Reduced Data Standard Assessment Procedure
Energy Performance of Buildings Certificates: glossary, originally published by the Ministry of Housing, Communities & Local Government in 2014, defines the Reduced Data Standard Assessment Procedure (RdSAP) as: ‘…the government approved methodology for producing an EPC (Energy Performance Certificate) for existing dwellings. For existing dwellings much of the information required to assess the energy performance is not readily available so an on-site survey is needed to collect it. To minimise inconvenience for the homeowner, the method to assess energy performance was adapted to include a set of assumptions about the dwelling based on conventions and requirements at the time the dwelling was constructed. This means that less information is required from the homeowner for the assessment than for a newly constructed dwelling.’
On 15 June 2025, this software tool and calculation methodology which is used to create EPCs for existing buildings, the (rdSAP) will be updated from RdSAP v9.94 to RdSAP v10.0. It is the most significant change in the procedure in some 10 years, with a vastly increased number of data points that go towards the final rating and the inclusion of ventilation, as well as electricla heating systems such as heat pumps.
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