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Daylight Factor
The daylight factor (the ratio between interior illuminance measured at a given point – to the exterior illuminance under overcast sky conditions) is normally used to evaluate if there is sufficient daylight in a room (for a certain visual task). The spread of daylight factor (DF) values gives an indication of the variations of daylight perceived through the rooms. People prefer (according to Loe, 1997) an interior with a measure of “visual lightness” combined with “visual interest”. An average DF of 5 % or more will ensure that an interior looks substantially daylit (according to the British Lighting Guide, CIBSE 1997).
The radiance simulation done for SOLTAG shows that the living room has an average DF of 12.7 %, the bed- room 8.7 %, the bathroom 9.7 %. These DF levels will ensure generous daylight conditions and through this a high degree of desirable visual interest. The entrance hall with a DF of 0.9 % will create a transition of experience between the outdoor light conditions and the larger rooms of the apartment.
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Luminance
The luminance corresponds to the amount of light reflected or emitted off surfaces. Establishing luminance ratios between surfaces of a given room permits evaluating its daylight quality and visual comfort. Luminance ratios higher than 1:20 (high contrast) are considered to be potential sources of visual discomfort (glare), whereas ratios of 1:1 (low contrast) can make a room look dull. The following luminance evaluation has been made by using high dynamic range
pictures taken in the demo house. The luminance output is presented in false colour with numerical luminance values.
Click to enlarge the diagram
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