Building Architecture – Sun Path Analysis

Architecture has evolved over the years and today the facade plays an important role in defining the architecture / form of the building. With modernity, glass has become eminent material for façades for its aesthetic appeal and functionality. However, the inappropriate or inefficient use of glass may result in unwanted heat gain inside the building. While choosing the right energy efficient glazing solution, the façade design needs to incorporate the building location and an understanding of solar geometry with respect to the building. Every building design is classified as Passive Design strategy & active design strategy.

• Passive design, results when a building is created and simply works "on its own". The plan, section, materials selections create a positive energy flow through the building and "save energy".

• Active design uses equipment to modify the state of the building, help maintain energy efficiency and provides comfort; i.e. Fans, pumps, etc.

A good passive design reduces heat gain thereby reducing the dependency on active designs such as air-conditioning system, lighting system etc..,
One of the important passive designs is the Sun Path.
BASICS OF SUNPATH
Earth's orbit is an ellipse, not a circle. The distance between earth and sun varies as revolution occurs. Earth's axis is tilted to a plane of elliptical orbit of 23.5 degrees which causes seasons. Northern hemisphere faces sun in June & Southern hemisphere faces sun in December.
To understand the sun path we need to visualize a skydome - Imaginary "dome" over building site. Every hour of day, we can "mark" points where sun's rays penetrate sky dome. This creates sun path for day. Most critical part of day is the "solar window"

Components of a Sun Path
Position of sun in the sky is defined by azimuth angle & altitude angle. Solar azimuth (Y) is angle along the horizon of position of sun, measured to the east or west of true south. Solar altitude (X) is the angle measured between the horizon & the position of the sun above the horizon. These enable you to locate the position of the sun at any time of day, month and location.

Southern hemisphere : The movement of the sun is east to west through north.

Northern hemisphere : The movement of the sun is east to west through South India falls in this hemisphere. High intensity sun fall is received in the South & South west directions. North is exposed to very low solar radiation.

SHADING DEVICE

Shading is one of the key strategies to achieve thermal comfort and it also impacts the daylight penetration. An ideal shading strategy or device will block maximum solar radiation while still permitting daylight, views. Shading device also depends on climatic conditions and nature of building.

• Horizontal shading device such as overhangs are best for south where solar altitude is high. For Indian Climatic type, shadings are ideally suited for Southern direction

• Vertical Shading device such as vertical fins are best for east and west where solar altitude is low

To understand the calculation & effect of shading device on glass and building performance, keep watching this space. The same will be covered in next edition :

Building Architecture – Sun Path Analysis Part :02

To know more write to us at : designstudio@saint-gobain.com.