Section B - energy
The reduction of carbon dioxide and other greenhouse gases to the atmosphere is the central pillar in Westminster’s Climate Emergency declaration. The carbon neutral target (2030 for council activity and 2040 for the city) will ensure that we collectively play out part in preventing the 1.5 degree increase in global temperatures.
The planning system is a key lever for reducing energy use and associated carbon reduction in the built environment. This is significant as emissions from buildings constitute 86% of emissions in Westminster. The London Plan policies should be adhered to and those that relate to carbon reduction in buildings are:
- SI2: minimising green house gas emissions - major developments are required to minimise greenhouse gas emissions and peak energy demand in accordance with the energy hierarchy
- SI3: energy infrastructure - large scale developments are required to determine future energy infrastructure requirements and establish the most effective energy supply options, in accordance with the heating hierarchy
- SI4 managing heat risk - major developments are required to address internal overheating and minimise adverse heat impacts on the wider environment in accordance with the cooling hierarchy
The City Plan policy on Energy complies with these regional requirements and sets out the requirements for zero carbon development in the city. Planning policies set minimum standards and all development types where possible should adhere to the principles set out in this section.
Operational energy
Development should seek to make the fullest contribution to minimising energy use and reducing carbon emissions by implementing interventions in a planned and prioritised manner that optimise efficiency before utilising sustainable energy sources. The London Plan Energy Hierarchy (shown in the City Plan, Page 138, Figure 30) demonstrates the prioritisation of interventions through their Be Lean, Be Clean, Be Green, Be Seen approach. This should be incorporated into the design rationale for all development proposals in Westminster and reflected in any evidence that is used to support planning applications.
Further detailed guidance on how to design and deliver good sustainability outcomes in development are available:
London Energy Transformation Initiative Climate Emergency Design Guide
RIBA Sustainable Outcomes Guide
1. Be Lean: use less energy
All development proposals are expected to minimise operational energy demand and maximise efficient use. A sustainable design approach should consider:
- using energy use intensity targets (energy use [kWh]/m2/year) to better inform your design approach and success criteria for sustainable design
- employing passive design principles, including building form, orientation, location, and shading
- embracing a ‘fabric first’ approach, optimising insulation, air tightness and thermal mass to maximise the efficiency of your development. In line with GLA guidance, major residential developments should achieve a minimum 10% improvement on building regulations performance by energy efficiency alone. This increases to a 15% improvement for major non-residential schemes; and
- using efficient and integrated systems to minimise energy demand from heating, cooling and lighting and ventilation
Passive solar design
The design rationale for buildings in the city should, where practicable, maximise the opportunities for natural lighting and the heating of spaces in buildings through conduction, radiation and convection. Despite the physical constraint of many development sites, this design approach is important (particularly for residential use) as it helps to determine the orientation of the building, the type of materials that are used to optimise thermal efficiencies, use of insulation and the size and location of windows, optimising solid to void ratio.
During the cooler months, heating premises through solar design is desirable but it is important to ensure that the same design rationale does not cause overheating during the summer months.
Strategies to consider to passively cool buildings include dual aspect design to allow for windows on opposite facades to create cross ventilation, shading devices like blinds and where appropriate overhangs. The incorporation of green infrastructure into developments not only as living walls and roof but tree planting, natural sustainable drainable systems and other spaces also provide a cooling effect on buildings.
Cooling hierarchy
1) Reduce the amount of heat entering a building through orientation, shading, high albedo materials, fenestration, insulation and the provision of green infrastructure.
2) Minimise internal heat generation through energy efficient design.
3) Manage the heat within the building through exposed internal thermal mass and high ceilings.
4) Provide passive ventilation.
5) Provide mechanical ventilation.
6) Provide active cooling systems.
Managing heat risk
Our climate resilient approach to the built environment is not only important for reducing carbon emissions but also for the health and wellbeing of the people that occupy those buildings. Overheating in buildings occurs when people are exposed to high levels of heat for extended periods of time. This can take place not only in existing buildings but also new developments. For vulnerable populations, especially older people, the results can be fatal. In Westminster we are experiencing hotter summers and the density of development in the city means that the urban heat island effect is experienced in many parts of the city by our communities. Ensuring that existing and future building occupants are familiar with the measures that effectively cool homes will help minimise the risk to people’s health.
2. Be clean: supply energy efficiently
Once energy demand has been minimised, we would expect all developments to demonstrate how they will supply clean energy efficiently to further reduce their emissions impact. Where possible, developments should aim for all onsite heating and hot water provision to be fossil-free, prioritising electrified or hybrid heat sources.
In locations where the density is sufficient for decentralised heat networks to provide a realistic solution, we would expect developments to use a communal low temperature heating system and select an appropriate heat source in accordance with the GLA’s recommended heating hierarchy.
Heating hierarchy
a) Connect to local existing or planned heat networks.
b) Use zero-emission or local secondary heat sources (in conjunction with heat pump, if required).
c) Use low-emission combined heat and power (CHP) (only where there is a case for CHP to enable the delivery of an area-wide heat network, meet the development’s electricity demand and provide demand response to the local electricity network).
d) Use ultra-low NOx gas boilers.
Combined Heat and Power (CHP) and Heat Networks
Combined Heat and Power (CHP) describes the process of producing both heat and electricity at the same time. Decentralised heat networks describe the network of pipes that distribute heat from a central source, for example a CHP plant to a number of sites which could be homes, offices, schools or a combination of buildings. Heat networks offer an efficient and competitive solution for heating buildings in areas with high heat density and provide long-term flexibility for decarbonisation through the replacement of heat generation plant with low carbon technologies.
