The efficient use of water reduces running costs and carbon emissions, as less energy is required to supply water and power appliances, particularly those which require water to be heated. It also reduces a building’s impact on the wider energy supply network.
Local Plan Policy OS3 requires a water efficiency design standard limiting average per capita water consumption to 110 litres per person per day; however developers should aspire to the Royal Institute of British Architects water target of 75 litres per person per day.
Water efficiency calculations are based on fixtures and fittings, in line with Part G Building Regulations residential schemes and BREEAM best practice performance for non-domestic buildings. The standard can be achieved through energy efficient fittings, for example water efficient showers, baths, dual flush toilets, waterless urinals, washing machines, dishwashers, and automatic or sensor taps.
In addition, applicants should incorporate other water saving measures:
- Rainwater harvesting, for example water butts; and underground storage tanks
- Grey water recycling, for example direct use systems (for watering plants); biological systems using sand filtered methods, wetland and septic tanks; and mechanical filters (for using the water to flush toilets)
- Reclamation of wastewater
- The water calculator
- Sanitation, hot water safety and water efficiency: Approved Document G
- BREEAM Non-domestic Buildings Technical Manual
Sustainable flood risk management
Allowances for climate change should be made in assessing flood risk to help minimise vulnerability and provide resilience to flooding. Climate change allowances are predictions of anticipated change for peak river flow and peak rainfall intensity.
Drainage systems should be considered at the earliest stages of site selection and designed to integrate into developments. The National Design Guide, the NPPF, Local Plan Policies OS3 and EH7 refer to the need to incorporate sustainable drainage systems, which mimic natural patterns to ease surface water run-off, often through storing the water and then releasing it slowly into a watercourse.
Sustainable drainage systems help to deliver a climate resilient development with a low carbon footprint and high environmental credentials, contributing to the delivery of healthy places, high quality green spaces, biodiversity and future-proofing, and provide opportunities for the integration of blue and green infrastructure to maximise multiple benefits. Techniques can include a wide range of measures, including permeable surfaces (e.g. car parking), swales, basins, attenuation ponds and wetlands.