PDX_24_Lighting 2 Flashcards
A light source in the field of vision
That causes interference/distractions with a visual task
Direct glare
Extreme contrast in late
difference in brightness levels
Glare
Zone for direct glare is the area above 45° angle from the light source
Critical glare
Or like tours is reflected from a viewing service into the high and interferes with the viewing task
Reflective glare
Annoying pain caused by high luminance is in a field of view (most common cause our windows and luminaires)
Discomfort glare
Flexion which partially or totally scares the details to be seen by reducing contrast. The common problem with specular surfaces.
Veiling reflection
The rating that indicates the percentage of people that will find the given discomfort glare acceptable. 70% is the minimum, else it’s time to fix it.
Visual comfort probability (VCP)
The amount of light produced versus the power input (lumens/watt)
Efficacy
Ratio of indoor illuminance to available outdoor luminance
Daylight factor (DF)
The light reflected from exterior obstruction excluding the ground reflected light
Externally reflected components (ERC)
Product of visible transmittance multiplied by the window to wall ratio. An EA of .20-.30 provides good day lighting.
Effective aperture (EA)
Set minimum standards for energy efficiency on incandescent and fluorescent lighting
Insert date!
Energy policy act (EPACT)
Daylighting analysis method that produces a family of daylight factor contours with in a room rather than individual daylight factors at specific points
Graphic day lighting design method (G DDM)
Device for giving light
Lamp
A complete light fixture including lamps
Luminaire
Overhang that’s exterior, interior, or both, used with the clerestory to reflect light up on to the ceiling and reduce direct flight adjacent to the window
Light shelf
0.2 x (window head height into room)
Daylight factor
- 5 x (window head height into room)
2. 0 x (window head height into room with light shelf)
Effective daylight zone
2.5 x the head height of the window (head height of the window above the desk playing)
Workplane daylight illuminance
Electric lighting in non-residential buildings uses approximately this percentage of total electric energy
25%-60%
The greatest challenge and lighting a commercial office space is providing adequate lighting for very visual tasks while,
Avoiding glare.
Number used when estimating the maximum Energy used per square feet
2.3 W per square foot
“When they have a choice, people will always gravitate to those rooms which have light on two sides”
Christopher Alexander’s “pattern language”
Also termed ‘bilateral light’
Daylighting qualifies for a lead credit if a day late factor of __% in __% of all occupied spaces is achieved.
Daylight factor of 2% in 75% of all occupied spaces
Acceptable daylighting factor for typical office work
1.5-2.5%
Acceptable daylighting factor for reading/Handwork
2.5-4.0%
Acceptable daylighting factor for drafting/fine Handwork
4.0-8.0%
The standards sky design condition established by the Commission Internationale d’Eclairage (CIE) for daylight and calculations is:
Completely overcast sky
At a solar altitude of 30°, one can expect at daylight illuminance of about __lux with no direct sun and __lux with direct sun.
10,000 lux with is no direct sun, and 40,000 lux with direct sun
The skylights allow glass to face north for illumination not south for solar heat gain
Sawtooth skylights
Recommended horizontal to vertical aluminates ratio for general diffuse light is:
2.5:1
In general with his side lighting system any interior area more than __ feet from a window will need to be electrically lit.
More than 30 feet from a window
Incandescent bulbs have this type of filament
Tungsten
A tungsten filament is placed within a sealed bulb containing
An inert gas
Incandescent bulbs produce about this much waste because of heat production
90% waste
And have a short lamp life
Incandescent bulbs have a short lamp life of about
700–1000 hours
This bulb family contains an inert gas AND halogen. Uses a fused quartz envelope that allows for higher temperature. A chemical reaction takes place pulling the tungsten from the wall of the glass back to the filament, extending its life.
Tungsten halogen incandescent bulb
Glass tube holds mixture of inert gas and low-pressure mercury vapor. Uses a ballast to supply proper starting and operating voltages, limiting the current.
Advantages are high efficacy, about 80 lm per watt, low initial cost, long life, and dimmable.
Fluorescent bulb
In fluorescent bulbs, there are classes denoting noise and heat ranging from:
Class A is good for quiet areas and
Class F is acceptable for noisy areas
A lamp within a lamp that runs at a very high voltage. An electrical arc is struck across tungsten electrodes in a glass tube filled with gas and metals. Metals produce the light once they are heated to a point of evaporation.
Disadvantage is that they produce a light that is not flattering to human skin, so not used for commercial/retail/residential applications.
High intensity discharge (HID)
Strands of glass about the diameter of a human hair. Hundreds/thousands bundled into cables. Transmit light signals over long distances.
Fiber optics
Set minimum standards for energy efficiency on incandescent and fluorescent lighting.
Energy policy act (EPACT)
90-100%light output directed to ceiling and upper walls. Has to bounce off for horizontal plane. 12-18 inches from ceiling minimum. Uniform lighting, lack shadows, Low brightness, and highly diffuse.
Indirect
Offices, lounges, waiting areas
60–90% directed upward.
10% – 40% directed downward.
Monotonous system.
Semi indirect
Offices, lounges, waiting rooms, corridor
Equal distribution up and down.
12” minimum from ceiling.
Efficient system
Diffuse/direct – indirect
Get for classrooms, standard office workspaces, merchandising areas
60–90% directed downward
10–40% directed upward.
Inherently efficient, shadowing minimized, pleasant.
Semi direct
Offices, classrooms, shops, working areas
Light directed downward. Ceiling illumination floor and furnishing reflection. Low surface illumination, typically requires perimeter lighting. Sharp, theatrical atmosphere.
Direct
Highlights, local, supplemental lighting, and privacy atmosphere if concentrated
Most commonly used for residential and commercial. And ceilings where not sufficient space above ceiling to recess, and existing ceilings.
Surface mounted
Residential /commercial. Includes luminist ceiling when entire ceiling is made of lighting.
Recessed fixtures
Dropped below level of ceilings, hanging.
Used for indirect systems and where light sources need to be closer to task area.
Suspended fixtures
Typical efficacy:
Incandescent
12 lumens/watt
Typical efficacy:
Fluorescent
55 lumens/ watt
Typical efficacy:
Metal halide
90 lumens/ watt
Good for libraries
Typical efficacy:
High-pressure sodium
90 lm/watt
Streetlights
Typical efficacy:
Sunlight
115 lm/watt
Minimum lighting level required at emergency area
One footcandle at floor level
Illuminated exit signs are required
The shield of metal, wood or plastic used to screen a light source from normal ankles viewing.
Baffle
The device used in fluorescent and H ID luminaries. Supply controlled voltage to heat lamp filaments in preheat and rapid start circuits. Limit the lamp current wants the lamp is started.
Ballast
