Typical methods of improving energy efficiency of buildings to the nZEB standard, such as better external envelope insulation, using better windows, or introducing a proper ventilation system, may prove inadequate. Often, it is necessary to apply unconventional systems and renewable energy sources. Each case has to be analyzed considering the location, building technology, usage of the building, and even conservation officer's requirements. To verify the effectiveness of standard activities in various climates, the following locations in Europe were chosen: Athens, Stockholm, and Warsaw. For evaluation, two methods were applied: the monthly balance method and the simplified hourly method 5R1C.
TopBackground
Directive 2010/31/EU defines a ‘building’ as a roofed construction having walls, for which energy is used to condition the indoor climate. That definition can be applied to isolate the analysed system from the surrounding environment and identify its components to be analyzed by defining system boundaries (Figure 1).
Figure 1. Energy flow in a building system
Energy in buildings is essential to provide:
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Proper internal air temperature (heating, cooling - as needed),
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Air humidification or dehumidification (if required),
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Indoor air exchange (providing fresh air, removing contaminants, air treatment processes: humidification, dehumidification, etc.),
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Artificial lighting,
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Hot water preparation,
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Power supply of various types of electrical appliances (wide range: electric kettle, washing machine, dishwasher, television set, elevators, fans, pumps, control systems, etc.), and
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Technological processes or preparing meals.
The required energy supply depends also on external determinants, such as climate, landform features, interaction with other buildings, and local vegetation.
The energy required to meet human or technological needs must be supplied, but renewable sources can be applied instead of conventional sources. Balancing energy needs and energy on-site production has led to the concept of zero-energy buildings.
A nearly zero-energy building is defined as a building that has a very high energy performance (Directive 2010/31/EU). The supply of nearly zero or a very low amount of energy required to match particular building requirements can be provided by the use of energy from renewable sources. Producing the energy from renewable sources on-site or nearby makes it possible to decrease distribution losses and contributes to the creation of a decentralized energy system.
A modernization process of a building towards the nZEB standard should include a detailed identification of its actual state in terms of construction, internal installations, control systems, and finally the actual mode of operation, with emphasis on the behaviour of inhabitants.
Then, the next step is possible, including: