Special Subjects

Select the article

Download the files

Antiseismic Planning

The antiseismic Regulation was voted as a law of the State and applied in 1959 (19/26-2-1959), was partly revised in 1984 with Ε.Δ.2α/01/44/Φ.Ν.275/4-4-84. In 1992, the New Greek Antiseismic Regulation passed (F.Ε.Κ. Β΄ 613/ 12-12-1992), which adjourns the former regulation of 1959 and it is applied in conjuction with the modifications of the Regulation of 2000 (Ε.Α.Κ. 2000) - F.Ε.Κ. 2184 Β΄/20-12-1999.

There are factors that concern the seismic activity of the area of the construction, the ground hazard, the importance of the structure, the behavioral factor, the laying out factor etc. So, the Greek space is divided in 4 seismic activity areas, the zone "I" is of low seismic activity, while zone "IV" is of extremely high-risk of seismic activity. The constructions are divided in 4 importance categories: from great importance (telecommunications, public buildings, museums etc) to minor importance (rural buildings).

The Antiseismic Regulation defines that:

  • The construction should not suffer damages in small earthquakes (elastic behavior).

  • The construction should undergo controlled plastic deformations in great earthquakes which have little possibility to occur during the construction's useful life span.

Therefore, the construction should not collapse from the expected strong effect during its life span (60 years). Thus, we allow the deformation of a construction in the plastic area during a strong earthquake, as it is not advisable in the rare case of a strong earthquake to aggravate the construction with significant cost so as to ensure the elastic behavior.

Practical Rules of Antiseismic Construction

Those are ruled which are also understandable from non experienced people and concern the form of the constructions and construction materials.

The shape of a technical work plays an important role to the work response at the seismic movement. We can generally say that the simple, symmetric construction, which is not elongated, horizontally or vertically, has a uniform and constant distribution of its stiffness and endurance, bears horizontal elements which are vertically connected properly and has the right foundation having in mind the ground's special characteristics.

The choice of the construction materials is also of ggreat importance, apart from financial or other factors. Their basic characteristics should be the high plasticity, the big ratio of endurance/weight, their homogeneity and the ability of their durable connection.


Thermal insulation

The first regulations of thermal insulation appear in 1974 in the European Countries (France, Germany) in order to spare energy through the proper thermal insulation of the buildings. In 04/07/1979 (FΕΚ 362) the regulation passes in Greece. Gradually though, in the 1980's, Europe discovers the Bioclimatic Architecture. According to this theory, the buildings should not only be thermally insulated, but also properly oriented in reference with the sun position (winter and summer) and the winds that blow in the area. The ecological construction is introduced in late 80's, which puts the question: "What point is sparing energy when the materials used are carcinogenic for those who use the building?"

  • How are a building's thermal loss created?

    A closed space which is heated, radiates heat to its cooler surrounding environment. The heat also escapes from the shell imperfections. These loses can be dealt with the various insulation methods. The proper ventilation of a house should not be hindered by the fraction of the cracks and the deterioration of the unwanted air penetration. The air inside a residence should be renewed, for a healthy living. There should be enough ventilation, even when the outer temperature is low. The air flow should be made unhindered, in all living areas. All main areas should have openings and all service areas should be ventilated. The influx and the outflux of the air can be natural, mechanic or combined. The openings (windows etc) and the mechanical ventilation should be protected enough so as not thermal energy would aimlessly escape.

    The proper thermal insulation, combined with a satisfactory airconditioning system, ensures a comfortable stay in the residence. During winter, it protects the inner space from the cold and during summer from intense heat. It ensures economy on the initial installation cost and the heating operation costs, reducing the temperature interchanges with outdoors or with spaces of different temperatures. It can spare you money from maintenance costs, while it raises the life span of the building, protecting it from damages and corrosion.

    Researches have shown that a proper thermal insulation, which demands the 2-5% of the building's initial constructing cost, can spare up to 50% of its heating operation cost.

  • Advantages and Disadvantages of some thermal insulation methods

    Basically, the walls can be insulated with four techniques:

    From the indoor side.

    In this case, the insulating material is placed from the indoor side and is protected by a solid building material which functions as the coat.

    This method of insulation has the following advantages:

    • It has limited construction time.

    • It is a cheaper solution compared to the outdoor thermal insulation.

    • No further protection from outdoor influences is needed.

    • It is a simple construction.

    • The space is heated very quickly.

    • You can construct it regardless of the weather conditions.

    • However, there are also disadvantages:

    • The inner space is decreased

    • The space is cooled very quickly. The thermal capacity of the outer wall remains unexploited.

    • The problem of the thermal bridges is not solved.

    • The construction materials are in risk of contractions and expansions due to temperature flactuations. Cracks may appear and rain water could penetrate.

