**3.9 Design for energy efficiency**

All energy in their most rudimentary and primary level is derivable from nature even though it exists in various forms. Energy efficiency can be examined both from the embodied and operational dimensions. At the operational level, energy efficiency entails use of low energy-consuming appliances, while at the embodied level, it entails use of low-impact materials for buildings. It can also be considered from the perspective of passive and active strategies. While passive strategies promote natural solutions, active strategies deploy technology to achieve efficiency. Integration of passive strategies and circular design principles has been shown to be complementary to promoting resource efficiency in buildings [58]. In addition, the use of renewable energy is a major component of circular economy as it ensures minimal use of fossilbased fuels and a cleaner energy regime [18, 59].
