DAYLIGHTING DAYLIGHT Indoor space lighting by the natural

DAYLIGHTING DAYLIGHT Indoor space lighting by the natural sun light and even the sky light coming through the lighting openings to the space directly or reflected by the external obstacles. Characteristics: • Changes in parameters during the day and year • Side lighting (windows) – characteristic rendering of spatial objects and a luminance distribution in the room (visual comfort) • Glare issue – checking the values of luminance (sun and sky) • Solar radiation – influence on thermal comfort in space

DAYLIGHTING Sky is considered as a area light source. Status of this light source during the day and year change dynamically depending on the position of the sun and the sky conditions and thus change the value of illuminance by the day light. Due to this it is introduced relative evaluation, which is not significantly affected by these changes. Nevertheless the value is definite only when predetermined sky characteristics. Assessment is based on the worst-sky conditions (CIE overcast sky). Luminance level is affected just by the reflective properties of the surrounding due to the multiple reflections of the sky light between the surface and the bottom layer of clouds. The sun position is neglected and the luminance of the sky is dependent just on the elevation angle . Luminance distribution is dependent on the reflective properties of the surrounding surface.

DAYLIGHTING Dark terrain: cd/m 2; cd/m 2, ° Snowy terrain: cd/m 2; cd/m 2, ° cd/m 2; lx where L – luminance value for the elevation angle Lm – average luminance value of the sky Eh – illuminance of the exterior unobstructed horizontal plane – elevation angle above the horizon

DAYLIGHTING Resulting illuminance E consists of three components: (lx; lx, lx) where Ep direct (sky) component of illuminance Ee externally reflected component of illuminance Ei internally reflected component of illuminance

BASIC TYPES OF DAYLIGHTING SYSTEMS 1) Side-lighting openings – windows in the walls of the building (illuminance decreases rapidly with the distance from the window, in many applications is this kind of uniformity acceptable and welcome) 2) Top-lighting openings – openings at the ceiling/roof construction 3) Lightways Windows performs next to the illuminance of the space another important role in visual contact with the outside environment. Basic parameters: location dimensions transmission impurity

DAYLIGHT EVALUATION (%, lx) where D – daylight factor E – illuminance level in the control point at the height of working plane Eh – illuminance level of unobstructed external horizontal plane under specified conditions (CIE overcast sky) Daylighting standards for the Czech republic: ČSN 73 0580 -1 Denní osvětlení ČSN 73 0580 -2 Denní osvětlení obytných budov ČSN 73 0580 -3 Denní osvětlení průmyslových budov

DAYLIGHT EVALUATION Class of visual activity Characteristics of visual activity The relative viewing distance Examples of visual activities I extremely accurate 3330 and higher Daylight factor value minimal Dmin (%) average Dm (%) The most accurate visual activity with limited use of magnification with the requirement to exclude errors in the resolution, the most difficult control. 3, 5 10 very accurate 1670 to 3330 Very accurate visual activity at the production and control, high-precision drawing, hand engraving with very small details, very fine art works. 2, 5 7 accurate 1000 to 1670 Accurate production and control, drawing, technical drawing, difficult lab work, demanding examination, fine sewing, embroidery. 2 6 medium accurate 500 to 1000 Medium accurate manufacturing and inspection, reading, writing (hand machine), machine operation, routine lab works, examination, treatment, rougher sewing, knitting, ironing, cooking, racing sports 1, 5 5 V rough 100 to 500 Rougher work, handling objects and materials, food consummation and service, recreational activities, basic and recreational physical education, waiting 1 3 VI very rough less then 1000 Cleanliness maintenance, showering and washing, dressing, walking on the public open roads 0, 5 2 VII overall orientation - 0, 25 1 II IV Walking, material transport, storage, the overall supervision

DAYLIGHT EVALUATION 1) Daylight factor • Values of Dmin have to pass at all points in space for the given activity • Values of Dm have to pass for a top lighting and combined lighting with a higher part of top-lighting than side-lighting • Spaces with the long term staying of persons: Dmin=1, 5% and Dm=3% 2) Uniformity, r = Emax / Emin Side-lighting: Class I to IV, r > 0, 2 Class V to VII, r > 0, 15 Top-lighting: automatically satisfied by compliance Dmin and Dm

GLARE 1) Glare Users have to be avoid to glare at the overcast, cloudy or clear sky conditions. • Sun glare have to be excluded in all work environments at least for a working areas • Luminance of the light openings during the normal viewing direction can not cause glare. The important is the choice of the normal viewing angles to the lighting openings. • When the angle between the plane of the window and the normal viewing angle is < 60°, luminance of the lighting opening Lo<4000 cd/m 2, and the ration of the observed object and the sky luminance Lp: Lo > 1: 200

GLARE Possible limitations of direct sun radiation to keep thermal comfort • Suitable orientation of the building, reduction of glazed areas on sunless side • Special glass absorbing IR component • Tilting of the glass facade • Sun shades (interior, exterior, horizontal, vertical, fixed, moveable) Limitation of glare caused by light openings: • Metalized glass of thin films with reduced transmittance • Sloping the windows reveals with a high reflection coefficient and the similar adjustment of window frames and walls • Illumination of the window walls

COMBINED LIGHTING – Permanent supplementary artificial lighting Permanent artificial lighting intended to supplement the natural lighting of premises, when the natural lighting is insufficient or objectionable if used alone. Used when for the certain visual activity natural light is not sufficient. Use of the combined lighting has to be approved by the authorities and is able to use just in justified cases (e. g. Old building refurbishments and so on) Function: supplementing the daylight eliminating the silhouette effect Design of the combined lighting (PSALI – permanent supplementary artificial lighting) Standard requirements: ČSN 36 0020 -1