Inside insulation is an alternative or supplement to retrofitting outside insulation and/or core insulation. Whilst in these systems the supporting masonry lies on the warm side of the insulation, which means it is usually physically uncritical, the potential or risk of condensation should always be taken into account. There are usually two decisive reasons for using inside insulation and improving the thermal protection:
Architects and engineers that were trained before or in the 1990s, often associate inside insulation with constructional damage. The were taught that dew can form in constructions with inside insulation by means of comparative calculations of walls with outside and inside insulation using the Glaser procedure. The solution then was: Careful planning and conscientious installation of inside insulation only in combination with interior vapour proof barriers and retarders.
However, part connections and openings, and also deformations (e.g. beam ends of wooden joist ceilings) represent a problem that is difficult to solve. The positive effect of preventing water vapour diffusing into the inside of the part and therefore condensation through films and/or vapour inhibitors is offset with a reduction of the drying potential for e.g. for moisture penetrating from outside. The summer process of drying moisture toward the inside of construction exposed to driving rain is obstructed by part layers with a high vapour diffusion resistance which can lead to a build up of moisture in the wall cross-section.
In contrast to system structures with vapour proof barriers or inhibitors, the properties of capillary-active inside insulation systems allow longer-term drying, even of previously damaged parts due to the retention of the drying potential. The creation of condensation is accepted because the capillary activity ensures fast and large-scale return of the moisture throughout the entire year. During the past decade, the group of capillary-active insulating materials has proven the most ‘application-safe’ for inside insulation.
The multi-dimensional calculation programs that have been available for some years and are now extremely well calibrated and are used to simulate the thermal and hygric behaviour of façade constructions prove this impressively.
These classic construction types and the functioning e of inside insulation have been available in two basic variants for decades.
The preferred system can be selected based on the quality of the existing wall. If the wall is even and strong, directly adhered composite boards are recommended, otherwise facing shells are usually the most inexpensive alternative.
Note:In principle, moisture penetration into the construction from outside must be minimised for vapour reducing or inhibiting inside insulation by means of functional driving rain protection. Most of the absorbed moisture is transported toward the inside wall surface especially in the cold winter months, because of a lack of drying potential for drying outwards e.g. low temperatures and the lower energy input because of the inside insulation. There is a risk of frost damage and mould infestation.
The so-called ‘capillary-active inside insulation systems’ were developed in the 1990s to bypass inherent system problems connected to certain vapour barriers or inhibitors. Pioneers were calcium silicate building materials that are still used as inside insulation today, outside their classic range of use in high-temperature areas. Today, there is an extensive range that includes a variety of materials and material combinations.
Capillary-active inside insulation work without inner vapour proof barriers or inhibitors. Therefore, in the cold season water vapour diffuses into the construction. At the point at which the dew point is reached, usually on the ‘outside’ of the inside insulation, parts of the water vapour condenses and condensation is created. Compared to water that penetrates from the façade side, there is a higher tolerance because, in contrast to vapour barrier systems, there is a higher drying potential toward the inside. Despite this, steps should also be taken to ensure functional driving rain protection to minimise the risk of frost damage, in particular on the outside of the brickwork.
The capillary-active inside insulation solves both described moisture problems - formation of condensation and outside moisture penetration - by increased fluid transport toward the room and accelerated evaporation. This helps avoid high local levels of moisture and limits the overall moisture in the construction.
Capillary-active inside insulation is a multifunctional system that combines various hygrothermal material properties. The coordinated interaction of moisture buffering, vapour and fluid water transport within the materials and/or between the system components is decisive for the operability and the ‘performance’ of the inside insulation. For this reason individual system components may not be replaced without consulting the manufacturers first.
We can only provide general advice here due to the large amount of different systems. It is always recommended following the processing instructions of the system suppliers (manufacturer information).
Moisture-saturated walls that have contact with the ground can be restored successfully by subsequent interior water proofing in combination with inside water proofing. Even if the currently valid version of the ENEV (2009) does not contain explicit and mandatory U-value requirements for the interior water proofing, the requirements for the hygienic minimum thermal protection need to be met at least in the case of heated cellar rooms. This usually means that an insulating layer needs to be installed, which makes the issue of where installation is required obsolete, and compliance with the requirements of the EnEV mandatory.
German energy saving efforts began in 1977 with the ordinance on thermal insulation (WSchV) that was aimed at saving energy in buildings.
Taking economic viability into account, the objective of the law is to ensure that all buildings are almost climate-neutral by the year 2050.
