Building Services semester 1 - Lighting

Controlling daylight Methods: - Beam sumlighting - Prismatic glazing - Light shelves (a ______ detail) - Use of Atriums -Solar _____

atrium, tubes

Luminance: - The _________ of a surface - e.g don't put white desks in an area of high lux as the white surface will reflect light back

brightness

Intensity - Measured in _______. -one _______ is based on the idea of one candle power - Intensity = _____ of light source

candela, candela, power

Luminous Efficiacy = the ___________ of converting the electrical input into ________ output

efficiency, lighting

INCANDESCENT LAMPS: - Passage of electricity through a filament raises the temperature of the molecules and they emit light. - Not very efficient and lots of energy used to ____ wire. - The bulbs also degrade, producing less leight but using just as much energy

heat

Lighting measures: - Candela = _________ - Lumen = ____ - Lux = ____________

intensity, flux, illuminance

Reflectance of the ________ surfaces of a room has a big impact on the DF. Reflectance values range from 0 (______) to 1 (______). The R average formula can be used to calculate a weighted score

internal, black, mirror

ILLUMINANCE - DAYLIGHT - 100 kilolux is exceeded less than 1% of the time - 10 kilolux is exceeded for 73% of the time - Illuminance at an office desk is typically 0.5 kilolux - This is exceeded outdoors for 95% of the time - Therefore, there is a large potential for using daylight for ________ illuminance, however the daylight levels are ________

internal, variable

Daylight factor = SC+ERC+IRC, where: -SC (%) = ___ _________ - light directly from the ___ - ERC (%) = ____________ reflected components; light received from the ground, buildings and other surfaces - IRC (%) = __________ reflected surfaces - light received from inside the room

sky factor, sky, externally, internally

___________ emiprical formula can be used to calculate the mean DF

Littlefair's

Occupant satisfaction generally increases with a well ______ space, providing that problems with _____ and overheating are avoided

daylit, glare

LUMEN LIGHTING DESIGN METHOD: - standard way to design lighting in most spaces - Determines the lighting requirement for a room - Accounts for ______ and _______ illuminance - Based on assumptions that are not always correct: -- Room is ____________ -- There is a regular arra of luminaires Feeds into the lumen formula

direct, indirect, rectangular

DAYLIGHTING: Daylight appears free, however windows: - Provide an easy ___ flow path - Have poor _____ insulation properties - Allow outdoor pollutants in - Cause overheating due to _____ gains

heat, sound, solar

COSINE RULE: when light strikes a surface at an inclined angle it will illuminate a larger surface area than if it strikes at right angles. ___________ will therefore be reduced

illuminance

As the light source gets further away, _________ decreases. This principle relates to the inverse square law.

intensity

SURFACE COLOUR SPECIFICATION: The _______ colour atlas; colour is specified in three terms: - ___ (the actual colour) - _____ (a measure of whiteness/blackness) - ______ (intensity of the colour, where pale/neutral is 1, satuated/intense is 14)

munsell, hue, value, chroma

Flux: - ____ of ____ of light energy - Units = _____ - One _____ is the luminous flux emitted within one steradian by a point source of light of one candela.

rate, flow, lumen, lumen

Daylight factor depends on: - Position of the _________ point with respect to the sky and windows - size of the window - type of glass - details of the glazing bars - dirt on the glass - Obbstructions externally or internally - internal and external reflectance factors

reference

DAYLIGHT: - light from the whole sky - in overcast conditions does not vary - Brightest at the ZENITH SUNLIGHT: - direct from the ___ - position _______ during the day - Depends on latitude, time of day and year

sun, changes

Illuminance: - Density/amount of light energy hiting a _______ - This is usually the primary consideration when designing lighting for buildings. - Can range from __lux for domestic settings, ___lux for offices, to __,___lux on a hospital operating table

surface, 50, 500, 50,000

Solid Angle concerns the spread of light in _____ dimensions. Unit of solid angle is _________.

three, steradian

Outside illuminance varies considerably throughout a ____ and during a ___. An illuminaiton level of _,___ lux is exceeded for 85% of the normal working day throughout the year. (500 lux from artificual lighting is considered generous)

year, day, 5,000

DISCHARGE LAMPS A high _______ is applied across the ends of the lamps IONISATION - some atoms become ionised, producing +ions and free elctrons (-) EXCITATION - as electrons accelerate they collide with gas atoms and displace outer electrons to higher energy levels. When electrons return to their original position the enrgy they lose is emitted as photons of radiation - E.g flourescent tube lighting. Coating on tubes gives out the white light - if no coating applied, the only UV light would be emitted

voltage

Transmission factor for glazing is usually assumed at _._

0.8

DAYLIGHT FACTOR = amount of light at a point within a room expressed as a percentage of that available simultaneously from the ____________ sky. These factors are a ________ measure of light; as the levels of daylight outside decrease, so will the levels inside but the DF will always give the same % value. Artificial lighting systems are designed for an ________ measure

unobstructed, relative, absolute

LIGHT COLOUR SPECIFICATION: The ___ Chromaticity diagram, describes any colour as a mixture of ___ (x), _____ (y) and ____ (z). - Works on the basis that x+y+z=1, therefore only need to plot x and y to specify a particular colour

CIE, red, green, blue

Lumen formula: -Average illuminance at the working plane is standard data provided by _____ - Plan area of working plane - floor plan of area - Initial lamp luminous flux - data obtained from manufacturer - Utilisation factor - is a ___________ between 0 and 1, based on decrease in illuminaiton due to distance and the inter-reflection of surfaces. Data obtained from manufacturer - Room reflectance - Data from CIBSE. dark rooms have _____ values -Room index - need this value (plus room reflectance) to calculate UF (when calculating UF, if you get a value of 54, UF = _.__, as it's a coefficient between 0 and 1. - Maintenence factor - another coefficient - as dirt builds up onto a fitting, lighting output will decrease - SHR = Surface to mounting height ratio. Ensures uniformity across the room.

CIBSE