Why is technology waste generated when going from a Cat A to Cat B design?

Technology, specifically fan coil unit waste is often generated because the interior space of a commercial building undergoes two fit outs before a customer moves in. This can lead to systems being reconfigured, technology being moved or discarded as it is no longer fit for purpose.  

When the building is first constructed it is designed to offer basic functional services at the initial Cat A fit out stage. However, these requirements can change each time that a client rents commercial space. A second fit-out, known as Cat B fit out, takes place to customise the fittings and services design to meet the new spatial requirements. From a Mechanical and Electrical (M&E) perspective, these services include air conditioning in the form of fan coil units (FCUs).

Once the space has undergone this Cat B fit out, it is common that the original positions of the FCUs from the Cat A fit will not be best placed to provide air conditioning for the new layout. This creates a potential mismatch between the requirement of providing air conditioning to an original open-plan Cat A interior space and the more complex airflow picture created after completion of the Cat B fit out. This then requires reassessment of the M&E design and can lead to the installation of additional FCUs and the removal of FCUs that are no longer in the correct positions or that are oversized.

Government figures from Defra show that non-hazardous construction and demolition waste in the UK stood at 59.1 million tonnes in 2020. The drive to reuse, reduce or eliminate waste to landfill and the growing call to take a circular economy approach to construction, will only intensify interest amongst designers, contractors, and customers to find new ways to eliminate waste. The Cat A to Cat B fit out process presents an opportunity to do just that.   

In this blog, we will investigate how and why FCUs can become part of technology waste generated in the Cat A to Cat B transition to highlight the importance of recognising these issues in fan coil design at an early stage of a project. This topic is covered in our white paper ‘Reducing waste in development fit outs through effective fan coil solution design’. It shows how designers and specifiers can successfully take steps to reduce the impact of Cat A to Cat B fit outs on fan coil units to maximise their flexibility and minimise waste.  

Why can fan coil units become part of technology waste in Cat A to Cat B fit outs? 

Going from a Cat A fit out, where the building has basic amenities and an open plan layout, to a more custom design delivered by a Cat B fit out, will change the air conditioning dynamics of the newly partitioned space. This requires a re-evaluation of the efficacy of the FCUs, and they can become part of the technology waste generated.

A Cat A fit out tends to have large FCUs positioned around the perimeter of an open plan environment to condition high volumes of air required by the open space design. This gives the building owner commercial space that can be presented to potential tenants as a blank slate. This can then be built upon as they seek to customise the area for their business needs. In the past this used to involve putting up a partition or two, having a couple of corner offices and this had minimal effect on the conditioning requirements.

However, in a modern commercial environment, offices are being configured in a far more complex way. An architect will produce a layout that provides details of requirements to provide meeting rooms, break-out areas, individual offices, board rooms, kitchens, cafeteria, and server rooms to name but a few. The M&E designer will then have to calculate the new heating and cooling loads for each of these spaces which will be affected by the number of people in the room and any heat generated by equipment or appliances. 

The original large FCU may now not be suitable to condition the air in a smaller space. Most FCUs have a 0-10v fan signal, and they are usually designed to run at about half speed to allow some variation above and below to cope with fluctuations in demand. However, whilst the power on a large FCUs can be turned down, once the signal gets to around 2v it is not running at its optimum design conditions, and this can lead to the fan going into stall due to the low signal voltage. 

The result is that some of the large FCUs can get removed during a Cat B fit out and each one is replaced by two smaller FCUs that are better able to meet the demands of the new layout. Sometimes the larger FCUs can be reused elsewhere in the project but often they cannot and are therefore surplus to requirements. The manufacturers will not take back these units as they have been installed, and commissioned and the units have been running during the Cat A stage, so they are effectively regarded as second-hand. The M&E contractor may take the large FCU and store it for use on another project, however, it is highly likely that most go as scrap for metal recycling. 

The removal of the original ‘Cat A FCUs’ takes time, costs money, generates more embodied carbon as well as creates waste. The tenant bears the costs associated with buying and fitting the new FCUs. However, it doesn’t end there as, at the end of the lease period, the new tenants may require alterations to the layout that result in the repositioning of existing, or the purchasing of new FCUs, to condition the space to the heating or cooling demands. Cue more waste, more cost and more carbon emissions in a process that can repeat itself each time a lease is changed, and new tenants take up residence.

To make the sustainability picture look even bleaker, Savills reports that since Covid the average length of lease has dropped with a ‘threefold increase in leases shorter than two years between 2018 and 2020’ so buildings are likely to see an increase in the number of times this cycle repeats in their lifetimes. 

Therefore, any design measures that could improve the waste associated with this recurring Cat A to Cat B cycle must be worth considering as they can improve the efficiency of the process and save time, money, carbon, and cost. That’s quite a combination.

Where can I find more information on how to minimise fan coil unit waste caused by fit outs?

More information on how to create designs that minimise fan coil unit waste is contained within our Ability white paper ‘Reducing waste in development fit outs through effective fan coil solution design’.

If you would like to learn more about anything covered  in the white paper or would like our experienced team to help optimise your fan coil solution designs, contact our team and we will be happy to help.

Troy Chambers