COST MODEL | OFFICE REFURBISHMENT ACCOMMODATING CHANGE The draft London Plans commitment to circular economy principles and the London Energy Transformation Initiatives aim for a net-zero carbon built environment make refurbishment more appealing. Aecoms Nichola Gradwell and Simon de la Cruz explain the effect on engineering services Office refurbishment R eusing building elements such as the structure and existing fabric can reduce demolition work and waste, and save cost. The speed of a refurbishment means buildings can be brought to market much quicker than new builds. A refurb can ensure a property is adapted to meet the changing needs of tenants that are driving towards smaller spaces, serviced offices and interconnection with other organisations within the building. Design trends need to be considered to ensure a functional space is produced that is flexible and can accommodate a range of fit-out options. With more stringent minimum energy efficiency legislation, there is a need for existing buildings to implement new and efficient technology that will uplift their credentials, while addressing the demand for decarbonisation. Landlords are seeking to sweat their asset to achieve energy savings without breaking the bank. Refurbishment projects can range from minor upgrades of plant and superficial replacement of existing fit-out installations, to wholescale replanning and optimisation of the space, potentially increasing the net lettable floor area. Minor refurbishments offer largely cosmetic upgrades, retaining much of the engineering installations where there is adequate remaining lifespan and capacity. The reuse of pipework risers, main plant and life-safety systems is assumed, with only light touches to landlord and toilet areas, and new Cat B fit-out provision. Medium refurbishments aim to extend the life of the building and provide innovative spaces. They also offer an opportunity to enhance the energy and sustainability performance of a property. The retention of the faade often means the existing thermal properties of the envelope are fixed, so energy improvements will need to come largely through upgrades to the building engineering services. This includes the replacement of MEP central plant and the addition of intelligent controls systems. Thermal and visual comfort will be reassessed to determine whether plant capacities need upgrading; however, in this type of scheme, no major structural alterations are envisaged and there are only minor repairs on the faade. The net lettable space will probably be stripped out and floor layouts replanned to make room for additional functional areas. Refurb cost drivers The retention of riser pipework requires intrusive surveys to understand their internal condition, and testing to determine water contamination risks, especially if any parts of the system are to remain operational during the project. Many systems such as lighting control, building management and fire alarms are often at their original design capacity, and either cannot be extended or the components are no longer manufactured to facilitate their maintenance. Existing buildings are usually based on a lower occupancy for ventilation, lifts, fresh air and cooling/power loads, so these systems need to be reviewed. The introduction of energy efficient lighting, coupled with controls upgrades and lifts with destination control and regenerative drives, can have a big impact on energy in-use performance of the building, so the life-cycle cost of this type of upgrade indicates significant added value. In addition, the drive for energy efficiency, and legislation aimed at decarbonising the energy grid, have resulted in a sharp turn away from gas-fired boilers and district heating networks powered by gasfired CHP. The favoured space-heating approach now uses ground, water or air source heat pump solutions. However, these are not easily introduced in refurbishments because of space and location restrictions. The lack of sufficient external space for the heat-collection arrays required for ground source heat pumps means air source is a better option. However, noise needs to be balanced out against the desire for recreational space, usually most easily provisioned on rooftop terraces. Restricted floor-to-ceiling heights can often mean that four-pipe fan coil solutions are not feasible and VRF systems are necessary. Having multiple tenants drives engineering services cost, as electrical panels, plate heat exchangers, riser design and metering increase as a factor of the number of tenancies. Converged networks to run voice, 34 January 2021 www.cibsejournal.com CIBSE Jan21 pp34-36 Cost model.indd 34 18/12/2020 14:52