Buildings are the largest consumers of energy - ahead of industry and transportation. In Europe alone, they consume almost 40 % of primary energy. Around 85 % of this is used for space heating and hot water and 15 % for electricity. The savings potential is correspondingly high if energy in buildings can be used more efficiently.

Building automation as the key to energy efficiency

EN 15232 is the most important standard for building automation and defines four efficiency classes.

© Siemens AG

A decisive lever for permanently low energy consumption is building automation across all trades, which uses intelligent functions to increase a building's energy efficiency and simultaneously improve comfort. Building automation also helps building operators to control energy flows and costs.

According to a study by Biberach University of Applied Sciences, demand-driven building automation can achieve savings of up to 20 % for heating, for example. Additional automated functions such as frost protection switching for window ventilation or automatic thermal control can save up to an additional 10%. In the case of room cooling, the potential is between five and 10 %, and for lighting even up to a maximum of 40 %.

The EN 15232

The most important standard for evaluating the functions of building automation and technical building management is EN 15232 "Energy performance of building types - Influence of building automation and building management". It classifies buildings with regard to the control of technical HVAC equipment, lighting and shading as well as the interaction between these systems. It defines the four efficiency classes from "A = high energy efficiency" to "D = not energy efficient". This standardization makes it clear what savings potential is possible in the operation of technical building systems, but also what technical requirements must be met.

If efficiency class A is to be achieved, a large number of conditions must be met, such as networked room automation or automatic demand recording. The central element for the requirements of class A is cross-trade communication and control. An example illustrates this: With a conventional manual blind control system, successful savings depend solely on user behavior. The control system is not networked with other functions, which corresponds to the lowest efficiency class D.

This is completely different with a solution that meets all class A requirements: Here, the blind control is integrated into a combined, networked control system for lighting, sun shading devices and HVAC systems. The building automation system also evaluates the current demand. The data is supplied by sensors in the interior or in a weather station. When outside temperatures are high, for example, the blinds can automatically reduce the amount of light coming in to save energy for air conditioning. If there are people in the room who need dimmed light for a presentation, the system reacts differently to when the room is unoccupied. The result is both user-friendly and energy-optimized operation.

For this interaction, heating, ventilation and air conditioning devices must be able to communicate with lighting and shading devices in order to exchange the required information directly with each other. This communication can take place without interfaces via bus systems. Examples include the KNX system, a global standard for the networking of home and building system technology originating from the electrical engineering sector, or the LON (Local Operating Network) and BACnet (Building Automation and Control Networks) systems used in HVAC technology. In addition to demand-oriented and energy-efficient control, joint communication also offers the possibility of combining all systems in a single management station with one user interface for all systems. This makes operation easier and helps to visualize potential savings.

Integrated planning for electrical and HVAC

However, such a networked solution requires integrated planning of electrical and HVAC technology right from the tendering stage. In Germany in particular, there is still some catching up to do in terms of actual implementation. Here, room automation systems are usually put out to tender in the electrical engineering sector and the primary systems in the heating, ventilation and air conditioning technology sector. Communication between the trades, which is necessary for demand-driven control, is not always taken into account. Due to the separate tenders, different bus systems are often used, which can only communicate with each other with difficulty or not at all. As a result, energy efficiency is not taken into account in projects and great potential for energy savings is wasted.

The aim of integrated planning is to plan and network all trades in such a way that a building automation system is connected to all electrical and HVAC trades, thus enabling cross-trade regulation and control in accordance with EN 15232. All products and solutions integrated into the building must be planned jointly with building owners, architects, planning offices, but also with product suppliers and system integrators, and the interfaces must be uniformly defined.

The RMB795B control center from Siemens bridges the gap between trades at the control level by allowing communication between electrical and HVAC technology on a KNX basis.

© Siemens AG

An example shows why this is so important: presence or multi-sensors can be used to control the heating in a room, but also to control the lighting. In addition to presence detection, multi-sensors also implement other functions such as brightness control, which are also required for a high energy efficiency class. When electrical and HVAC technology are tendered separately, two sensors are installed in the room that only influence the control of their own trade independently of each other. This results in higher costs when ordering products and during commissioning. It is therefore recommended that the room is tendered as a linked trade and not divided into individual trades.

In addition to the linking of electrical and HVAC trades, the networking of rooms with individual primary systems is also an important aspect of integrated planning. As specified in the EN 15232 standard, the current demand for heating, cooling and air is determined by sensors in the room, first passed on to the relevant sub-distribution board and then to the heating, ventilation or cooling system. In this way, only the required demand is generated and distributed to the rooms, which leads to high savings in primary energy. With such a connection, central timer programs can also be installed for all trades, which affect the setpoints in the rooms and the primary systems.

Technical implementation

In order to achieve the highest possible energy efficiency class for building automation functions, there are various solutions, systems and products to choose from depending on the size of a project.

If the room and primary system areas are commissioned separately, interfaces between the heating and cooling requirements for each room and the timer program at management level must be clearly defined so that data can be seamlessly transferred from the room to the primary system. Because the electrical and HVAC systems are connected at room level, only a single bus system is required, which means lower costs for cabling and commissioning. To transfer the data to a primary system, a controller collects the demand from the rooms and passes it on to the primary system after averaging.

As a full-service provider, Siemens offers solutions for small, medium-sized and large commercial buildings that connect all systems with each other. Examples of this include KNX-capable sensors and actuators from the "Gamma" range. Thanks to different versions and surface finishes, the components are suitable for many design styles and requirements. Thanks to the globally widespread KNX standard, products from different manufacturers can also be integrated.

The "RMB795B" control center from Siemens bridges the gap between the different trades at the control level by allowing communication between electrical and HVAC technology on a KNX basis. As an interface between the temperature control in the rooms and the primary control, the control center receives the heating and cooling requirements from the rooms - depending on the time of day, room occupancy, outside temperature or heat sources such as PCs - and forwards them to the controllers of the primary system. On the primary side, manufacturer-independent KNX heating/cooling controllers and non-bus-compatible controllers with a heat demand input can be connected. Timer programs, which are important for commercially used buildings, are integrated into the central control unit as a fixed application.

For the management of this overall system and for operating the system, Siemens offers "Synco IC", a cloud-based solution that makes it easy to set up the internet connection for the system. The data from primary systems and room automation can also be synchronized via secure access; this allows mobile access to the control system using PCs, smartphones or tablets. A system overview shows pending alarms at a glance as well as any potential savings that have been identified. Error messages are sent by e-mail to the person responsible, so that quick access is possible in the event of a fault. With Synco IC, maintenance and monitoring of all systems can be carried out remotely, saving customers time and money.

Conclusion

Building automation can make a significant contribution to the energy efficiency of new and existing buildings. The European standard EN 15232 uses four efficiency classes to describe and regulate the functions and effects. In this context, the highest efficiency class A requires cross-trade and demand-driven control.

In order to achieve this, different trades must be networked and interfaces clearly defined right from the tendering stage. With its range of sensors and actuators, control centers and other connecting applications based on KNX, Siemens offers the prerequisites for integrated planning of electrical and HVAC systems and thus for the highest possible energy efficiency class in building automation in accordance with EN 15232.

Author:
Patrick Schönmehl is a promoter for Standard Controls at the Siemens Building Technologies Division in Frankfurt.