On Construction SAP Calculations

Sustineo are able to provide initial SAP Assessments through to final On Construction Domestic EPC lodgement

Standard Assessment Procedure (SAP) calculations are required to demonstrate compliance with Part L of the Building Regulations for all new build dwellings, conversions, refurbishments and extensions with glazed areas greater than 25% of floor area.


There are two stages to the SAP process.




At this stage a SAP calculation is prepared based on the plans and specification prepared, often by an architect or other similarly competent person.  The SAP calculation may be undertaken by anyone, but as the final EPC, following completion of construction, can only be lodged by an Accredited On Construction SAP Assessor, it makes a great deal of sense for the SAP Assessor to be involved from the outset. 


The design stage SAP assessment takes account of the envelope of the dwelling, the envelope adjacency, the thermal efficiency of the envelopes and openings; the heating; cooling; water heating; lighting, ventilation; the location and position of the dwelling in relation to its surroundings and the provision of renewable energy sources (e.g. PV). Once all the necessary data has been collected from the As Designed plans and documents, the SAP software will make a series of calculations which will show whether or not the dwelling, As Designed, meets the current Building Regulations. 


There are two key calculations generated by the software, the Dwelling Emission Rate (DER) and the Dwelling Fabric Energy Efficiency Rate (DFEE) which are  expressed as the amount of energy demand in units of kilowatt-hours per square meter of floor area per year (kWh/(m2/year).  These figures are compared with the notional Target Emission Rate (TER) and Target Fabric Energy Efficiency Rate (TFEE) which is the maximum rate for a dwelling identical to the building being assessed (calculated by the software using the same figures inputted to calculate the DER and DFEE) permitted by the current Building Regulations.  If the DER and/or the DFEE exceed the TER and/or DFEE then the dwelling As Designed does not meet the Building Regulations.


In the event that the dwelling, As Designed, is non-compliant as determined by SAP 2012 then the SAP Assessor and/or the design team will need to look for solutions to enable the design to pass the Building Regulations.  This is the second part of the Design Stage and way to achieve compliance has been found the SAP Assessment would usually be forwarded to the Building Control Officer for approval.


The documents produced area as follows:


  • Checklist

  • SAP Input

  • SAP Worksheet

  • DER Worksheet

  • TER Worksheet

  • Overheating Calculation (if required)

  • Predicted Energy Assessment

  • Code for Sustainable Homes Report (if required)

  • Thermal Bridge

  • DFEE Worksheet

  • TFEE Worksheet

  • Cost Worksheet

  • Developer Sign Off



Once the new dwelling has been constructed  the SAP Assessment will need to be updated to take account of any further changes which may have taken place and at this point it will be critical for the Developer to provide written confirmation that all the information used and relied upon to generate the As Built SAP Assessment is indeed As Built. Any deviation from the original design and specification must be documented.  In most cases an Air Test Certificate will be required.


The On-Construction EPC and Compliance reports must now be submitted to Building Control and must be carried out by an accredited OCDEA.  The EPC will be lodged on the official EPC register and the OCDEA who may be audited by his or her Accreditation Body.  The lodged EPC is a public document which will be available for immediate download from the official register and interested parties, e.g. buyers and renters, are entitled to rely upon it.

Sustineo can provide Stage 1 and Stage 2 SAP Assessments.