Unravelling the complexities of Part L2 for boilers

RICHARD WALKER, explains why the changes to Part L of the Building Regulations were necessary and how they affect the selection of boiler plant.Since 45% of the UK’s energy is used in buildings — for heating, lighting and general power — a high level of carbon dioxide, the greenhouse gas associated with climate change and global warming, is emitted as a result. Carbon dioxide represents 80% of all greenhouse gases emitted, and half of this carbon dioxide is thought to come from buildings. Over recent years it has become clear that the UK must generate heat more efficiently — both in domestic and non-domestic premises — to reduce the amount of pollutants emitted into the atmosphere. It is widely accepted that carbon-dioxide emissions are causing global temperatures to increase, with estimates suggesting a further 4 K rise by 2100. The consequences of ignoring these changes are all too apparent; devastating floods and hurricanes are recent reminders of the serious impact climate change can have. Several government policies and programmes have sought to ensure commercial and public sector organisations become more energy efficient — the Kyoto Protocol, the Climate Change Levy, the Low Carbon Buildings Programme and the Enhanced Capital Allowance Scheme to name just a few. However, it was the EU Energy Performance of Buildings Directive that really had an impact on the Part L Building Regulations review, and resulted in the latest revisions. Amongst other things, the directive promoted the improved energy performance of buildings and set out minimum standards for efficiency. The subsequent Part L2 consultation document was published in 2004, and the new legislation was implemented in April 2006. Holistic approach It is hoped that by 2010 changes to Part L will have delivered a saving of 1.4 Mt of carbon per annum. Part L2 offers a holistic approach to building design; after all, there is little point having a highly efficient boiler coupled with ineffective insulation and poor controls. Part L2 is about all disciplines collaborating to achieve an overall goal — working together to improve insulation, air tightness, energy usage for heating, cooling, ventilation, lighting, controls, commissioning, metering, monitoring and maintenance. It is important to remember that, with a requirement for a 28% improvement compared to 2002 building programmes, it is now less likely that specifications will change at the installation stage — which can only be a benefit to everyone involved. Part L2 of the Building Regulations is supported by approved documents ADL2A and ADL2B, which relate to new and existing buildings, respectively. The documents require new buildings, and in some instances existing ones, to be assessed for total annual energy usage and carbon emissions using National Calculation Methodology. Detailed guidance on the minimum acceptable performance of heating, cool- ing, ventilation and hot water systems is contained in a document from the Department for Communities & Local Government document and entitled ‘The non-domestic heating, cooling and ventilation compliance guide’. Since this guide does not deal with the requirements applying to the whole building, specifiers and building managers must also consult the appropriate approved document, ADL2A or ADL2B, to ensure heating systems fully comply with the regulations. Key points Section two of ‘The non-domestic heating, cooling and ventilation compliance guide’ covers central-heating systems incorporating hot water boilers fired by natural gas, LPG and oil. Several terms are referred to in the guide, and it is important for specifiers and building managers to understand what they relate to and how they affect a building’s energy efficiency rating. There are three points to be particularly aware of. • Seasonal boiler efficiency.
• Effective heat generating seasonal efficiency.
• Heating efficiency credits. Seasonal boiler efficiency (SBE) is used for all single-boiler installations and for multiple boiler systems using identical boilers in an existing installation. It is a weighted average of the efficiencies of a boiler at 30 and 100% of its output, which is usually quoted by the boiler manufacturer. Effective heat generating seasonal efficiency (EHGSE) applies to a central-heating boiler system and is obtained by adding a number of heating efficiency credits to the seasonal boiler efficiency. Heating efficiency credits are percentage points that can be claimed for central-heating boiler systems (for example sequential control, weather compensation, BMS and thermostatic radiator valves) fitted in existing buildings, according to certain qualities and features of the system. These credits do not apply to new buildings. By using section two of ‘The non-domestic heating, cooling and ventilation compliance guide’ and the appropriate approved document ADL2A or ADL2B, specifiers and building managers can calculate the minimum provisions for boilers and central heating systems for new and existing buildings. For example, boilers installed in new buildings other than dwellings (whether this is a single boiler or a mix of boilers) must be 84% efficient in total, so long as each of them has a minimum SBE of 80%. The boilers must also have minimum controls with weather compensation; in some instances the controls must be zone specific. For example, specifying a Potterton Commercial Derwent Compact Plus condensing 125 kW boiler (SBE of 92%) with a Derwent Compact Plus 100 kW atmospheric boiler (SBE of 83%) gives a total EHGSE of 91.8%, and would therefore pass. For existing non-domestic buildings, all boilers, or a mix of boilers and heating efficiency credits, should have an EHGSE of 84% for gas (85% for LPG and 86% for oil). Again, the boilers must also have minimum controls with weather compensation, and in some instances the controls must be zone specific. Here, a Derwent Compact Plus (SBE of 83%) and thermostatic radiator valves at 1% would total 84%, and the installation would pass. Communicate With the Government’s ambitious energy-efficiency targets to meet, and commercial and public sector buildings being a major contributor to the UK’s carbon dioxide emissions, it is clear that specifiers and building managers must take on board the requirements of Part L2. It is important to remember these are minimum requirements, and we believe that more needs to be done to communicate the changes —because many people are still unsure how to meet the demands of the new regulations, let alone exceed them. With this in mind, Potterton Commercial has produced a leaflet to help specifiers and building managers to understand the new requirements.* *Summary of Minimum Provisions for Central Heating Boiler Systems in Non-domestic Buildings According to the Revised Building Regulations. For a copy please call 08706 050607. Richard Walker is national sales and marketing manager with Potterton Commercial.

Related links:

• www.pottertoncommercial.co.uk