A development of 500 homes

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Description of fictional building

500 new build homes in a sub-urban location. A biomass district heating network is proposed to meet the RSS ENV5.B3 policy requirements.

Baseline energy use and CO2 emissions

Baseline energy use = 7,389,450 kWh

CO2 emissions = 2,145,014 kgCO2/yr

Energy use and CO2 emissions figures calculated using Part L 2006 SAP methodology via NHER software.

Things to check:

• Is baseline energy use calculated using approved software?
• Does baseline energy use include cooking and appliances?
• Are Part L fuel emission factors used?

Requirements of Part L 2006

Part L 2006 sets out minimum levels of insulation and heating/lighting efficiencies for new homes but also requires the expected regulated CO2 emissions (the DER or Dwelling Emission Rate) to be calculated and for it to be lower than a Target Emissions Rate (TER) set by Part L.

The new homes are to be insulated beyond minimum standards, use a biomass boiler powered district heat network and low energy lighting to exceed Part L 2006 by 44%.

DERs are provided and are less than TERs for all house types. Figures are calculated using Part L 2006 SAP methodology via NHER software.

Revisions to Part L in 2010 and beyond

Part L will be revised in 2010 with a 25% improvement in CO2 emissions required over current standards. This will increase again in 2013 and in 2016 new homes will need to be net zero carbon. This will require increased use of DLZCTs to meet these tougher carbon emission standards.

Things to check:

• DER is lower than TER? This can be with or without DRLCTs for Part L requirements but only covers regulated emissions.

Requirements of the Code for Sustainable Homes (CfSH)

Each CfSH level has mandatory CO2 emissions credit (Ene1) requirements and additional credits can be obtained for carbon emission reductions from low carbon technologies (Ene7).

Ene1: Dwellings achieve a 44% improvement (DER vs TER) with the biomass boiler powered district heat network, this is sufficient for CfSH level 4* mandatory requirements and 8 credits.

Ene7: The biomass heat network reduces CO2 emissions by 898,422 kgCO2/yr. This is a 42.0% saving on total emissions (including unregulated cooking and appliances). This is therefore sufficient for 2 Ene 7 credits.

Things to check:

• Calculations (SAP calculations showing DERs) are provided both with DRLCTs (for Part L and CfSH Ene 1 credits) and without DRLCTs (for evidence for CfSH Ene7 credits).
• For CfSH Ene 7 credits all savings are in terms of total carbon emissions (kgCO2/yr) including appliances and cooking.

Requirements of RSS policy ENV5.B3

RSS ENV5 policy B3 requires new developments of more than 10 dwellings or 1000m_ of non-residential floorspace to secure at least 10% of their energy from decentralised and renewable or low-carbon sources, unless this is not feasible or viable

 Evidence (SAP calculations showing the energy use with and without the biomass heat network) shows that the biomass heat network provide 4,714,750 kWh/yr of energy or 64% of total energy (including unregulated energy uses) exceeding the RSS policy requirements.

 It should be noted that the biomass although the biomass boiler is providing 64% of the energy it is not saving 64% energy. The heat is still required, it is just coming from a low carbon source.

Things to check:

• Calculations (SAP calculations showing energy use) are provided both with and without DRLCTs (to enable compliance with RSS policy to be shown).
• Savings are in terms of total energy requirement (kWh/yr) including appliances and cooking.

Other passive design and energy efficiency solutions

It should be noted that other passive design and energy efficiency measures such as increased insulation or higher efficiency boilers may be more cost effective ways of saving energy and carbon. This will help with Part L compliance and CfSH Ene1 credits but are separate to the requirements of RSS ENV5.B3 which requires a more decentralised approach to renewable energy and is not only about reducing carbon emissions.

Other decentralised and Renewable or Low Carbon Technology (DRLCTs) solutions

There are a number of decentralised and renewable and low carbon technologies which could meet the RSS ENV5.B3 requirements for a 500 home development. This example used a biomass heat network but other solutions are available and may be more suitable for specific sites.

Things to check:

• Energy supplies are from decentralised and renewable or low carbon technologies and not from passive design and energy efficiency measures.