Knowledge Base

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• Filtration
  • Air changes (number)

    The ratio of the amount of air of ventilated into a room over 1 hour divided by the volume of the room at an overpressure of 50 Pa.
    n₅₀ air exchanges (requirement values):
    For existing buildings: 7
    Modern new building (HU): 5-10
    Modern new building (DE): 2-6
    Low energy building: 0.17-5
    Passive house: 0.17-0.6

  • Filtration

    Percolation or infiltration. The amount of air (replacement) that is freely released from the tempered space through openings (e.g. windows) and material fitting gaps. This is a kind of natural ventilation.
    (Infiltration: the amount of air entering from the outside.)

• Thermal characteristics
  • Thermal envelope

    The set of surfaces delimiting the heated, cooled spaces of the building or the thermal insulation layer installed on all the separated elements of the tempered interior (including thermal bridges up to and including known and scaled thermal bridges) without interruption, typically outside.

  • Thermal conductivity

    Mark: λ (lambda)
    Unit of Measure: W/mK
    A thermal characteristic that indicates how many Watts (W) of energy is released, when a material with uniform thickness (1 metre), in the event of –  1 K (Kelvin) (generally understood: 1°C) temperature difference between its two sides under a unit of time. depending on whether it is assessed from a thermal conductivity or thermal insulation point of view).
    The value λD or declared (reported) is measured under normal (lab) conditions specified by the Manufacturer. This is different from λT or design value. The design value of the thermal conductivity can be determined by the following means, (with knowledge of the declared value):
    λT = λD x FT x Fm x Fa
    Where:
    λT = thermal conductivity factor to be taken into account under the intended environmental conditions
    λD = heat conductivity declared under standard (known) environmental conditions
    FT = temperature correction (conversion) factor
    Fm = humidity correction (conversion) factor
    Fa = the aging correction (conversion) factor

  • Thermal resistance

    Marking: R
    Unit of measure: m²K/W
    (Typically RD i.e. declared by the manufacturer, declared-calculated value as the ratio of thickness (m) to λ (W/mK) )
    A calculated thermal characteristic that indicates the resistance of a particular layer (typically thermal insulation layer) to heat transmittance.
    The higher the R value the greater the resistance to heat transmittance.

  • Thermal mass

    The mass is represented by the different separating structures of the tempered spaces of the building (floor + wall + slab).
    Different materials can be considered as active heat storage to different depths of thickness, depending on their thermal conductivity.
    E.g. 2200 kg/m³ concrete active heat storage mass is 422 kg/m², 1700 kg/m³ solid brick wall: 184 kg/m², 800 kg/m³ multi-cavity brick: 36 (!) kg/m², 600 kg/m³ wood 18 kg/m².
    The higher the heat storage performance of a layer of material, the longer it can store heat in winter and the slower it heats through summer.
    The heat storage mass of the building is the sum of the heat storage mass of all heated rooms. The specific heat storage mass of the building is the mass of the unit heat storage projected on to the net heated floor area of the building.
    Based on the specific heat storage mass, the separated structure of the building:
    – heavy if m > 400 kg/m²
    – light if m < 400 kg/m²

  • Thermal bridge

    It could be geometric or structural.
    Geometric: when due to the shape of the structure (building corner, window box, inner wall connection to external wall, etc.), the heated, warming surface is smaller than the cooling surface (vice versa in summer).
    Structural: when a material with a better thermal conductivity and lower thermal insulation capacity is installed in a given part of the building compared to the surrounding materials (e.g. wreaths, lintels, reinforced concrete frames, etc.).

  • Thermal transmittance

    Sign: U
    Unit of measure: W/m²K
    A value specific to a particular building structure. Shows the amount of heat being transferred over the unit surface of the structure over a unit of time in the event of a temperature difference per unit.
    The thermal transmittance is a reciprocation of the thermal resistance.
    U = 1 / (Rse + Σ (d / λ) + Rsi)
    The thermal characteristics standard sets requirements for the U-value for each building structure.

  • Heat transfer coefficient

    Heat transfer on two delimiting surfaces of the test substance (e – external , i – internal )
    In addition to the thermal resistance R, account shall be taken of the degree of heat transfer on both sides.
    Rse – external, Rsi – internal surface resistance, in detail:
    From bottom to top Rsi 0.10 / Rse 0.04
    Horizontally Rsi 0.13 / Rse 0.04
    From top to bottom Rsi 0.17 / Rse 0.04

• Vapour properties
  • Vapour control ability

    The structural (material) layer, that can let through a specific amount of vapour, which changes the humidity of the space bounded by the vapour control membrane, in a way that is pre-planned.

  • Vapour diffusion ability

    Mark: sd
    Unit of Measure [m]
    Sd is a vapour diffusion capability, the magnitude of the resistance of a building material to water vapour diffusion, the thickness of the air layer equivalent to the resistance, expressed in metres.

  • Dew point, condensation

    Dew point is the temperature at which the vapour in the air condenses. The temperature at which a given humidity reaches the so-called saturation humidity, i.e. absolute humidity (maximum amount of moisture absorbed by air) is practically the temperature of 100 % humidity. On a surface that cools to (or below) dew point, the humidity condenses.

  • Relative humidity

    There are two distinct terms under the term humidity:
    – absolute humidity showing the amount of water vapour in the air (g/m³),
    – relative or relative humidity showing the ratio of water vapour in the air at a given temperature in relation to the possible saturation.
    Air temperature (°C): -10;  -5;   0;    5;   10;   15;   20;    25;    30;
    Water content (g/m³): 2,4; 3,4; 4,8; 6,8; 9,4; 12,8; 17,3; 23,1; 30,4;

    Relative humidity is the humidity that is scaled to 100% liquid water at a given temperature. Higher temperature air can absorb and store more water, lower temperature can store less.
    E.g. 90% relative humidity at -2 °C, means much less water vapour in absolute terms than 50 % relative humidity at +20 °C. (That’s why the cold air in the winter is dry, or the warm air in the summer is more humid.)

