Daylight factor


Also found in: Medical.

Daylight factor

The ratio of interior illuminance at a given point on a given plane, usually the workplane, to the exterior illuminance under known overcast sky conditions. This is one of the key values when analyzing the quantitative aspects of daylighting. Since the outside illuminance varies a lot with weather conditions (8,000–25,000 lux), the interior illuminance alone does not provide much useful information. The acceptability of the amount of daylight reaching an interior space for a specific task can only be determined in relation to the situation outside. There is little use in computing the relation of outside and inside illuminances under sunny sky conditions.

daylight factor

The ratio of the illumination at a point on a given plane to the illumination on a horizontal plane from the whole of an unobstructed sky of assumed or known luminance distribution; a measure of the daylight illumination at that point.
References in periodicals archive ?
El Factor de Luz Diurna, Daylight Factor, ha sido por anos una de las metricas mas usada a pesar de las limitaciones.
The results have indicated the minimum, average and maximum illuminance and daylight factor in the high-rise residential building affected by building shading effect, whereas, 30m of building separation is the best distance between buildings in terms of planning to obtain the acceptable daylight and to enhance the daylight performance in the building.
Realistically, there is no uniform sky that is uniformly illuminated so that values of the percentage daylight factor in building spaces can be directly measured.
Below we present the daylight factor and the daily total radiant energy of the courtyard space.
Calculation of daylight factor DF [%] was carried out for the determination of an effect of three different types of window glasses on the indoor daylighting level in the investigated office.
The most commonly used metric for measuring daylight in a building is called the "daylight factor"--expressed as a percent of available exterior daylight.
As an example, for London weather data with a daylight factor of 3%, 250lux (23.2fc) would be exceeded for 75% of office hours (0900-1730) (CIBSE Guide A).
An ambitious aim was to make the classrooms fully daylit, but even a complete side wall of glass allows a daylight factor only of 3.5 per cent at the back of the room.
Reductions in lighting consumption are awarded for increasing daylight factors; a 20% reduction is available for a daylight factor greater than 10%, a 10% reduction available for a factor greater than 5%, and a 5% reduction available for a factor greater than 2%.
This study examines the impacts of aperture size (daylight factor) for four combinations of toplighting strategies and glazing types on the total yearly energy loads for a prototypical open office space situated in four different climates.
For the simulation of this new single zone atrium house, we used Autodesk Ecotect program to calculate the daylight factors in the worst case condition (mid winter at noon) and chose a better fenestration design for the house.