Sustainable Technologies for Nearly Zero Energy Buildings

In this chapter, the design and assessment of indoor living comfort conditions are presented from an engineering perspective. This means that perceived physical process that occur in the indoor environment and influence the response of the residents’ bodies and ability to perform work are transferred into several groups of physical indicators and ranges of acceptable values to ensure a pleasant, healthy, and productive environment. Indicators are used in the process of building design as well as in the process of the in situ assessment of indoor environment quality, (IEQ, also called ‘building ergonomics’ or ‘building ecology’) during the operation of the buildings.

The development of societies depends now more than ever on reliable energy supplies. We are in the century in which there will be a transition from the dominance of non-renewable fossil flues to low carbon societies that will be based on the use of renewable energy sources. Nevertheless, it is expected that non-renewable sources will remain significant energy carriers in the coming decades. In this chapter, natural energy sources as primary energy sources are presented. The chapter starts with a presentation of solar, tidal, and geothermal energy sources, followed by a presentation of the energy and environmental properties of renewable and non-renewable fuels. The chapter ends with descriptions of technologies that are used for on-site, near-by, and distant production of electricity.

Building physics study the processes that occurs in the building structures that influence the indoor comfort and safety of inhabitants. A group of building physics professors at European universities, founded by Professor Karl Gertis, defined the following fields of interest: heat transfer in buildings, water and water vapour transfer in building structures including psychrometric process, lighting, building acoustics, fire development and fire protection in buildings, and urban microclimates. In this chapter, heat transfer in buildings and the basic psychrometry of air will be discussed as these process are directly involved in the assessment of the energy performance of a building. Elementary and essential indicators of building structures and buildings will be presented, and dynamic heat transfer in building structures will be discussed briefly.

In this chapter, methods for the experimental determination of thermal properties of building envelopes are presented. These methods are used for commissioning, the process performed by independent experts prior to handling over the building to the customer, in the process of energy labelling of the buildings or to evaluate the most cost effective measures for the renovation of the buildings. Some semi-professional tools and equipment will also be presented, as they are very useful for the preliminary evaluation of different aspects of living comfort and energy efficiency for students and designers.

In the European Union, heat is dominant form of energy needed in buildings. More than 50% of total final energy demand in EU is in form of heat and more that 80% of heat is needed at temperatures less than 250 °C. In buildings, heat is needed for space heating, domestic hot water heating, and air-conditioning and for space cooling when cold is produced by heat-driven sorption systems and, in small amounts, for cooking. Heat generators are appliances that convert the internal energy of am energy carrier and exchange heat to the heat transfer fluid at the highest energy efficiency and the lowest environmental impact as possible. In this chapter, the best available technologies for the on-site generation of the heat from fossil fuels and renewable energy sources are presented, as well as the advantages of near-by district heating systems.

In addition to the large scale power plants presented in Chap. 2, there are several technologies for dispersed or in situ generation of electricity. In general these technologies use local renewable energy sources in the form of solar and wind energy or biomass. Small scale hydropower plants are a highly efficient technology with high durability and low maintenance costs; nevertheless, they will not be presented here because these devices are only useful for near-by electricity generation. Fossil or gaseous biomass fuels can be used for electricity generation on-site with the combined generation of heat and electricity. As an emerging technology, hydrogen driven fuel cells will also be presented in this chapter.

Buildings in northern and continental European climates need to be heated more than the half of the year to maintain required indoor thermal comfort; even in the Mediterranean countries space heating is needed at least occasionally. The energy used for the space heating of residential buildings has the largest share in energy demand for operation of building; consequently, the determination of the building energy efficiency class, most noticeable indicator on Energy Labelling Certificate (see Chap. 12), is based on the energy needs for space heating. Even in non-residential buildings, energy demand for heating has significant impact on the overall energy efficiency indicators and on the share of renewable energy sources used for operation of buildings. It is also important to be aware that the operation of the heating system must not compromise the other aspects of indoor living quality, such as indoor air quality (IAQ) or excessive noise. A space heating system can be decentral, local or central. Decentral heating systems consist of a stove or heater as heat generator, which is located in a heated room and provided heating only for that room. Heat generated in a heat generator is transferred into the room by radiation and convection to indoor air and structures. Central heating systems are more commonly used in mild and cold climates as they provide better indoor thermal comfort conditions and have higher overall energy efficiency of the heating. In this case, heat transfer fluid, a distribution system, and end heat exchangers in heated space are needed in addition to the heat generator. In Chap. 6, local and central heat generators are presented. The current chapter presents the design of components and the assessment of the energy efficiency of central space heating systems.

