Clara Bagenal George of Elementa Consulting and Adam Mactavish of Currie & Brown review the energy policies in the draft new London Plan and assess their implications for new development

4 15 dpr sf headquarters 107 web

Source: Elementa Consulting

DPR Construction’s head office in San Francisco is a CIBSE award-winning, net zero energy renovated office building

01 / Introduction

The consultation draft of the Greater London Authority’s new London Plan was released in December 2017 with the public consultation running until early March. The new plan sets out the vision and planning policies that will shape strategic development in the city and provides a framework for the development of local plans across the capital. Although still at draft stage, the new plan provides clear pointers as to the strategy and priorities that will influence future development in the capital. 

This article considers the implications of some of the policies within the sustainable infrastructure chapter of the draft plan, particularly those that affect energy use and pollution associated with new buildings. The main changes are considered point by point below.

 02 / Overview of the draft London Plan

At first glance the energy policies proposed in the draft new London Plan are an evolution of those currently in force. There is still a focus on “be lean, be clean, be green” and a requirement for development to show a 35% improvement in carbon performance compared with Part L 2013. However, on closer inspection there are big changes in almost all areas of energy policy. If adopted, these are likely to have a big impact on developers’ energy strategies. 

Some of the headline policies proposed for the new plan that will change major developments include the need to: 

  • be at least air quality neutral (with large developments having a positive impact on air quality)
  • achieve higher minimum standards for energy efficiency 
  • meet a heating hierarchy that prioritises secondary as well as clean heat and power from zero-emission sources
  • demonstrate how overheating risk and peak power demand will be minimised
  • future-proof the development so that it can achieve zero-carbon emissions on site by 2050
  • monitor and report on energy use for at least five years 
  • include proposals for minimising embodied carbon during construction.

In addition, the plan confirms that from 2019 the need to offset any residual regulated carbon emissions associated with new development will be extended to non-residential development. In the current London Plan this requirement is only for residential development.

1. Focus on air quality

New developments must not lead to air quality deterioration in areas of poor air quality and should use design to minimise exposure to air pollution. All schemes should be at least air quality neutral, while those in “opportunity areas” (areas earmarked for development) should be air quality positive (improve overall air quality). Steps that developments can take to address these requirements include use of low or zero-emission heating and power sources in addition to measures to reduce levels of, and exposure to, transport-related air pollution. 

Implications for energy strategies

While not directly linked to energy standards, this policy could have a major impact on development in London, especially in “air quality focus areas” (those identified as most needing improvement) or “opportunity areas”. Some schemes may still be able to use combustion-based sources of heating or power, such as gas boilers or combined heat and power (CHP), where this has lower emissions than the previous building. In many cases, however, it is anticipated developments would be expected to avoid onsite combustion-based heating systems, meaning there is likely to be a substantial rise in electricity-based systems such as heat pumps. 

2. Higher energy efficiency standards

The current London Plan suggests that buildings should meet the development’s regulated (ie, Part L) carbon emissions using energy-efficiency measures (for example, by reducing demand). The London Plan requires buildings to achieve a 35% reduction in carbon emissions (for example, by connecting to district heating or installing zero-carbon energy sources). The new plan proposes to go further by requiring that domestic space achieves a 10% improvement on Part L requirements purely through energy efficiency, with non-domestic space needing to achieve a 15% improvement. These new targets are above that historically achieved in new London development. In 2016, the average improvement achieved through energy efficiency proposed in planning submissions was 7.4%.

Implications for energy strategies

The focus on energy efficiency will mean that project teams will need to review their fabric specifications, glazing ratios and positioning, as well as other factors such as airtightness, ventilation strategy and reducing thermal bridges. Highly glazed domestic developments are likely to be among those most affected, as these already routinely use high-performance triple glazing just to achieve Part L compliance.

While there may be some impact on development cost, the Greater London Authority’s analysis suggests that the new standards are achievable using well-established technologies and specifications.

3. A new heating hierarchy

The current London Plan specifically requires developments to evaluate the feasibility of using CHP for energy supply and to connect to existing heat networks (predominantly powered using CHP). In response, these systems have been specified for the majority of major developments. In 2016, approved energy strategies for over 48,000 homes and 1.7 million m2 of non-domestic development incorporated the use of CHP. 

