VENTILATION & AIR HANDLING Key to reducing Scope 2 emissions


As institutions work toward reaching their net-zero goals, addressing Scope 2 emissions through smarter AHU solutions presents a clear opportunity, argues Geoff Edwards.


Geoff Edwards www.axair-fans.co.uk


Director of projects Axair Fans


A


s universities and other institutions strive toward ambitious net-zero targets, tackling carbon


emissions has become a pressing priority. Under the Greenhouse Gas (GHG) Protocol, UK universities are required to record their Scope 1 and 2 carbon emissions as part of their sustainability commitments. Despite efforts to curb emissions by 43% between 2005 and 2021, reports indicate that nearly 59% of institutions failed to meet this goal. With the 2030 target demanding a 63% reduction, and the worldwide pledge to make universities and higher education colleges completely carbon neutral by 2050, there is still a long way to go. So how can universities, and the energy consultants supporting them, make meaningful progress? One highly effective strategy that


may help to reduce the 1.4million tonnes of carbon dioxide emissions that the 133 UK universities are accountable for is through


CASE STUDY London’s historic Guild Hall, a Grade I listed landmark with an adjoining Grade II wing, was grappling with escalating energy costs and rising carbon emissions due to its ageing belt driven ventilation fans. Through the Salix Public Sector Decarbonisation Scheme, the client secured grant funding to undertake a full fan array retrofit. By replacing 28 old fan sets with modern, modular fan-array units configured around a basement plenum chamber, the project achieved a substantial reduction in ventilation energy, while cutting noise levels significantly. The investment, will pay for itself in very short payback periods.


The M&E consultant was on site


to extract detailed AHU duty and absorbed power data, passing all information to the Axair retrofit


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upgrading air handling unit (AHU) fans. By focusing on this key area of energy consumption, institutions can significantly cut their Scope 2 emissions while enhancing operational efficiency and reducing costs. Emissions are categorised into


three scopes: Scope 1: Direct emissions from


owned or controlled sources, such as natural gas for heating. Scope 2: Indirect emissions from


purchased electricity used to power equipment, including AHUs. Scope 3: Other indirect emissions, such as supply chain operations and travel.


Indirect emissions AHUs fall squarely within Scope 2, as they rely on electricity to power fans and motors. Traditional belt-driven fans, common in older systems, tend to be highly inefficient. According to the International Energy Agency, to meet net zero targets, not only must new buildings be zero carbon ready, but 20% of existing buildings must be retrofitted for carbon neutrality by 2030. So, retrofitting these old AHU units with energy-efficient EC (electronically commutated) plug fans can drive significant energy savings and carbon reductions in a short amount of time.


The case for upgrades For consultants working with universities, the business case for upgrading AHU fans is compelling. In a 2019 retrofit project using EC plug fans, CO₂ emissions were reduced by 2,980 tonnes per year, with 5,987 MWh of energy savings annually. The average payback period ranged from two to five years, making these upgrades a financially attractive option. Key benefits of retrofitting air handling units (AHUs) with EC plug fans include improved energy efficiency, as modern plug fans operate closer to peak efficiency than old belt-driven fans, thereby reducing electricity consumption; lower carbon emissions due to decreased energy use, which helps institutions cut their Scope 2 emissions; reduced maintenance costs arising from fewer mechanical


Retrofitting EC plug fans can drive significant energy savings and carbon reductions in a short amount of time


components, lowering maintenance requirements; and enhanced operational resilience, as multiple fan arrays ensure continued operation even if one fan fails, thereby increasing system reliability. Sustainability efforts in the


built environment are increasingly recognised through BREEAM certification. AHU retrofits can directly contribute to credits in five of the ten BREEAM categories, particularly under Ene.01 Reduction of Energy Use and Carbon Emissions. Institutions aiming for high BREEAM ratings can significantly benefit from investing in efficient air handling systems. Beyond environmental and


operational benefits, upgrading AHUs can unlock financial incentives. Universities may bid for a share of a multi-million-pound fund to facilitate low carbon energy upgrades or resources to implement sustainability projects. Investing in AHU fan retrofits allows institutions to lower their long-term energy costs while enhancing their reputation as leaders in sustainability. When replacing outdated belt-


driven fans, multiple fan arrays featuring EC plug fans offer the best solution. These modern systems provide greater control over airflow, pressure and energy use, ensuring optimal performance. For new AHU installations, manufacturers can integrate EC plug fans from the outset, benefiting from improved efficiency, streamlined maintenance, and compliance with regulatory standards. ■


matching of fan performance curves to actual load requirements, drastically improving part load efficiency. The plenum chamber distributed airflow evenly, increasing efficiency and reducing operational noise, while fan arrays were anchored to existing locations to avoid any masonry work or alterations to the listed fabric. Installation was carried out in


Axair’s custom fan-array and control units installed at the London Guild Hall


team who used these parameters alongside proprietary fan-selection software. Over eight weeks and 24 design iterations, Axair developed a custom fan-array solution consisting


of a mix of single module, dual module, and an eight fan module fan unit installed within a sealed plenum chamber in the basement plant room. This configuration allowed for precise


a phased manner, keeping most ventilation systems running throughout the process. Extra care was taken in areas containing sensitive archive materials, where downtime was minimised. The old fans were removed, and the new modules were installed and connected to the client’s building management system. Some integration delays occurred, but these were resolved through collaboration between the supplier and system engineers.


EIBI | MAY 2025


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