Energy efficiency

What is it all about?

Energy efficiency in buildings is a multifaceted topic. A variety of international regulations, including EN 15232, the European Energy Performance of Buildings Directive (EPBD 2010), ISO 50 001 and sustainability and energy certificates such as LEED or Energy Star, have led to the creation of technical standards such as open communication protocols (BACnet) and specialized applications designed to optimize the energy efficiency of building and room automation systems. Energy savings up to 30 percent can be achieved by raising awareness, making energy consumption transparent and introducing targeted energy management and control. We provide information for buildings larger than 10,000 m².

Let’s get the basics

Definition: “The energy performance of a building shall be determined on the basis of the calculated or actual annual energy that is consumed in order to meet the different needs associated with its typical use and shall reflect the heating energy needs and cooling energy needs (energy needed to avoid overheating) to maintain the envisaged temperature conditions of the building, and domestic hot water needs.” (Source: Energy Performance of Buildings Directive of the European Union [EPBD 2010]).

Coming to the details

EN 15232 standard graphic

Energy flow model


  1. is the energy needed to fulfill the user's requirements for heating, lighting, cooling etc, according to levels that are specified for the purposes of the calculation

  2. are the "natural" energy gains – passive solar, ventilation cooling, daylight, etc. together with internal gains (occupants, lighting, electrical equipment, etc)

  3. is the building's net energy use, obtained from [1] and [2] along with the characteristics of the building itself

  4. is the delivered energy, represented separately for each energy carrier, inclusive of auxiliary energy, used by heating, cooling, ventilation, hot water and lighting systems, taking into account renewable energy sources and cogeneration. This may be expressed in energy units or in units of the energyware (kg, m³, kWh, etc)

  5. is renewable energy produced on the building premises

  6. is generated energy, produced on the premises and exported to the market; this can include part of [5]

  7. represents the primary energy usage or the CO2 emissions associated with the building

  8. represents the primary energy or emissions associated with on-site generation that is used on-site and so is not subtracted from [7]

  9. represents the primary energy or CO2 savings associated with exported energy, which is subtracted from [7]

What is Wikipedia saying about energy efficiency?

Want to see how it REALLY works?

See Siemens BT reference cases, about energy efficiency e.g.

Did you know that...?

  • ...a single Google-search uses about as much energy as an energy-saving light-bulb uses in one hour? Click here to find more information about building-specific needs of Data centers.

  • ...the energy consumption of the global internet produces about the same amount of CO2 per year as global air-travel does? Click here to find more information about building-specific needs of airports.

  • ...properly designed lighting strategies can save 50-80% of lighting energy? Click here to find more information about building-specific needs for Life Science.

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