Earthship Belgium vzw

March 20, 2010 (revised February 11, 2011) - For optimum use of the wintersun solstice to heat the earth walls, the windows of the greenhouse of an earthship needs to be placed in the correct angle. So, what is this right angle?

The correct angle varies from place to place. The purpose is that the winter sun at its highest point during the winter solstice, shines perpendicular to the windows. This is done to prevent loss by reflection. In contrast, the beams of the high summer sun will be reflected optimal.

For this it is necessary to determine the hight of the sun during the winter solstice on our northern latitude. We have used data from Uccle, a beautiful central point in Belgium. The difference a little more north or south is so minimal that it is negligible. So these data are suitable for the whole of Belgium.

During the winter solstice the sun at his highest is rounded to 15^o degrees above the horizon (minutes and seconds are negligible). Therefore the ideal angle for the windows of the greenhouse is 75^o degrees.

Summer solstice versus Winter solstice - Illustration: W. Raets and D. Deman

In the above illustration, this means an Earthship that is situated 1 meter deep in the ground and has a lenght of 9,60 meters from the front greenhouse windows to the rear tire wall. The wintersolstice sunrays can reach the rear tirewall. The height of the ceiling is approximately 2,80 meters at the level of the front separation wall. The ceiling height near the rear tire wall is approximately 2,55 meters, in the green house approximately 3.65 meters.

By building the lower part of the separation wall (between the greenhouse and the living room) partly with earth rammed tires, you create extra heat storage, because of the extra sunlight it can collect.