Overview Of Interior Insulation Systems

With internal insulation systems, buildings can be renovated in an energy-efficient way, where external insulation is impossible.

They still exist, the construction workers who categorically reject interior insulation. And that, although the advantages of every insulation measure are obvious: heating energy can be saved, comfort is noticeably increased and mold formation can be avoided (if carried out properly). The adversaries of internal insulation will now note that all of these advantages also apply to external insulation. And there is nothing to oppose it. However, external insulation is not possible or sensible on every building.

If buildings with facades that are listed or worth preserving are to be renovated in terms of energy efficiency, there is absolutely no alternative to interior insulation. However, external insulation may also be impossible for buildings that cannot be decorated with a neat facade, for example if the border is not sufficiently thick or if the required alignment of buildings is not sufficient. In other cases, there is not enough roof protrusion for external insulation or it can be produced.

In addition to the knockout criteria for facade insulation on the building side, there are also those based on disagreement between the building owners. Just think of an apartment building that is owned jointly. One owner sees the need for energy renovation, the other does not want to know about it. Then there is often no alternative to interior insulation for those wishing to renovate.

And then there are actually buildings in which an interior insulation is even more sensible than an exterior one. In buildings that are only used temporarily, such as churches, club houses or holiday homes, internal insulation enables heating up much faster, since the massive wall structure does not have to be heated.

Basics of building physics

The goal of any insulation measure is always an energetic improvement of the construction. The installed material and the material thickness result in the thermal resistance R as well as the thermal transmittance U. The thickness of the insulation material is determined depending on these values. The high requirements of the EnEV 2009 are not always realizable in existing buildings - and inside insulation is very often installed. Because the principle of “the thicker the better” does not always apply to interior insulation. With increasing insulation thickness, the building physics risks increase, so a maximum insulation thickness is not automatically the best solution. If the EnEV 2009 standards cannot be implemented, the goal is then the minimum thermal insulation according to DIN 4108-2. The minimum thermal insulation serves to prevent surface condensate (and thus mold formation) and is intended to ensure a hygienic indoor climate for the residents and to improve thermal comfort.

Uninsulated walls have a significantly lower temperature than the room air when the outside temperature is cool. This temperature difference is perceived as uncomfortable by humans because the body loses radiant heat to the cold surface. By installing an interior insulation, the temperature on the wall surface increases, the temperature difference between the air temperature in the room and the surface temperature of the wall is reduced to a low value. At the same time, drafts are avoided. As a result, the human body feels - even at a lower room air temperature! - greater comfort.

The classic facing shell is extremely flexible. It can also be used on uneven or non-stick surfaces, has good insulation performance and effectively improves the soundproofing effect of the solid wall.

Like all insulation measures, interior insulation changes the building physics of a building. For this reason, the building inventory must be carefully surveyed and the system must be precisely tailored to the situation. By installing an interior insulation system, the heat transfer from the inside through the wall to the outside is significantly reduced. The temperature gradient shifts in the wall. The masonry cools down more at low outside temperatures and the moisture in the masonry dries more slowly. Special attention must therefore be paid to moisture management. Driving rain, for example, places a high load on the construction. Functional driving rain protection (exterior plaster, water-repellent, diffusible coating, facing brick, clothing,…) is therefore essential for interior insulated walls. Ascending moisture must also be excluded. If necessary, appropriate measures must be taken to prevent rising damp before the internal insulation and the masonry must be dried out.

Since constructive thermal bridges lead to colder component surfaces and these in turn tend to form condensate, thermal bridges have to be eliminated. Integrating ceilings and interior walls should therefore be insulated with suitable detailed solutions (e.g. insulation wedge).

Severe moisture damage can result from the backflow of warm room air on the cold side (back) of the insulation and the resulting condensation. For this reason, the airtight design (e.g. through full-surface gluing of the insulation boards or other suitable measures) is one of the most important requirements when planning and executing internal insulation.

Which system?

After the decision for interior insulation has been made, it still has to be determined which system is to be used. There are now innumerable systems that differ in the type of insulation, processing, construction and especially in terms of their diffusion behavior. In the latter case, a distinction is made in principle between two variants: diffusion-tight or diffusion-restricted (or diffusion-inhibiting) and open-diffusion (or capillary-active) systems.

Diffusion-tight and diffusion-restricted systems

With the help of suitable materials and constructions, the penetration of moisture from the room side into the insulation material is prevented in diffusion-tight systems. Diffusion-proof plastic foams, for example, vapor barrier films or corresponding coating materials prevent the vapor diffusion flow into the wall. The diffusion resistance of the vapor barrier film must be large enough so that there is no condensation on the cold side of the insulation and thus a possible impairment of both the existing construction and the insulation material and its insulation effect. Such a design is in principle state of the art, but requires great care in the design, in particular in the film joints, in connections (windows, doors, floors, ceilings) and penetrations (pipes,Sockets, etc.). Internal insulation with vapor retarders have very good insulation properties despite the slim construction. If executed correctly, they offer reliable moisture protection from the inside and can thus also be used in rooms with high humidity (e.g. domestic bathrooms and kitchens).

