As of October 2010, the new version of Part L of the Building Regulations came into force, updating the 1995 requirements for new and replacement heating systems. Incorporated within the new rules are stipulations for both a zone valve and a room thermostat to be fitted to new system heating zones and all radiators installed with thermostatic radiator valves.In an average home where heating and hot water is over 80 per cent of energy use, fitting zone valves ensures that hot water is not supplied to a zone when it is not required for heating and so reducing the amount of boiler operating time. Adding time control to each zone at a relatively small cost gives great flexibility, previously only restricted to larger buildings.With the focus on the aim to reduce carbon emissions from new buildings by 25% from 2016, domestic residences are?