Getting to grips with Part L

ANT WILSON of FaberMaunsell outlines the effect of energy-efficiency issues in the new Building Regulations for building-services engineersThe latest amendments to Part F (ventilation) and Part L (conservation of fuel and power) of the Building Regulations include a number of significant changes for building services engineers. They come into force on 6 April 2006. According to the Office of the Deputy Prime Minister (ODPM), a large proportion of the UK’s carbon emissions come from use of buildings, so the Government sees the control of energy usage in buildings as a key part of the strategy to meet its Kyoto commitments. Consequently, the latest version of Part L seeks to build on the progress of previous versions, by reducing carbon emissions through stricter energy-performance targets for new and refurbished buildings. In parallel with these changes, Part F has been more closely linked to Part L, so that as buildings become more airtight, provision is made to ensure adequate ventilation. Airtightness In fact, airtightness is now the cornerstone of a raft of measures required to reduce heat losses and control excessive solar heat gains, along with improved insulation and better control of glazing. Airtightness tests are now an obligatory element of the regulations, compared to what amounted to a voluntary arrangement in the previous version. In practical terms, this means that practical completion will not be achieved unless the building complies with airtightness regulations. At the same time, use of the National Calculation Method to assess thermal performance has been made mandatory in the new regulations, doing away with the elemental method used in previous versions. To achieve compliance, therefore, designers will have to use the SAP (Standard Assessment Procedure) for all but the largest dwellings, the SBEM (Simplified Building Energy Model) or accredited commercial software. This requirement to reduce heat losses and gains through the envelope of the building means that building-services engineers need to get involved far earlier in the design stages of a project than is traditionally the case. Of course, this is something we have been urging for years but which is becoming a necessity with the new regulations. Assistance In this respect, we can provide architects with additional assistance, making more use of modelling techniques to ensure an integrated approach to building performance. For example, modelling techniques can be used to assess the relative performance and financial benefits of exterior solar-shading elements compared to the simpler use of a spandrel below the working plane. As far as the building’s services are concerned, there is now a requirement to provide ‘energy-efficient and properly commissioned fixed building services with effective controls’. This raises several issues. First, there is a need for effective interpretation of this wording. For example, what is meant by ‘energy efficient’ and how do we measure ‘effective control’? A considerable amount of documentation is available to help make the right design decisions. For example, there are documents for making a thermal assessment of curtain walling, and the heating and cooling guides have been combined into one useful document. Similarly, there is a toolkit available for assessing the use of low- and zero-carbon (LZC) systems. These are not prescribed in Part L, but there will be many occasions, especially in air conditioned buildings, where LZC systems will be required to offset the energy consumption of less efficient systems and achieve overall compliance with targets. Commissioning Another bonus for building-services engineers is the requirement for ‘proper commissioning’ in line with CIBSE Commissioning Code M. Again, this means that time will have to be built into the construction schedule. And, of course, if the building is properly commissioned, rather than being rushed as is usually the case, we should also eliminate the time-honoured tradition of building-services engineers getting it in the neck when something does not work properly. As well as designing the services properly, it is also incumbent on us to ensure that the building owner has all the necessary information to run the plant and maintain it effectively to achieve an efficient building. The new regulations not only reinforce the need to provide a Building Log Book containing all this information, they also require that this information is easy for end users to understand. The general implications of the new regulations for building services engineers are clear. We need to ensure that we are familiar with the changes, interpret them accurately and know where to find the information we need to provide the right systems. At the same time, we must keep up to speed with the latest developments and know when new technologies become commercially viable. Last, but certainly not least, we must also take more care to ensure that end users are properly informed of the services in their building and are armed with the necessary information to use them to best effect. Ant Wilson is with FaberMaunsell, Marlborough House, Upper Marlborough Road, St Albans, Herts AL1 3UT.

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