What is involved in the As Designed (Draft) Stage of a SAP Calculation?

The accredited energy assessor uses the plans and drawings provided to prepare summary information for the building.  This includes calculating the total floor area of the dwelling; the floor area of the lounge or living room; the areas of the heat loss floors, heat loss walls and heat loss roofs; the dimensions of external windows and doors; and storey heights etc.

The assessor then calculates the performance of the thermal elements from the specifications provided. These are expressed as ‘U’ values; the rate at which heat passes through the fabric of the building.  The higher the ‘U’ value, the greater the rate of heat loss.

The assessor then inputs all this data into the approved software to produce the SAP calculation.  Data is entered relating to:

  • Type of dwelling;
  • Floors;
  • Walls;
  • Roofs;
  • Openings (windows, doors, roof lights);
  • Ventilation;
  • Main and secondary space heating;
  • Hot water generation;
  • Renewable technologies, including photovoltaic panels and solar water heating;
  • Energy efficient lighting.

The software determines whether the proposed dwelling will comply with the requirements of the Building Regulations with regards to the conservation of fuel and power.  The assessor is able to use the software to model different variations of the design if the initial specification doesn’t show compliance.  The assessor can then advise the designer of the shortfalls and recommend solutions as required.

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