Daylight factor


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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 ?
The most popular and most used formula to measure and analyze day lighting performance in buildings is the percentage daylight factor [1],[2]&[3].
The baseline-modeled home has a maximum 20 percent window-to-floor area (with no skylights) with windows evenly distributed on all facades to achieve an average daylight factor of five percent.
The objective of study is to analysis the influence of light shelf device on the illuminance and daylight factor levels.
In this study, daylight availability was predicted using parameters such as daylight factor, daily radiant energy, and sunlight patterns.
For example, "for many years the yardstick metric of the Daylight Factor (DF) was the benchmark metric.
And, with the importance of light and the extent of its power to change moods and environments upper most in my mind, I may well continue to venture into the arena of ballast factor, daylight factor, cosine law and even units of luminance.
LEED requires a minimum daylight factor (DF) of 2% in 75% of all space occupied for critical visual tasks.
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.
As an example, for London weather data with a daylight factor of 3%, 250lux (23.
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.
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 shows that toplighting systems designed to meet a 2% daylight factor are not optimal.