Reflections on practical experience
Jo Harris’s experience of the real world is that there is an abundance of opportunities for improving the energy efficiency of building-services systems — without compromising the indoor environment.
Sustainability is a word that you can’t miss at the moment and most industry events cover the subject in one way or another. There are many companies doing excellent work in this arena, but there are even more still trying to address just the energy-reduction side of sustainability.
Legislation is driving us to reduce our energy consumption, and there is also the financial driver of energy costs rising year on year. There are stories of over-zealous building operators turning off air conditioning to do their bit to save some money but without concern of the effect on the environment in which people are working. There is a balancing act between creating and maintaining the right environment and reducing energy consumed by building services. The priority in this economic climate should be to ensure we do not affect staff productivity as this has a direct impact on the bottom line of the company.
There is an approach to energy saving that we would advocate. It starts with finding out where the energy is being used. Do you know how much energy your heating system is using compared to your lighting? If you don’t know, then how can you start tackling energy inefficiencies?
Many organisations are engaging users to drive energy-saving initiatives. This is commendable, but is it having the desired response and actually reducing the energy bill each month? A lot of time and effort is required, and the rewards may not outweigh the effort. It is good to help staff understand the work the company is doing in this area, but the bulk of the effort, I would suggest, should be in the M&E services of the building.
One of the first things to do is get the energy-metering strategy in place with sub-metering down to the right levels. It is not a quick win; it will realistically take about 18 months to really work out where the energy is going, but you need to understand what is happening and be able to take into consideration the seasonal changes. Then you can compare your energy performance year on year and demonstrate the savings that you are making.
The commissioning of new buildings is a subject BSRIA has been trying to address with the promotion of the Soft Landings framework. One example of where poor commissioning has an impact was seen on a building constructed in 2005 and which for a long time consumed more energy than predicted. This was a laboratory building, and all its extract fans had been operating at 100% because the controls had not been successfully commissioned. Investigation showed that they were using three times as much air as required.
Replacing the controllers and running the correct amount of extract made a huge impact, not just the energy saved by the extract fans themselves but also on the amount of conditioned air not being wasted. Another useful side effect will be that the fans can be expected to have a longer life expectancy as the running hours run will be reduced. These sorts of savings don’t always get highlighted during energy-saving reviews but they will benefit the organisation financially.
In air-conditioning and ventilation systems the selection of air filters and cleaning of coils can also have energy benefits. Filters are being designed to provide the optimum balance between maximum filtration efficiency and minimum pressure drop. With a minimum pressure drop, the fan sees less resistance and less power is consumed by the fan to deliver the air required — hence the need for clean filters and clean coils.
Time schedules provide another quick win when looking for energy savings; revaluating the occupancy patterns of a building can highlight where savings can be made. One client of ours which runs its building 24 hours a day, but it is only occupied from 7 a.m. to 7 p.m. from Monday to Friday. Looking at the access-control system over a period of a week built up a picture and validated the assumption that generally very few people are in before 7 a.m. and that most people are gone by 7 p.m. — so outside of these hours the environmental controls can be allowed to go out of the limits and energy can be saved.
Investment in lighting-control systems can also provide good payback, but it is important to revisit and again match the use of the building. On one recent visit we had a comment from an occupier that said she did not go into the meeting rooms anymore to borrow chairs because the occupancy sensor would activate the lights and they would stay on for two hours. Not all occupiers have the same commitment to energy saving, and controls need to take into consideration all types of people.
Legislation brought in under the Energy Performance Of Buildings Directive required occupiers with control over air-conditioning systems with a cooling capacity of over 12 kW to have an air-conditioning inspection carried out by an accredited engineer. BSRIA conducts such air-conditioning inspections, and we have found that many simple actions can be carried out to improve the energy efficiency of the systems. Most savings can be made from component cleaning and regular maintenance. Evaporators are designed to release heat, and clean coils can do this more efficiently.
Research funded by the EU has highlighted that small air-conditioning systems appear to offer the largest average energy savings of around 60%, but complying with the requirement to get a system inspected is not a high priority of building owners. Penalties for non-compliance are either non-existent or not persuasive enough to encourage more uptake.
Some air-conditioning systems are still being run with simultaneous heating and cooling. The remedy is paying attention to the controls, including recalibrating sensors and setpoints and tuning control loops. Too many building-control systems are under utilised by the operators, who are failing to invest in the systems or staff training to utilise them effectively.
Building controls can play a big part in reducing the energy consumed by building-services equipment. EN15232 2007 ‘Energy efficiency in buildings — influence of building automation and control and building management’ provides a guide to where the savings can be made through better use of controls and suggest a 20% saving as a conservative figure.
The main message is there are plenty of energy-saving initiatives available to you. One of our clients started back in 2007 and is still finding things they haven’t thought about. In addition, a business never stands still, so you need to adapt.
The thing to remember is that there will always be ways to save energy in your building in order to improve.
Jo Harris is manager of the sustainable buildings group at BSRIA.
