EP1525357A1

EP1525357A1 - Wall construction and component for the same

Info

Publication number: EP1525357A1
Application number: EP02751048A
Authority: EP
Inventors: Christoph Schwan
Original assignee: Urbigkeit Stefan
Current assignee: Urbigkeit Stefan
Priority date: 2002-06-19
Filing date: 2002-06-19
Publication date: 2005-04-27
Anticipated expiration: 2022-06-19
Also published as: EP1525357B1; DK1525357T3; CA2489925C; AU2002368033A1; WO2004001148A1; ES2343238T3; ATE463626T1; US20050257467A1; US8806824B2; CA2489925A1; DE50214348D1

Abstract

The present invention relates to a wall construction for an exterior brick wall of a building, comprising a rear brickwork and a front brickwork, which is characterized in that the front brickwork (2) is made at least in part of constructional elements (11), particularly bricks, building blocks and the like, which at their side facing the rear brickwork (5) are designed to be reflective for heat radiation. The invention further relates to a constructional element, in particular a brick, a building block or the like, for use in the production of the front brickwork of such a wall construction which on the side which in the walled-in state faces inwardly, is provided with a layer (8) which is reflective for heat radiation.

Description

Wall structure and component therefor

The present invention relates to a wall structure for a brick outer wall of a building with a rear masonry and a facing shell and a component for such a wall structure.

For better understanding of the present invention, the attached FIGS. 2 to 7 show cross sections through previously common masonry and also through types of masonry with reinforced insulation layers.

The wall cross-section according to FIG. 2 illustrates a single-layer masonry made of conventional bricks 12, for example bricks or sand-lime bricks. The masonry has a regular thickness of 36.5 cm, and it is provided with plaster 1 (external plaster) or 6 (internal plaster) on both sides. The wall structure combines load-bearing and facade functions in one. As far as building physics are concerned, the thawing zone is located in the interior of the wall cross-section depending on the indoor climate, the working heating system and the weather conditions. There is formation of condensation and measurable moisture penetration of the building material with a corresponding increase in the coefficient of thermal conductivity. The water that has become drippable migrates capillary to the outer wall and is dried there more or less quickly depending on the wind speed and relative humidity of the outside air. Under unfavorable conditions, the thawing zone occurs on the inside of the wall or immediately behind it, so that condensation water also forms on the inside of the room, combined with all side effects such as the formation of black mold. Such structural damage almost always occurs when heat-insulating materials, including furniture or pictures, are attached to the inner surfaces of such outer walls, since they shift the thawing zone inwards. In the case of the homogeneous construction, the thermal insulation capacity depends on the masonry thickness and the moisture level. A normal wall of this type made of solid bricks does not achieve the required insulating ability, so that the brick and tile industry has long been bringing bricks with a high porosity onto the market. Masonry of this type achieves the required minimum insulation values, however at the expense of the storage capacity.

The wall construction according to FIG. 2 absorbs the incident solar energy well. The sun's energy is even transmitted particularly well in the moist condensation zones. In this regard, it is a good and proven wall construction, but it will no longer meet the requirements of the future Energy Saving Ordinance (EnEV).

The wall structure shown in FIG. 3 corresponds to that of FIG. 2 with the exception that it is provided on the outside with a generally approximately 80 mm thick insulation layer 4 which is mechanically attached to the masonry. The exterior plaster 1 is, in particular, a synthetic resin plaster that is reinforced in different ways, for example with PVC fabric. Since the insulating effect of this construction is mainly generated by the insulating material, the wall thickness is reduced to the statically required dimension of 24 cm.

3, static and insulating functions are distributed over two different building material layers. The thawing zone in this construction is usually in the front third of the insulation layer 4. The water that has dripped there is directed capillary to the outer surface of the insulation layer, where it is dried by the air flowing past. The external insulation causes a delay in the passage of thermal energy the consequence that the load-bearing masonry cross-section remains in a significantly higher energy state.

