Thursday, June 11, 2015

More updates on the design

Along with the positioning of the massive rammed earth walls, to optimize internal comfort, Transsolar has suggested rotating the building 10° to the west. This shift would let in enough sunlight for comfort without overheating the building, and it would have a positive impact on the solar chimney effect (don't worry, I'm getting to what that is).

Our original design featured a green roof, but that had been determined to be unrealistic in terms of workability and technical feasibility. During the rainy season it would become soaked with rain and become very heavy and during the dry season, nothing would grow so the roof would lose its intended cooling effect. The advice from Transsolar was to instead build a roof in two layers with a gap in between to allow air to circulate and which would act to reduce the heating effect inside the house. 

In this region of Ghana, air circulation plays an essential part of internal comfort. Since the rammed earth wall on the north side hinders cross ventilation, a solar chimney can be an alternative. How it works is that air from the room will mix with the warmer air that flows through the gap in the roof which will then rise through the solar chimney. All it needs to activate it is a window (of at least 0.2 m2) on the south facade which can be left open at night to create the airflow.  As an extra added effect, the chimney may allow for some diffuse lighting to enter the room through its opening.