Understanding the new Building Regulations

Leakage testing
The air tightness of buildings is addressed by the New Part L of the Building Regulations. If a building fails to satisfy the National Calculation Methodolgy, reducing air leakage is one of the few remedial measures possible.
Changes to the Building Regulations could require the energy performance of commercial buildings to be reduced by 28% compared with the 2002 regulations. NIGEL POTTER discusses the philosophy behind the latest regulations.The new Part L of the Building Regulations will apply from 6 April 2006. The details are in four Approved Documents: ADL1A for new dwellings; ADL1B for extensions to dwellings; and ADL2A and ADL2B for non-domestic buildings. The new regulations are timed to comply with the European Union’s Energy Performance of Buildings Directive issued in December 2002 and support the UK Department of Trade & Industry’s Energy White Paper in February 2002. The ODPM and DEFRA announced the detail of the new measures on 13 September, and the draft Approved Documents are available on the ODPM website. The aim of the EU is to reduce the overall energy consumption as measured by the total annual carbon dioxide emissions (kg/m2 of gross floor area). General requirement For non domestic buildings the general requirement is to reduce the energy consumption by 20% for air-conditioned and mechanically ventilated buildings (15% for naturally ventilated buildings) and to use renewables to provide 10% of the energy. In the majority of commercial cases, using renewable energy will not be appropriate, so the energy reduction will therefore need to be at least 28% compared with the same Notional Building conforming to the 2002 Building Regulations. The EU requires member states to implement a methodology for calculating energy performance of buildings. Fabric heat losses, daylight calculations, internal lighting efficiency, airtightness of the envelope, heating and ventilation system type and efficiency and other parameters all must be taken into account. The UK energy calculation procedures are contained in SAP 2005 for dwellings and iSBEM for non-domestic buildings. In the Approved Documents, ADL2A for example, there are maximum measures set for U-values for walls, roofs, windows and rooflights, doors, roof ventilators and floors, for the area of rooflights, specific fan power for mechanical ventilation systems and for airtightness. There is also a minimum for lighting efficiency. Notional Building All these values for the proposed new building need to be input into the model to determine the asset rating compared with a Notional Building of the same size and shape. If this value is not providing a 28% reduction, changes must be made to building elements, systems or airtightness. For example, it is not difficult to provide rooflights with U-values less than the requirements and in the range 1.4 to 1.9 W/m2K, but these small changes will not cut the energy savings as much as they reduce internal lighting requirements. Achieving a 10% renewable benchmark with a reasonable payback will be challenging in many buildings. The designer will need to address and cost a wide range of options including solar heating (evacuated tube), solar photovoltaics (remembering to consider the availability of supply which is currently severely limited, heat pumps probably offering the greatest potential, combined heat and power (CHP), light pipes, phase-change storage and wind generators. Wind generators have prolonged paybacks and are known to be problematic with planning authorities. The energy performance of the proposed building needs to be demonstrated before construction. Before the building is handed over, all the parameters as actually installed and tested, including airtightness results, need to be re-input to the National Calculation Methodology. The required carbon-emission target must be attained to satisfy Building Control. One of the few remedial measures at this late stage in construction will be to reduce the air leakage of the building. Integrated culture Meeting all the above requirements will require a much more integrated culture within the industry. Building-services elements need to be included within the architect’s basic building design and calculations for potential solar overheating. Buildings should be designed, for example, on the basis that 28°C is not exceeded (in office spaces) for more than 20 hours a year. This is therefore a much more multi-disciplinary approach to building design. The mandatory building log books and energy metering, along with the eventual required maintenance schedules for H&V equipment etc., will support this drive to increasing the energy efficiency of buildings. The inclusion of extensions in the Building Regulations all support this drive. For example, ADL2B requires consequential improvement to the existing elements for buildings over 1000 m2, with a proposed extension greater than 100 m2 and less than 25% more floor area; if the extension is greater than 25% then ADL1A applies. The consequential improvement is not expected to cost more than 10% of the cost of a new building, but whichever of the available options are chosen, in total the cost of the extension after April 2006 will almost certainly be more than 10% higher than now. If replacing wall or roof elements which have U-values outside the specified range or replacing boilers, air-conditioning units or controls over 15 years old do not eat in to the 10% budget, installing renewables will. Airtightness There is another revision of the Building Regulations programmed for 2010, which, among other issues, will drive down airtightness targets. However, the heavy reliance on second-tier documentation, which can be changed at any time without resort to changing the regulations themselves, means that more changes could be seen at any time in the next five years. Nigel Potter is technical-development manager with BSRIA, Old Bracknell Lane West, Bracknell, Berks RG12 7AH. www.bsria.co.uk
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