luz e sombra na arquitetura
ombre et lumière dans l'architecture




a. Radiation

Energy in the form of electromagnetic waves, emitted by vibrating molecules of a surface. Unit of measurement: kilowatt-hour, joules etc

b. Luminous flux
The time rate of light flow. Unit of measurement: lumen (lm)

c. Luminous  intensity

The amount of luminous flux emitted by a light source in a certain direction. Unit of measurement: candela (cd) or lumen per steradian

d. Illuminance

The density of luminous flux reaching a surface, called ‘illumination’. Unit of measurement: lumen per unit area: footcandle (lm/ft2) or lux (lm/m2)

e. Luminance

Luminous intensity reflected at a surface in a certain direction. The amount and composition of luminance is determined by the properties of the lit surface. The human eye sees luminance and not illuminance and ‘brightness’ is the subjective perception of luminance. Unit of measurement: footlambert or candela per unit area (cd/m2)

f. Correlated colour temperature (CCT)
Relates the temperature of a radiating object and the colour of light it produces. The CCT of daylight ranges from 4 000 K (sunrise and sunset, when mainly the long-wave red light passes through the atmosphere) to 12 000 K (midday, when mainly the short-wave blue light is scattered). Unit of measurement: Kelvin (K)

g. Light transmittance

The ratio of transmitted flux to incident flux.

h. Light reflectance

A percentage of reflected flux divided by incident flux.

i. Daylight factor (DF)


The percentage of the interior illuminance at a certain point divided by the exterior illuminance of the standard overcast sky (5 000 lux). It is measured on a horizontal plane 60 to 85cm above floor level. The aim of calculating DFs is to assure that there is sufficient incoming daylight at the most critical condition. Nonetheless, recommended DFs (between 2 and 5%) are not high enough to achieve an optimum use of daylight.

j. Glare

A subjective phenomenon of excessive brightness contrast between foreground and background within the visual field, i.e. when the eye perceives a much higher luminance than the one it is adapted to. Depending on the level, this sensation may cause discomfort or disrupt the eye’s ability to distinguish objects from their background. Can be a result of direct sunlight, contrast between dark and bright surfaces or indirect light.

k. Veiling reflection
A form of reflected glare that happens when the incident light is reflected by a glossy task surface, thus obscuring details by reducing the contrast.


Atria are original from ancient Greek and Roman and also Arab courtyard  houses. Nowadays, an atrium is described as a covered courtyard.  

Courtyard - or the Spanish word patio - is an uncovered internal void within or between buildings.  

Clerestory is a type of side window whose sill height is above eye level.  

Lantern is a glazed turret on the top of a dome. 

In light shafts, daylight is delivered from higher above than in common clerestories and channelled through long and narrow spaces.  

Roof monitor is raised section of the roof with perpendicular or sloped surfaces and a glazed opening on its top.  

Skylights are horizontal apertures on the roof and parallel to it.