When the construction process starts, the plot is purchased and the building permit is in hand, it is important to understand what building materials will be used to make the building itself last as long as possible, to ensure moisture and heat resistance, and to be convenient for the builders themselves. The choice is quite wide – expanded clay, ceramic, aerated concrete, multi-layer reinforced concrete external wall panels, etc. It has to be said that, abroad, much more attention is paid to the use of the building and the various quality parameters than in Latvia, where price has always been the determining factor.
Ceramic blocks are becoming increasingly popular in Central Europe, for example in Germany, Poland and Austria, because it has been scientifically proven that their quality and the quality of living conditions they create are higher than other materials. Ceramic blocks, also popularly known as ‘big clay bricks’, are similar in size to blocks from other manufacturers, but have several advantages. The advantages of ceramic blocks are the dryness or moisture content of the block, the strength of the material, the fire safety, it is fairly quick and easy to brick and, which is important at our latitudes in terms of both comfort and cost-effectiveness, energy efficiency.
Summarising the information on ceramic blocks, it can be concluded that this material is one of the most suitable for house construction in our climate. It is made of clay, a natural material that is able to remove moisture quickly, ventilate well and quickly, and walls made of it are also safe for the health of the occupants, as they are able to ensure a good indoor microclimate. Although the thermal resistance of ceramic blocks is similar to, for example, aerated concrete blocks, ceramic materials have a high thermal stability and inertia (how long a material “holds” heat and cools down) due to their density. This means that the material stores heat well and returns it slowly, allowing rooms to naturally maintain an optimum temperature in all seasons. Even in the hottest summer months, rooms that are not cooled by air conditioning will not overheat as quickly as, for example, a lightly constructed house. And for those who are concerned about the environmental friendliness of the material, ceramic is natural. Another positive feature of the material is its compressive strength, which shows how much compression the material can withstand before it collapses. It is many times higher than that of aerated concrete or expanded clay blocks. It also provides good sound insulation, which is due to the bulk density of the ceramic blocks.
It is sometimes pointed out that ceramic materials are more difficult to drill and punch, but for a skilled craftsman with good equipment this should not be a barrier.
A potential buyer should pay attention to the level of moisture in ceramic block and other materials such as aerated concrete. All masonry external wall constructions have an initial external wall moisture higher than their equilibrium or design moisture. This can arise from the manufacturing process (also known as process moisture), from the masonry, from plastering, or from the effects of precipitation. The drying time of this moisture may vary between materials.
When comparing aerated concrete blocks and ceramic blocks, the experts work with the following data: aerated concrete blocks have an initial moisture content of 35% by weight, but after a year this drops by 10 percentage points to 25%. For aerated concrete blocks, the equilibrium moisture is given as 5%. Ceramic blocks, on the other hand, have an initial moisture content of 0% by weight and an equilibrium moisture content of between 0.6 and 2% (that is, 50% humidity). The open pore structure of ceramic blocks helps to achieve this, allowing moisture to escape much more quickly than from denser materials with closed pores. Given the significant differences in the initial moisture content of aerated concrete and ceramic blocks by weight (35 % and 0 % respectively) and the mortar used in their construction, the total initial water content of an aerated concrete wall is many times higher.
Why is it important to know the moisture content? Because it affects the thermal insulation performance of a building: the higher the moisture content of a structure, the lower the thermal insulation. In addition, if the humidity level decreases slowly enough, there is a risk that mould may soon settle in the external walls, as the relative humidity is very high and intensive (and prolonged) ventilation is needed to dry out the moisture.
Scientists from different disciplines have been monitoring the energy performance of experimental houses for several years. Five test stands or experimental houses were set up in special conditions in the Latvian Botanical Garden, using locally available building materials. These were milling beams with an insulation layer and a log imitation interior, veneer panels with thermal insulation fill and fibrolite, ceramic blocks with an external insulation layer, aerated concrete blocks with an external insulation layer and experimental ceramic blocks with thermal insulation granule fill in their cavities. The energy efficiency and sustainability of renewable indoor climate maintenance systems in Latvian climatic conditions were measured.
Measurements showed that, for example, the ceramic block construction immediately after construction met the designed thermal transmittance, and the relative humidity measurements in this stand (relative humidity up to 50%) were already within the optimum humidity range (30%-60%) in the first months of operation. In contrast, the aerated concrete structure, due to its high moisture content, did not achieve the designed thermal transmittance and the relative humidity in the bench was significantly higher than the desired optimum.
Six months later, measurements showed that the energy consumption required to maintain the same air temperature was still significantly lower in the ceramic block booth compared to the aerated concrete booth, as the thermal transmittance of these walls was fully within the design parameters, while the aerated concrete structures were still outside them. In the following heating season, the ceramic block still had a lower thermal energy consumption than the aerated concrete (due to the fact that the aerated concrete still had a higher moisture concentration). Complex microbiological analyses were also carried out on the stands, which showed significant microbiological contamination in the aerated concrete stand – especially in the risk areas. Relatively minor contamination was found in the other stands.
Cost is also an important factor when building your dream home, because no one wants to overpay. A cubic metre of ceramic blocks is equivalent in price to some other blocks, such as expanded clay or aerated concrete. So a potential buyer has to weigh up the pros and cons when choosing a masonry wall material and which masonry wall material parameters are important to them.