The International Energy Agency (IEA) predicts that the final energy demand for cooling worldwide will increase from current 4 to 9 EJ per year by the year 2050. There are several reasons for increased energy demand. The contemporary architecture trend of “all-glass” architecture is a significant reason for the increased energy need for cooling of the buildings. An increase number of domestic appliances cause increased use of electricity and, therefore internal heat gains that must be removed by cooling systems. The EU population is getting older, and it is estimated that in the year 2030 almost one third of population in EU will be older that 65 years; elderly people are more vulnerable to heat stress. As a consequence, more cooling systems will be installed. During the last century, cities become larger and built with low albedo materials (low reflection of shortwave solar irradiation) with limited green areas. As a result, urban and street canyon heat islands are more intense. It has been calculated that in a mid-size city, an urban island could cause increase the need for cold for 10 kWh/m² of building area per year. Climate change is another reason for the increased energy demand for the cooling of buildings. The United States Environment Protection Agency (EPA) predicts that in hot climate regions the demand for energy for cooling will increase due to global warming by 5–20%. Note An urban heat island is defined by the difference in the maximal daily outdoor air temperature in the built environment and surrounding countryside; a street canyon heat island is defined by the difference in maximal daily outdoor air temperature in the particular street canyon and in the city. In cities with more than one million inhabitants, the intensity of the urban heat island could be as high as 6–10 °C; the intensity of the street canyon heat island in tall streets without trees could be 1–3 °C in non-windy conditions.

Domestic hot water (DHW) is needed for personal hygiene and washing. In low-energy and passive buildings, energy consumption for DHW water heating can exceed the amount of energy used for heating the building. DHW systems are included in the energy use assessment of the buildings as one of the so-called EPBD (Energy Performance of Building Directive) systems. Since DHW is needed throughout the year, solar energy or ambient heat can be utilized with high efficiency and with significant impact on the share of renewable energy sources in energy for the operation of the building. The rational use of DHW has a major influence not only on the rational use of energy but also on environment protection. Lower DHW consumption decreases drinkable water use, which is pumped from natural reservoirs or treated in water-cleaning systems and transported to the buildings. Lower DHW consumption reduces the drain of waste water that must be treated in central water cleaning utility systems. Note 1 Despite the fact that water covers 70% of our planet, only 2.5% is not salty. Of this amount, only 0.3% is drinkable (Water in the city, European Environment Agency, 2012). Note 2 In the City of Ljubljana (population: 300,000), overall fresh water consumption is approx. 200 L per inhabitant per day. The majority is used in households (68%), trade and shopping centres (10%), and industry (4%). The water supply system is continuously refurbished to decrease network leakage. Water losses in network were over 100% of the supplied water in 1991; were decreased to ~30% in 2011 (Municipality of Ljubljana, VO-KA, 2017).