In line with the GLA’s energy hierarchy, we encourage developments located in the heat network priority areas (see map in City plan, page 139, figures 31) to connect to an existing network in order to maximise the efficiency of the existing infrastructure, minimise overall emissions and deliver the best outcome.
Air Quality is a significant issue in the city and combustion from gas boilers and CHP contributes to this problem. Where a gas fired CHP system is proposed, the requirements for air quality assessment and monitoring must be adhered to and an air quality neutral assessment must be provided for any applications incorporating CHP. We would expect any proposal for CHP to demonstrate how they will use secondary heat sources and outline the timeline for switching to fossil free generation as part of long-term decarbonisation strategy for the network.
Pimlico District Heating Undertaking (PDHU) is the oldest district heating scheme in the UK and the largest in London. It was developed and built in the 1940s and 1950s, making use of waste heat from Battersea Power Station to provide local heat and hot water for residents. Heat is produced from two gas-fired combined heat and power engines (CHP) and three large boilers co-located in the main energy centre in Churchill Gardens. PDHU can supply energy more efficiently than can be achieved in conventional boilers and power stations through a combination of electricity (which is sold to the national grid) and heat (which is pumped through 5km of underground pipes to supply end users in Pimlico). The system currently supplies heat to over 3,200 households across three estates, 50 commercial customers and four schools. The council is seeking solutions to de-carbonise PDHU by replacing some of the gas-fired plant with low carbon heat pump technology.
Benefits achieved from PDHU include:
- providing year-round heating/hot water service to residents at lowest cost (4.53p/kWh)
- saving over 15,000 tonnes of carbon a year compared to individual conventional boilers – with significant potential to improve this though use of hybrid heat generation technology
- providing localised energy source, displacing the demand for grid-supplied electricity
- income from heat sales to the commercial properties helps lower residents’ charges and reduces the risk of fuel poverty; and
- sales of electricity generated from the CHP engines provide an added income stream of £1m per year
Site wide approach to energy
In our housing renewal areas, a site-wide / master planning approach should be taken to energy incorporating the energy, heating and cooling hierarchies. Ensuring that our communities in these areas have access to affordable energy not only when the schemes are built out but into the future requires a futureproofed energy infrastructure. Being able to access future changes in technology is key to Westminster’s Climate Resilient approach.
3. Be Green: use low and zero carbon technologies
We would encourage developers to maximise their on-site renewable energy generation, regardless of whether the minimum on-site carbon reduction target has already been achieved, to will allow the development to minimise its operational emissions and grid-based energy consumption. We consider the main low and zero carbon technologies opportunities in Westminster to be solar technologies and heat pumps.
Heat pumps
Heat pumps utilise the difference in temperature between the ground (or the air or water depending on the type) and the room that they are heating. The low temperature heat is transferred through the heap pump to heat the space in the room or building. This low carbon technology can be hugely efficient when integrated into new building especially for example for underfloor heating. As part of a refurbishment or retrofit scheme their scale and integration into existing townscape needs to be handled sensitively, taking into account outdoor condenser units which some heat pumps utilise, and the noise pollution associated with them.
Solar technologies (solar thermal and solar PV)
Despite the temperate climate and large number of tall buildings in the city solar energy can be effectively harnessed and converted to electricity (solar photovoltaics) or to heat water (solar thermal) in a building. There is an extensive range of panels available (including solar slates) with a variety of colours, thicknesses and glazing options available and visual impacts can be mitigated through siting and design. Opportunities to incorporate solar technologies may be reduced in some instances given the prevalence of listed building and conservation areas in Westminster, however the council strongly advocates such technologies and wants to work with applicants to find the best solution – this can be discussed at pre-application stage. As a general principle the aesthetics of the technology are appropriate within the city and they can be installed in conjunction with green roofs to maximise climate resilience on sites.
For further information, see:
London Solar Opportunity Map (GLA)
Town and Country Planning Permitted Development Order 2015
Energy Efficiency and Historic Buildings: Solar Electric (Photovoltaics) (Historic England)
4. Be Seen: monitoring and measuring
The actual energy use of a building once occupied is just as important as the planning for energy supply and use prior to development taking place. This will determine how much of the planned energy savings have been realised and the direct contribution the building makes to tackling climate change in reality.
It is well established that a performance gap exists between predictions of energy consumption from building compliance tools determined at the development design stage and the actual measured energy use of a development once completed and occupied. To achieve net zero-carbon buildings we will need to better understand their in-use performance so that we can address and reduce the performance gap moving forwards. Ensuring a development operates as designed is also an important consideration in safeguarding the wellbeing and financial implications for building users.
Provision of energy monitoring data is essential to understanding this and we therefore encourage developers to submit this information to the council post-occupation to understand how the building is being used compared to projections at application stage and what can be learnt for future developments. Collection of this data over time will also help to create a city-wide picture of energy usage to inform strategic decisions.
Westminster’s Charter sets out the steps businesses can take to annually monitor the energy performance and emissions of their buildings and in doing so collectively contribute to achieving the climate emergency goals for the city.
The GLA is producing ‘Be Seen’ guidance which will set out requirements for post-construction monitoring (to align with London Plan policy SI2). The guidance will state that reporting requirements should be secured through a Section 106 agreement and a template will be included.