Assembled using data and expertise provided by funding from the Technology Strategy Board Building Performance Evaluation Programme, this report shows the extraordinary 95% overall energy savings achieved at the Mayville in the first winter of operation, the greatly improved comfort conditions of the occupants, and the surprising fact that it need cost only 3% additional capital expenditure to refurbish and retrofit a building to achieve all these Passive House (Passivhaus) benefits, compared to a simple, basic refurbishment to meet minimum standard Building Regulations requirements.