The Government has confirmed its intention for all new homes to be zero carbon by 2016 with a major progressive tightening of the energy efficiency building regulations - by 25% in 2010 and by 44% in 2013 - up to the zero carbon target in 2016. This will highlight the need for renewable technologies such as ground source heat pumps, to be effectively integrated into new buildings. The BERR’s report ‘The potential for Micro-generation’ suggests that 28,000 heat pumps will be installed by 2012, a ten-fold increase on current volumes.

The interest in heat pump technology is therefore increasing and to provide an effective solution it is important that the key issues on how these systems are integrated into buildings are understood.

• Heat Distribution Systems and Domestic Hot Water
• Installation Options
• Part L Compliance Strategies
• Code for Sustainable Homes
• Grant Support For Kensa Heat Pumps

Heat Distribution Systems and Domestic Hot Water
Heat pumps ideally suit well insulated, new buildings with an underfloor heating distribution system throughout, with land to bury the ground arrays. They can also be used in other applications; however the benefits may be reduced.

Heat pumps work most efficiently delivering water at the coolest possible temperature into the heat distribution system. For this reason, underfloor heating – with its larger heat emitting area – is generally preferred. If radiators are favoured, they should generally be designed with a flow temperature of 45oC which means they will need to be slightly larger than any radiator linked to a conventional boiler and due to the higher temperature will have higher running costs.

Underfloor heating should be considered if the floor construction features a screed layer since the flow temperature could generally be reduced to around 30-35°C. The likelihood of screed being used is far greater within traditionally built apartment developments than two storey dwellings, which generally have a joisted first floor construction. Where suspended timber floors are present, any underfloor heating pipework, typically installed within the joist void, would need to be embraced by a steel heat transfer plate which not only increases cost but also slows the build programme. Since the flow temperature into these underfloor circuits would need to be increased to around 45°C (to drive the heat through the overlying chipboard and final floor finish), there is no greater operating efficiency than if the heat pump was serving radiators.

Any Kensa heat pump can be linked to a mains pressure cylinder to provide domestic hot water although the required output temperature – 45-50°C – will impact efficiency. One alternative is to provide a mains pressure cylinder complete with immersion heaters and link to an Economy Seven or an Economy Ten tariff so the water can be heated during low cost periods. If only Economy Seven is available, a larger cylinder might be required to reduce the occasions when higher priced electricity is used to produce hot water. All cylinder manufacturers provide models which can receive an input from solar panels, if installed, to reduce dependence upon electricity.

Installation Options
Kensa is a manufacturer with an objective to remove any ‘mystery’ linked to heat pump technology and the installation of the appliances. The most challenging element to any project is the ‘application engineering’ to ensure the correct sizing of the groundworks, heat pump and distribution system. Far more straightforward is the physical on-site work linked to the installation of a heat pump. This work can be handled by any plumbing contractor without the need for prior experience, extensive training or specialist tools. As a result, plumbers already working for the contract builder can provide the service eliminating the need to contract with ‘specialist’ installers who might seek premium rates for their supposed ‘expertise’. It should be emphasized that the installation of a heat pump should take no longer than the fitting of a gas boiler once the groundworks have been completed. Since Kensa fit a multitude of sensors on their units, the heat pump can be commissioned by a Kensa engineer over the telehone to reduce project costs.

Generally, it would be sensible to split the overall installation scope so that a separate contractor is handling the groundworks. If there is sufficient land for Slinkies, any groundworks contractor would be able to dig the horizontal trenches – following a plan supplied by Kensa - and install the pipework leaving the plumbing contractor to perform a pressure test. If vertical boreholes are required, Kensa can recommend a number of drilling contractors who, generally, would also install the pipework and grout.

Part L Compliance Strategies
In 2006 the UK Building Regulations changed and one of the main requirements for meeting the energy efficiency criteria of the regulations (Part L, in England and Wales, Part J in Scotland) is now based on CO₂ emissions from the proposed building.

SAP is the Government’s standard methodology for assessing the energy consumption in new domestic 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 of energy.

Ground source heat pumps have significantly lower CO₂ emissions than traditional fossil fuel heating systems due to their high efficiencies. Using figures produced by the BERR in conjunction with BRE, a ground source heat pump can show up to a 43% saving in CO₂ over gas and a 57% saving over oil.

SAP 2005 now uses a dwelling’s CO₂ emissions as a standard methodology for assessing the energy consumption in new domestic dwellings and proving compliance with Part L. The lower the CO₂ emission the more energy efficient the building is. Installing a ground source heat pump will increase a building’s SAP rating and help the building meet current Building Regulations.

Such is the CO₂ reduction, there might be an opportunity, in some cases, to downgrade the insulation specification and still achieve an acceptable CO₂ emission rate. However, this tactic is not recommended simply because any increase in the property’s heat load will result in a higher flow temperature, a less efficient heat pump and higher running costs. Later editions of the SAP software are likely to demonstrate even higher efficiencies for heat pumps.

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