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Implications for growth of Part L update

Part L 2013 is intended by the government to strike a balance between delivering an important “technical step” towards its ambitions for zero-carbon buildings and ensuring that the overall effect of regulation upon consumers and businesses does not stifle growth. The 2013 standards are moderately tighter than those in Part L 2010, and will require a review of current solutions which are being used to comply with 2010 standards.

These new regulations came into force from 6 April 2014. There will be similar transitional arrangements as for Part L 2010. This means that developments with building regulations approval granted before 6 April will have 12 months to begin on site.

It should be noted that this update summarises changes to Part L for England only. Wales is now setting its own Part L standards which should be published in the coming months.

The headline figure for new non-domestic buildings is a 9% reduction over Part L 2010 standards. This is calculated across the build mix, and will require greater improvements over 2010 standards for some buildings. It is expected that the standards are achievable through fabric and efficient services alone in most building types, so renewable energy will not necessarily be required.

As with Part L 2010, the CO2 target is based on a current set of fabric and service specifications, or “notional buildings”. These specifications have been strengthened to achieve the 9% improvement, but to make the target more equitable for different building types, a wider set of notional buildings has been introduced. The 2010 side-lit building (eg, buildings with windows on the vertical facades) has been split into two separate notional buildings in 2013: side-lit buildings with heating only (eg, a naturally ventilated office) and side-lit buildings with both heating and cooling (eg, an air conditioned office or retail space). This is in addition to the continued use of separate notional buildings for top-lit buildings (buildings with roof-lights, ie warehouses) and un-lit buildings (eg, theatres and cinemas).

Air permeability in the notional building now varies more often depending on size. This relaxes the CO2 target in smaller top-lit buildings where it was demonstrated that higher air tightness was more difficult.

Other changes include a modification to treatment of lighting, so the value of constant illuminance control is considered, while over-lighting of zones is directly penalised. The benefit of low-CO2 district heating has been increased and provision for accredited construction details removed, meaning all details should be calculated or the default values used.

Lastly, some minimum standards for non-domestic building services (eg, when replacing chillers, fan coil units or lighting) have been strengthened. These changes are detailed in the Non-Domestic Building Services Compliance Guide. For existing non-domestic buildings, the standards for extensions and for replacement windows have not changed.

The government has released temporary SBEM software in advance of approved third-party compliance software. This will help industry develop compliant Part L 2013 designs. Various approved third-party compliance software is expected to be available shortly.

Jointly written by Christopher Pountney, senior engineer, and David Ross, regional director, for AECOM

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