Irradiating solar energy strikes the insulation layer 4 almost immediately, where it is prevented from entering the wall construction. The outside thin, about 5 mm thick plaster layer 1 is heated, but cools down very quickly due to its low absolute heat storage capacity. During irradiation phases, the heating by irradiation also promotes the drying of the insulation layer 4 to a desired extent. This construction is very disadvantageous in the case of dark coloring which strongly absorbs solar energy, since the then considerable temperature stresses can lead to the formation of cracks in the plaster layer 1. The manufacturers of these insulation systems therefore rightly advise against dark coloring. Overall, this wall construction is almost completely shielded from the radiation gains.

Recently, structural damage has become known in this construction, which is due to the strong cooling of the surfaces by radiation of thermal energy, with only a small amount of thermal energy being conducted to the surface due to the insulating layer. The strongly cooled surfaces become a condensation level in relation to the outside air. They are therefore wetted by condensation or misted with frost. The consequences are algae growth on the surfaces and wetting of the insulation material.

In summary, it should be noted that the wall structure according to FIG. 3 is a proven wall construction, but in which the solar radiation energy is shielded in a disadvantageous manner. Corresponding buildings are heated exclusively via the heating system, which is unfavorable in terms of energy.

The wall construction according to FIG. 4 corresponds to that of FIG. 3, but according to the new EnEV with a considerably reinforced insulation layer 4, the recommended one The minimum insulation thickness is 20 cm. The technical function is essentially the same as in FIG. 3. However, static problems can arise due to considerable additional weights in the insulation layer 4 and significant cantilever moments in its anchoring.

In terms of building physics, a significant reduction in the heat transfer is achieved by reinforcing the insulation layer 4. The arrangement according to FIG. 4 is, however, at considerable risk of damage, since the insulation layer thickness lying in front of the thaw zone can no longer be overcome by the capillary pressure. With polystyrene insulation materials, the capillary conductivity is very low anyway due to the material structure. In the case of fibrous insulating materials, the capillary line is essentially only possible parallel to the outer wall surface due to the structure. This construction is therefore only possible when using vapor-tight insulation materials, for example double-layer foam glass panels using the adhesive process with additional mechanical anchoring. The wet zones fail as an insulation zone. The developing process leads to the complete dampening of the insulation material. Such a construction is only conceivable if effective vapor barriers are arranged in front of the insulation material. However, such vapor barriers prevent water vapor diffusion through the wall, which is commonly understood to mean the "breathing" of a wall.

Even in connection with the indispensable vapor barriers, the wall structure according to FIG. 4 is questionable even in a humid, warm summer climate with a rotated temperature and vapor pressure gradient, since condensation will form on the inside of the insulation material. The vapor barrier located there is then - because it is physically external - a source of structural damage.

As far as solar energy is concerned, those already mentioned in the arrangement of FIG. 3 occur because of the increased insulation thicknesses adverse effects intensified. Additional structural damage can result from the fact that - as long as the insulation layer 4 is not yet completely wet - the outer layer 1 cools down far below the outside air temperature and thus becomes a dew zone for the winter outside air. There is formation of frost and subsequent moistening of the outer layer. With the onset of the vegetation phase in early spring, moss and algae are formed on the moistened areas with subsequent destruction of the outer skin. Overall, the solution according to FIG. 4 is to be assessed as a faulty construction which is liable to damage the building structure and at considerable cost, which, despite the provisions of the EnEV leading to it, must be strongly discouraged.

Fig. 5 shows another traditional wall structure, consisting of a load-bearing masonry 5 made of bricks or sand-lime bricks or other masonry materials, including concrete. The masonry 5 is usually about 24 cm thick, and it is provided with plaster 6 on the inside of the room. An approximately 5 cm thick flowing air layer 3 is arranged in front of this wall 5. The weather skin consists, as a rule, of approximately 11.5 cm thick exposed masonry 2 made of facing bricks or other suitable facing material. The rear masonry 5 forms the outer supporting wall of the building in question with predominantly static functions. The flowing air layer 3 has the task of drying condensation in the front wall cross section, which reaches the outer surface of the wall capillary. The facing layer 2 serves as a facade and weather skin.