In the case of vapor-tight insulation panels, no separate film is installed, but the insulation material itself is practically vapor-tight, e.g. B. foam glass or vacuum panels. The insulation boards are fully glued to the substrate and can be plastered, coated or clad on the room side. The risk of damage or design errors compared to systems with vapor control is lower with foam glass insulation, but usually higher with insulation with a vacuum panel. However, the use of expensive insulation materials such as vacuum insulation boards can still be useful, particularly when limiting insulation thicknesses, such as in window reveals, radiator niches or filigree building structures

Diffusion sealing

A disadvantage of diffusion-tight systems is that such a wall construction can hardly contribute to buffering fluctuations in indoor air humidity, which can only be compensated for in buildings without air conditioning systems by changing the window air. Consistent and correct ventilation is therefore essential with such internal insulation. In addition, the drying out of the existing structure inside, as would otherwise be possible in summer, is prevented, which is particularly necessary for brick and truss structures. Examples of vapor-tight interior insulation systems are vacuum insulation panels (e.g. weber.therm vacuum interior insulation system), foam glass (e.g. foam glass), hard foam panels with appropriate lamination (e.g. aluminum) or coating (e.g. Styrodur interior insulation system in connection with tile cladding) or insulation material (such as mineral wool, wood fiber boards, cellulose, hemp, flax, sheep's wool) with a tight vapor barrier.

Diffusion braking

Diffusion-braked systems are constructed similarly to diffusion-tight systems. A moisture-adaptive vapor barrier, which is used instead of a conventional one, has a variable diffusion resistance and adjusts to the surrounding relative humidity. In winter, when the risk of condensation increases, it prevents the penetration of moist room air into the construction, in summer it is open to diffusion and thus promotes the drying out of the component towards the room. It is not necessary to install a separate sealing level if the insulation material itself has a high diffusion resistance.

Diffusion inhibiting

Diffusion-inhibiting systems are safer to use than conventional constructions with a simple vapor barrier, since they still allow moisture to dry out of the construction. Examples of diffusion-inhibiting interior insulation are hard foam panels (e.g. weber.therm EPS interior insulation system, Styrodur interior insulation system), composite panels made of EPS and plasterboard (e.g. Knauf InTherm, Rigitherm 032), composite panels made of plasterboard and mineral wool if a vapor barrier is integrated (e.g. Rigitherm MW), wood wool -Multi-layer panels with integrated vapor barrier (e.g. Tektalan TK-DB from Knauf Insulation) or a facing shell with mineral wool insulation and moisture-variable vapor barrier.

The proportion of capillary-active interior insulation systems is increasing steadily. Thanks to their completely permeable structure, they can buffer moisture peaks in the room air.

Diffusion-open, capillary-active systems

The share of capillary-active systems in the insulation market has increased steadily in recent years. These systems do not require a vapor barrier or vapor barrier. Both the insulation material and the top coating are permeable to water vapor. Any moisture from the room air is absorbed, temporarily stored in the system and released back into the room when the room humidity is low. In this way, moisture peaks in the room air are buffered and the room climate is positively influenced. Since selective moisture in the area of thermal bridges can be practically ruled out in capillary-active interior insulation systems, these systems are also particularly suitable for mold remediation.

Capillary-active interior insulation systems have been on the market for some years and are recommended for use without internal vapor barriers. The two essential, but not the only materials are calcium silicate (e.g. systems from Calsitherm, epasit, Isotec, Getifix, Zero, …) and so-called mineral foams (e.g. systems from Alligator, Fema, Getifix, Heck, Keim, Knauf Perlite, quick-mix, redstone, Saint-Gobain Weber, Sto, Ytong multipor, Zero, …). These extremely porous materials have high capillary activity and good sorption capacity. However, they usually have a poorer insulation effect than vapor-retardant insulation systems. For this reason, great efforts have been made for years to produce thermal insulation materials with a high thermal insulation capacity and at the same time capillary conductivity. Different, highly specialized materials are now combined. In its iQ-Therm system, Remmers, for example, combines the application safety of proven capillary-active calcium silicate materials with the high thermal insulation performance of organic foams.

The core product is a highly insulating polyurethane foam panel with regular perforations perpendicular to the surface, which are filled with a highly capillary-active mineral mortar. The slabs are coupled to the interior wall surfaces with a coordinated mineral adhesive mortar and then plastered over with a porous mineral light mortar. Even with a 30 millimeter slim plate, this system achieves a very low lambda value (thermal conductivity) as well as a capillary moisture transport capability, which can remove all expected moisture contents of the construction.

