How can FCU design increase the overall sustainability performance of a building?
The overall sustainability performance of a building depends upon the carbon impact of the many different materials and building systems that are used in its initial construction and ongoing operation. Fan coil units (FCUs) contribute both to the overall embodied carbon of the building and, as they require energy to provide heating and/or cooling to the building, they can also influence its associated operational carbon footprint.
Effective design of fan coil solutions can help to:
- Reduce the construction waste and therefore embodied carbon that is often generated when going from the initial Cat A fit out, to a subsequent fit out, known as Cat B, required once it is rented to a client
- Reduce operational carbon by ensuring that the fan coils used in the design are highly efficient and minimise their power consumption
- Increase the durability of fan coil systems to maximise their working life in the building before they need to be replaced, thereby limiting additional embodied carbon that is attributed to the asset as its ages
The waste generated from Cat A to Cat B fit outs can be due to the existing Cat A FCUs no longer being in the right position, or of the right size, to efficiently condition the newly partitioned Cat B space. This can result in fan coils being moved or replaced by alternative units. This generates construction waste as well as adding extra time and cost to the fit-out stage of the project.
The issue of waste generated during Cat A to Cat B fit outs is not just a one off in commercial buildings. The Royal Institute of Chartered Surveyors (RICS) estimates that buildings may have as many as 30 to 40 fit outs in their lifecycle. The cumulative effect on embodied carbon of construction waste can therefore significantly affect the overall sustainability performance of a building. Finding designs that use fan coils that can minimise waste and disruption can therefore have a positive and ongoing effect on sustainability. We cover the effect good design of fan coils can have on sustainability in our white paper ‘Reducing waste in development fit outs through effective fan coil solution design’.
How can fan coil design affect embodied and operational carbon to enhance a building’s sustainability?
Fan coil design requires FCUs to be installed into a building. Their installation will add to the building’s embodied carbon and their efficiency will contribute to the building’s ongoing operational carbon. Therefore, good FCU design that can limit fan coil waste and run the units at optimum levels of efficiency will have a positive impact. The design will be able to influence both levels of embodied and operational carbon and help to enhance the building’s sustainability.
Embodied carbon
Embodied carbon is the total carbon emissions generated to produce a built asset. It encompasses all the carbon emissions associated with manufacturing all the construction products used to make the building. The embodied carbon of each construction product includes the energy needed to extract raw materials, manufacture the product, transport, and install it on site.The longer that product continues to operate the more its carbon contribution is spread out over the lifetime of the building. Hence specifying adaptable FCUs that remain in place throughout the Cat A to Cat B fit out cycle, prevents the building from requiring new units that will add more embodied carbon and increase its whole life carbon footprint. A method of measuring the contribution of building services to embodied carbon is provided by the Chartered Institution of Building Services Engineers (CIBSE) in their TM65 methodology. Manufacturers of FCUs have the option of providing key information requested by TM65 to ensure that the embodied carbon contribution of their product, including any recycled content, is accounted for within the overall building services calculation.
Operational Carbon
Operational carbon is the energy used to power and run the building once it is 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, provision of hot water and lighting. Therefore, specifying FCUs with improved efficiencies and lower power consumption can have a positive effect on reducing operational carbon and the whole life carbon of the building. The design of the control valve of an FCU can lower operational carbon. The heating and cooling loads supplied by the FCUs are controlled by varying the water flow rate. Controlling the flowrates at each FCU will affect the total flowrate of the system. The better the valves can control flow at the FCUs, the lower the pressure needed to keep the whole system operating. This translates into less work required by the pump, reduces the energy it requires to operate, and has a positive impact on reducing operational carbon. There are two main types of valves that are commonly fitted: can either be the traditional pressure independent control valve (PICV) or the newer innovation, the electronic pressure independent valve (EPIV).
Pressure Independent Control Valve (PICV)
A PICV provides:
- Flow control - to enable adjustment of heating or cooling outputs
- Flow adjustment - to allow flow rates to be set at their design values
- Differential pressure control - to ensure that a constant differential pressure can be maintained across controls values independent of pump or valve changes elsewhere in the system
The mechanical valve comprises an automatic flow regulator in the form of a flow cartridge that maintains a certain flow rate based on the cooling or heating load required. The PICV can suffer from an effect known as ‘hysteresis’. This is where the accuracy at which the flow rate setting is maintained depends on whether the pressure differential across the valve is rising or falling. It can lead to two different flow rate readings being obtained depending on whether the pressure on the valve is rising or falling. PICVs require additional devices to measure the flow rate of the system and usually require a minimum differential pressure of up to 30kPa to operate.
Electronic Pressure Independent Valve (EPIV)
The EPIV does the same job as the PICV, however, instead of having a cartridge that sets the flow, the EPIV has an ultrasonic flow rate meter which calculates the flow going through the pipe and a two-port control valve with an intelligent actuator. This allows the valve to continuously modulate to always provide 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 15 to 1 kPa depending on system load. This fine control possible with an EPIV means it can be fed into the Building Control System, reducing the system pressure requirement and in turn reducing the load and energy consumption of the pump when compared to systems using PICVs. The sustainability of buildings is measured by schemes such as BREEAM, LEED and NABERS, and specifying FCUs with lower operational carbon contributions that will stay in place and not add to embodied carbon by being uninstalled and replaced, can make a significant difference when seeking better ratings and more sustainable buildings.Choosing product manufacturers who have achieved an environmental management system certification, such as ISO 14001, can help to realise additional sustainability benefits in these schemes when measuring the responsible sourcing of materials.
Where can I find more information on the best fan coil designs to enhance sustainability?
Effective fan coil design can increase the overall sustainability performance of a building when assessing both its embodied and operational carbon contributions to the built environment. For more information on this and other factors that help reduce waste, save time and cut capital costs on a project you can download our Ability white paper ‘Reducing waste in development fit outs through effective fan coil solution design’.
If you would like to learn more about fan coil design and sustainability or how effective design relates to any other topics covered within the white paper, please contact our experienced team who will be happy to help.
Troy Chambers
