Week 2a: Lighting environment

Light is not visible on it’s own, it’s visible because

It hits a surface

What can happen when light hits a surface

Refraction, reflection and transmission

Why do we see a red door as red

Because red is the only colour not being absorbed but reflected

What is light

Electromagnetic radiation visible to the human eye, ranging from wavelengths (labda) between 380 nm and 780 nm

Why can you not say UV light or infrared light

Because we can’t see it, it is radiation

What does the human light sensitivity curve mean

The brightness perception of green and yellow are stronger than blue and red

When are cones active and what do we call that vision

Daytime and photopic vision

What is radiometry

Deals with quantities associated with radiation including light

Why are all photometric quantities psychophysical

They are related to human perception

What is luminous flux + unit

Amount of light energy per second emitted per second in all directions, weighted against the spectral sensitivity curve of the human eye + lumen

What is luminous intensity I + unit

Describes the luminous flux emitted into a certain solid angle + candela

Solid angle + unit

Relationship between the sphere and the area we are looking at

Formula solid sphere

Area / r²

What is the solid angle of a sphere

4*pi

What is luminous reflectance p

Percentage of visible light reflected by a surface

What is luminance + unit

Light perceived from the surface + cd/m²

What is illuminance + unit

Light on the surface + lux

The definition of luminance is: luminous flux emitted by that surface in the direction towards the perceiver, per solid angle and per unit of apparent area. What does apparent mean?

By taking the apparent area into account, luminance accurately measures perceived surface brightness regardless of the viewing angle.

Glare

Too high luminance or luminance contrast that cause discomfort

What are the two types of glares

Discomfort and disability glare

Formula contrast

C = (L0 - Lb)/Lb or C = Lmax/Lmin

Transmission + refraction + reflection = ?

1

Types of reflection

Specular, diffuse and mixed

Why is illuminance great for measurements and directions

Because it is easy to measure and because we can decide what a surface needs for minimum light source without being influenced by the material

What is the pain threshold for luminance

100,000 cd/m²

CCT abbreviation + unit

Correlated colour temperature + Kelvin

What is CCT

Temperature of a black body radiator that emits light similar to the light source

CRI abbreviation

Colour rendering index

CRI definition

How well a light source renders colours

Luminance distribution and adaptation implication

Not only enough light for comfort and tasks, but also a well lit environment

Rule of thumb for luminance distirbution

1:3:10 (ten times as bright on your task, direct environment and then environment)

How long does it take to adapt from bright to complete darkness

20 to 30 minutes

How long does it take to adapt from complete darkness to bright daylight

5 minutes

What do we find relevant in our view

Ground (people, activity), sky and landscape

Impact of too little or too much light on health of the user

Circadian misalignment, vision loss, safety

Which three colours are cones

Red, blue and green

Image forming pathway in your head

1. Rods & cones

2. Visual cortex

Non-image forming route in your head

1. ipRGC

2. Supra Chiasmatic Nucleus

3. Pineal gland

ipRGC abbreviation

Intrinsic Photosensitive Retinal Ganglion Cell

What is the peak sensitivity of the ipRGC

480 nm

Which hormone is suppressed when the ipRGC is triggered

Melatonin

5 quality criteria healthy dwellings

1. Daylight availability

2. Glazing

3. View

4. Direct sunlight

5. Solar and brightness control

Daylight factor formula

DF = Ep / Eh (Ep = position, Eh = outdoor)

Daylight factor: worst case is overcast sky, what is the luminance gradient ratio

Horizon: Zenith, 1:3

Picture

In the middle on top

Name all arrows

• Blue: DFsc (sky component)

• Green: DFext (external reflected component)

• Red: DFint (internal reflected component

Increase daylight availability: Urban planning

Reduce obstruction outdoors

Increase daylight availability: architectural planning

Position and size of the window openins

Increase daylight availability: space planning

Bright indoor environments

What does the window look like

Average

What does the window look like

Wide

What does the window look like

High

What does the window look like

Wide and high

What does the window look like

On top in the middle

Name the skylights

Clerestory, monitor, sawtooth, skylight

Quality criteria for luminous transmittance

tau > 0.5

Criteria: From (…) meter from the facade, one should have (…) degrees of unobstructed view

2, 28

Top: 1,2,3 Bottom: 4,5

1. Reflection

2. Absorption

3. Scattering

4. Direct

5. Diffuse

What is y and a

Elevation angle and azimuth angle

Design methods to reduce glare from daylight

1. Increase indoor illuminance

2. Decrease the source by shielding

What is the difference between solar control or sun shading devices in the south, north and east/west

• South: Dynamic and high daylight levels, easy shading

• North: Constant daylight, shading early morning or late evening

• EW: Complex

Things to consider when adding solar and brightness control

• Flexibility

• View

• Type of architecture

• Outside perception

Three steps for built environment design strategies for daylight

1. Define what is required from the user’s perspective

2. Design according to the possibilities and limitations

3. Find solutions that are sustainable without comprimising user’s needs