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DER and TER are acronyms relating to carbon emissions.

You may have seen reference to a DER or TER within a planning condition or building regulations documentation, and more than likely be completely baffled as to what it actually means! The terms relate to the targeted and actual carbon emissions of a new home.

Energy assessors use these emissions figures to guide the design team, and establish where a building may be underperforming against UK compliance requirements.


What is DER and 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.

Many design factors can affect the DER, from fabric efficiency to fuel choice and air tightness.

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