Last edited 11 Sep 2014

Zero carbon non-domestic buildings

The Climate Change Act was introduced in the UK in 2008, creating a long-term, legally-binding framework for tackling climate change. It set a target of reducing carbon emissions by 80% compared to 1990 levels by 2050, with a reduction of at least 34% by 2020.

A strategy for how this was to be achieved was set out in The Carbon Plan published in December 2011. Buildings form a significant part of the plan as they account for around 45% of our total carbon emissions.

In December 2006, the Labour government committed that from 2016 all new homes would be ‘zero carbon’. The Labour budget in 2008 announced the government's intention that all new non-domestic buildings should also be zero carbon from 2019. This commitment was confirmed by the Coalition government in December 2010.

This means that the timeframe for zero carbon non-domestic buildings is three years behind that for zero carbon homes. Consequently, progress towards defining a zero carbon standard for non-domestic buildings is similarly behind, with a series of consultations ongoing.

At present, it is considered that the overall approach to achieving zero carbon non-domestic buildings should adopt a similar 'fabric first' hierarchy of measures to those proposed for domestic buildings:

  1. Fabric efficiency to reduce the demand for heating, cooling, mechanical ventilation and electric lighting.
  2. Meeting the remaining demand for services with high efficiency equipment.
  3. Supplying that equipment with low carbon energy.
  4. Offsetting remaining emissions by generating further renewable energy off site (such offsetting measures are called ‘allowable solutions’).

There are a number of key questions that must then be answered relating to the application of these measures:

  • What standards should be set for the different levels of the hierarchy? A range of possible standards exist for ‘carbon compliance’ (the first two elements of the hierarchy) each achieving different overall reductions in carbon emissions compared to the 2006 building regulations.
  • How those standards should be defined and assessed.
  • Whether minimum standards should be set for different elements.
  • How to differentiate between types of non-domestic building.

These questions are highly complex and involve detailed cost benefit analysis.

For example, technically, it may be possible to comply with a zero carbon requirement by adopting low carbon technologies rather than by a creating an energy efficient fabric, and from the developers perspective this might be cheaper in the short term. However this might not minimise whole-life costs (due to the ongoing costs of fuel, maintenance and replacement). In addition, technological solutions are prone to operate below their optimal level of efficiency because of the behaviour of occupants, poor commissioning and maintenance. Futhermore, optimising the building fabric would be likely to give a building better resilience to climate change and continuity of energy supply.

On the other hand, build quality has a big impact on the effectiveness of energy efficient fabric, and is much more difficult to correct than user behaviour. Also, technology replacement offers the potential for future improvement in efficiencies that are difficult to achieve with building fabric.

These are more difficult questions to answer than for domestic buildings, as there are such a diverse range of possible building sizes, forms, types and locations to consider.

In addition, unlike domestic buildings, electric lighting is a very significant component of energy use and this results in a more complex trade off between natural lighting and fabric thermal efficiency. It is also becoming apparent that continually increasingly standards for U-values has a diminishing return relative to cost whilst there is considerable scope for efficiency in services equipment.

There are also a number of options for how a zero carbon standard might be enforced, however it is likely to be based on assessing carbon compliance using existing techniques which compare the relative performance of the proposed building with a notional building of the same size, shape and use. Notional buildings may be defined as ‘mixed mode’ as standard to give some incentive for developing an energy efficient building form. In addition, minimum efficiencies are likely to be set for key measures such as U-values and solar gain as well as the main services equipment and electric lighting.

As with zero carbon homes, unregulated energy (such as appliances) are likely to be excluded from emissions calculations.

The standards to be achieved will be set out in the building regulations and associated approved documents, in particular Part L, the conservation of fuel and power. The overall standards set in the current 2010 Part L are based on achieving a percentage reduction in carbon emissions compared to the carbon emissions of a building of the same type, size and shape built to 2006 standards. Revisions of Part L in 2013 and 2016 will require larger reductions in these carbon emissions compared to the 2006 standards, progressing towards the ultimate goal of 'zero carbon' by 2019.

There area a number of concerns with zero carbon non-domestic buildings, other than the obvious uncertainty that will remain until the final standards are known:

  • There is some concern that the standards will be watered down before 2019.
  • Developers may decide it is easier and adopt ‘allowable solutions’ rather than meet the carbon compliance standards.
  • It is questionable whether the standards really achieve 'zero carbon'. In particular, as with other standards such as BREEAM and LEED, they focus on operating emissions rather than capital emissions (ie they do not take account of carbon emissions resulting from constructing a new building).
  • It is not clear how the long-term maintenance, user behaviour or any future alterations to new buildings will be regulated.
  • Questions remain about measures to deal with the difference between the predicted and actual energy performance of buildings which can be significant.
  • There is concern about whether the time-frame for change is realistic.
  • There is uncertainty about which allowable solutions should be permitted, and how they should be provided.
  • It is not clear what the relationship will be between planning permission requirements and building regulations requirements.
  • Zero carbon standards will not tackle the existing building stock.

NB in 2012, a British Council for Offices study found that in 77 commercial developments across central London on-site renewable energy generation with a whole-life cost of £174 million, produced carbon emission savings of just £18 million.

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