrid is a better choice with its specific above-floor cutoff characteristic.
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Design Note: IntenCity's very low profile allows it to mount either on the beams or suspended between the beams, and can satisfy most layouts despite their dimensions.
Tunnel Entrance
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Tunnel lighting may have numerous configurations and standards.
The diagram illustrates a single row layout to illuminate road surface and tunnel walls from the center ceiling position.
Center lighting with the IntenCity GLF Series:
1) reduces shadowing when tall vehicles pass,
2) brightens the side walls to lessen motorist anxiety,
3) may require greater traffic control during maintenance.
Side lighting with the IntenCity GLS Series:
1) may direct light more to the driving surface,
2) uses downlight to brighten the side walls,
3) requires less traffic control during maintenance.
The GLF provides illumination on walls, driving surface and +30° ceiling uplight at each wing. This provides maximum illumination for tunnel applications.
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Instant-On or Dimming can offer improved and novel lighting.
Mid-tunnel luminance levels are sometimes lower than entrance and exit luminance, and LEDs are well suited for such applications.
For greater energy savings and visual effect, vehicle detection systems and timers may gradually brighten banks of LED luminaires from dim to full on as vehicles enter, and fade as
traffic exits. This can't be done with HID or Fluorescent.
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GLF-1600 Longitudinal Distribution
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NOTES
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.