As far as building physics is concerned, water vapor diffuses from the inside of the room into the cross-section of the supporting wall. This water vapor changes due to condensation in the thawing zone into drippable water, whereby the heat of condensation arising in this way shifts the dew point slightly towards the outer wall zone. From there, the water migrates capillary outside to the air layer 3 and dries there. Water migrating inward turns into water vapor.

In terms of thermal insulation, the wall structure according to FIG. 5, assuming the use of conventional heating systems of the applicable thermal insulation ordinance, is no longer sufficient. Only the plastered inner shell 5 is included in the heat transfer calculation. The air layer 3 and the facing wall 2 are already considered to be the outer zone. The radiation energy from the sun is absorbed by the facing wall 2, so that it will also warm up in winter under favorable conditions. However, the flowing air layer 3 dissipates part of the thermal energy. Heat conduction by convection between the outer shell 2 and the inner wall 5 only takes place to an insignificant extent. However, part of the incident solar energy is transmitted from the outer shell 2 to the inner wall 5 by radiation and thus reduces the temperature gradient between the inner surface of the room and the outer surface of the supporting wall layer. The heat storage capacity of this wall structure is moderately good with regard to the energy gains from the sun's radiation.

In principle, the arrangement of FIG. 5 is a good wall construction, which is preferably used in coastal areas in northern Germany. However, it does not meet the minimum thermal insulation requirements and is completely inadmissible under the new EnEV.

6 shows a wall construction that has become widespread in the meantime, in which, for example, a 24 cm thick load-bearing inner wall (rear masonry) 5 with a facing insulation layer 4, a rear ventilation zone 3 and, for example, 11.5 cm thick weather skin made of facing stones 2 are provided. In terms of building physics, this wall construction is to be assessed roughly like the construction according to FIG. 3. The facing layer 2 is not assessed from a thermal point of view. she can can be replaced by any other type of front and rear-ventilated facade. With regard to solar radiation, there are only minimal differences to the wall structure according to Fig. 3. It is a good wall construction with sufficient heat storage and sufficient insulation, which, however, will be assessed as insufficient according to the future EnEV.

The rear masonry 5 essentially takes on static tasks. Since a 24 cm thick brick or sand-lime brick wall does not offer sufficient thermal protection, the rear masonry 5 of the arrangement according to FIG. 6 must have an at least 60 mm thick insulation layer 4 on its side facing the facing wall shell 2 in order to meet the requirements of DIN 4108. Between the insulation layer 4 and the inside of the facing shell 2 there is the air gap 3 in the illustrated example, about 50 mm wide, for the rear ventilation of the facing wall 2. An interior wall plaster is again indicated at 6.

Such a conventional wall structure is based on the standardized requirements for thermal insulation in building construction. The standard (DIN 4108) is based on the idea of a "heat flow", and the standardized insulation technology therefore tries to increase the insulation capacity of a wall structure by installing materials with low thermal conductivity. This works quite well even if the insulation materials are dimensioned correctly A change in meaning has occurred in the course of the development of DIN 4108, which was initially only intended to prevent condensation damage. For years, the aim of the standard has been to save energy more and more. Consequently, the minimum thicknesses of the insulation layers have been continuously increased over the years ,

The new standard currently being prepared (the EnEV already mentioned above), as shown in FIG. 7, sees 20 to 30 cm thick insulation layers 4 in _.

Connection with airtight buildings (without ventilation through windows) and the installation of air conditioning.