In addition to the insulation materials mentioned, capillary-active interior insulation systems can also be achieved with wood fiber insulation boards (eg from Gutex, Pavatex, …).

The iQ-Therm system from Remmers combines the application safety of capillary-active systems with the high thermal insulation performance of organic foams: a perforated polyurethane foam board combined with mineral mortar makes it possible.

Alternatives to the plate

Wherever it would be too complicated, cumbersome or too costly to apply insulation boards, for example in the case of curves, in old buildings with uneven masonry, half-timbered beams or in corners that are difficult to access, other forms of insulation must be used. In addition to insulation fillings or blow-in insulation, insulation plasters are primarily used here. Insulating plasters are available with a purely mineral composition or with an organic lightweight aggregate. While the aggregate for the purely mineral insulating plasters is mostly volcanic rock perlite, extruded polystyrene (EPS) is generally used as an organic lightweight aggregate. Purely mineral insulating plasters are available from Getifix, Heck, Klimasan Perlit, quick-mix or Redstone, for example. EPS insulating plasters include dracholin, stern, quick-mix, sakret, swivel,Saint-Gobain Weber, … in the program.

With insulating plasters, unevenness in the subsurface can be easily compensated. When used as internal insulation, this has the advantage that there are no cavities in which condensate can form or accumulate. Insulating plasters also adapt to any geometric shape and the appearance of historical plaster surfaces can also be reproduced with them. The fact that insulating plasters are rarely used is due to their high thermal conductivity compared to other insulating materials. Insulating plasters with organic additives have a thermal conductivity between 0.065 and 0.080 W / mK, with those with inorganic additives it is even between 0.075 and 0.10 W / mK. This means that relatively high layer thicknesses must be applied in order to achieve the desired or prescribed insulation effect.

Airgel insulation boards have extremely low thermal conductivity values because they have the smallest pores.

High-tech for the wall

With a new insulating plaster developed in Switzerland, these disadvantages are a thing of the past (see also Malerblatt 3/2013, page 52). The Swiss materials research institute Empa and the Swiss plaster manufacturer Fixit AG have jointly developed a plaster based on airgel that insulates more than twice as well as today's insulating plaster. Airgel consists of around five percent silicate, the rest is air. The material was already used in the 1960s to isolate spacesuits. Before the material in a plaster was suitable for everyday use, the Empa building physicist Thomas Stahl and his colleague Severin Hartmeier from Fixit had to solve some technical problems.

Airgel beads are extremely light and can be easily crumbled between your fingers. After briefly rubbing, only a fine powder remains of the beads. Before the plaster was really suitable for use in plastering machines, it took a number of tests, both in the laboratory and in outdoor exposure. For Thomas Stahl, the benefits of insulating plaster for internal insulation are obvious: “An interior lining made of insulating plaster can be applied much faster. The plaster also lies directly on the masonry and leaves no gaps in which moisture can condense.”The endurance of Thomas Stahl and Severin Hartmeier was finally rewarded. The plaster suitable for construction sites has been available in Switzerland since the beginning of 2013, and should also be available in Germany in 2014.

But the high-tech material airgel has not only revolutionized interior insulation in the form of a plaster. Sto launched an interior insulation board in autumn 2011, which is also based on airgel technology. This technology enables the production of insulation materials with microscopic, open-pore structures. The cavities are so small that the air molecules contained in them are severely restricted in their thermally conductive mobility. This results in the extremely low thermal conductivity of the innovative insulation boards of 0.016W / mK. Conversely, this means that the panels have an extremely high insulation effect and that even extremely thin panels (depending on the wall designer between 15 and 40 millimeters) can meet the legal requirements. The usable space is hardly affected by such internal insulation. But even in combination with proven insulation systems, the new interior insulation can show its advantages, for example in narrow soffits or radiator niches, which can also be insulated very efficiently.

Growing market

Internal insulation is by no means outdated and, if carried out professionally and carefully, is just as risky. Innovative systems not only make interior insulation safer but also more efficient. Above all, however, interior insulation is likely to be a future market. Dr. Wolfgang Setzler, managing director of the ETICS trade association, which also includes the leading manufacturers of interior insulation systems, estimates that around 300 million square meters of wall space are available for interior insulation in Germany alone. But that's not all. Dr. Setzler sees another aspect, which is why the painter is well advised to include interior insulation in his range of products: "The renovation of interior spaces and thus also the interior insulation will be a growing market in the future, because renovations will take place four times as often as outside." And where else anyway is being renovated,internal insulation is particularly economical. In Germany alone, around 300 square meters of space are available for interior insulation.

Composite panels consist of a plasterboard on which an insulation material is laminated. In addition to EPS, as here, mineral wool can also be used.

Susanne Sachsenmaier-Wahl Photos: Knauf, Redstone, Remmers, Sto Source: Malerblatt 11/2013