This report summarises the methodology and results of a research project commissioned by BRE Trust to quantify how much the improvements to social housing arising from the Decent Homes programme (2001-2010) have reduced costs to the NHS in treating housing-related injuries and illnesses. It uses the same basic methodology developed to calculate the costs of poor housing in England described in The real cost of poor housing (Roys et al 2010). The report also discusses: - additional costs to society of non-decent homes - the impact of less serious, but still significant, levels of Housing Health and Safety Rating System (HHSRS) hazards - the work that remains to be done in terms of dealing with homes that are still non-decent - the importance of maintaining standards in dwellings that are currently decent.