Chapter 15 Lighting Flashcards
What is candlepower (cp)?
The unit of luminous intensity approximately equal to the horizontal light output from an ordinary wax candle.
What is a lumen (lm)
the unit of luminous flux; that is – a measure of the amount of visible light that the human eye can detect from a lamp or light source
What is illuminance?
Describes the measurement of the amount of light falling onto (illuminating) and spreading over a given surface area
The density of luminous flux incident on a surface in lumens per unit area
What variables are involved when determining the proper quantity and quality of light is a space?
What tasks are being preformed in the space
the age of the person preforming tasks
reflectances of the room
In general, what is the illumination ratio between task lighting and general lighting for most local codes power budgets?
General lighting to be 1/3 illuminance of task lighting
What are the considerations when determining light quality?
Glare, contrast, uniformity, and colour
What are the two types of glare?
Direct glare: when a light source in the field of vision causes discomfort and interference with visual task
Reflected glares: when a light source is reflected from a viewed surface into the eye
What is the visual comfort propability?
The visual comfort probability (VCP) - the percentage of people who, when viewing from a specified location and in a specified direction, will find the situation acceptable in terms of discomfort glare
Where is the critical zone for direct glare?
45 degree angle
What are veiling reflections?
When a reflected glare interferes with the viewing of a task.
it is an interaction between light source brightness, the position of the task, the reflectivity of the task, and eye position
In terms of lighting, what is contrast?
The difference in illumination level between one point and nearby points
In most situations, what should the brightness ratio be between a task and:
A) immediate surroundings
B) nearby general surroundings
C) remote surroundings
A) 1:3
B) 1:5
C) 1:10
In addition to daylight, what are the 4 types of light sources?
Incandescent, fluorescent, high-intensity discharge (HID) , light-emitting diodes (LEDs)
What is efficacy?
How efficient a light source is at converting electrical energy into Luminous Flux. It is the ratio of how many lumens are created for a given watt of electrical power consumed.
At 100% efficiency 1 watt of electrical power would produce 683 lumens.
What is an incandescent lamp?
Tungsten filament placed within a sealed bulb containing an inert gas -when electricity is passed through, the filament glows
What are advantages and disadvantages of incandescent lamps?
Advantages: inexpensive, compact, easy to dim, warm colour
Disavantages: low efficiency, short life, highheat out put
What are fluorescent lamps?
A combination of inert gas and low-pressure mercury,
when the lamp is energized- a mercury arc is formed that creates ultra-violet light.
The uv light strikes the phosphor-coated bulb
causing fluoresce and produces visible light.
What are the advantages and disadvantages to fluorescent lamps?
Advantages: high efficiency, relatively low costs, long life, variety of colour temps
Disadvantages: difficult to control precisely, expensive to dim,
What is a high-intensity discharge lamp?
Produce light by passing an electric current through a gas or vapour under high pressure
What is a light-emitting diode lamp? (LED)
A semi-conductor device that uses soild-state electronics to create light.
What are the advantages and disadvantages to LED lamps?
Advantages: brightness, long life, low power consumption, no heat, controlled by a digital interface
Disadvantages: cost more, lower lumen output
What are the 6 lighting systems?
direct: provide 90 to 100 percent of the light output on the task
semi-direct: provide 60 to 90 percent of the down and 10 to 40 percent of light toward the ceiling
direct-indirect: provide equal amounts of light up and down
indirect: throw from 90 to 100 percent al all light toward a reflective ceiling
semi-indirect: provide 60 to 90 percent of the light toward the ceiling and 10 to 40 percent of light toward the task
general diffuse (task ambient): provides a general background illumination level
What are the methods lighting fixtures can be mounted / installed?
Surface mounted
Recessed
suspended
wall mounted
furniture mounted
freestanding
accessory
How is Colour temperature in lighting measured?
A single number rating of their dominant colour based on the temperature in degrees Kelvin - lower the number, wormer the colour -higher the number, cooler the colour
What is a lamps characteristic spectral energy distribution?
Measure of energy output at different wavelengths, or colours
What is the colour rendering index?
CRI is a measure of how well one light source renders the colour of an object when compared with the same object lighted with a reference source of similar chromatically whose CRI is 100
What is the process for designing a lighting installation?
Determine the function/visual tasks of the space as well as existing conditions
Select lamp type based on factors determine in fist step as well as colour rendition and economy costs
Select luminaire with technical and aesthetic aspects in consideration
Determine quantity and location of the luminaries
What is the zonal cavity method?
A system that determines the number of luminaries required to provide a given footcandle level
using the efficacy of the lamp (lumen per Watt), the number of lamps in luminaire, the coefficient of utilization of the luminaire, gradual loss of light output over time (lamp lumen depreciation factor), luminaire dirt depreciation factor
What is lamp lumen depreciation factor?
The gradual loss of light out put of lamps over time
What is luminaire dirt depreciation factor?
Conditions under which a luminaire will be used, which affects the amount of dirt collected on the lamps overtime
What is the coefficient of utilization (cu)?
A number used in zonal cavity method that represents how efficient the luminaire distribute the light from the lamps under various degrees of finish reflectivity of the floor, walls, and ceiling
How may light switches are in a three way switch?
2 switches - the 3 in three way switch represents the number of conductors
What does a photocell control do?
Dims electric lighting when it is not need due to maximizing day light. This can reduce perimeter energy by 50-60%
What problems can daylight cause that need to be addressed when designing?
Unwanted heat gain or loss, glare, imbalanced lighting
What is daylight factor (DF)?
The daylight factor is defined as the ratio of horizontal indoor to outdoor illumination by daylight under continuously overcast sky conditions, expressed as a percentage.
What is recommend DF level for ordinary visual tasks and difficult visual tasks?
Ordinary: 1.5% difficult: 4%
What 3 methods can be used to meet building code jurisdictions for power that can be used for lighting in a building?
Building area method: limits total power used by giving a maximum allowable power in watts per sqft
Space-by-space method assigns LPDs to common space types
Energy cost budget method: determines energy cost for specific building design through computer simulation
What is lighting power density (LPD)?
total power used in a building by giving maximum allowable power in watts per square foot
