CASE STUDY | 11 BELGRAVE ROAD The offices designed by Eric Parry Architects include a rooftop pavilion and large gym system with the highest air demand fully open at all times, while controlling the AHU fan speed to regulate the supply air volume accordingly. It means that youre not adding extra pressure to the system by over-closing dampers, explains Irvine. Unfortunately, because the design review was happening while the job was being tendered, Irvine says the budget didnt stretch to the additional cost of more expensive VAV dampers and the additional controls wiring. He adds that there was a bit of back and forth between reviewer and designer to discuss what recommendations could be implemented. Based on the initial modelling submission, Delta Q was going to recommend a Nabers score of 5 for the scheme. However, the reviewer explained that if Max Fordham modelled additional scenarios, including reducing the cooling set point from 24C to 23C, the increased design granularity would enable the scheme to achieve the additional half-point, taking its score to 5.5. WHY METERING IS KEY There is an incentive to meter properly. All centrally supplied heat and power has to be metered under Nabers, and if the metering cannot exclude a service for a tenant, then it must be included in the landlords energy use assessment. Irvine says the metering requirement for Nabers is not particularly onerous. What you need to do for Nabers isnt a huge step up from what youre doing already in a lot of commercial jobs, because most tenants want accurate Measuring Instruments Directive 2004/22/EC compliant meters to monitor their energy use in any case. However, he does say that Nabers requires the designer to be a bit more thorough on exclusions. For example, there is a central hot-water system that feeds the end of trip basement showers, caf, retail units and gym but in the energy use assessment, the landlord only has to include the hot-water energy for the basement showers. It can exclude the energy for the other areas, as they will be sublet. Nabers also excludes small power and lighting to tenanted areas, over which the landlord has no control. 50 February 2023 www.cibsejournal.com While, ostensibly, Nabers only looks at landlord central energy use, if you produce a poor tenant guide it could end up impacting your rating In addition to the modelling, the reviewer asked Max Fordham to produce a tenant fit-out guide to explain to tenants how to complete their Category B fit-out to best integrate with the landlords systems. This is what weve modelled in Nabers, so that you, as a tenant, have to install something in line with the landlords intention, with this level of performance or better, says Irvine. Its about tying down the performance spec of the fit-out. While, ostensibly, Nabers only looks at landlord central energy use, if you produce a poor tenant guide it could end up impacting your landlord rating, which is why achieving Nabers in use needs to be a collaboration between the tenant and the landlord, says Irvine. Even with the additional work, he adds, getting the Nabers UK Design for Performance rating of 5.5 was the easy bit. The scheme is currently under construction, with completion anticipated for the end of 2023. Up to this point, everything is theoretical; now we have to wait at least a year, post-completion, and the building has to be at least 70% occupied before we can submit meter readings to [system administrator] BRE for it to give the scheme its Nabers UK Energy for Offices rating. Even then, the rating will only be valid for one year; after that, meter readings have to be resubmitted on an annual basis to enable BRE to issue new ratings based on current performance which should keep the facilities management team occupied for many years to come. CJ