**6.2 Use of renewable, bio-based, and waste-based materials**

Specification of materials for the project favored conventional building materials as indicated in **Table 3**. Even though lightweight composite materials are lighter and faster to erect as partition walls, none were used for the buildings. High reliance on cement as a major building material makes the buildings less energy-efficient in terms of the embodied energy content of cement and cement-based materials. This can be mitigated by reducing the quantity of cement used in housing development by using cement substitutes usually referred to as supplementary cementitious materials (SCMs). There is also the need to adopt construction methods that would minimize the use of Portland cement and other energy-intensive materials. A number of alternative building materials that combine low embodied energy with speed of erection have been identified in Nigeria and they include interlocking bricks for mortar-less wall construction, expanded polystyrene panels for internal walls, and composite building panels for walls and ceilings. Similarly, bio-based materials most of which are by-products of agricultural processing have been found to be very useful, though poorly deployed in the Nigerian context. Apart from timber, no bio-based material was specified in the buildings.
