The document discusses several cost effective building materials including fly ash bricks, concrete masonry units, and soil cement blocks. Fly ash bricks are made from fly ash and water and cost 20% less than traditional clay bricks. Concrete masonry units use 1/3 less energy than burnt bricks and allow for steel reinforcement. Soil cement blocks are made from locally available soil, cement, and quarry dust and provide insulation without needing plaster.