Ground Source Heat Pumps can help dwellings achieve compliance with Part L Building Regulations by reducing the DER/BER (Dwelling Emission Rate / Building Emission Rate) of buildings. This means that the CO2 emissions will be lower for a Ground source Heat Pump than other non-renewable fuels. The following table was produced by the DEFRA in April 2008 and gives CO2 emissions per kWh for different fuels.

Although a Ground Source Heat pump uses electricity (which has the largest emission rate) as it can operate with a COP of 4, i.e. for every one kW of electrical energy used it produces 4 kW of thermal heat, the actual CO2 emission rate for providing heat to a building is 0.135kg CO2/kWh. This shows a CO2 reduction of 29% over gas and 46% over oil. By selecting a Ground Source Heat Pump to provide a building’s heating requirement the DER/BER of the building is reduced and hence the building is more likely to pass building regulations on the CO2 emission requirements.

For examples on how changing fuel sources, increasing insulation or adding solar panels to buildings, can alter a building’s DER and TER (Target Emission Rate), we suggest you visit www.playtheregs.com. The site is a simple on-line SAP assessment program written by the National Home Energy Rating (NHER) scheme and gives an indication on how changing a building’s characteristics can alter its SAP rating and carbon emissions.   (Data courtesy of KENSA)

Part L1A of the building regulations (England & Wales)

The primary goal of Part L1A of the Building Regulations (2006) is to reduce carbon dioxide emissions. These new requirements aim to reduce carbon dioxide emissions by about 20% compared to the standards required by the previous regulations introduced in 2002.

A new single method of compliance in terms of a dwelling’s carbon dioxide emission rate (DER) has been introduced to maximise the flexibility available to developers in the way they meet the requirements of the regulations. This aims to promote innovation in design, construction and related industries.

There is now only a single method of compliance with Part L1A. The three alternative methods that were applicable under the Building Regulations (2002), i.e. the elemental method, the target U-value method and the Carbon Index, no longer apply.

There are five compliance criteria under Part L1A as follows:

Criterion 1: The predicted carbon dioxide emissions must be no greater than a target value.
Criterion 2: Defined limits on design flexibility must not be exceeded.
Criterion 3: Excessive solar gains must be prevented in order to avoid overheating in summer.
Criterion 4: Specific requirements regarding the quality of the construction and commissioning must be achieved.
Criterion 5: Data to enable the production of an Energy Performance Certificate must be provided, plus information on the operation and maintenance of heating systems, etc.

To meet the first criterion, the Dwelling carbon dioxide emission rate (DER) has to be no greater than a corresponding Target carbon dioxide emission rate (TER). Both the DER and TER are calculated using SAP 2005 - the government’s standard methodology for assessing the energy consumption in new dwellings.

Target Emission Rate (TER)

The TER is based on a notional dwelling of the same size and shape. The TER is estimated using a parallel SAP calculation based on the same dimensions as the proposed dwelling, but using a set of reference values for the building fabric and the heating systems etc. These reference values include: U-values for the main building elements that correspond to those required to meet the elemental method of compliance with Part L1 of the Building Regulations (2002); a conventional gas fired boiler with radiators and hot water cylinder (with SEDBUK efficiency of 78%); and natural ventilation with extract fans and air permeability of 10 m3/hm2 at 50 Pa.

For properties heated by fuels other than gas, the carbon dioxide emissions for space and water heating and ventilation are multiplied by an additional factor - the fuel factor. This is why the TER will change when you choose heating systems which run on fuels other than gas.

Dwelling Emission Rate (DER)

This is the estimated annual carbon dioxide emissions per square metre due to space heating, domestic hot water, ventilation and internal fixed lighting, minus any carbon emissions saved by the generation of electricity. Within the DER calculation a default is used for internal fixed lighting which cannot be changed. The DER is an output from the SAP calculation.

SAP rating

SAP is short for Standard Assessment Procedure and is the Government’s standard methodology for assessing the energy consumption in new dwellings. The latest version of SAP is SAP 2005. The SAP scale runs from 1 (poor) to 100 (excellent) and is based on estimated annual energy use for space heating, domestic hot water, ventilation and internal fixed lighting. A SAP of 100 now represents zero energy cost for these items. It can be above 100 for dwellings that are net exporters.

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