German energy conservation act (EnEV)
The EnEV is a summary of the ordinance on thermal insulation and the heating systems ordinance. It is an intelligent solution aimed at reducing the energy requirements (heat requirements and heat generation) of buildings. The EnEV refers to engineering standards and implements European legal specifications.
Buildings with normal inside temperatures are formulated using the annual primary energy needs and the transmission heat loss.
The transmission heat loss HT describes those heat losses through the building envelope (walls, windows, roof, lower building section etc.).
Fxi = Temperature correction factors acc. to table
Ui = Heat transition coefficient in [W/(m²K)]
Ai = Surfaces of the individual parts in [m²] for which the heat transition coefficient U and the temperature correction factor are constant
∆UWB = Heat bridge transmittance in [W/(m²*K)]. This takes heat losses as a result of heat bridges into account. In a simplified procedure, this is set to 0.05 W/(m²*K)
A = heat transferring enclosing surface in [m²]
The transmission heat loss HT of an element of the building envelope depends on the heat transition coefficient (U-value) of the associated part and its surface.
In the case of constructional measures connected to energetic restoration of external construction components of a building, for instance windows or façades and/or external walls, the EnEV 2009 prescribes that the companies need to document their work and issue a private document, a so-called a company declaration. This aims to ensure that the requirements of § 26a EnEV 2009 and the minimum technical requirements are met. There are corresponding forms online.
Over the past 100 years, the emissions of greenhouse gases, both from private households and also industrial operations, has increased significantly. This has led to an increase in the surface temperature of the earth of around 0.6 °C, which is causing natural disasters of previously unknown severity. Across the globe, scientific, business and political circles are working on saving the earth as a habitat. The Kyoto protocol is a first political step toward reducing greenhouse gas emissions.
The most important natural greenhouse gases include
In addition, artificially produced gases, like hydrochlorofluorocarbons (HCFC) and fully fluorinated and partly fluorinated hydrocarbons (CFC, HFC) also have a climate-relevant impact.
The global CO₂ emissions now total approx. 25 billion tonnes annually.
The CO₂ emissions per capita in the USA are approx. 20 tonnes annually, in Germany approx. 14 tonnes annually and in most development countries 0.5 - 3 tonnes annually.
Measures to reduce emissions
There is a new ordinance on thermal insulation that came into effect for new buildings and important modifications in January 1995. The goal of this ordinance is to reduce the energy consumption and the connected CO₂ emissions by 30 percent.
Heat transition coefficient
The heat transition coefficient states the heat flow in watts that crosses a structural component per m² and 1 Kelvin temperature difference.
U = Heat transition coefficient in [W/(m²K)]
RT = Thermal resistance in [(m²K)/W]
Rsi = Heat transfer resistance inside in [(m²K)/W]
Rse = Heat transfer resistance outside in [(m²K)/W]
Ri = Heat transmission resistance of the individual part layers in [(m²K)/W]
R = d/λ with d= Density of the part layer in [m] and λ = Calculated value of the thermal conductivity in [W/(m²*K)]
Heat transfer coefficient
The transport of heat from a part surface into the air and vice versa is called heat transfer.
The DIN V 4108-4 is used to calculate and/or determine the heat transfer coefficients.
The following table values apply for even surfaces, if there is no special information about the underlying conditions:
(the DIN EN ISO 6946 apply for uneven surfaces and special underlying conditions)
Overall heat transfer coefficient
The thermal resistance RT of an even part made of thermally homogeneous layers comprises the heat transfer resistance R and the heat transmission resistances Rsi and Rse.
RT= Rsi + d/Lambda + Rse in [m²K/W]
The following applies for several part layers:
RT= Rsi + Total Ri + Rse in [m²K/W]
Total Ri = Total of the heat transmission resistances of the part layers [m²*K/W]
The iQ-Lator is not only used to calculate U-values of one-dimensional surrounding constructions (external walls, also with contact with the ground, and roofs), it is also possible to carry out a hygrothermal assessment. This program can be used to generate various designs and the heat, and also provides estimates relating to the moisture transport by the construction. According to definition or modification of the construction or the climate condition, the fast calculation algorithm provides results that allow a realistic assessment of the construction.
The calculation scheme upon which the iQ-Later program is based is described and derived in detail in the following program: Nicolai, A., The generalised COND algorithm for the hygrothermal assessment of constructions, construction physics, WILEY-VCH publishing house, 2012, 34, 24-31.
The brief introduction here describes the principle of the procedure.