In an assessment of the UK's environmental credentials, Sir John Sorrell has outlined what he considers to be necessary steps in the creation of sustainable cities.Writing for the BBC News website, Sir Sorrell stated that a certain amount of reinvention needs to take place in order to tackle climate change.To his mind, living in a sustainable city means three things. The first of which is whether or not grants and local tax incentives are available in order to help people make their homes greener."Keeping an even temperature inside any building means serious insulation," he said."Homes in an average large city produce more than two million tonnes of CO2 each year. This is because the vast majority of older houses leak heat."In addition, Sir Sorrell highlighted the need to cut private car use and commented that this would necessitate some "brave decisions" on the part of civic leaders, as well as an increase in greenery to counter urban heat.Housebuilding firm Dockleaf recently espoused the notion of government grants for homebuilders in order for them to use renewable features in new homes.