DAY LIGHTING

If you want know about Principles of daylighting design or Climate and thermal comfort or Climate and elements of climate or Site climate or Koppen climate please click the link above.


1) Daylight

DAY LIGHTING ONE
  • Daylight, is the combination of all direct and indirect sunlight during the daytime.
  • This includes direct sunlight, diffuse sky radiation.

Artificial Light

  • Light source – Itself
  • Control by designers

Natural Light

  • Light source- Sun , Sky
  • Control by –Transmission & Distribution

2) Day light section

DAY LIGHT SECTION

Light can be distributed in 3 ways.

  • Reflected (r) = Transparent surface
  • Absorbed (a)= Opaque surface
  • Transmitted (t)= Translucent surface

In all case    :   r+a+t=1

In case of opaque   :   t=0, r+a=1

3) Type of reflection

Specular :

  • Each incident ray is reflected at the same angle. Surface is a plane mirror.

Spread :

  • The angle of reflection is same as angle of Incident, from a convex mirror the reflected rays will be divergent.

Diffuse :

  • Light reflect from a matt surface will be diffused.
TYPE OF REFLECTION

4) Sky conditions

i) Clear sky

CLEAR SKY
  • Sky that has less than 30% cloud cover.

ii) Cloudy sky

CLOUDY SKY
  • Sky having more than 70% cloud cover.

iii) Overcast sky

OVERCAST SKY
  • Sky completely covered by clouds, no sun visible.
  • The daylight factor in a particular building space depends upon a number of design factors including
  1. Size of daylight apertures (windows, etc.);
  2. Room geometry (height, width, and depth);
  3. Reflectance of room surfaces and contents;
  4. Reflectance of exterior surfaces affecting daylight entering the aperture;
  5. The effects of day-lighting enhancements (such as light shelves).

5) Light shelf

  • A light shelf is a horizontal surface that reflects daylight deep into a building.
  • Light shelves have high-reflectance upper surfaces, which reflect daylight onto the ceiling and deeper into the space.
LIGHT SHELF
  • Reflecting material on the top of the light self.
  • Allow a deeper penetration of light .
LIGHT SHELF ONE
  • Reduces hot spot at window. Use of artificial light can be reduce.
LIGHT SHELF TWO

6) Components of daylight

  • Sky component
  • Externally reflected component
  • Internally reflected component
COMPONENTS OF DAYLIGHT
  • A daylight factor (DF) is the ratio of the light level inside a structure to the light level outside the structure. It is defined as: DF = (Ei / Eo) x 100% 

Ei = illuminance on the indoors working plane,

Eo = simultaneous outdoor illuminance on a horizontal plane

  • The daylight factor concept is valid only under over cast sky conditions. When there is no direct sun light . 

DF = SC + ERC + IRC

Higher the window, greater the D.F. & deeper the penetration of light into space.


Related video

Leave a Reply

Your email address will not be published. Required fields are marked *

error: Content is protected !!