The issue of whether to demolish or refurbish older housing has been debated for over a century. It has been an active policy area since the late 1880s, when the Government first authorised the statutory demolition of insanitary slums. In the 1960s, revulsion at the scale of 'demolition blight' and new building caused a rethink, leading to a major reinvestment in inner city neighbourboods of older housing. In the past 5 years, debate on demolition and new building has been intensified by the Government's Sustainable Communities Plan of 2003, with its proposals for large-scale clearance and building. Environmental arguments about renovating the existing stock have gained increasing prominence as people have sought to defend their communities from demolition. The evidence on whether demolition would reduce the amount of greenhouse gases we emit into the atmosphere is unclear and disputed. This paper summarises the evidence and arguments, and attempts to clarify the most realistic, achievable route to major reductions in energy use in homes. The arguments that apply to housing also apply to most other buildings and therefore to the overall built environment, which accounts for half of all carbon emissions. Three main sources of evidence have helped in the development of this paper, but there are many other studies we draw on in the discussion. Firstly, the Environmental Change Institute at Oxford University has argued that around three million demolitions are necessary by 2050 if we are to reach the stringent energy reduction targets that will be required in our housing stock [Boardman et al., 2005. 40% House. Environmental Change Institute, Oxford]. Its demolition figure is based on complex modelling that with small modifications can produce very different numbers. Its assessment does not take account of the embodied carbon costs such as volume of new materials, energy use in producing concrete, steel and other structural and infrastructural elements, and other factors affecting the environment Such as land use, infrastructure and area blighting. We discuss these issues in order to clarify the scale of the challenge and the relative value of demolition or renovation. Secondly, the Sustainable Development Commission JSDC, 2006. 'Stock Take': Delivering improvements in existing housing. Sustainable Development Commission, London] argues the urgent need to upgrade the existing stock on the grounds that 70% of all homes that will exist in 2050, even with the ambitious new building programme now announced, are already built. The maximum feasible demolition of two million existing homes by 2050, based on experience to date, suggests that under 10% of the current stock will have been demolished by then. We argue that upgrading this stock to high environmental standards can actually be achieved more cheaply than demolishing it, and with as significant a carbon reduction. Thirdly, the German Federal Housing, Urban and Transport Ministry has announced an ambitious energy reduction programme that will upgrade all pre-1984 homes in Germany by 2020, an estimated 30 million units.' This is based on evidence from several CO2 reduction programmes since 1996, showing the feasibility of upgrading. An 80% cut in energy use has been achieved, making the performance of the renovated homes at least as good as Germany's current exacting new build standards. The evidence from Germany is more grounded than any that has so far been produced in the UK, as it is based on several thousand examples. The paper also discusses the social and political problems of demolition. There is widespread opposition to large-scale demolition of older stock, mainly pre-1919 terraced homes, which is currently the most 'leaky'. This older property is a prime target for demolition in the Environmental Change Institute's proposals and the Government's plans. The environmental benefits of refurbishment are shown, based on work by the Empty Homes Agency, evidence from English Heritage, the Building Research Establishment and the Prince's Foundation. Work on refurbishment shows that existing homes, often in brick-built terraces, are relatively easy to upgrade and, with careful reinvestment in the existing buildings, can achieve as high environmental efficiency standards as current new build. We consider major social, economic and environmental benefits of refurbishment compared with demolition, including: a reduction in the transport costs, reduced landfill disposal, greater reuse of materials, reuse of infill sites and existing infrastructure, reduced new building on flood plains, local economic development, retention of community infrastructure, neighbourhood renewal and management. We weigh these benefits against the full costs of demolition and rebuilding, involving much higher capital costs, higher material wastage, greater embodied carbon inputs, the polluting impact of particulates, greater use of lorry transport for materials and waste, greater use of aggregates, more noise and disruption. On the social issues of housing need and fuel poverty, we argue that refurbishment and infill building are socially more acceptable, cheaper and create far lower environmental impact, while reducing fuel poverty. The incentive problems associated with renovation and the barriers to delivering it are also discussed. The evidence we have uncovered counters the suggestion that large-scale and accelerated demolition would either help us meet our energy and climate change targets or respond to our social needs. Many arguments remain unclear, but the overall balance of evidence suggests that refurbishment most often makes sense on the basis of time, cost, community impact, prevention of sprawl, reuse of existing infrastructure and protection of existing communities. It can also lead to reduced energy use in buildings in both the short and long term. Many factors will influence what happens in practice, but it seems unlikely under any scenario that the rate of demolition will accelerate far above current levels. Upgrading the existing stock is likely to gain in significance for environmental, social and economic reasons. Adopting policies that aid the retention and upgrading of the existing stock will help develop the necessary skills and technologies, save materials and land, and enhance the integration of existing communities in need of regeneration. (C) 2008 Queen's Printer and Controller of HMSO. Published by Elsevier Ltd. All rights reserved.