Implemented by the Government in 2007; the Code for Sustainable Homes (CSH) is designed to bring about a step-change in sustainable homes building practice. It aims to achieve this by setting new standards for the key elements of housing design and construction that affect the sustainability credentials of a new home.
The Code measures the sustainability of a house design by considering its performance in nine specific categories and rating the whole house as a complete package.
Points for sustainability and environmental performance are awarded to a house design in each of the nine categories and the sum total of the points achieved is converted into a star rating system, which ranges from Level 1 (36 points) to Level 6 (90 points).
The way to reach various levels of the Code has been kept flexible to enable points to be gained using different approaches to house design. However, certain minimum standards have been set at each level for some categories, such as energy efficiency and water use.
For example, in order for a house design to achieve Level 1 it must be 10% more energy efficient than a home built to the 2006 Building Regulations standards. It must also be designed to use no more than around 120 litres of water per person per day. Surface water management and site waste management must also be included in the house design and all materials used in its construction must achieve at least a ‘D’ grade in BRE’s Green Guide 2007.
While these criteria are compulsory in order to reach Level 1, they only deliver 2.7 points in total, which means that the house design must be awarded a further 33.3 points for its sustainability and environmental credentials. Housebuilders and designers can achieve these in a number of ways such as including accessible drying space, energy efficient lighting, storage, flexible living spaces and external recycling systems within the house design.
When it comes to achieving Level 3, the house design must be 25% more energy efficient than one built to the 2006 Building Regulations standard. It must also be designed to use no more than 105 litres of water per person per day. The house would be expected to deliver similar levels of surface water management and site waste management as the Level 1 house, as well as use construction materials that achieve a ‘D’ grade in the Green Guide.
Again, as with the Level 1 house, these measures only achieve a proportion of the required points to reach Level 3, just 10.3 of a total of 57. Therefore, the house design must again include a range of additional design features to improve its overall sustainability credentials and environmental performance.
This method of offering the housebuilder the flexibility to choose how the desired level of the Code is achieved adds another level of complexity to the design and build process.