5 - Daylighting And Lighting Flashcards
(22 cards)
Why should daylighting (not sunlight) be used over artificial lighting?
Artificial lighting produces heat
What is the energy efficacy of daylight compared to artificial?
Daylight 120-130 lm/W (lumens)
Artificial 80lm/W
What does the amount of daylight in a room depend on?
The size of the opening
Amount of light reflected within the room
Room depth
What is the maximum depth of a window if the room only has a window on one side?
2 times the height of the window
What is the maximum depth of a room with windows on opposite sides?
5 times the height of the window
What are the 5 factors of daylight penetration?
- Type of shading device at window
- Glass & window treatment
- Level of artificial lighting within the room
- Room with depth >2h needs permanent artificial lighting
What is the daylight factor equation?
( Inside illuminance / outside illuminance ) x 100
What are the ranges for daylight factor and what do they mean?
> 2% - room gloomy with only daylight
2-5% - mostly daylit but some supplementary artificial lighting needed
< 5% - room strongly daylit but major thermal problems from large windows
What are the factors for daylight factor?
- Size of daylight apertures
- Location of daylight apertures
- Access to daylight
- Room geometry
- Visible transmittance of glazing
- Reflectances
- Daylight enhancement devices
What are the optimum dimensions for a lightshelf?
d1/d2 should not be greater than h1/h2
Min ceiling height 3m
Iight shelf as reflective as possible
What are the 3 important properties of glass re: thermal and lighting?
- Amount of light that can pass through (transmittance)
- Amount of heat that can pass through by conduction
- Amount of heat that can pass through by radiation
What are the 2 main purposes of views?
- Psychological need to have a connection with the outside world
- Reduce eyestrain by providing long distance views
What are the 2 main disadvantages of artificial lighting?
- High energy consumption
2. Heat production and subsequently higher cooling demands
What are the 4 main ways of reducing energy consumption by artificial lights?
- Maximise daylight
- Use the appropriate lighting system
- Use the correct lamps
- Design a system that is responsive to daylight and users needs
Lighting basics?
- Lamp = bulb
- Luminaire = light fitting that incorporates the lamp
- Controls = switch
What is the rule of thumb for calculating electrical energy required to illuminate an area?
3 Watts req to illuminate 1sqm to 100 lux
What are the best types of lamps?
LED and fluorescent
What are the 3 main types of switching? (Electrical)
- Central timing (turns lights off after set time)
- Occupancy detection
- Automatic dimming through detection of daylight
What is Luminous Flux?
Amount of light produced by a lamp (lumens)
What is Illuminance?
Amount of light (luminous flux) falling on an area (lumens per sqm, lux)
What are the differences between solar PV and solar thermal?
Solar PV cheaper, easier to install with less regulations thus less hassle.
What is Efficacy?
Ratio of ( light emitted / power consumed) by a lamp