It can be objected to the conventional wall structure, especially for thicker insulation layers, that the standardized calculations on the water vapor passage (diffusion) show uniformly that the thaw zone, i.e. the area in which diffusing water vapor becomes drippable water, is usually in the front third of the Insulating material sets. There is therefore a dampening of the insulating material which reduces the insulating effect. With the usual insulation thicknesses of 6 to 10 cm, the dew point is 2 to 3 cm in front of the outer surface. The remaining distance from the water can be covered by capillary conduction. In this wall construction, rear ventilation is arranged to remove the moisture. For this, an air layer at least 50 mm thick must be provided, which must be designed in such a way that air, like in a fireplace, continuously brushes the insulation layer and thus excess moisture, which has migrated to the surface of the insulation layer by capillary action, is removed by the air flow and transported outdoors , For this, the arrangement of supply and exhaust air openings in the facing shell is necessary. However, their drying effect is only guaranteed if the air has a relative humidity of less than 70% and all areas of the insulation surface are also coated.

For design reasons, full drying of the insulation is only possible in rare cases. Mostly there are unexplained flow and buoyancy conditions. In particular, the air throughput is interrupted by window openings and similar structures, so that there is permanent moisture penetration of the insulation material in the affected zones. A considerable part of the thermal energy is lost in this construction due to radiation against the facing wall, since the usual insulation materials only have a minor effect on heat radiation. The one radiated into the facing wall Thermal energy is also removed by the air flowing through the air gap 3.

If one looks at the conventional construction from the point of view of the radiation gain from sunlight in the heating season, the installed insulation material turns out to be very disadvantageous because it hinders the flow of energy from outside to inside. In addition, the flowing air layer extracts the radiated energy by convection of the facing wall before it can benefit the backing.

Another problem is that the insulating material must be applied with great care, because ventilation on the side of the supporting wall prevents the insulating effect of the insulating material. The care of the manual work required here - because the construction is covered - cannot be checked.

Even with the arrangement according to FIG. 6, the large wall thickness of 48 cm is also very disadvantageous with regard to the economy of a building. (Living space loss). Another disadvantage is the very complex connection details for masonry openings. The rear ventilation in the area of masonry openings is difficult to solve. There is also a risk of pests colonizing in the warm, humid environment between the brickwork and the bulkhead, particularly through the air intake openings at the base of the brickwork shell.

With thicker insulation layers of 20 to 30 cm thickness (Fig. 7), as will be required in the future, the layer thickness in front of the thawing zone is already 8 to 10 cm thick. This distance can no longer be overcome by the water. The water thus remains in the insulation material, where it soaks through the area of the thawing zone. The soaked area becomes ineffective as an insulation layer. It turns into the opposite of thermal insulation, namely a zone of increased heat conduction. With the self-rocking other The process thaws the dew zone further inwards and ultimately reaches the wall cross-section. The masonry is wetted, which is a source of considerable structural damage. As soon as a more or less closed water layer has formed within the insulation material, this acts as a vapor barrier, which leads to the standstill of the water vapor diffusion that was still active until then. In addition, the thickness of the brick wall construction leads to considerable loss of living space and usable space due to the then considerably enlarged insulation layer, which in many cases makes such a construction uneconomical. It is unclear whether an air layer thickness of 5 cm is still sufficient with this construction.

It should also be borne in mind that insulation materials cannot significantly store thermal energy. The necessary heat capacity is lacking. Experience has shown that the damage described above does not yet occur with insulation layers between 8 and 12 cm thick. However, the still effective insulation effect is noticeable in the form that the energy deficit caused by radiation and insufficient heat supply leads to a lowering of the surface temperature significantly below the temperature of the ambient air. The surface of the insulation layer thus becomes a condensation surface in relation to the outside air. On cold and cloudless winter nights, frost forms and the surface of the walls becomes damp. Moss and algae formation are the inevitable result. In the specialist literature, such damage reports have recently been piling up - with increasing insulation thicknesses.

