5 - Daylighting And Lighting

Question 1

Why should daylighting (not sunlight) be used over artificial lighting?

Answer 1

Artificial lighting produces heat

Question 2

What is the energy efficacy of daylight compared to artificial?

Answer 2

Daylight 120-130 lm/W (lumens)

Artificial 80lm/W

Question 3

What does the amount of daylight in a room depend on?

Answer 3

The size of the opening
Amount of light reflected within the room
Room depth

Question 4

What is the maximum depth of a window if the room only has a window on one side?

Answer 4

2 times the height of the window

Question 5

What is the maximum depth of a room with windows on opposite sides?

Answer 5

5 times the height of the window

Question 6

What are the 5 factors of daylight penetration?

Answer 6

1. Type of shading device at window
2. Glass & window treatment
3. Level of artificial lighting within the room
4. Room with depth >2h needs permanent artificial lighting

Question 7

What is the daylight factor equation?

Answer 7

( Inside illuminance / outside illuminance ) x 100

Question 8

What are the ranges for daylight factor and what do they mean?

Answer 8

> 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

Question 9

What are the factors for daylight factor?

Answer 9

1. Size of daylight apertures
2. Location of daylight apertures
3. Access to daylight
4. Room geometry
5. Visible transmittance of glazing
6. Reflectances
7. Daylight enhancement devices

Question 10

What are the optimum dimensions for a lightshelf?

Answer 10

d1/d2 should not be greater than h1/h2

Min ceiling height 3m

Iight shelf as reflective as possible

Question 11

What are the 3 important properties of glass re: thermal and lighting?

Answer 11

1. Amount of light that can pass through (transmittance)
2. Amount of heat that can pass through by conduction
3. Amount of heat that can pass through by radiation

Question 12

What are the 2 main purposes of views?

Answer 12

1. Psychological need to have a connection with the outside world
2. Reduce eyestrain by providing long distance views

Question 13

What are the 2 main disadvantages of artificial lighting?

Answer 13

1. High energy consumption

2. Heat production and subsequently higher cooling demands

Question 14

What are the 4 main ways of reducing energy consumption by artificial lights?

Answer 14

1. Maximise daylight
2. Use the appropriate lighting system
3. Use the correct lamps
4. Design a system that is responsive to daylight and users needs

Question 15

Lighting basics?

Answer 15

1. Lamp = bulb
2. Luminaire = light fitting that incorporates the lamp
3. Controls = switch

Question 16

What is the rule of thumb for calculating electrical energy required to illuminate an area?

Answer 16

3 Watts req to illuminate 1sqm to 100 lux

Question 17

What are the best types of lamps?

Answer 17

LED and fluorescent

Question 18

What are the 3 main types of switching? (Electrical)

Answer 18

1. Central timing (turns lights off after set time)
2. Occupancy detection
3. Automatic dimming through detection of daylight

Question 19

What is Luminous Flux?

Answer 19

Amount of light produced by a lamp (lumens)

Question 21

What is Illuminance?

Answer 21

Amount of light (luminous flux) falling on an area (lumens per sqm, lux)

Question 22

What are the differences between solar PV and solar thermal?

Answer 22

Solar PV cheaper, easier to install with less regulations thus less hassle.

Question 23

What is Efficacy?

Answer 23

Ratio of ( light emitted / power consumed) by a lamp