*2.3.2 Water quality and conservation (water efficiency)*

Reducing water consumption and protecting water quality are key objectives in sustainable buildings. The construction industry is said to be responsible for more than half of carbon emission, water consumption and land fill wastes in the UK with 13% of the raw materials used [10]. According to the report, about 35% of human water use is unsustainable. The percentage will likely increase if climate change worsens, populations increase, aquifers become progressively depleted and supplies become polluted and unsanitary. Humans currently use 40–50% of the globally available freshwater in the approximate proportion of 70% for agriculture, 20% for industry, and 10% for domestic purposes with the total volume increasing progressively. The low-cost houses are poorly serviced and existing water systems are in a deplorable state [31]. Contrastingly, the report on water usage in Nigeria has 69% for agriculture, 10% for industry, and 21% for domestic purposes [32]. Comparatively, Nigeria uses twice the volume of water for domestic purposes, water conservation should be of great concern for future housing.

Provision of portable water is a major challenge to both the rural and urban dwellers in Nigeria. Consequently, the Federal government declared a State of emergency in the water sector. The Nigerian President, Mohamed Buhari noted that access to piped water services which was 32% in 1990 has declined to 7% in 2015 [33, 34]. With global warming, the volume of available water continues to dwindle. Most urban dwellers in Nigeria buy water from vendors while those in highbrow areas live on boreholes. The rural dwellers make use of whatever is available from streams, to hand dug wells and sometimes borehole water from well-meaning neighbors. Motorized wells and boreholes are more prevalent in towns and cities. Every household have a borehole with grave implication for soil stability. Aside the increased cost implication to the home owner in the cities and towns, the rural dwellers do not have access to portable water. Quality water from public facilities are zero to non-existence. The declared state of emergency has no meaningful impact on its availability. Therefore, the requirement for water efficiency needs serious consideration for Nigerian housing provision.
