Sustainability targets: Considering fan coil system design in Cat A fit out stage

To help keep the construction industry on track with efforts to reduce the carbon footprint of buildings, the pilot version of UK Net Zero Carbon Buildings Standard was launched last year. This sets ambitious targets for both embodied and operational carbon, which will reduce further over time. Embodied carbon refers to the total carbon emissions generated to produce a built asset. So, each time an FCU is installed or replaced, it adds to the overall total for the building. As FCUs also require energy to provide heating and/or cooling to the building, FCU performance can also influence its associated operational emissions.

Reduce embodied carbon with adaptable FCUs

Replacing equipment before the end of its natural lifespan, and in the case of new builds, before it’s even been used, as often happens during Cat B fit outs, is a significant contributor to increased levels of embodied carbon. This happens when a new tenant requires reconfiguration of the internal space. As a result, the existing FCUs installed during a Cat A fit out are no longer in the right position, or of the right size, to deliver the desired temperatures in the new layout. 

This issue of waste is not just a one off. The Royal Institute of Chartered Surveyors (RICS) estimates that buildings may have as many as 30 to 40 fit outs in their lifecycle. As a result, it’s estimated that fit outs are responsible for around a third of emissions over a building’s lifespan. This is recognised by the UK Government, which published guidance on the specification of FCUs in public sector buildings in the ‘GPU Hub Specification’. The guidance favours the use of adaptable FCUs which have DC motors with multiple fan sections. In turn, this allows individual spigots to deliver independent variable volume supply to multiple control zones. 

That’s because FCU designs that use adaptable fan coils are designed to be reconfigured, so they are ideally suited to the changing demands of Cat B fit outs. This can therefore help to reduce waste, save time and money, improving the long-term sustainability of the building. These are all benefits that can be transferred to the private sector. It also makes sense to specify durable equipment, as a long lifespan means less frequent replacement. The best way to ensure this is to choose a reputable manufacturer, and FCUs backed up with a minimum five-year guarantee. 

The role of flow rates and control valves in reducing operational carbon 

When specifying FCUs, it’s important to understand how the design of the control valve can affect operational carbon. This refers to the energy used to power and run the building once it’s constructed and occupied. It accounts for 23% of the total carbon emissions from UK buildings, with 17% attributed to direct emissions. These are emissions covered by building regulations and include space heating and cooling. Therefore, specifying FCUs with improved efficiencies and lower energy consumption can have a positive effect on reducing operational carbon. The heating and cooling loads supplied by the FCUs are controlled by varying the water flow rate. The lower the pressure needed to keep the whole system operating, the less work is required of the pump, reducing the energy required to operate the system. 

There are two main types of valves: traditional pressure independent control valve (PICV) or the newer innovation, electronic pressure independent valve (EPIV). PICV can suffer from an effect known as ‘hysteresis’, where the accuracy of the flow rate setting depends on whether the pressure differential across the valve is rising or falling. This can lead to two different flow rate readings. Therefore, additional devices are required to measure the system’s flow rate. To operate effectively, a minimum differential pressure of up to 30kPa usually needs to be maintained. The EPIV does the same job as the PICV. However, instead of having a cartridge to set the flow, it features an ultrasonic flow rate meter that calculates the flow through the pipe. It also includes a two-port control valve with an intelligent actuator. 

This allows the valve to continuously modulate the correct water flow rate, and unlike the PICV, it does not suffer from hysteresis. The EPIV can also operate at much lower pressures than the PICV, typically from 1 to 5 kPa, depending on system load. This precise control means it can be fed into the Building Control System, reducing the system pressure requirement. This, in turn, reduces the load and energy consumption of the pump when compared to systems using PICVs. 

Reducing embodied and operational carbon is key to meeting net zero targets, and well-designed FCUs can play a vital role. By choosing durable, adaptable FCUs that feature efficient technologies like EPIVs, M&E consultants can help future-proof buildings, cut emissions, and support long-term sustainability. 

You can download our white paper on ‘Reducing waste in development fit outs through effective fan coil solution design’ or request a CPD on the same topic here.