In addition, people need a sufficient supply of fresh air to keep them healthy and to maintain their health. According to the rules of construction technology, this is achieved by a regular air change once an hour. Due to accidental leaks in the window area, this air change was previously more or less guaranteed. In the case of an airtight building, as is the case with the current draft speaker in Federal Housing Ministry is required (EnEV 2000), this is only conceivable in connection with air conditioning systems. Such systems work with a fresh air admixture of 20 vol.% / Hour, so that the fresh air supply is reduced five times. The oxygen content of the room air is therefore correspondingly low. Recent research shows that such air-conditioned rooms can have a dramatic increase in radon levels. There are also surveys that residents of such rooms suffer above-average from respiratory diseases.

Attempting to save energy through thicker layers of insulation in connection with an airtight closure of the building is therefore obviously associated with considerable deterioration. The arrangement according to FIG. 7 is therefore to be rejected. It is a wall structure that is unlikely to be implemented, although it fully meets the requirements of the future EnEV. A wall thickness of 62 cm (minimum thickness) will not be accepted by an economically thinking client. There are also almost insoluble problems in the event of a fire if the insulation material ignites. Execution of the insulation layer from foam glass is out of the question for reasons of cost. Overall, this solution represents an uneconomical incorrect construction with a high susceptibility to structural damage.

It is an object of the present invention to provide a wall structure for brick outer walls of the building, which not only provides adequate building thermal insulation at a relatively low outside temperature, but also promotes exogenous energy input as well as structural damage due to wetting of the wall structure due to comparatively low space requirements Reliably counteracts condensation.

This task is based on a wall structure for a brick outer building wall with a backing and a facing shell solved according to the invention in that the facing shell is at least partially constructed from structural elements, in particular bricks, building blocks or the like, which are designed to reflect heat radiation only on their side facing the rear masonry.

A component, in particular brick, building block or the like, for use in the production of the facing shell of such a wall structure is provided according to the invention only on its side facing inwards in the walled-in state with a layer reflecting heat radiation.

The invention is based on the knowledge that the conventional wall structure shown above only takes into account the problem of heat conduction within the building materials, because the “k numbers” (heat coefficients in W / (m ² × ° K) contained in the standard only say something The passage of heat energy in the building material.However, energy losses do not arise from energy sales within the building materials, but solely from the fact that heat energy is released into the environment.How the energy transfer from an outer wall to the environment cannot be deduced from the k-numbers and is not the subject of the relevant standards.

It has now been found that the loss of thermal energy to the environment occurs predominantly (approximately 85%) through the emission of electromagnetic waves in the infrared range. The much smaller part of the heat transfer into the environment takes place through convection, i.e. through direct transfer of the kinetic energy contained in the particles to passing air particles. The extent of this thermal energy transfer fluctuates depending on the wind speeds and the moisture status of the wall surfaces and the air flowing past.

The heat transfer through building materials into the outer layers can be tolerated if the energy radiated there can be returned to the building. The latter is done in the present case by the invention Formation of the facing wall on the inside. Since electromagnetic waves in the infrared range basically behave like visible light, they can also be reflected like this.

One might think of incorporating reflective layers in the form of high-gloss aluminum foils or commercially available aluminum-vaporized plastic foils into a brick, multi-layer wall structure. However, the installation of such foils is generally not possible because of construction problems, but also because such materials would be highly undesirable diffusion barriers.

According to the invention, on the other hand, components of the facing shell itself, in particular brick or sand-lime brick facing stones, but also bricks of the facing shell provided for subsequent plastering or other materials used for producing facing shells in masonry technology, are designed to reflect heat radiation on their side facing the rear masonry, preferably by them with a reflective layer, e.g. made of evaporated aluminum or other materials with a reflective effect. Components of this type (bricks) can be bricked up in the usual way, water vapor diffusion being ensured via the joints, in particular mortar joints, of the facing shell.

In the wall structure according to the invention, the thermal energy coming from the inside and emitted to the outside is largely reflected in the heated masonry cross section. This works with rear-ventilated facing shells as well as with mortared facing shells, because the backfilling mortar hardly hinders the reflective effect due to its porosity. However, the rear-ventilated facing is preferable. Additional layers of insulation become unnecessary. As far as they are to be used, they can be kept very weak. Experience has shown that driving rain in full-wall masonry penetrates to a depth of around 60 mm. In this case, the driving rain does not reach the reflective layer in the case of a facing wall shell that has a thickness of more than 60 mm, so that it therefore has no influence on the drying behavior of the facing wall shell.

