It is of course widely accepted that efficient energy usage within a building is essential. But during the operational life cycle of a building, how is it possible to ensure that this usage is continuously optimised? The answer lies in the implementation of demand based BACS (Building Automation & Control Systems).
There are different approaches when it comes to defining the energy performance of a building. As building professionals we may select the definition that best suits a specific building or our needs. One definition is that provided by the European Union Directive for Energy performance of Buildings (EPBD). It says that the energy performance of a building means the amount of energy actually consumed to meet a building’s different needs for heating, hot water heating, cooling, ventilation, lighting and auxiliary energy.
Building on this, the European Union mandated CEN (European Committee for Standardisation) has standardised within CEN TC247, calculation methods in order to improve energy savings. This in turn has been approved to BS EN 15232 – 2012 Energy Performance of Buildings – Impact of Building Automation, Controls & Building Management. KNX is only one of a number of organisations lobbying for a greater awareness of this Standard and the benefits it can bring building users in terms of saving energy within a building.
Classification of control
In BS EN 15232-2012, BACS energy performance Class A covers a building with automatic high energy performance building automation and control systems, TBM (Technical Building Management Systems) and includes integrated individual room control, including demand control.
Class B includes buildings with advanced building automation and control systems and TBM; Class C buildings have a standard building automation and control system only whilst Class D buildings have no energy efficient building automation and control system. Different efficiency factors are also laid out for different types of buildings.
All of these types of buildings have the potential to save energy, but should be treated individually according to the way they are used, occupied and so on. In addition, different types of room may be included within one large building and the control of energy supply to each room may require different forms of control. Overall, however, networked and automated demand based controls are key to maximum energy efficiency.
Typically, improving a mixed use office building from a Class C space to a Class A rating, may involve the use of ventilation plant within its restaurant that is optimised through the use of time controls and air flow control using fans with variable speed drives. Lighting in a particular office can be improved from Class D to Class A by dispensing with manual switching in favour of automatically controlled lighting with presence detectors and the introduction of air quality sensors. Some changes may require additional hardware, but many are simply adjusting the strategy of the existing software.
Monitoring and analysis
In principle, the aim should be to achieve Class A energy performance under BS EN 15232 wherever feasible. This approach inherently acknowledges that the continual monitoring and analysis of the performance of the building services is essential so that operational parameters can be continuously adapted and any additional measures can be decided upon.
Integrating building controls makes the monitoring and analysis process easier, as well as promoting easier installation and on-going maintenance. For example, in an office with lighting control, fan coil unit heating/cooling, automatic blind control and perimeter low level heating, there are major advantages if they are all controlled on a single KNX bus network.
There could be just one wall mounted control device for all these services even though the installation may consist of a number of products from different manufacturers. With the KNX open protocol these different applications can work together on one single bus network. This allows them to share information about the space being controlled and helps to provide the most energy efficient solution.
Implementing this form of integrated control across a large site will result in major savings compared with the traditional approach of stand-alone controls, which cannot communicate with each other and may require installation, maintenance and upgrades to be carried out by a number of different suppliers with different sets, cables, components and plant.
It is also important that in the life cycle of a building, the control system can be changed as the building’s usage or layout also changes over time. KNX based control systems and products are designed to cater for this eventuality, offering upgrade paths and expansion capability since all KNX certified products are totally compatible. The building manager has a vast range of KNX technology to select from.