May 21, 2019

Bioclimatic houses: Energy benefits up to 80%

According to experts, a bioclimatic house can save energy up to 80%, compared to an old building.

Bioclimatic design is the design of indoor and outdoor spaces based on the small scale of the area, with the ultimate goal of providing thermal and visual comfort conditions, taking advantage of natural climate phenomena.

Bioclimatic architecture is one of the most important factors of ecological construction, which deals with the control of environmental parameters at the level of building units by studying the following directions:

  • The study of the structured environment and the problems that arise from the design of the buildings
  • The selection of building materials, taking into account both their thermal and optical properties and their toxicological action

Buildings in Greece are responsible for 40% of the final energy consumption (thermal, electrical) which, due to its high cost, damages the user and pollutes the atmosphere with carbon dioxide. The applications of bioclimatic design are numerous in Greece as well as in the world. Laws have been enacted in many countries and bioclimatic planning is a key criterion for the development of residential complexes as well as in individual buildings. In particular, in Greece, a bioclimatic house can have a 30% energy savings compared to a conventional building, and compared to an older building, this savings can be as high as 80%. This saving is not limited to the annual energy costs but also includes the reduction of the size of the electromechanical installations. In addition, there are benefits at both environmental and social levels, through the reduction of pollutants emitted and the improvement of the quality of life. With the bioclimatic design of a building, the benefits are multiple and include their thermal protection, both in winter and in summer, with appropriate techniques applied to the building shell (thermal insulation, airtightness of the openings, shading). An additional key ingredient for bioclimatic design is the use of solar energy, both for indoor heating and for natural lighting throughout the year.

Passive-active systems

Two major technology systems have been developed to exploit solar energy for the heating and cooling of buildings: active and passive systems. Among them there is a third, the hybrids. Passive systems are those that do not use hi-tech and mechanical means to exploit solar radiation. They rely on the natural flow of thermal energy, exploit the physical properties of the building materials and use the building elements (walls, floors, ceilings, roof) for the collection of solar energy and the storage of heat. They can be divided into three major categories depending on the purpose for which they are used:

  • Passive solar heating systems
  • Passive systems and physical cooling techniques
  • Physical lighting systems and techniques

Active systems require the use of mechanical tools – simple to high-tech (pumps, heat exchangers, fans, etc.), and require complex mechanisms for collecting, transporting and storing the heat that has come from the solar radiation bound. In order to obtain thermal and visual benefits throughout the year, the above systems must be combined in their operation.

Basic bioclimatic design techniques

 The most commonly applied techniques of bioclimatic design can be divided into the following categories:


The most energy-efficient shape of a building is the one for which there are small heat losses in the winter, while solar gains in the summer are the smallest possible. In addition, particular importance should be given to the small-scale on each side of the building. Usually, the northern side is also the coldest because it does not receive direct sunlight and because winter winds usually have a north direction. The eastern and western facades receive an equal amount of solar radiation, but the western remains warmer due to the combination of solar radiation and high meridian air temperatures. The southern side is the brightest and warmest and receives sunlight throughout the day. Space that has a lower requirement in temperature comfort should be placed on the northern side to be a barrier to heat losses, essentially interfering between the heated spaces and the external environment, while the optimal orientation for the arrangement of the openings in a building is the southern orientation. The shape of the building for the optimal exploitation of solar radiation in Greece is elongated along the axis East-West. A small deviation of 20th does not substantially alter the performance of the south-oriented openings.


Particular importance in the design of a new building should be given in the shading, so as to control the amount of solar radiation coming from the openings. It is an important element of the building shell, as it contributes significantly to saving energy for heating and especially cooling the building, creating thermal comfort conditions, and adjusting the quality of natural lighting, reducing the risk of fogging. The type and dimensions of the system are determined by factors such as the orientation, the location of the exposures, and also taking into account the following factors:

  • ensuring the operation of the openings (visual communication, natural ventilation, natural lighting)
  • the adverse effects of the system on the opening and the sun-protected area
  • Stability, durability, and handling
  • initial construction costs and maintenance costs Sun protection systems can be divided into two categories, mobile and fixed. Fixed shades in most applications are some extension of the slab, the vertical and horizontal projections, as well as the horizontal concrete precast or some metal at the height of the window. Instead, mobile sunshades are some additional sunscreen devices made of lightweight materials (metal, aluminum, plastic, wood), which, with the appropriate mechanisms (manual or automated), can rotate following the sun’s trajectory. In addition, outdoor green areas can also provide sun protection for the building, both with direct shading that can be achieved by trees and with lower vegetation, which due to the green color significantly reduces the sunlight that is attacking the soil, while at the same time improving and conditions for natural ventilation.


