This is one of the initial steps for buying or selling a home, examining the property’s EPC. It’s even useful if you’re not planning on a move and want to improve your home's energy performance and save on bills (who doesn’t want to do this?) First and foremost, to calculate an Energy Performance Certificate (EPC), you need a qualified assessor to carry out the assessment on your home. They will then look at many key areas of your home that will give them an idea of how much and how energy is used within the property.  

These areas can include the following: 

• •  Checking if the heating and water system is efficient, i.e. boiler make and model

• •  Checking there is sufficient insulation in walls, floor and roof

• •  What type of glazing are in the windows?

• •  Even what light bulbs are fitted

• •  How airtight the building is (Not sure how airtight your home is? Did you know ATSPACE provided this service?)

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As they progress through the property, they will allocate a score for each section, depending on how efficient and in what condition the areas are in. From this, they will calculate the energy efficiency score, which will provide the EPC rating for the property. 

Below is a breakdown of the points system and how each tier is scored: 

• •  A Rating = 92-100 SAP Point

• •  B Rating = 81-91 SAP Points

• •  C Rating = 69-80 SAP points

• •  D Rating = 55-68 SAP points

• •  E Rating = 39-54 SAP points

• •  F Rating = 21-38 SAP points

• •  G Rating = 1-20 SAP points

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Once this process is complete, you will be issued with an Energy Performance Certificate (EPC), which will include both the environmental impact of your property along with its energy efficiency. It will detail specific figures of your property, such as your average fuel costs, CO2 emissions, and a full summary.  

It will also provide information on how to improve your score and what measures you can take to achieve this.  

This could include things such as: 

• •  Upgrading your windows glazing

• •  Increasing insulation levels in the walls, floor and roof

• •  Improving your water and heating system, such as upgrading your boiler to a more efficient spec

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How do you calculate the EPC? 

There are two types of EPC and two different ways of calculating one.

• •  On Construction EPC: produced from a SAP Calculation for new build properties. This is calculated using the Standard Assessment           Procedure method (SAP).

• •  EPC: produced via a site survey by a domestic energy assessor on an existing property. This is calculated using the Reduced Data             Standard Assessment Procedure method (RDSAP).

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SAP is a desk top calculation and is carried out from a set of drawings and specifications provided by the client. The SAP calculation for a new build property has two stages: the design stage SAP and the As Built SAP. 

The calculations determine a Target Emissions Rate (TER) and a Target Fabric Energy Efficiency (TFEE) rate. The Dwelling Emissions Rate (DER) and Dwelling Fabric Emissions Rate (DFEE) must be lower than the TER and TFEE to achieve a pass in the SAP calculation. 

The TER and TFER are automatically generated by the SAP software and assume a dwelling with a 25% improvement over building regulation requirements.  

The SAP calculation is based on the volume of the property, all the main elements (floors, walls, roof, doors and windows), thermal bridging, insulation, heating and lighting. All of these items are input into the calculation with set standards for the u values or efficiencies. 

The SAP calculation is divided into separate sections for each element. Each element has stand-alone targets, with the individual and total sum creating the final result. 

The As Built SAP is as it sounds and is completed once the property has been built and a final EPC will be produced. 

A domestic energy assessor carries out RDSAP visiting the property and conducting a survey on the property, noting all the information required for the EPC. The information is then input into a software program that will produce the EPC. 

The RDSAP is not as accurate as a SAP, as many assumptions are made within the software. These are based on defaults using the building regulation requirements for each element based on the approximate age of the property. 

All ATSPACE’s SAP assessors are also qualified domestic energy assessors, so they are qualified to produce EPC’s (Energy Performance Certificate) from SAP calculations.