In the case of poorly crafted work, driving rain can penetrate the facing shell through cavities in the mortar joints. In extreme cases, water flows down on the inside of the facing. However, such water will not reach the rear wall cross section behind it, which is preferably separated from the front wall shell by an air layer. With conventional and proven constructions, the only way - as is already the case - is to ensure that this water, for example at the base of the wall, can flow out again.

The gains in radiation from sunlight are also remarkable in winter. These are also not significantly hampered by the heat radiation reflecting design of structural elements of the facing wall, for example by vapor deposition of an aluminum layer. A reflection of the radiated energy back into the facing shell is not possible because no light waves can develop between the reflecting layer and the backing. This would require at least the wavelength of infrared light. On the other hand, the radiation of the thermal energy can at best be slightly impeded by the fact that bright metallic surfaces are bad emitters.

The use of wall material that is only reflective on the inside for the facing wall leads to adequate thermal insulation even in conventional masonry construction. This means that this proven construction method, which leads to very satisfactory architectures, can be retained in the future stay. This is undoubtedly of considerable economic importance for the brick and sand-lime brick industry.

Embodiments of the invention are explained in more detail below with reference to the accompanying drawings. The drawing shows:

1 shows a cross section through a wall structure according to the invention,

Fig. 2 to 6 cross sections for different versions of conventional wall structure, and

Fig. 7 shows a cross section through a wall structure corresponding to Fig. 6, but which is provided with a thicker insulation layer in view of the future Energy Saving Ordinance (EnEV).

The exemplary embodiment shown in FIG. 1 for the novel wall structure of a brick outer building wall has a load-bearing rear masonry 5 made of conventional bricks, which are usually about 24 cm thick. In principle, however, weaker reinforced concrete walls and the like can also be considered. Analogous to the conventional wall structure according to FIG. 5, the wall structure also includes a facing shell 2, which in the illustrated embodiment is approximately 11.5 cm thick. An insulation layer corresponding to insulation layer 4 of the known arrangements according to FIGS. 3, 4, 6 and 7 is dispensed with. There are air chambers 9 without supply and exhaust air openings between the outside of the rear masonry 5 and the inside of the facing wall 2. In the exemplary embodiment shown, the air chambers 9 are approximately 30 mm thick and are separated from one another by horizontally extending webs 10 bridging the space between the facing wall shell 2 and the rear masonry 5 in order to suppress air circulation. A generally standing air layer is formed in the air chambers 9. This standing layer of air acts as a very good one , ,

Insulation layer, and it replaces the usual insulation materials in this area. An interior wall plaster is again indicated at 6.

The facing shell 2 is constructed from structural elements 11, which can preferably be brick or sand-lime brick facing stones, but can also be natural and artificial stone slabs, fiber cement slabs, plastic panels or the like. Bearing and butt joints, especially mortar joints, are indicated at 7. The components 11 of the facing wall shell 2 are coated with heat radiation reflecting only on their inside, for example provided with a reflective layer 8 made of evaporated aluminum.

The entire masonry according to Fig. 1 is bricked in the usual way. Here, the rear wall shell 5 is first erected. The facing shell 2 is created in a second operation from an external scaffold. In order to avoid contamination of the high-gloss reflective layers 8, a soft plate, for example a stone wool plate, is to be maintained, preferably with masonry of the facing stones in the space between the facing wall 2 and the facing wall shell 5, which is to be hoisted in accordance with the progress of the work.

