Equipment to meet the new standards

Published:  01 December, 2010

Mitsubishi Electric, heat pump
Limiting solar gain is one of the most effective ways to reduce a building’s carbon footprint by limiting solar gain in Summer to reduce overheating. This is Hatfield Police Station. (Photo: Levolux)

Mark Grayston examines how heat-pump technology is more than capable of satisfying the requirements of Part L of the new Building Regulations.

Part L of the Building Regulations is now one of the most influential pieces of legislation for the construction industry, with its focus on energy consumption and emissions. The latest version came into effect in October 2010. setting even higher standards and aiming for a national overall CO2 saving of 25% from all new non-domestic buildings against the 2006 standard. The CO2 savings required vary from 18 to 38% depending on the building type.

The technologies used in a building’s services are at the heart of the issue. Part L 2010 reflects increased performance in the latest technologies and changes in the way CO2 emissions from the main energy sources — whether fossil fuel based, or, increasingly, renewables — are calculated.

The consumption and generation of electricity is one of the main areas of change. The 2006 CO2 emission factor for consuming electricity was 0.43kg/kWh used, and the 2010 value has been increased to 0.517 kg/kWh. A heat pump must therefore have a higher efficiency to match the CO2 emissions as other fuels whose emission factors have not changed so significantly.

Looking at heating, a heat pump is required to have a COP of around 2.35 to achieve the same CO2 emissions as a modern 90%-efficient gas-fired boiler.

However, most modern heat pumps already outperform this, with COPs typically ranging between 3 and 5. SEER and SCOP (seasonal energy efficiency ratio and seasonal coefficient of performance) are also key within the new Part L 2010, and heat pumps can help to deliver high seasonal efficiency ranging from 3 to 6.

Also key is the CO2 emission factor when generating energy. Electricity can be generated using photo-voltaics (PV), and for every kWh so produced, it is classed that PV can mitigate 0.529 kg CO2 — helping reduce emissions and add to the renewables on site.

As with Part L 2006, each new building is allocated a target CO2 emission rate (TER). This represents the minimum performance for a new building — expressed as CO2 emissions (kg/m2/year of useful floor area).

The method for calculation is Government-approved and is already reflected in the new SBEM software, updated for 2010. Other software whether ORCalc or DSM based is also available, but many are still being finalised.

To satisfy the TER, the building specification needs to be significantly better than the minimum standards. The most effective approaches are to design the building more effectively by limiting solar gain in Summer to reduce overheating and to increase natural ventilation to reduce the installed capacity of mechanical cooling.

Although the use of renewables is not required by Part L, using them will help significantly towards meeting the aggregate 25% emission reduction requirement. A renewable element is, however, still likely to be required as part of local council planning permission. With the help of modern technology and equipment, significant energy and, therefore, CO2 reductions can be made, which can help to meet the TER. These technologies include air conditioning, commercial and residential heat-pump boilers, ventilation and heat recovery, photo-voltaics and control systems.

These products can play a key role in helping achieve the 25% reduction in CO2 emissions, and the points of impact vary from the seasonal efficiency of a product, to whether it is qualifies for Enhanced Capital Allowances or if it is appropriately controlled and metered.

Controls measures such as intelligent time control, optimised start and weather compensation all help towards effectively controlling building services. With regards to ventilation specific fan power and seasonal temperature efficiency count, as well as the use of demand control.

As PV is renewable energy, Part L 2010 requires its output to be separately monitored. The effective output and efficiency of PV can also be influenced by the type, area, orientation and inclination of installation.

In terms of internal climate, the main points to consider concern the seasonal efficiencies of the heating and cooling equipment, which in simple terms is the annual heating or cooling load divided by the energy consumption over the same period.

Seasonal COP (SCOP) is calculated using a weighting method similar to that of SEER (seasonal energy efficiency ratio), where system efficiency is calculated at various loads and ambient temperatures to create a real seasonal efficiency. SCOP for commercial heating is calculated to a further level where the flow temperature is also varied with ambient temperature.

The 2010 notional building is a good standard for comparing products. For electric heat pumps, the 2010 building has a heating SCOP of 2.43 and a hot-water SCOP of 2.57. New commercial heat-pump boiler systems can offer an SCOP of 3.68 for an air-to-water system and 5.14 for a water-to-water system.

The 2010 notional building has a seasonal cooling efficiency of 3.6. The best equipment can easily exceed this target, with modern heat pumps offering a seasonal efficiency of 5 to 6 or more.

Without the correct level of control, energy-efficient equipment will never achieve its optimum efficiency, and this is where energy metering use plays an important part. At least 90% of the estimated annual energy consumption of each fuel to be assigned to various end use categories has to be monitored, making it essential that building operators meter the equipment. From this data the building user can optimise equipment and make further savings in the future.

Part L 2010 therefore puts in place not only the need to install efficient equipment but also to control and meter it effectively so that the building achieves maximum efficiency and CO2 reductions. In addition to achieving TER, limiting solar gains, achieving minimum standards for building fabric and services, and meeting standards for air permeability and thermal bridging, information and training should be available to the owner to allow the building to be operated efficiently.

We have not referred to Part L2B yet, which concerns the application of Part L to existing buildings. The key point is that its changes are meant to be evolution, not revolution. It is therefore important that we understand them, especially as they need to be taken into account with changes to Part F, which covers ventilation and indoor air quality.

The 2010 changes to Part L of the Building Regulations will continue to have a major impact on the design and construction of new buildings and on the refurbishment of existing buildings.

Mark Grayston is product marketing executive at Mitsubishi Electric.

Mitsubishi Electric has produced a free, CPD-accredited guide to Part L 2010. It is available at their website below or by emailing a request to air.conditioning@mitsubishielectric.co.uk



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