SAP Calculations & EPCs in UK (cheaper rates)

SAP Calculations and EPCs for new builds, extensions and conversions

What is SAP Calculations

SAP stands for 'Standard Assessment Procedure'. It is the only Legal Government approved system for evaluating the energy rating for a new Building. It is mandatory for the SAP assessors to be authorized and registered with a certification authority. A SAP rating is the calculation that is required in order to produce a Predicted Energy Assessment and an On Construction Energy Performance Certificate.
Building Regulations require that a SAP calculation and a Predicted EPC is submitted for new dwellings prior to the commencement of work.

A SAP calculation indicates a score from 1 to 100+ for the annual energy cost based on:

• The elements of structure

• The heating and hot water system

• The internal lighting

• The renewable technologies used in the home

The higher the score the lower the running costs, with 100 representing zero energy cost. Dwellings with a rating in excess of 100 are net exporters of energy.

SAP calculations allow comparison to be made of the energy running costs of dwellings anywhere in the UK. This is achieved because the calculations are predominantly location independent and are based upon a notional standard occupancy that overcomes variations associated with physical location and the different ways in which people utilise their homes.

A SAP calculation for a new dwellings is a desktop exercise, the client or their designer submits drawings, plans and specifications of the development to the assessor. It is recommended that the SAP calculation is undertaken early in the design process, this will help to prevent any costly redesign of the dwelling.

SAP calculations usually involve 4 stages:

Design - draft stage

From the plans and drawings provided by the designer, the assessor prepares summary numerical information which includes 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 dimensions of external windows and doors story heights and so on. From the specification provided, the assessor calculates the thermal elements' performance. 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 this data into 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 Building Regulations' requirements 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 should then advise the designer of the shortfalls and recommend solutions as required.

Design - final stage

The client, designer and the assessor agree the finalized version of the design. It may involve amendments to the initial design in order to achieve SAP compliance. Data from the finalized design is input into the computer program. From this, the assessor produces reports that the client or designer needs to submit to Building Control. This will include a Predicted Energy Assessment (this provides a rating of energy performance based upon the specified design).

Built - draft stage

For most new dwellings, an air pressure test will normally be required (for small sites of 2 dwellings or less an air leakage value of 15 m3/(h.m2) may be used in the calculation no test is required). The client or designer provides the results of the air pressure test (if required) to the assessor and also advise of any variations from the specification. The assessor will edit the SAP calculation to reflect the air pressure test results and any variations to the specification. The software is used to check that the completed dwelling still meets the Building Regulations' requirements with regards to the conservation of fuel and power. If it does not the assessor recommends remedial action. For new build dwellings, the assessor checks to ensure that the dwelling is registered on the Government's central database register of national property addresses. If it is not the assessor arranges for the address record to be created.

Built - final stage

The assessor finalizes the SAP calculation and creates the Energy Performance Certificate (this provides a rating of energy performance based upon the dwelling as built). By law, the EPC must be displayed in a new dwelling put up for sale on the open market. There are other documents required by Building Control such as the SAP worksheet report and the SAP data input report. The assessor provides the client with the Energy Performance Certificate and SAP Calculations.

Building Regulations require that an Energy Performance Certificate is provided prior to a completion certificate being issued.