Department of Energy and Climate Change (DECC) https://www.gov.uk/guidance/standard-assessment-procedure SAP Assessments Standard Assessment Procedure Standard Assessment Procedure SAP 2012 methodology Department of Energy and Climate Change 'Standard Assessment Procedure' https://www.gov.uk/guidance/standard-assessment-procedure gov.uk/guidance/standard-assessment-procedure SAP Standard Assessment Procedure Standard Assessment Procedure Government Standard Assessment Procedures SAP Calculations Standard Assessment Procedure highest accredited energy standards government guidance page on SAP Standard Assessment Procedure