The present wall construction is based on the knowledge that the dissipation of thermal energy from a wall takes place predominantly through radiation in the infrared range of the electromagnetic wave spectrum, that this radiation can be reflected by glossy layers, preferably metal layers, that air is completely transparent to radiation and also that standing or hardly moved Air layers are by far the best insulation against the energy transfer from particle to particle. Furthermore, this wall structure takes into account that electromagnetic waves can only develop in areas with the minimum length of a light wave, but not between densely interconnected substances like that Inside of the components 11 of the facing wall and the reflective layer 8 applied there.

The standing air layer formed in the air chambers 9 - rear ventilation is not necessary here - thus acts as a highly effective insulation layer. According to the standard, this air layer already has a thermal resistance of 0.17 (m ² x K / W). Since a standing layer of air almost completely prevents heat conduction due to the transfer of kinetic heat energy due to its small mass, the wall construction shown is approximately "energy-tight" with regard to this process. In the case of a standing air layer, the facing shell 2 also acts as heat-insulating and heat-storing.

The thermal energy introduced into the outer wall of the building by the space heating reaches the outside of the load-bearing inner wall 5. The energy arriving there is radiated from there in accordance with the radiation laws. It must be weighted here that, depending on the energy status of the wall construction, at least 85% of the energy is given off by heat radiation. The energy radiated on the outside of the rear masonry 5 strikes the reflection layer 8 and is therefore reflected back according to the laws of reflection. According to available studies, a high-gloss aluminum layer is able to reflect about 80% of the radiated energy. This portion of the thermal energy is therefore completely preserved in the masonry cross-section.

A smaller proportion of the inside of the facing wall layer 2, namely the proportion of the joints 7, is not mirrored. There, approximately 10-15% of the energy radiated on the outside of the rear masonry 5 can penetrate into the facing wall shell 2. However, this low energy input into the facing shell is desirable since the outer shell 2 should not cool below the temperature of the outside air. There it would be one Defrosting zone in relation to the outside air with the disadvantageous consequences analogous to the phenomena according to the wall structure in Fig. 4.This energy input into the outer shell 2 is also harmless because with this wall structure the front wall shell can also be included as an insulating layer due to the standing air layer. This property of the facing wall thus sufficiently compensates for the initial energy loss via the wall joints 7. On the other hand, the vapor-permeable wall joints 7 of the outer shell 2 take on the necessary moisture balance between the inner wall 5, the air layer 9 and the facing wall 2. The entire wall structure is therefore open to diffusion. This is of great importance because the thawing zone of this wall construction is either in the standing air layer or in the facing wall, depending on the weather and heating conditions.

Since the almost complete reluctance of the heat radiation energy coming from the inside in connection with the standing air layer and because of the technical cooperation of the outer shell gives a considerable improvement in the insulating ability of this layer structure, the use of insulating layers, such as the insulating layers 4 in the arrangements of the Figures 2, 4, 6 and 7, are completely dispensed with. In addition to the reduction in wall thickness, which is accompanied by a considerable gain in living and usable space, this leads to a considerable saving in construction costs in the value of the insulation materials saved (currently around EUR 13 to DM 30 / m ² wall area). This saving is significantly higher than the higher costs for a reflective coating on the inside of facing stone 2. It should be noted that the air layer between the inner and outer shell of the wall structure can be arranged upright because an insulation material is not built into this wall structure and therefore it too there is no need for ventilation and drying of an insulating material.

A calculation of the heat transfer coefficient (k-number) for the existing wall structure without taking into account the described Reflection effect results in the calculation method of DIN 4108 a value of 0.876 W / (m ² x K). This value is already considerably below the value of 1.56 W / (m ² x K) required by the applicable thermal insulation regulation, namely approximately half the permissible value. If the heat recovery gain from the reflective layer is introduced into this calculation and dimensioned carefully as a factor of 0.40, the so-called “k number” is reduced to a value of

0.40 x 0.876 = 0.350 W / (m ² x K).

This value corresponds exactly to the maximum requirement of the new EnEV. It should be emphasized that this excellent result is achieved without the use of insulating materials.

