﻿Taking stock of energy efficiency
It is now clear that meeting carbon targets for the UK’s building stock will rely heavily on increasing the efficiency of existing buildings. Robin Putman explores the importance of effective maintenance and targeted refurbishment
In the last couple of years there has been a significant change in the focus of measures to improve energy efficiency and reduce carbon emission. Previously there had been heavy emphasis on improving new building standards and major refurbishments through Part L of the Building Regulations. Now, there is wider recognition of the value of improving the energy efficiency of existing stock more effectively — not least because most of today’s commercial buildings will still be in use 30 years from now.
In parallel, many organisations impacted by initiatives such as the CRC Energy Efficiency Scheme, Energy Performance Certificates and Display Energy Certificates are looking for relatively ‘quick wins’ in reducing energy and emissions. In many cases, the economic climate is also forcing an emphasis on maintenance and refurbishment, rather than moving to new premises.
All of this puts a strong focus on the performance of building-services plant, either on its own or with the performance of the building fabric. Consequently, those involved in the maintenance of plant and fabric — either in-house or outsourced — have an important role to play.
In terms of plant maintenance, while ensuring that the plant is working and delivering the required conditions remains a priority, this now needs to be combined with a greater emphasis on operational efficiency. Heating systems are a case in point. There are many instances where the boiler plant keeps the buildings and the occupants warm, but it may not be doing so in the most efficient fashion.
For instance, where a lead boiler handles the base heating load and additional boilers are brought on-stream to meet peak loads there may be occasions where the standby boilers experience standing losses — leading to dry cycling. A good maintenance regime will optimise combustion efficiency, but there may be a good case for investing in additional works to monitor and control individual boilers more effectively to ensure they only fire in response to genuine demand for heat from the building. Thus maintenance and refurbishment can work hand in glove.
Chillers provide a similar challenge, requiring maintenance to maximise performance of each chiller circuit combined with a thorough evaluation of the control strategy as part of the maintenance regime. Given that full-load and part-load conditions affect the energy consumption of individual chillers substantially, evaluating the control strategy will ensure that chillers are switched on and off in a way that achieves optimum performance.
In all of these cases, it is also important that such measures are reviewed regularly as an integral part of the maintenance strategy — reinforced by the requirement of CIBSE TM:44 for 5-yearly efficiency checks for chillers. The frequent changes in building occupancy levels and patterns of occupancy that are now common in commercial buildings dictate that the maintenance regime should have the inherent flexibility to adapt to any such variation.
There are clearly many situations where optimising maintenance will not improve energy performance as much as the end user requires, or the plant may no longer be able to satisfy legislative requirements. In such cases, refurbishment should be considered — and may be extensive or limited to individual systems. Again, the expertise of the maintenance engineer can be applied to arrive at the best solution, now and into the future.
This principle has been clearly demonstrated in relation to the phase out of HCFC refrigerants. Many building operators that are now reliant on supplies of recycled HCFCs since January are faced with the decision whether to refurbish existing plant to work with HFC refrigerants or buy new plant. In such cases, a thorough appraisal will take into account ongoing maintenance requirements and energy performance to determine the most appropriate option.
Similarly, and for a variety of reasons, many building operators have a desire to introduce low-carbon technologies to their buildings as part of an overall refurbishment. In these cases, it is vital that system designers have a sound understanding of the existing systems and where newer technologies can be integrated and controlled to maximum benefit.
Refurbishment can also offer the ‘quick wins’ referred to earlier, and lighting is a prime example of this. Many older lighting technologies offer limited control options Upgrading the lighting to newer light sources, such as dimmable T5 fluorescent lighting, opens the door for more sophisticated control strategies that will reduce wastage — as well as improving luminous efficacy, reducing installed electrical load and extending lamp life.
Where the same team has responsibility for maintenance of both services and building fabric there is scope for major improvements. For instance, it may be most cost-effective for a building owner to refurbish the fabric and improve its thermal performance, enabling existing services plant to operate more efficiently. This approach can often extend the life of the plant, as long as it is maintained effectively through that longer life.
Underlying all these issues is the need to recognise that maintenance has evolved to encompass a wider range of issues than simply keeping plant running. Pro-active evaluation of performance in the light of building usage, ensuring efficient as well as reliable operation and consideration of how new technologies can be incorporated are now part and parcel of the modern maintenance strategy.
Robin Putman is technical services director with Cofely.