Ventilation is the process of the dilution of indoor air pollutants by exchanging the indoor air with the exterior air. This can be done because, in general, outdoor air is less polluted that indoor air. With ventilation, the amount of indoor air pollutants must be lowered to a level that does not affect the perceived quality of the indoor environment, decrease the productivity or influence the health of residents. Several hundreds of pollutants can be found in indoor air because they are emitted from human bodies, animals, plants, as well as building materials and processes. Water vapour, CO₂, CO, solid particles and odours are the most indicative pollutants in residential buildings. Requirements and methods for the determination of amount of supply fresh air needed to reach the desired category of indoor air quality (IAQ) are presented in Chap. 1. In this chapter, the principles and types of ventilation, design of ventilation systems, energy performance indicators and measures for increasing energy efficiency of ventilation systems are presented. When determining the energy needs for ventilation, as described in Sect. 5.​3, it is assumed that supply air is delivered into the building at the indoor air set-point temperature (during heating and cooling periods). Consequently, energy needs for ventilation are included in the energy needs for heating (Q_NH) and cooling (Q_NC) and the final energy demand for ventilation is only related to the energy use of electricity for the operation of the fans in the case of mechanical ventilation. Ventilation systems can be extended to air-heating or air-cooling systems. In such systems, heat is delivered or extracted by air that is supplied into the building (rooms) at higher (up to ~40 °C) or lower temperatures (down to ~18 °C) in comparison to the indoor air set-point temperature. Air-conditioning systems are another type of extended ventilation systems using air as a heat transfer fluid for heating and cooling. In contrast to air-heating and air-cooling systems, such systems also regulate the humidity of the indoor air. Besides providing the required indoor air quality, the process of ventilation can be used for the removal of the heat of internal sources and solar radiation to cooling the building’s thermal mass during summer nights to avoid overheating and decrease the energy needs for cooling the building. It is common for all those processes that a much larger quantity of supply air is required in comparison to IAQ requirements. Only “pure” ventilation systems will be presented in this chapter.

Human beings gather more than 80% of their information about their surroundings by visual perception. The information that we receive is influenced by the characteristics of the light source, the optical properties of objects reflecting the incoming light into the surrounding space, and the way we perceive light by sight and visualise “what we see” in our brain. Light is electromagnetic radiation with wavelengths that can be perceived by human vision. Such radiation is emitted from the emitter with sufficiently high temperature in the case of daylight or incandescent lamps, by electricity-excited gas atoms and molecules in the case of low and high pressure discharge lams, by photoluminescence (the process of emission of light after absorption of nonvisible electromagnetic radiation in the case of fluorescent lamps or by electroluminescence), of the process of the emission of light after the recombination of electrons and electron holes in light-emitting diode (LED). LED technology has proven to be so efficient, so long lasting, and with such large possibilities of adaptation to users and daylight that almost no other electricity source of light is in use for lighting of buildings nowadays. While light has great influence on our health, wellbeing and productivity, this chapter focuses on the energy aspect of indoor lighting. Although extraordinary increases in the energy efficiency of artificial light sources has been achieved, the goal of designers should be focused on daylighting, which is the most acceptable and pleasant way of illumination for people. As up to 30% of delivered energy for the operation of the office and commercial buildings is still needed for lighting, the efficient combination with daylighting and advanced controlling of artificial lighting must be provided in nZEB. Additionally, visual comfort indicators are included in building assessment schemes, such as BREEM or DGNB (see Chap. 14).

According to official EU data, about 35% of buildings in EU are more than 50 years old and, as a consequence, extremely poorly energy efficient. It is assumed that if the overall energy efficiency of the buildings in EU were to be improved, the final energy consumption could be decreased by as much as 6%, resulting in a 6% decrease of CO₂ emissions. Two key documents were published to increase energy efficiency of the buildings: the Energy Performance of Building Directive (EPBD 2010) and the Energy Efficiency Directive (EED 2012 [Directive 2012/27/EU of the European Parliament and of the Council of 25 October 2012 on energy efficiency, amending Directives 2009/125/EC and 2010/30/EU and repealing Directives 2004/8/EC and 2006/32/EC (Official Journal of the European Union L 315/1)]). This chapter focuses on the presentation of energy performance certificates of building, which is one of the most recognizable outcome of directives (ec.europa.eu/energy/en/topics/energy-efficiency/buildings).

Actions and goals towards sustainable societies should address the design, construction and use of buildings. The building sector has significant impact on the use of natural resources and the quality of the environment. Recent studies shown that half of natural resources used are related to the building sector. At the same time, the construction and operation of buildings are responsible for the largest share of greenhouse gas emissions. The European Commission has adopted several directives regarding improved energy efficiency, the wider use of renewable energy, and the use of sustainable materials and products to guide designers and evaluate the impact of buildings in all stages of their life cycle. In this chapter, the most widespread methods for the environmental labelling of products based on the life cycle assessment approach and methods for the holistic certification of buildings’ environmental impact are presented.