The UK faces increasing challenges around water scarcity and sustainability, and how buildings are designed decides how much water they draw. Part G of the Building Regulations sets out the standards for water efficiency in new and existing buildings. What follows covers what the Part G water efficiency standards actually require, where they bite in UK construction and how they contribute to sustainable water use.
What Are Part G Water Efficiency Standards?
Part G of the Building Regulations deals with sanitation, hot water safety, and water efficiency in new and refurbished buildings. It sets out to minimise water use in residential buildings without compromising comfort and functionality for occupants. The effect is to reduce overall demand on water supplies, which is the mechanism by which the regulation promotes more sustainable use of the resource.
The regulations in Part G include several key requirements:
Water Efficiency Calculations: New dwellings must meet a target water use of no more than 125 litres per person per day, or as low as 110 litres in areas with tighter local restrictions.
Hot Water Safety: Measures to prevent scalding from hot water must be implemented, including thermostatic mixing valves.
Sanitary Fittings: Guidance on efficient fittings like taps, showers, toilets and baths to reduce water wastage.
These standards help ensure that new homes are designed with sustainable water use in mind, reducing the impact on the UK’s water resources.
Why Part G Compliance is Integral to Building Design
1. Reducing Water Consumption
The UK has seen a growing demand for water, with the Environment Agency warning that the country could face water shortages by 2050 if action is not taken. Complying with Part G cuts the water a building consumes, and that takes pressure off local supplies.
By requiring water efficiency calculations, Part G encourages the use of water-saving fixtures and technologies, such as dual-flush toilets, low-flow taps and efficient showerheads. According to the Waterwise organisation, installing water-efficient fixtures can reduce household water use by up to 40% Waterwise - Water Efficiency. That conserves water, and it lowers utility bills for occupants.
2. Supporting Sustainability Goals
Part G supports the UK’s sustainability goals, particularly around climate change and environmental conservation. Water-efficient buildings are better equipped to manage periods of drought and reduce the need for water abstraction from rivers and aquifers, which can have negative ecological impacts. The UK government’s 25 Year Environment Plan highlights the importance of using water more sustainably to ensure that the country’s water needs are met in the future.
By adhering to Part G, developers and architects contribute to a more sustainable built environment, supporting efforts to reduce the carbon footprint associated with water heating and treatment.
3. Improving Building Marketability
Water-efficient buildings are increasingly sought after by buyers and tenants who are aware of their environmental impact and want to reduce living costs. Compliance with Part G can make a building more attractive in the market, as lower water use translates to lower water bills for occupants. A study by Savills found that sustainability features, including water efficiency, can increase a building’s value by up to 10%.
Part G compliance is a regulatory necessity, and it is a competitive advantage in the property market.
How to Achieve Compliance with Part G Water Efficiency Standards
Achieving compliance with Part G involves careful planning and design to ensure that water use is minimised without sacrificing functionality. Here are key steps for compliance:
1. Water Efficiency Calculations
To comply with Part G, developers must submit water efficiency calculations, typically using the Water Efficiency Calculator for New Dwellings (WEC). This calculation assesses the predicted water consumption based on the types of fittings and fixtures installed, ensuring that the building meets the target usage of 125 litres (or 110 litres) per person per day.
2. Specifying Water-Efficient Fixtures
The fittings drive the calculation, so specification is where Part G compliance is won or lost. That means low-flow taps and showers, dual-flush toilets and appliances such as dishwashers and washing machines with high water efficiency ratings. These fittings reduce the total water consumption of the building and bring it within the required standards.
3. Integrating Rainwater Harvesting and Greywater Systems
Part G also encourages the use of alternative water sources, such as rainwater harvesting and greywater recycling, to reduce demand for mains water. These systems can be particularly effective in reducing water use for non-potable purposes like toilet flushing and garden irrigation. The BRE Group reports that rainwater harvesting systems can reduce a household’s mains water consumption by up to 50% BRE - Rainwater Harvesting.
Compliance with the Part G water efficiency standards is now a normal part of building design in the UK. The standards reduce water consumption, support sustainability goals and improve marketability, and between them they help create a more sustainable and resilient built environment. As water scarcity presses harder, Part G compliance stays on the critical path for developers, architects and building owners committed to responsible water use.
For anyone designing or constructing buildings, prioritising water efficiency from the outset does more than satisfy the regulations: it builds for a sustainable future.