About Shadow Studies

You can use shadow studies to optimize building designs for natural day lighting and make sure that they are meeting local regulations. An optimized building will be able to maintain a suitable interior temperature and provide adequate natural lighting, leading to significant energy savings. The position of the Sun and the path it takes in the sky affects the shape and duration of shadows of a building. By learning more about the expected paths that the Sun takes through the year, you can predict the shadow patterns that the building creates.

This page discusses:

Position of the Sun

We use celestial coordinate systems to determine the position of the Sun and other objects in the sky. The horizontal coordinate system is one such method, in which you can use your local horizon as a fundamental plane. The position of the Sun and other objects in the sky can be expressed in terms of azimuth and elevation, with reference to this fundamental plane.

Azimuth

The azimuth shows how far the Sun is from the North. To find the azimuth, draw a projection of the Sun on the ground, and measure the angle it makes from the North. For example, if the Sun rises at due east and sets at due west, the azimuths for sunrise and sunset would be 90 degrees and 270 degrees respectively.

Elevation

The elevation shows how high the Sun is from the horizon. To find the elevation, draw a line between the Sun and the view point, and measure the angle it makes from the ground.

Note: The elevation is at its highest value during a summer solstice, and at its lowest value during a winter solstice.

Annual Path of the Sun

The Sun follows a different path throughout the year, with respect to a point on the Earth. This happens due to the axial shift of the Earth, with respect to the Sun. As a result, the shadows that are created during summer season, for example, would be different from those created during winter. The following concepts can be used to study shadows created through the year:

Analemma

The analemma plots the position of the Sun in the sky at the same time of the day throughout the year for a given location. The analemma can be used to understand the extreme positions of the Sun for the same time of the day, throughout the year. For example, you can use the analemma to find all possible building shadows for noon time in a year.

Solstices and Equinoxes

The path of the Sun changes throughout the year. For most places on Earth, the path of the Sun is the longest during summer solstice and shortest during winter solstice. Summer solstice day has the longest period of daylight, while the winter solstice night has the shortest period of daylight. During equinoxes, the duration of day and night are nearly equal.

This table lists the most important dates for shadow studies:
NameDateNorthern Hemisphere nameSouthern Hemisphere nameDescription
March Equinox (Northward Equinox)19 March to 21 MarchSpring EquinoxAutumn (or fall) EquinoxThe Sun's path during the March equinox is directly above the Earth's equator, after which it will move northward. The Sun rises due east and sets due west.
June Solstice (Northern Solstice)20 June to 22 JuneSummer SolsticeWinter SolsticeThe Sun's path is directly above the Tropic of Cancer in the Northern Hemisphere. The Sun is at its closest point to the North Pole.
September Equinox (Southward Equinox)21 September to 24 SeptemberAutumn (or fall) EquinoxSpring EquinoxThe Sun's path during the September equinox is directly above the Earth's equator, after which it will move southward. The Sun rises due east and sets due west.
December Solstice (Southern Solstice)20 December to 22 DecemberWinter SolsticeSummer SolsticeThe Sun's path is directly above the Tropic of Capricorn in the Southern Hemisphere. The Sun is at its closest point to the South Pole.

Note: Due to the axial tilt of the Earth, the Sun is visible over the horizon from the North Pole and the South Pole continuously for half a year. The daylight in polar regions lasts from several days to several months around summer solstice, as you move closer to the pole.

Heliodon

The heliodon mimics the total area in the sky in which the Sun moves throughout the year. In the 3D area, the heliodon is a combination of analemmas and sun paths. For any selected date, the heliodon displays 12 sun paths that simulate the movement of the sun in different months of the year. You can select an analemma or sun path from the heliodon while performing a Cast Shadow study.