This study has developed from a natural intervention being carried out by the Energy Efficiency Conservation Authority (EECA) to insulate domestic houses in New Zealand and is a major collaborative effort, which will shed light on the effectiveness of insulation in improving health and wellbeing. The impact of housing refurbishment on health has not previously been examined. There is considerable government and policy interest in promoting healthy housing and there is strong community interest in ensuring the housing stock is improved in order to lower health risks.