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Frequently Asked Questions (FAQs)

Jersey SAP Calculator

1. What is an indicative Thermal Mass Parameter (TMP) of a dwelling?

Taken from the SAP2012 document:
Thermal mass  TMP (kJ/m2K)
Low100
Medium250
High450


2. What is a Building Part?

Building parts are used to define parts of the building that have been constructed at different times. If there was an extension to a dwelling then this would be defined as an additional building part to the main dwelling and would include definitions for the constructions included in the extension for the walls, floor, roof etc.

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4. Why is the DER less than the Energy Use shown on the energy performance certificate?

The DER value (Dwelling Delivered Energy Rate) is the rate of delivered energy consumed in the dwelling, in kWh/m2. The Energy Use value shown on the EPC certificate is the rate of primary energy, in kWh/m2, corresponding to the delivered energy that is consumed in the dwelling. The primary energy is calculated as the sum of the product of all the delivered energy consumed in the dwelling and the relevant primary energy factor of the fuel used to produce it. The primary energy attributed to a dwelling accounts for space and water heating, space cooling, ventilation, and lighting, less the energy saved by energy generation technologies.

5. How do I use the tool to demonstrate compliance for an extension to an existing dwelling?

Updated August 2018: When constructing an extension, two stages to modelling your building will need to be entered.
1. Select the type of analysis 'new extension to existing dwelling' and model the existing part of the dwelling as it currently is, but ready for the extension work, e.g., some elements may no longer exist or are no longer exposed due to the planned works. When this stage of the model is complete select 'define extension' from the results tab and a snapshot of the project will be taken to be used as part of the calculation.
2. Following this, the project should now be updated to model the extension part of the dwelling, and include any consequential upgrades to the existing part, e.g., replacing the heating system or other modifications.
When the calculation is run this will be tailored, along with the compliance report produced, to the requirements of Technical Guidance Document 11.1B.

6. How do I know if the fuel prices used for generating the energy performance certificate are current?

The fuel prices used during the calculation of an Energy Performance Certificate are shown in a table at the end of the certificate. This includes the prices for all of the relevant fuels used in the dwelling.

7. What is meant by delivered energy?

Delivered energy is a measure of the energy consumed in a building. It does not take account of the type of fuel used to produce it or the generation, transmission, and distribution efficiencies and losses associated with this fuel source.

8. What is meant by primary energy?

Primary energy is a measure of the energy consumed in a building that factors in the type of fuel used and the associated processing required to generate, transmit, and distribute energy from this fuel source.