NET ZERO & ZERO CARBON BUILDINGS
Focusing on operational carbon to make new and existing buildings greener
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With carbon reduction targets for all sectors expected to become more challenging in the next carbon budget, reaching Net Zero should truly be a core focus area. In light of this Graham Temple, marketing manager at Mitsubishi Electric suggests that minimising operational carbon in buildings should be a priority
he UK has set a goal of achieving Net Zero carbon emissions by 2050. It seems the country is on the right track, with recent research from the Climate Change Committee (CCC) showing the UK has experienced a consistent decline in emissions over the last three decades. As a result, the CCC has suggested we are ‘likely’ to have met our most recent carbon budget, which ran from 2018 to 2022. However, while progress has been made,
there is still some way to go. With carbon reduction targets for all sectors expected to become more challenging in the next carbon budget, reaching Net Zero should truly be a core focus area. In light of this, reducing the carbon impact of building performance is a priority, with a need to minimise the operational carbon (the carbon produced during a building’s use phase) in buildings specifically. Some of these emissions may be direct – such as burning fossil fuels like gas or oil on-site for heating and hot water – while others might be indirect operational emissions, created when electricity used in the building is generated from fossil fuels. In fact, the UK Green Building Council highlights that 19% of the UK’s carbon footprint is from operational emissions produced from energy used to heat, cool and power buildings.
Evolving regulations to cut operational carbon emissions
Various standards and legislation are being implemented to keep building emissions – including operational carbon emissions – down. For example, Energy Performance Certificates (EPCs) are central to several government policies around building performance, particularly energy efficiency. The prime example is Minimum Energy Efficiency Standards (MEES), which the government uses to drive higher energy efficiency in new and existing buildings. If a commercial building does not achieve an EPC rating of B by 2030, it cannot be leased or sold, impacting its asset value. Given that the current minimum is E, many commercial buildings face the challenge of significant upgrades to meet the new standard. The property industry estimated that in 2021, 60% of existing stock would not achieve a B rating and that landlords would have to invest in efficiency refurbishment at double the usual rate over the next seven years. There is also work being done to develop specific definitions and targets for ‘net zero’ buildings, and some businesses in the construction, property and installation sectors are adopting voluntary standards and more accurate measures of building energy use. They are also examining the buildings they own or occupy in terms of corporate sustainability and ESG strategies and are finding ways to estimate operating costs and carbon emissions.
All of this means that there must be a greater focus on measuring and then reducing operational carbon to help keep overall emissions down, and ensure increasingly stringent standards are being met – and that buildings don’t become ‘stranded assets’ in the near future.
Four key steps to bring operational carbon emissions down
The UK Green Building Council defines a net zero operational energy building as: “When the amount of carbon emissions associated
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with the building’s operational energy on an annual basis is zero or negative.” Building owners looking to achieve this must start by looking at their HVAC systems, as they are significant energy users. Whether a building owner is targeting a higher EPC rating or simply wants to improve the energy performance of their building, a systems approach is key to success.
Four areas to focus on include:
1.Banning the use of fossil fuels for heating and hot water Targeting operational net zero means removing the use of fossil fuels on-site. Buildings are increasingly moving away from using any natural gas or oil for heating and hot water and switching to an ‘all-electric’ approach. Heat pumps are one of the most widely used alternatives to the gas or oil boiler, and they provide energy-efficient electric heating and meet domestic hot water requirements. Modern commercial heat pumps can now deliver water temperatures up to 90oC, so they can be applied in buildings with significant hot water demands, for example, from showers and gyms.
2.Focusing on heat recovery to minimise waste Modern HVAC equipment is energy efficient, but performance can be optimised further. One way to do this is through heat recovery, where ‘waste’ heat is used as an energy source, taking heat energy ejected from one part of a building and applying it in another. For example, this strategy can be used
through mechanical ventilation with heat recovery (MVHR). Heat energy from air expelled by the ventilation system is transferred to incoming outdoor air before it enters the occupied space. This reduces the amount of heating required for incoming air, saving energy. On a larger scale, the heat recovery principle is also used in ambient heat loops. These can be particularly useful for mixed-use
developments where heat extracted from office or retail cooling systems is transferred to on-site residences such as apartments using heat pump technology.
3.Controlling energy use to improve building performance Building controls are critical in helping building managers monitor and manage energy use – especially given the growing requirement for data collection on building performance. In addition, the ability to spot trends gives facilities and energy management teams the insights to take action where energy is potentially wasted.
4. Selecting the right HVAC equipment to meet Net Zero
One of the most challenging aspects of the focus on the carbon impact of buildings is how it may affect the specification process. For example, highly energy-efficient equipment may have a higher embodied carbon footprint than an alternative which uses more energy in the long term, affecting the building’s operational carbon. Some important questions for specifiers include: at what point does the equipment’s operational efficiency outweigh higher embodied carbon? Or how long does a high-efficiency product with high embodied carbon have to operate before its whole life carbon balances against a lower-efficiency product with lower embodied carbon? As building designers, owners and managers aim to create low-carbon buildings that contribute to building a greener future, operational carbon is a key area to keep in mind. With the UK experiencing increasing temperatures and stricter carbon emission regulations, evaluating how our existing building stock, initially designed for a cooler climate, will cope with rising temperatures in the next ten years has become crucial. Mitsubishi Electric has released a CPD guide on this topic, so for a more in-depth look at this subject, please download at
https://bit.ly/3stzTZz
BUILDING SERVICES & ENVIRONMENTAL ENGINEER FEBRUARY 2024 21
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