During cooking, bathing, washing and breathing, moisture is released into the air in the form of water vapour. A family of four easily produces ten litres of moisture each day. When this is not removed from the dwelling in the correct manner, dampness can occur. This is not only unpleasant, it is also a health risk. In principle, ventilation is the best solution for this problem. Calcium silicate is capable of absorbing water vapour, until the degree of dampness in the dwelling is reduced. The wall’s capacity to absorb water vapour and then release it again is determined by the 24-hour variation in the relative humidity and by the type of material. For each m2 calcium silicate wall, this capacity is 0.17 litres of moisture by absorption and 0.13 litres by desorption. The depth of penetration of the moisture is 5 to 6 mm here. For a house with 130 m2 calcium silicate this comes to approx. 17 litres moisture per 24 hours. The water vapour production depends to a large extent on the occupants' behaviour, but will seldom be less than 15 litres per 24 hours. The water vapour regulating capacity of calcium silicate is therefore sufficient to keep the moisture climate in a house manageable. This is often also known as “the calcium silicate breathing”. This means a good and natural moisture regulation, which is beneficial to a healthy living environment.
Heat accumulation
While a room is being heated-up by the central heating or by the sun shining in, the Silka calcium silicate walls absorb some of the heat. When the air temperature falls, the heat is radiated back into the surroundings. This creates a heat-levelling effect with positive influence on the comfort level. In addition, extreme temperature swings are absent, which leads to a further positive effect: energy savings. The degree to which heat can be absorbed and radiated back is known as the heat accumulation capacity. This capacity is principally determined by the specific heat and the mass of the building material. The specific heat of calcium silicate is approximately 840 J/(kg.K). The density is approximately 1750 kg/m3. This creates a high heat accumulation capacity, which means that calcium silicate stays cool longer in the summer and conversely it remains warm for longer in the winter. Because of the heat accumulation, changes in the outside temperature are not felt as quickly indoors. The heating does not have to respond as often, which results in a more constant indoor temperature.
Thermal insulation
The Buildings Decree (“Bouwbesluit”) includes requirements for the energy performance coefficient (EPC). These requirements are met if the calculated typical energy use is not higher than the maximum permitted energy use. Improving the thermal insulation of a building is an attractive proposition to save energy. Good insulation ensures that the heat is better retained within the building. The excess heat can be stored in the building's material mass. When the ambient temperature falls later, this heat once again becomes available. The thermal resistance of a façade structure (the Rc-value) is the sum of the thermal resistances of the individual components of this structure. The Buildings Decree contains the following requirement for the Rc value of facades: 2.5 ((m2.K)/W). The Rc value is calculated from the heat transfer coefficient (A) and the thickness (d) of a wall. For inner leaves of cavity walls built using calcium silicate, a calculated value of 0.93 (W/m.K) can be used for A.
Sound insulation
Good sound insulation increases the quality of the social climate and thereby the durability of a house. This involves both noise from adjacent accommodation areas and noise from outside. The mass of the construction components largely determines the soundproofing properties of a building structure. Another determining factor is the flanking sound transmission by connecting building components. Because of its high density, the soundproofing properties of calcium silicate walls are naturally good already. The detailing of the connecting building components is, however, important. This aspect should be given special attention during design and building. The soundproofing should meet two important requirements. The first is the typical soundproofing index for airborne sound llu;k, the unit that reflects the airborne sound insulation between two rooms. The second requirement relates to the insulation index for impact noise lco. In accordance with the Buildings Decree the requirement llu;k = 0 and lco = +5 dB applies between an enclosed room in one dwelling and an accommodation area in the other dwelling. The requirement llu;k and lco = -5 dB applies between an enclosed room in one dwelling and a non-accommodation area in the other dwelling.