• Inverted roof

  When the thermal insulation is placed above the waterproofing of the flat roof (outside). Straight layer order; when waterproofing is above (outside) the thermal insulation. Flat roof with DUO or double thermal insulation, when there is thermal insulation both above and below the waterproofing. Any type of material can be used as thermal insulation below the waterproofing layer, but only a closed cell structured material can be used above it. (e.g. XPS)

• Aggregated energy characteristic

  Value (kWh/m² years) which indicates the specific energy consumption of the building under consideration. It takes into account not only losses, but also gains (e.g. solar energy) and thus develops the quality class of the building from A+ to I, from “Minimal energy consumption” to “Remarkably much consumption”.

• Primary energy

  A combination of energies for heating, domestic hot water production, air systems, cooling and lighting. Natural energy sources are used to meet these energy needs, such as coal, oil, natural gas, solar energy or natural uranium.

• Specific heat loss factor

  The ratio of the cooling surface and the air volume of the tempered building depending on the average heat transfer factor of the building structures. (W/m³K)

• Energy performance certificate

  A document from which you can learn about the energy consumption of a building. The energy consumption will determine the classification of the property’s energy certificate. The energy performance certificate is the result of a three-level verification. The final result is the Aggregated Energy Characteristic (kWh/m² years) which indicates the specific energy requirements of the building under consideration.
  The process of energy monitoring:
  1. Determination of heat transfer values for separating structures.
  2. Determination of a specific heat loss factor.
  3. Determination of an aggregated energy characteristic.

• Fire hazard class

  Classification of the substance, mixture, which, on the basis of the physical and chemical properties of the substance, mixture, is characterised by its behaviour and hazard from a fire protection point of view. The definition mainly refers to substances stored in a room.
  The former A, B, C … classes has been replaced by (1) (2) (3), which is simplified:
  1. “Explosive class” include materials classified in class A or B prior to the entry of the new OTSZ. (National fire safety codes & standards)
  2. “Flammable class“ include materials classified in the fire hazard class C or D before the entry of the new .
  3. “Non-flammable class“ includes materials classified in the fire hazard class E before the entry of the new OTSZ.

• Reaction to fire

  Category characteristic of the behaviour of building materials and construction structures against fire, determined on the basis of a test in accordance with the relevant technical requirements; A1, A2, B, C, D, E, F.

• Load capacity

  A characteristic of a construction product, that regards the ability of the product to withstand the load that is pre-planned during construction and then during the intended period of use of the building, without any characteristic change in performance.
  Like the “step-proof ability”, it is not defined, so it can be identified as the compressive strength of the product. (In the professional view, the load capacity is less than the step-proof “value”.)

• Compressive strength

  The resistance of a (building) material to deformation due to compressing forces, which depends on the density and structure of the material. The compressive strength of the different building materials varies over a wide range.
  Sign: Rv
  Unit of measure: N/mm² → MPa (1000 kPa)
  For some thermal insulation materials, a significant compressive strength cannot be determined because they are compressed (already) under a relatively low load and are therefore characterised by a compressive strength for a significant compression (short-term loads; 10 % long-term load; 2 % ).

• Walkable

  The type of short-term load capacity of a construction product – typically thermal insulation material – that no residual deflection occurs in the product after the load has ceased.
  Given that this colloquial term is not standardly defined, some technical mediums consider a material to be step-resistant with a compression of 10 % due to a compressive strength of ≥10 % and others at ≥150 kPa.
  The minimum compressive strength of RAVATHERM XPS products is ≥300 kPa, so they are all considered as “step-resistant”.

• Durability of compressive strength, compressive strength design value

  The degree of load capacity that a given (building) material can tolerate permanently, without any change in size or quality.
  In the case of thermal insulation materials, the long-term load capacity is characterized by a compressive strength at 2 % material compression over the long term. The long-term load capacity of the RAVATHERM XPS is described by the CC performance feature. This allows for a maximum total compression of 2% over 50 years at the specified maximum compressive strength.

  Floor structures and slab foundations shall be calculated with this value in the case of other permanent loads!
  Important! Durable load capacity (CC) is not the same as the compressive strength value for the 2% compression of the insulation material, as specified by some manufacturers.
  Interesting fact: thermal insulation products are usually classified using the compressive capacity values measured at 10% compression, or sometimes (for some XPS products) their compressive strength. However, the strength values for 10% compression are not design values, because thermal insulation materials usually suffer permanent deformation over a certain compression under the influence of a certain load. They suffer further deformation following so-called initial compression under long-term load.
  E.g. The EPS, which is similar to XPS – according to product standard MSZ EN 13163, expanded polystyrene foam – thermal insulation materials no longer behave elastically over 2-3 % compression, the cells suffer permanent deformation.

• Closed cell polystyrene foam

  Polystyrene thermal insulation material (extruded XPS) made by extrusion process. Its material structure is crystalline, the walls of cells are common to adjacent cells. The material is solid, have good thermal insulation properties and not sensitive to moisture. Durable, long-term high thermal insulating performance, thus saves energy and reduces global carbon dioxide emissions.

• Thermal insulation

  A product characterised by a heat conductivity of λ ≤ 0,07 W/mK can be considered as a thermal insulating material.
  Since most building materials have good thermal conductivity (concrete, steel, stone, solid brick, etc.) only the building structures with thermal insulation are economical and can ensure adequate comfort.