Heat networks are still favoured in the draft new London Plan in heat network priority areas. However, the new plan significantly downgrades the role of gas CHP, placing it after the use of waste heat and heat from zero-emission sources in a new heating hierarchy. The changing positioning of CHP is for two reasons. As a combustion-based technology, it will impact local air quality more than electricity-based systems, which have zero local emissions. Also, the significant reduction in the amount of carbon associated with electricity from the national grid in recent years means the carbon-saving benefits of gas-fired CHP have fallen dramatically. 

Implications for energy strategies

Instead of gas CHP systems it is likely new developments will be turning to heat pump technologies to provide the “be clean” element of the hierarchy (the stage that focuses on supplying heating and hot water efficiently). Heat pumps may be linked into ultra-low temperature (4th generation) heat networks that incorporate a range of different heat sources, including secondary heat (for example, that rejected from chillers) and that extracted from the ground, water and air.  

Energy strategies will need to identify how heat is best delivered by connecting to, or creating, local networks or by more localised building level systems. An increased focus on using electricity to supply heat to developments (for example, via heat pumps) means that as well as using these technologies, developments will need to show how they are working to reduce the impact on local supply infrastructure by reducing peaks in demand (see 4. Reducing peak demand, right). 

4. Reducing peak demand

The demands made by new development on existing energy supply infrastructure will be increased where both heating and power are provided by electricity. Both the wholesale price of electricity and the carbon factors of grid electricity are high at times of peak electricity use.  During the cold spell at the end of February this year, the wholesale price of electricity peaked at £1,000 per GWh, more than 20 times the average wholesale cost. Currently this fluctuating electricity cost is not transferred to consumers, but should variable tariffs be introduced, electrically heated developments could be exposed to higher energy costs when the weather is coldest.

As a result, new developments are required to show how they will minimise or shift peak energy demand. More energy efficient buildings will help to reduce demand, but developers will also be expected to consider how they can go further using smart controls and energy storage. 

This policy helps to ensure developments do not add significant load during periods of high consumption, which will be critically important as more of London’s heat generation uses electricity.  

Implications for energy strategies

As well as reducing total energy consumption, developers will need to show how they are minimising peaks in demand, for example, by using thermal or battery storage, or by using smart systems proactively to manage power demand.

Packard foundation headquarters 01 26 web

Source: Elementa Consulting

Packard Foundation is a CIBSE award-winning new-build, net zero energy office building

5. Managing overheating

To address current and future risks of overheating, new developments will need to use a dynamic simulation model that meets CIBSE guidelines (TM52 for non-domestic and TM59 for domestic) and that considers future climate scenarios to which the building may be exposed. Rather than reaching for air conditioning as a solution, developers are required to consider how design and specification can reduce demand for cooling, for example through glazing design, solar control, floor-to-ceiling heights, exposed thermal mass and from the use of green roofs and walls. Where air conditioning is specified, developers should design these so that the waste heat is captured and reused, either within the development or by sending it to a local heat network. 

Implications for energy strategies

Developers will need to go further to show that not only are risks of overheating being effectively managed, but that this is being achieved through good design rather than by relying on mechanical cooling technologies. The need to capture waste heat from air conditioning may trigger a need to think more holistically about the connection of heating and cooling demand within a development. This may result in increased connection of systems that are currently kept separate. 

6. Zero-carbon plan

The ambition set by the mayor of London is that London will be a zero-carbon city by 2050. To achieve this, buildings that are designed today must not add to the huge challenge of retrofitting all buildings to zero carbon by 2050. This means that all new developments must have a plan in place of how to achieve zero-carbon on-site emissions without major retrofit or strip-out of services. 

It is anticipated that the electricity supply will continue to decarbonise so that by 2050 the supply is virtually, if not totally, zero carbon. To benefit from these changes, buildings will need to be capable of generating heat using electricity and must be sufficiently efficient that running costs are affordable and demands on the supply infrastructure are manageable. 

Implications for energy strategies

Developments must consider how they will achieve zero-carbon onsite emissions. This might mean designing heating systems capable of operating at ultra-low temperatures so that fossil fuel heat generators can be swapped out for heat pumps in the future, without having to change further pieces of the system, such as heat emitters.

7. Energy use disclosure

It is now well known that many buildings use significantly more energy in use than the amount projected during design. While this is in part because of the omission of unregulated energy (such as IT, other small power, lifts and escalators), the gap between envisaged performance and that achieved in reality is often substantial. To both assess how well London’s energy policies are working and to determine how buildings are performing in practice, new developments will be required to monitor and report on their energy use for at least five years. 

