As the front of the lot faces west, the building must maintain a suitable presence from the street while maximizing the southern orientation for solar heat gain in the winter. (treehugger.com)
Overnight and weekends when the kettle is not used, there are also no internal heat gains from people or computers. (treehugger.com)
Additionally, the hot water system runs all year round and can, therefore, contribute internal heat gains in summer. (elrondburrell.com)