Approved Document L2A A Guide to Compliance When Designing New Buildings Other Than Dwellings (Issued December 2006)

Approved Document L2A provides guidance on complying with the requirements of Regulation L1 dealing with the conservation of fuel and power. It is one of four Part L Approved Documents. This Customer Information Sheet deals specifically with the design of new building that are not dwellings and aims to clarify the documents contents for Local Authority Building Control customers. For information dealing with extensions to non domestic buildings, see the Information Sheet on Approved Document L2B. Separate Building Services Information Sheets are available on Approved Document L1A and L1B and these deal with deals with schemes involving dwellings. Scope The document outlines the energy performance standards required for new buildings which are not or do not contain dwellings, but also includes buildings containing ‘rooms for residential purposes’ such as nursing homes and student accommodation or the common parts of apartment blocks which are outside the scope of L1A. Demonstrating copliance From the 6th April 2006 all newly constructed buildings other than dwellings, and the construction of extensions to existing buildings where the gross floor area of the extension is both greater than 100m² and greater than 25% of the gross floor area of the existing building, will need to comply with the five separate criterion as set out in the approved document. These criterion are set out below: Criterion 1: The predicted rate of carbon dioxide emissions from the building (the BER) is not greater than the target rate (the TER) when assessed using the Simplified Building Energy Model (SBEM) or similar approved calculation tool. This SBEM tool is available to download free of charge from the BRE website (www.ncm.bre.co.uk). You are advised that a considerable technical knowledge may be needed to effectively use the programme. Due to this a learning guide is included as part of the download. Alternative commercial software is also becoming available. Other alternative approaches available may include passing out the thermal design to a third party. However, please ensure that any software used will provide the evidence needed by Building Control. There are currently no alternatives which solely use prescriptive tables for showing compliance. Therefore the only way of showing compliance is to use the SBEM model. Criterion 2: Within any design the performance of the building fabric and the heating, hot water and fixed lighting systems are no worse than design limits set out in the table below. This more flexible approach should give designers more scope for innovative designs. LIMITING U-VALUE STANDARDS (W/M²K) (Table 4) Element Area-weighted average For any individual element Wall 0.35 0.70 Floor 0.25 0.70 Roof 0.25 0.35 Windows* & roof lights 2.2 3.3 Personnel doors 2.2 3.0 Vehicle access & large doors 1.5 4.0 High usage entrance doors 6.0 6.0 Roof ventilators 6.0 6.0 *Display windows and similar glazing are not required to meet the standard Criterion 3: Those parts of the building that are not provided with comfort cooling systems should have appropriate passive control measures to limit solar gain. Criterion 4: The performance of the building, as built, is consistent with the prediction made in the BER calculations. This may mean reproducing the SBEM calculations to prove that any design variances on site can be proven to be acceptable. Generally the criterion will include air permeability and pressure testing. However, where the building is less than 500m² floor area OR a leakage rate of 15m³/(h.m²) is used in the calculation, then this requirement may be omitted. A way of demonstrating that the testing body has the appropriate skills is for them to be a member of the Air Tightness Testing and Measurement Association. Criterion 5: There should be provisions put in place (building log-book) to enable energy efficient operation of the building to be undertaken. This should be passed over to the building occupier on completion. The data used to calculate the TER and the DER (within the SBEM calculation) should be included in the log book. Only one method of compliance Unlike previous versions of Part L, there is now only one method of demonstrating compliance with the energy efficiency requirements and this is mainly based around the SBEM computer model. For government approved calculation methodologies – visit www.ncm.bre.co.uk Issue of completion certificates The Local Authority will not generally be able to issue certificates of completion under the Building Regulations until the following have been received: - The final SBEM calculation, A pressure test report (where applicable) and Any relevant certificates for the commissioning of controlled services in the building. Construction standards and design detailing Irrespective of the quality of insulating materials used, there is a major potential for heat loss and cold bridging caused by poor standards of construction in terms of air tightness and the continuity of insulation. For this reason it is important for the designer to ensure that the various insulated elements in a building are carefully detailed at junctions. Uncontrolled air leakage can be minimised by specifications calling for appropriate levels of sealing and The Stationery Office Robust Details Guide ‘Limiting Thermal Bridging and Air Leakage’ suggests suitable details for achieving this with typical methods of construction. Site supervision The importance of effective on-site supervision to oversee the quality of workmanship achieves the above standards should not be underestimated. The cost of delays in completion and remedial action could far outweigh the costs incurred in this process.

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