12 April 2010

Dear Margery

Thank you for your email regarding the Water Calculator for New Dwellings which was sent to the Communities and Local Government `Contact Us' email address on 3 December. I apologise for the delay replying.

You have requested the technical reports that underlie a change made to the Water Calculator for New Dwellings (formerly the Code Water Calculator) and in particular the scientific justification for the 'normalisation factor'.

In summer 2008, following concerns raised by those using the Code for Sustainable Homes, the Department for Communities and Local Government (CLG) commissioned research from Faber Maunsell into whether the Code water calculator was accurately modelling the calculated water use and encouraging water efficient design and to make recommendations on improvements to the calculator and identify any further research needed. This research was overseen by a steering group comprising CLG, the Department for Food, the Environment and Rural Affairs, the Environment Agency and BRE Global Ltd.

Faber Maunsell set out their initial findings and made a number of recommendations in a series of presentations and interim reports. They highlighted that understanding water use and user behaviour is still limited and that further research was necessary.

Their recommendations were reviewed and discussed by the steering group and in particular CLG's Technical Adviser on the Code, BRE Global Limited. Whilst many of Faber Maunsell's recommendations were adopted, for others where there was a lack of robust evidence an alternative approach was chosen to ensure transparency. This includes the approach taken for the `normalisation factor'.

The draft final report by Faber Maunsell and the BRE Global paper are attached as requested. The Faber Maunsell report is currently being reviewed and proof read prior to publication.

Yours sincerely,

Jeannette Henderson