    • There is a minor problem in the arrangement of the electrical installations.

    From the outdoor side.

    In this case, the insulating material is placed on the outside part of the wall. This method has the following advantages:

    • The space can keep its heat even if the heating stops, due to the walls thermal capacity.

    • In the spaces that head south, the heating from the solar thermal gain is preserved, as it is stored in the heavy inner walls.

    • The smooth operating of the internal spaces is not hindered during the construction.

    • Useful space is not reduced.

    • The outer wall surfaces are protected from the contractions and the expansions.

    • The coverage of the thermal bridges is ensured, especially in the concrete plaques, beams and columns.

    The disadvantages of this technique are the following:

    • Compared with the inner side insulation, this method is more expensive.

    • If the walls have many architectural extrusions, the application is not so easy.

    • Buildings with intense outer morphological outer interest cannot have this type of insulation.

    • Scaffolds are required if the building is multi-store.

    • To protect from the weather conditions, a special protection from the materials of the layers is needed.

    Thermal insulation with special bricks

    In this case, the wall is built with special heat resistant bricks. Those must comply with the K thermal penetration factor, which is obligatory by the thermal isnulation regulations, from their way of creation, their shape and dimensions etc. If K has to be increased, insulating material is added, which in many cases it is a part of the brick. This method has to present a lot of advantages but should be protected from moisture with the use of proper coats.

    Thermal insulation in the core between two walls

    This is the most common insulating method in Greece. Usually, the insulating material is placed between two walls and this may be the method's main disadvantage. The thermal insulation may be ensured, but the static endurance of the construction and the requested endurance from the antiseismic regulation is not certain that will be 100% satisfied. The construction of this type of thermal insulation can be improved even if thermal bridges are to be created in the worst case.

  • Thermal conductibility coefficient:

    This is not a constant, but a linear function which increases in conjuction with temperature. It usually has an average value. The thermal conductibility is negatively affected from moisture. This is easily explained from the fact that the water's thermal conductibility is 0,57 W/mk, much bigger than that of the immobile dry air. The values of the thermal conductibility factors given from the companies are good with a 5-10% deviation depending on the material. Wrong measurement and material incogruity are considered. Despite the steam barriers, the thermal insulating materials absorb humidity. Due to their attributes and their construction, most of these materials age of mechanical interactions and temperature changes. Thus, the initial balance of solid and air substances is altered. The mechanisms of aging of these materials remain yet unknown. What is certain is that the thermal conductibility coefficient always increases and never decreases.

  • Steam Spread Resistance coefficient(μ):

    The thermal insulating materials must be and must remain dry. The greater the resistance of a material to the steam spread the easier this will be and is determined by the undissociated steam spread resistance coefficient μ. This coefficient is a relevant measure, undissociated and defines how bigger is the resistance in the material's steam spread to a substance layer in relevance of an equally thick air layer. The lower this coefficient is, the more sensitive is a material to moisture.

  • The mechanical endurance:

    The mechanical endurance needed for a construction defines the thermal insulation system that will be used. Thus, materials with great mechanical endurance can be used as self-supported, other materials with less endurance can be placed in a support-net, while materials with very little endurance as filling materials. The constriction endurance is vital to floor thermal insulation. The knowledge of the in-between disfigures up to breaking is useful, since the material cannot be broken at once, but can sustain stressing. In many cases, information about the endurance of the materials when bent or tension is needed, especially in internal thermal insulations of floors with big openings or self-carrying constructions that are strained from the weather conditions.

  • Stability in dimensions:

    The given dimensions of thermal insulating plaques which are constructed with thermal procedures can be altered during the cooling and aging process. This can be avoided with artificial aging during the production phase so as to stabilize the dimensions. Great temperature variations lead to a linear shrinking to all solid insulating materials. Some thermal materials can have big expansion coefficients, which should be considered by the constructors upon placing. Moreover, the endurances of their dimensions should be checked, so as to congtrol their behavior.

  • Resistance to fire:

    The behavior of the thermal insulating materials in fire can have immediate financial complications. Despite their increased cost, more non-inflammable materials are used or at least materials which are hard or difficult to be set on fire. In general, better behavior in case of fire show the cellural glass, the fibre materials, perlite etc.

  • The special weight:

    The special weight is another useful attribute because even in the same material category, a lighter material can have worse thermal insulating abilities from a heavier one, because the latter has bigger and denser cells.

  • The ecological thermal insulating materials 

    Ecological are the thermal insulating materials, which:

    • Do not demand a great deal of energy to be produced.

    • Are recyclable.

    • Do not pollute the environment during their production.

    • Do not contain toxic/carcinogenic pollutants, hazardous for the man's health and do not omit such pollutants during installation, until their destruction.