People have different lifestyles – not every family has a car or a complete set of home appliances. But everyone needs a roof over their heads. So, the idea of building an energy-efficient home has always been of interest. Peasant huts in Europe and the tents of nomadic peoples were built using special know-how, even if was not always given scientific explanation. A masonry heater, which was traditionally used in houses in Eastern, Northern Europe and North Asia, was a fine example of energy efficiency (Fig. 3.2.17). The thick walls retained heat and the chimney with its different sections extracted heat from the smoke before it left the building.
Figure 3.2.17 The traditional masonry heater, a fine example of energy efficiency
More recently, in 1974, a sharp jump in oil prices made it much more expensive to provide buildings with energy and heat, inspiring architects and engineers to take a new look at building design. Houses started using new environmentally friendly technologies and alternative energy sources. Special demonstration buildings were built to show what could be achieved, and governments in some countries actively encouraged such projects.
The World Green Building Council was formally established in 2002 to facilitate the global transformation of the building industry towards sustainability. The council brings together more than 30,000 property and construction companies from 80 countries. Its members are constantly seeking new ways to reduce the resources needed at all stages of the life of a building: during its construction and use, when it is repaired and when it is finally dismantled. Green construction strives to reduce greenhouse gas emissions and water pollution, minimize waste, and protect nearby natural habitats. Such buildings are somewhat more expensive to build, but the extra investment pays for itself in five to 10 years.
Energy-saving buildings are called ‘passive’ or ‘active’, depending on their efficiency. A passive building may not need any heating or may consume just a tenth of the energy that an ordinary building does. But an active building not only requires very little energy, but produces energy – perhaps even surplus energy to feed into the central electricity grid. You may have heard of the expression, ‘smart building.’ What this means is that the building in question automatically analyses its energy consumption and carries out automatic control of various energy-using systems in the building.
Figure 3.2.18 Several low-energy buildings have been con- structed in the Viikki district of Helsinki, the capital of Finland. Panels that store energy from the sun have been built into the facades
Passive buildings
One of the main objectives of a passive building in northern countries with colder climate is to reduce heat loss. Ideally, a passive house is heated solely by the heat given off by its occupants and by the appliances used there. If additional heating is needed, preference is given to renewable energy sources.
Bricks made from recycled materials are often used for the construction of such a house.
It is not only the building’s walls that require thermal insulation, but also its floors, ceilings, attic, basement, and even the foundations. It is important to ensure that the design does not permit so-called ‘cold bridges’: apparently minor details and connecting points in the construction that can drain heat from a generally well-insulated building. These techniques can reduce heat loss from a building by almost 20 times!
Environmental certificates for buildings
Environmental certification standards for buildings have become widespread in recent years. The best-known and most used systems in the world are BREEAM (UK), LEED (USA) and DGNB (Germany).
The BREEAM environmental certification system, developed in 1990, has certified more than 200,000 buildings worldwide. The criteria for certification are the quality of building management, the health and well-being of its residents, energy efficiency, transport, water, materials, waste, use of the land plot where the building stands, and the pollution that it generates.
The LEED environmental certification system was devised in 1998 with the following criteria: sustainable site development, water consumption efficiency, energy efficiency, air protection, materials and resources, internal environment quality, and innovations.
Buildings can qualify for four levels of certification: Certified, Silver, Gold, and Platinum, depending on the criteria they meet.
The DGNB system of environmental certification, introduced in 2009, uses an integrated planning concept to assess ecology, economy, sociocultural and functional aspects, as well as a building’s location.
The first LEED Platinum building in the Middle East
Originally constructed in 1995, the head office of the Dubai Chamber of Commerce and Industry is a shining example of how an existing high-rise building that consumes a lot of energy and water can be transformed into a healthy, green skyscraper.
Between 1998 and 2013, energy and water consumption per person in the building was reduced by 63% and 92% respectively, saving almost $5.8 million through low and no-cost initiatives. After the renovation, the building earned the Energy Star label and the LEED Platinum certification.
In a passive house, careful design of windows is highly important: double-glazed window units are hermetically sealed, panes of glass are covered with a special film that admits light and warmth from outside but reflects them back when they attempt to pass outwards. The biggest windows face the direction from which sunlight mainly comes.
