You may have seen reference to a DER or TER, perhaps within a planning condition or building regulations documentation.

However most will be completely baffled as to what it actually means!

So What’s This DER TER?


The Dwelling Emission Rate (DER) and the Target Emission Rate (TER) are the headline CO2 figures which SAP Calculations measure. These figures will determine whether a new dwelling passes or fails on its carbon emission targets set within Part L of the building regs.

As a result of the design stage SAP Calculations, a carbon target (TER) will be arrived at – this is the target CO2 emissions rate which must be achieved by the proposed dwelling.

This figure is arrived at based on a notional dwelling of the same type, size and heating fuel as the one proposed.

Although there are several compliance criteria which determine a pass or fail within SAP (fabric, design, controlled services and fittings etc) if this headline target is not achieved the dwelling simply will not pass. The figure is measured in kg of CO2 per m².

Factors which affect the DER are numerous but could include fabric efficiency, fuel choice and air tightness.

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"Build Energy have been able to give us comprehensive assessment for SAP, EPC and Air Permeability........they have given us an excellent service and have gone the extra mile to get the test results right for our build."

Lisa Jackson

Jackson Planning