The Energy Hierarchy and building design
From January 2023 onwards, any and all planning applications in England must comply with the Building Regulations which came into effect in June 2022, requiring all new-build homes to produce 31% less carbon emissions than the previous limit.
Reducing overall carbon emissions – whose limit is set to become more and more stringent on the road to the goal of net zero emissions by 2050 – is a challenge builders and constructors can meet through innovation and the use of renewable energy.
First proposed in 2005 by Renewable Energy Association’s Director General Philip Wolfe, the Energy Hierarchy is an important tool for sustainability which has since been adopted – and adapted – by a variety of energy institutions and governments. This includes the ambitious London Plan, which aims to bring the English capital down to net zero by 2030, two decades ahead of the national target.
Air quality is a pressing issue for London. In 2020, the 2013 death of nine-year-old Lewisham resident, Ella Kissi-Debrah was the first in the UK to officially have air pollution named as its cause: she had been exposed to nitrogen dioxide, a by-product of diesel vehicles whose use was long encouraged with the goal of combating carbon dioxide emissions. The Energy Hierarchy aims for the reduction, rather than the replacement, of carbon dioxide emissions in the atmosphere.
The Energy Hierarchy is a list of energy options, in the order of priority in which they should be implemented. This helps to inform and assist the transition towards a sustainable energy system. From most to least desirable, the options laid out in the London plan are:
the first priority on the hierarchy is to avoid the needless consumption of any energy, whatever its source.
after minimisation of energy demand has been achieved, ensuring an efficient and clean energy supply is the second priority.
whenever possible, use energy from renewable, sustainable sources.
the least desirable option in the hierarchy is the use of sources such as fossil fuel, which are acknowledged as unsustainable and should be used only when all other options have been exhausted – and with the implementation of measures to counteract the emissions.
As energy strategies are implemented in the design of new buildings – and, when possible, in changes to existing buildings – another motto to remember is be seen – the importance to track, monitor, and promote progress.
Implementing Energy Hierarchy in building design
For a planning application to be accepted, the building must be designed to meet the above priorities, in the correct order, to the maximum possible degree. There are many ways to implement the Energy Hierarchy in building design. Below are some examples:
Reducing energy demand (be lean)
While much is ultimately left to the choices of future occupants – for example, whether they keep lights on unnecessarily, or purchase efficient appliances with lower energy requirements – there are many things that can be done to minimise needless consumption of energy from a design standpoint. For example, good building isolation will minimise or eliminate heat loss, closing thermal bridges and reduce the need for heating.
Planning orientation and site layout in a way that optimises natural lighting and ventilation will also minimise the need for artificial lighting and air conditioning; high efficiency lighting and mechanical ventilation with heat recovery and waste water heat recovery should also be considered. A green lease agreement for future tenants to conform to will also help towards ensuring the building’s energy needs don’t exceed calculations.
Supplying energy efficiently and cleanly (be clean)
Whenever possible, exploiting local energy resources such as heating networks is highly advised. Also known as district heating, heat networks supply heat to buildings through a network of pipes carrying hot water underground. The areas they cover can be vast or relatively small, and buildings connected to heat networks have no need for individual boilers and heaters. This allows the storing and reusing of energy, in a circular approach which greatly reduces energy waste.
Where no heating network is available, steps should be taken to see whether a network is planned for the area in the future before moving on to other solutions to optimise energy supply, such as the use of ultra-low NOx gas boilers.
Using renewable energy sources (be green)
After reducing energy needs and ensuring energy is supplied efficiently, steps should be taken to make up for any shortfalls in energy needs through renewable sources, commonly referred to as “green energy”. This may include solar, wind or geothermal energy; or bio energies, such as farm waste, wood, or biofuels.
The latter are not infinite as energy obtained from elemental sources, but their biomass can be used for energy after a relatively brief life cycle. Whilst combustion is necessary to release energy, this is compensated by the carbon dioxide absorbed during the life cycle of the biomass, and bioenergies are therefore considered carbon neutral.
If, despite all the above, the net zero-carbon target cannot be met, the use of sources with a heavier environmental impact will be necessary. Carbon emissions can still be mitigated through procedures such as carbon capture and storage – the long-term storage of carbon dioxide to keep it from being released into the atmosphere – but they should only be used when no other option is viable, as all experts agree that their use should be phased out.
As part of the London plan, a cash-in-lieu contribution is required to cover the shortfall in energy savings – but boroughs may agree to alternative arrangements, for example by letting the developer offset the shortfall through other interventions to cut carbon dioxide emissions in another site within the local area.
For England to reach its zero carbon target over the next 27 years, it’s vital for developers, local authorities, and members of the public to work together to tackle emissions – be it through intelligent building design, new technology, or less wasteful habits.
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