Daylight Flashcards
Describe the term (metric) Daylight Autonomy (DA)?
Daylight Autonomy is the percentage of time that daylight levels are above a specified target
illuminance within a physical space or building for a given duration of time.
Describe the key (basic) photometric parameters.
Luminous Flux is measured in lumens and refers to the total amount of visible light emitted by a source per unit of time. One lumen is the flux produced by a source with one candela of luminous intensity over a solid angle of one steradian.
1 lumen (lm) = 1 candela (cd) ⋅ steradian (sr)
The luminous intensity is measured in candela. it is the luminous power per unit solid angle emitted by a point light source in a particular direction.
circle Perimeter L = 2 ⋅ π ⋅ r Sphere Area A = 4 ⋅ π ⋅ r2 Solid Angle Ω = A / r2
Uniform light emitting source flux Φ = 1 cd ⋅ 4 ⋅ π ⋅ sr = 4 ⋅ 3,14 ⋅ cd⋅sr ≈ 12.57 lm
Illuminance is the measure of the amount of light (luminous flux) received on the surface. lux (lm/m2)
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls within a given solid angle. (cd/m2)
Describe the term “Visible Light Spectrum”
The visible light spectrum is the segment of the electromagnetic spectrum that the human eye can view. Daylight is the visible part of the electromagnetic spectrum
What is the visible transmittance of glazing?
Visible transmittance (VT) of glazing tells us how much natural light can pass through a window, glass, or any other transparent surface. A higher visible transmittance means more light is allowed to pass through, contributing to better natural lighting in a space.
Define the term “Daylight Factor”.
The daylight factor quantifies how well natural light is distributed throughout a specific area within a building in relation to the amount of sunlight available outside.
What is the difference between sunlight and daylight assessment?
The terms “sunlight” and “daylight” refer to different aspects of natural light, and their assessment in the context of building design and energy efficiency serves distinct purposes:
Sunlight assessment focuses on the direct sunlight that reaches specific points or areas within or around a building.
Daylight assessment is a broader concept that encompasses all available natural light during the daytime, including both direct sunlight and diffuse skylight. It measures the overall illumination levels within a space and evaluates how well natural light penetrates and distributes throughout the interior.
Describe the four areas of assessment in the European Daylight in buildings standard EN 17037.
Daylight
This area of assessment focuses on the overall provision of daylight within a building. It considers factors such as daylight availability, illuminance levels, and the distribution of natural light throughout the space.
View
The “View” assessment area emphasizes the importance of maintaining a connection between indoor spaces and the external environment. It considers the quality of views from indoor spaces to the outdoors, taking into account factors like the visibility of natural features, landscapes, or urban surroundings. A good view is associated with positive effects on occupants’ psychological well-being.
Sunlight
Sunlight assessment involves evaluating the direct and indirect exposure of spaces to sunlight. Proper sunlight assessment helps optimize the balance between daylighting benefits and the potential for glare or overheating.
Glare (bländning)
Glare assessment focuses on the evaluation and control of extreme brightness and contrast that can cause discomfort to residents.