The system of heating, air conditioning and ventilation uses resources more efficiently than in conventional buildings. For example, in winter, air leaving the building is ducted alongside air that is entering it, in a special heat exchanger, so that the warm air transfers its heat to the cold air. In the summer, hot air from outdoors is ducted underground where is cooled. Similar principles are used to take heat from used water.
Of course, even such carefully designed buildings sometimes need additional heating or cooling, but much less energy is required to provide it. Such advanced design has inherent problems: the air duct must be carefully monitored as accumulations of dust, use of artificial materials, or a conduction fault can affect air quality. It is also important to ensure that furniture in such buildings does not release any harmful substances into the air.
Solar cells and (if appropriate) small wind turbines are installed on the roof. The most economical lighting system (LED) is used, and it may even be possible to light the building by means of sunlight alone.
Added together, these and various other devices produce savings.
There is rising construction of passive energy-saving houses. Estimates suggest that in 2022, there were more than 120,000 passive house buildings around the world, including office buildings, shops, schools, and kindergartens (mostly in Europe). Begun as a concept implemented only in Germany or regions with similar climate conditions, it has now been adopted worldwide, with clearly defined applicability criteria for different climates.
Under cold climate conditions, the design process typically is focused on minimizing heat losses and optimizing solar gains. In milder climates, moderate insulation, including windows with improved performance, is sufficient, though building performance during summer requires more careful consideration. For hotter climates, the insulation requirements increase, and solar loads through windows, walls and roofs must be limited. In hot and humid climates, humidity loads need to be minimized. Examples of passive houses in climates as varied as Canada, the USA, Germany, China, Greece, Spain, Taiwan, Mexico, and the United Arab Emirates illustrate the range of possible solutions.
Figure 3.2.19 An infrared picture shows how effective the heat insulation of a passive house (right) can be in comparison with a conventional house (left)
Energy-efficient residence of the British prime minister
10–12 Downing Street is famous in London as the resi- dence of the British prime minister.
The 300-year-old building has been undergoing a phased modernization and refurbishment programme to become more energy efficient. Environmentally friendly initiatives introduced have included the following:
- controlled lighting using motion detection and low en- ergy lamps
- waste heat recovery from IT equipment to heat water
- thermal insulation
- low water-use fittings
- rain water harvesting for garden irrigation
- building management system with utility monitoring
- timber sourced from legal and sustainable sources
- more than 90% of construction waste
These renovations have earned 10 Downing Street a ‘Very Good’ BREEAM rating.
Climate-friendly school in the United States
The Sidwell Friends School in Bethesda, Maryland, and Washington, D.C has succeeded in reducing its energy consumption by 60% and water consumption by 90%.
Vegetables grown by students on the building’s roof using rainwater are served in school lunches. Water that is good enough to drink is only used for drinking.
The school is in a part of the USA that is often very hot, so the school building has its own system of cooling towers, which lower the temperature of warm air from outside before it reaches the interior. Air conditioning is only needed in the classrooms on exceptionally hot days.
Optical systems have been installed that regulate the flow of sunlight, channelling it to darker rooms in the building. Windows on the sunny side of the building have special shades to protect the interior from overheating.
Active buildings
The active building incorporates some of the same concepts of the passive, such as insulation, or optimal solar exposure of the windows. But it also promotes renewable energy systems, such as solar water heaters and/or geothermal heat pumps. The world’s first active energy- saving building was built in Denmark (which has an Internet portal for active buildings: www.activehouse.info). A draft EU directive from 2023 that regulates energy performance of buildings calls for all new buildings to be emissions-neutral as of 2030, with the aim of having emissions-neutral building stock by 2050. That means that such buildings need to have features of both passive and active buildings.
Active house in Denmark
‘Home for Life’ in Denmark is an example of CO2-neutral active house. It produces nine kWh/m2 energy per year – more than it consumes. A solar heat pump and
7 m2 solar collectors generate energy for heating and hot water, while 50 m2 solar cells generate electricity. Floor-to- ceiling windows cover 40% of the facade
- twice the area of a traditional house
- and help to illuminate and heat the rooms from the sunlight. All rooms are
equipped with sensors that register heat, CO2 levels and humidity, and an intelligent control system makes sure that the house adjusts to the family’s need for a healthy, comfortable indoor climate. Automatic window opening mechanisms let in fresh air, while sensors turn off lights when you leave the room.
Optical systems have been installed that regulate the flow of sunlight, channelling it to darker rooms in the building. Windows on the sunny side of the building have special shades to protect the interior from overheating.