A sufficient ventilation system is necessary to create a healthy environment as it introduces fresh air by removing gaseous pollutants and moisture from the interior. Adequate and properly designed ventilation also contributes to energy savings, as ventilation is usually associated with the heating and air conditioning of a building’s premises. Natural ventilation can be accomplished using techniques such as:

  • Through natural ventilation. Through-ventilation is accomplished by properly designing the openings in the shell and the internal masonry. Slots in the top and bottom of the partition walls allow air to circulate indoors and remove the accumulated thermal energy.
  • Chimney or ventilation tower. The ventilation chimney works by exploiting the phenomenon of natural attraction, as the hot air moves upward and thus creates current inside the spaces, transferring heat away from the building.
  • Hybrid ventilation (ceiling fans). This type of ventilation is used when there is no intense air flow around the building
  • Solar chimney. Its function is based on the Venturi effect and effectively contributes to the ventilation and moisture removal from the interior, as the high temperature of the air in the chimney significantly enhances the phenomenon of physical attraction and hence the renewal of air inside places. As long as the indoor air is constantly renewed, the solar chimney is recommended in areas with high relative humidity during the summer season.
  • Ventilated shell. It is a double-shell construction either on the roof or on the outer walls of the building, in which the outdoor air circulates.

Natural light

The use of natural lighting aims at achieving visual comfort within buildings and in saving electricity, as well as in general improving living conditions within the premises, combining light, view, ventilation, utilization and regulation of incoming solar energy. For the use of natural lighting for the benefit of the building in order to achieve visual comfort, it is necessary to ensure that the indoor operating areas are adequately (light level) and smoothly distributed, in order to avoid sharp variations level, which cause a “glare” phenomenon in the light of the work done inside the premises. Both the adequacy and the distribution of lighting depend on the geometric elements of the space and the openings, but also on the photometric characteristics of the opaque surfaces (color / texture) and the glazing (photoperiod / reflectivity).

Renewable resources

Bioclimatic design mainly uses renewable energy sources such as solar, wind, geothermal and biomass. They can provide the building with electricity, hot water and heating / cooling, and have been used in many cases and are particularly efficient for Greek buildings.

A planted roof

The planted tiles are one of the oldest bioclimatic design techniques. A planted roof consists of a layer of vegetation that grows on a flat roof. It can create a cooling effect on both the building’s interior and interior, offering thermal protection in the summer and winter as it is considered a thermal insulation medium. Especially in large cities during the summer, where the atmosphere can be stuffy, green roof coverage affects the microclimate and contributes to the reduction of toxic pollutants in the atmosphere, while in the summer it reduces cooling energy consumption by up to 30%.

Insulation – Thermal inertia

The purpose of these two techniques is to capture heat inside the building and to reduce thermal losses during the winter and to reduce solar gains during the summer season. In addition, there is an increased thermal inertia (ie the “resistance” that the building exposes to external temperature changes is large and therefore less affected by external conditions). Typical examples are mass walls, thermal storage walls and Trombe walls. The construction of a bioclimatic building is slightly more expensive than a conventional building. In the long run, however, the benefit of saving energy is multiple than the initial cost of building such a building. The benefits of this type of design are both energy and economic and environmental. Bioclimatic design helps improve living conditions, ensuring thermal and visual comfort, good air quality and ideal microwave. However, in order to achieve all of the above, careful consideration and implementation of all principles of bioclimatic design without deviations throughout the construction of the building and the use of installed systems must be undertaken.

Did you know that…

Bioclimatic residences and bioclimatic design in general are not a finding of recent years. As a result of the research, bioclimatic houses are also found in ancient Greece, with the example of Socrates’ Solar House (about 450-470 BC). Thus, from this time, they gave great importance to the architecture of each residence, so that there is maximum protection from the cold, but also the natural cooling during the summer season. For example, the northern wall of each house was thicker than the rest, while the entrances were made to the east or the south. Finally, great importance was given to the planting of trees and plants, so that there is the necessary shading.