How do I calculate shadow length

I am trying to ascertain how long the shadow will be of a building to be constructed near be at different times during the year. I am looking for a formula that will allow for the direction I am facing. Obviously as the sun moves from East to West it is only at certain times of the day this building will cause shadow that may or not affect my depending on the length. I should appreciate any help

im-fran

The length of the building's shadow can be computed if you know the height of the building and the altitude of the sun above the horizon (measured in degrees), like this:

Length of Shadow = Height of building/tangent(sun altitude)

The altitude of the sun changes throughout the day - obviously being lowest at sunrise and sunset and highest at around noon. It also varies by season - the sun is lower in the sky in December than June, and so the building casts a longer shadow.

Here is a web tool that allows you to determine the sun's position in the sky for any day and location:

Altitude and Azimuth of the Moon/Sun (USNO) (http://www.stargazing.net/mas/usno6.htm?Sun)

Use a three dimensional software program for this also, i.e.. Sketchup or 3d Studio max, as this will allow you to build a virtual model of your proposal, and check sunlight angles/ shadows etc