How do you calculate the sunshine loss caused by overshadowing by a building extension?

Answer 1

Firstly, you need to attain various solar zenith angles (angle of the sun in the sky) for your location. The sun is higher in summer, therefore casting less shadow, than winter, where it is lower. Furthermore, you will need to find out the angle of the sun throughout the day. As the sun travels through the sky, it will obviously cast different angled shadows.

When working out the shadow cast by the sun at various times and months, you need to factor in the height of the extension, and use trigonometry to project the shadow. You may want to do the existing buildings shadow diagram beforehand as means of comparing the two. It can be quite a long process to do accurately, however rough sketches will give you a good idea of the outcome. Firstly, you need to attain various solar zenith angles (angle of the sun in the sky) for your location. The sun is higher in summer, therefore casting less shadow, than winter, where it is lower. Furthermore, you will need to find out the angle of the sun throughout the day. As the sun travels through the sky, it will obviously cast different angled shadows.

When working out the shadow cast by the sun at various times and months, you need to factor in the height of the extension, and use trigonometry to project the shadow. You may want to do the existing buildings shadow diagram beforehand as means of comparing the two. It can be quite a long process to do accurately, however rough sketches will give you a good idea of the outcome.