Striding towards Zero Carbon

The next major revision to Part L
will come into force in October 2010. While this revision is not as radical as the last in 2006 it sets a challenging further 25 per cent reduction in Carbon Dioxide (CO2) emissions above current targets.

This revision is in response to the government’s policy statement ‘Building a Greener Future’ (2007) which sets out a target for new homes to be zero carbon by 2016 and a similar move towards zero carbon for non-domestic buildings by 2019. To achieve these targets the government has set in place further trajectory improvements planned for 2013. Therefore the latest revision can be seen as one more step along the short path towards zero carbon.

It is acknowledged that to achieve these high energy efficiency standards buildings will have to be constructed with a high standard of airtightness, which will necessitate good ventilation strategies to avoid poor indoor air quality; therefore Part F (Ventilation) has been revised simultaneously to meet these new demands.

THE TARGETS
The Target CO2 Emission Rate (TER) is no longer based on a 2002 notional building with an improvement factor; for 2010 it is based on a building of the same shape and size as that of the actual building. The developer must still equal or better the TER to achieve compliance.

A flat approach of 25 per cent reduction in CO2 has been set for dwellings, however for non-domestic buildings the 25 per cent reduction in CO2 is based on an ‘aggregate’ approach. Some building types will be required to deliver a higher percentage improvement, whereas other will need a lesser improvement. This acknowledges that some building types will be easier to achieve higher energy efficiencies than others. Importantly, the net overall outcome will achieve a 25 per cent improvement across the new building stock.

The compliance route remains unchanged from 2006 in that there is still an allowance for flexibility in design and specification, so long as the building achieves the TER. However, as was the case for 2006, there are still limiting values that are provided in the Approved Documents and other second tier documents. These limiting values, for example worse acceptable air leakage rates and maximum U-values remain unchanged, but there are new standards that apply for heat pumps and other renewable energy systems. Another new requirement has been introduced to assess heat loss through party walls and will form part of the heat loss calculation.

COMPLIANCE TESTING
There will continue to be a great emphasis placed on the quality of construction to ensure the energy efficiency of buildings in operation. Compliance testing, like air pressure testing will continue to be required, and the number of dwellings required to be pressure tested on each development will be effectively doubled. There will be encouragement for developers to test a larger sample to benefit from better values that can be used in SAP calculations and a penalty for dwellings that are not tested.

Information on the building must be provided to the building user to ensure that the building is used as it was designed. This is to help prevent the building using more energy than predicted by the designer due to occupant behaviour.

While the 2010 revision of Part L does require consequential improvements of existing buildings that are extended or where new fixed services are installed the improvements are much the same as those set in 2006.   

In conclusion the requirement of a further 25 per cent reduction in CO2 will be a tough challenge for the construction industry; especially so if using traditional building materials, techniques and services. There is therefore likely to be a great uptake and interest in developing innovative materials and systems, and an increasing use of low and zero carbon technologies.

BRE GUIDANCE
BRE in partnership with the Energy Saving Trust is offering half day training courses in regional venues between July-September for delegates to provide a practical review of the regulatory changes and how these revisions will affect the design, specification and construction of new dwellings.
•    Part L - Discover how amendments to Part L and the approved document Part L1A will affect design, construction and compliance of new housing.
•    Part F - Review how the revisions will affect ventilation strategies and the impact on air quality and occupant comfort.
BRE is also offering a one day course specifically for non-domestic buildings on dates in July and September. This course will help you to become familiar with the new version of iSBEM, v4.0.

Web: www.bre.co.uk/training