While it is not clear how public the reported energy data will be, the need to report on performance in practice is likely to be a strong incentive to ensure that the solutions proposed are effective and that they are well commissioned and used.

Implications for energy strategies

An increased focus on actual performance in practice will mean that developers will need to go beyond standard compliance-based energy modelling to better understand how the new building is likely to perform in practice. The use of methods such as CIBSE TM54 may help provide a more accurate estimate of likely actual energy use and the effectiveness of different energy efficiency measures. 

As well as affecting energy strategies, increased reporting of actual energy use, particularly if made public, is likely to strengthen the understanding of developments’ energy consumption and how they compare to in-use benchmarks (such as those published by the Better Buildings Partnership). It is hoped this will incentivise the reduction of in-use energy consumption through energy auditing and investment in energy-saving technology and improved commissioning and operations.

8. Embodied carbon

As the carbon associated with grid electricity continues to fall, the relative importance of operational and embodied (associated with construction materials and processes) carbon emissions is changing. Recognising the increasing importance of embodied emissions, the draft new London Plan asks developers to show how they are minimising these emissions in construction. There is no national standard method for assessing embodied carbon emission although a range of methodologies have been developed including the Impact method and datasets (used in BREEAM) and methods developed by the RICS and others. 

Implications for energy strategies

While not affecting operational energy, energy strategies should also set out the considered options and proposed approach to minimising embodied carbon. This might be through the reuse or recycling of existing materials, the selection of low embodied carbon specifications or products, and even designing the building to be easily deconstructed and reused at the end of its life. It is expected that a supporting supplementary planning document will provide further detail on the approach to looking at embodied carbon and other topics. 

Education hackbridge proposed visualisations 3 of 4 (1)

Source: Architype

Hackbridge primary school is a new-build school targeting net zero carbon (regulated and unregulated) and zero primary energy. It is Passivhaus certified

03 / What are others doing?

The draft new London Plan is just one of several recent policy documents calling for a renewed emphasis on delivering low-carbon development. However, the approaches used vary. 

The World Green Building Council (WGBC) has called for an “ambitious and dramatic transformation” of the building sector if global warming is to remain under 2°C, the limit enshrined in the Paris Agreement. The WGBC calls for all new buildings to operate at net zero carbon by 2030, and every building by 2050. The mayor of London is yet to set out a trajectory of targets to meet his zero carbon-by-2050 goals, but it is thought this will go beyond the current Greater London Authority definition of zero carbon (a cash offset for any residual regulated carbon emissions associated with new development using the design stage energy model).

The changes in the new London Plan show a renewed focus on zero carbon, but still use the UK building regulations’ carbon calculation methodology as a framework, requiring a percentage carbon emissions reduction compared with this baseline.

Many energy policies use a different methodology to that used in the UK and which underpins the London Plan. These involve an absolute kWh/m2 metric rather than a percentage carbon emission reduction. This includes Toronto’s Zero Emissions Buildings Framework, Vancouver’s Zero Emissions Building Strategy, the Canadian Green Building Council’s Zero Carbon Building Standard and the Passivhaus standard. This offers a consistent indicator to be measured at each stage of the design process – ultimately, and most importantly, during operation, to allow identification of the most successful approaches. 

The London Energy Transformation Initiative (LETI), a network of over 200 built environment professionals, is exploring the role of absolute performance targets addressing total energy use and energy efficiency in London’s future energy policy. This movement was initiated by Elementa Consulting. Its focus this year includes developing a standard “LETI appendix” for energy strategies. LETI has published numerous papers over the last year putting together recommendations for policy changes to put London on the path to a zero-carbon future, many of which have been adopted in the draft policy. For more information and to get involved in a LETI work group, go to www.leti.london. 

04 / A new generation of energy policy

The energy policies proposed in the draft new London Plan and in other major cities are greater both in ambition and scope of coverage than those seen previously. 

By explicitly incorporating factors such as peak demand, overheating and embodied carbon these policies are likely to stimulate changes in the ways in which energy is addressed in future development. By including an explicit requirement to report on in-use performance we should be able to consistently see, perhaps for the first time, how these requirements are actually influencing performance in practice.