The word "ecology" comes from the Greek words of ecos - meaning house, and logos - meaning science, knowledge. So it refers to the science of studying the habitat. It is thus a biological science studying the interaction between organisms, plants and their living environment. For this, ecology studies very closely the structure, the function and the productivity of supra individual biological systems and of the mixed environment (or the ecosystems).
The traditional roof is replaced in ecological houses with a soil layer which is meant to protect the house from low winter temperatures and high summer temperatures. Also, walls get protection from erosion. There is no need for deep foundation in the case of these houses, neither is there need for large area of heating material or for installations of heating and things like these.
Eco-friendly houses are more and more in the center of attention, especially because they are the most inexpensive option. An ecological building is the result of a special projection within a context. That means a location with its specific characteristics - urban, rural, more or less-built areas, integrated in a special landscape, and so on. This is meant to serve certain needs that the owners of the building have and which may correspond to a certain lifestyle. The ecological house must be a healthy house for a healthy person, for a healthy family. The bio-psychological state of its inhabitants depends on the way in which the house can respond their specific family needs and at the same time it depends on how much it costs to keep it in a good state for all its lasting period. The one who intends on building an ecological house must consider the fact that he/she is making a long-term investment, that this house won't be expensive to keep and there won't be many taxes; he/she would be able to live in an interior and exterior healthy environment.
As for the legislative part, there are regulations concerning the four categories - the thermal, hygienic, acoustical and visual comfort. Generally, all these can be incorporated within the standards of the "passive house." A passive house uses only 15 kWh/m2/year for heating the interior spaces.
All the building materials have an incorporated energy, the energy to extract the brute material, to process it, and then the one necessary for the production, transport and their fixation on the site. There is a number of recognized strategies to help reduce this incorporated energy. The wastes resulting after working on the building site and reusing them in new buildings can reduce both the energy necessary for the production of new materials, and their impact on environment. The materials which can be recycled contain less incorporated energy, which is necessary for extraction, transportation and processing. Locally-produced materials require less energy for transportation. For instance, the energy incorporated in concrete can be reduced by replacing a concrete quantity with ashes. But ecological houses typically use natural materials. Using the ecological building materials both for the structure of the house and for closing the facades and the roof, and also for the interior finishing and for furniture, is a very complex issue. We need to consider the quality of the interior air and the effects the adhesives or the types of paint can have on our health. The diseased house syndrome refers also to the correctness of executing certain details by which humidity is controlled, which can stagnate within building materials and can lead to condensation. The appearance of mildew is the last stage of the house's sickness. The control ought to be done earlier, in order to prevent this from happening.
All the solutions deal with energetic efficiency without renouncing any of the comfort standards referred to above. Aleksandar Nikolic, the author of the book entitled "Ecological Houses", clearly expresses his opinion on this topic: "The owners of self-heating solar sod houses or Eco houses do not have to worry about the heating material, they are protected from noise and vibrations, which places this solution amongst best achievements in the world." This Serbian lives in this kind of self-heating ecological house. According to statistics, such houses save about: 85% in heating, 100% in cooling, 30% in lighting and 18-40% in building material.