Jun 25, 2019

 

DAYLIGHT

“No space, architecturally, is a space unless it has natural light.”

— Louis I. Kahn

Daylight- The natural light of the day
Daylighting- The use of light from the sun and sky to complement or replace electric light with appropriate fenestration and lighting controls to modulate daylight admittance. It is a source of heat as well.

Objectives for applying daylighting systems:

  • Redirecting daylight to under-lit zones
  • Improving daylighting for task illumination
  • Improving visual comfort, glare control
  • Achieving solar shading, thermal control.

  • Diffuse light – The light which comes from larger and regular openings.
  • Direct light – The light which comes from the direct sunlight at the desired location on the floor or other surface.
  • Zenith light – The light which comes from the ceiling.
  • Reflected light – The light which comes from any surface and redirected into space.
    • A large light well may be referred to as an atrium.
    • These open directly on roofs, in most cases with pyramidal or gabled geometries, built with metal profiles and a glass closure.
    • This typology is recommended for buildings with a greater number of floors.

    Types of atriums

    • It allows the direct entrance of natural light into the internal region of the construction.
    • The use of translucent glass on its upper side allows high percentage of light but also tend to gain thermal loads, which increases temperature.
    • A layer of laminated glass or polycarbonate can be used which allows light to enter indirectly and reduces the light percentage.
    • These devices based on the saw tooth geometry of the roofs, with inclinations strategically arranged to receive light.
    • They are usually positioned in relation to the facade with less sunlight, allowing natural light without direct sunlight.
    • In this system it is essential to close by glass frames to prevent infiltrations from the rains.
    • The openings that protrude in relation to the roof, they can appear as small roofs superimposed on the ridges, creating small glazed projections that receive the entrance of natural light.
    • This system allows the continuous renewal of the air if mobile frames are used, allowing constant changes from the assumption that hot air tends to rise.
    • Domes provide a more far-reaching lighting effect in comparison with other zenithal systems.
    • Due to the large dimensions assumed, they tend to generate large thermal loads inside the buildings.
    • These systems carry light through reflections where it is not feasible to install other systems.
    • Internally the tubes are coated with reflective materials, generating different light intensities as a result of their dimensions and materiality
    • Prismatic glazing is designed to change the direction of incoming sunlight and redirect it by way of refraction and reflection.
    • It can be placed in the upper portion of a side window as a ray of light hits the prism, part of the light is then directed towards the ceiling to be later reflected, while the other part comes inside the room directly.

    a. Moveable prism system

    These offer solar protection and control the daylight: orthogonally incident sunlight is reflected while daylight entering from other directions is guided into the room.
    These can be installed vertically to facades or horizontally upon glazed courtyards or glass roofs.

    b. Stationary prism system

    These enlarge the blockage range and completely eliminate direct sunlight, allowing use especially in inclined glass facades and roofs.
    The plates are cut to suit and installed in insulated window panes, rooflights and glazed roofs. This guarantees protection from humidity and soiling.