Finally, the present construction is considerably more advantageous with regard to the radiation gains from sunlight, since these can act on the rear masonry 5 essentially unhindered via the outer shell 2 on the way of the radiation from the outer shell 2 through the air layer 3.

The radiation energy from the sunlight primarily heats the facing wall shell 2, so that it will heat up well above the ambient air temperature even on clear winter sunny days. With the usual wall building materials for facing shells, this is uniformly warmed after about 2 hours of radiation. The facing wall 2 in turn now - to a small extent by convection in the now somewhat more turbulent air layer in the air chambers 9, for the most part by radiation - emits the collected solar energy onto the rear masonry 5. The following effects are to be considered: The air layer in the air chambers 9 does not represent an obstacle to the passage of the heat radiation. It is therefore irrelevant to the radiation process.

Likewise, the reflection layer 8 does not hinder the radiation, since it is attached tightly to the back of the facing stones and thus reflection into the facing shell 2 is impossible. However, it must be taken into account that the reflection layer 8 is generally a relatively poor emitter, so that the radiation process to the backing 5 is somewhat delayed. However, this effect is desirable because it harmonizes with the very good heat capacity of masonry.

A favorable and compensating effect here is that when the facing wall 2 is heated, condensation water deposited there evaporates in the air layer of the air chambers 9, as a result of which the thermal conductivity of this air layer in this phase has an effect from the moisture adiabatic behavior of the air in such a way that it improves As dry air, it transports energy from the outside to the inside.

The wall construction according to the invention represents a revolution in conventional masonry construction, since for the first time physical effects and events are translated into a construction in which the correct conclusions are drawn in particular that the major part of the energy loss from a wall is not due to the thermal conductivity of the building materials is determined, but by the emission of electromagnetic waves in the infrared range.

With an additional effort that can be described as minimal, which essentially consists in equipping the facing masonry materials with a reflective layer, while avoiding expensive insulation materials, the tried and tested conventional masonry construction can be continued more economically than before, despite the restrictive provisions of the future EnEV, and new ones Be brought into bloom. Without this invention, the EnEV would have been the "end" for this design.

A possible variant of the facade cladding with mirrored facing stones shown in Fig. 1 is the use of thin-walled facade panels, e.g. from ETERNIT AG, which are equipped with reflective material on the back. The first partial result of a first series of tests, which was carried out on a north wall, was that this structure corresponds to an equivalent insulation layer thickness of 30 mm polystyrene hard foam and therefore the minimum thermal insulation is achieved, with condensation damage being reliably avoided.

The decisive factor for this wall construction is less the reduction of transmission heat losses than the improvement of the energy balance in the course of the heating period, which is largely determined by the fact that not only heat energy is retained in the building, but also that heat energy arriving from the outside enters the envelope surfaces is hindered as little as possible. Such effects naturally occur only slightly on sun-drenched areas of a building, i.e. on the east, south and west sides, and only slightly on the north sides.

In the case of a thin-walled construction, which essentially consists of reflective coated facade panels, which are attached to the outer surface of the wall by means of a suitable substructure and with joint sealing tapes in such a way that they can be regarded as "not ventilated", the following physical effects occur:

1) Reflection of heat radiation:

Depending on the respective reflectance of the coating, radiant heat energy originating from the inside is used in the radiation exchange standing areas with different radiation coefficients in the building.

2) Insulation by standing air layer:

The standing air layer hinders the transfer of energy from the inside to the outside due to its low thermal conductivity. The measurements showed good agreement with the thermal conductivities according to DIN 4108-6.

3) Heat recovery through condensation:

The standing layer of air adjusts to a high proportion of water vapor. The relative humidity within the air layer is 90% and more in winter. On the surfaces that are not affected by solar radiation at times, on the north sides even always, water vapor condensation occurs on the reflective inner layers, in which the heat of condensation, i.e. the amount of energy, is used to change the state of matter from liquid to gaseous at constant material temperature and in tables for water with 627 Wh / kg is released - similar to other heat recovery systems in the ventilation system area - and thus the temperature level in the air gap is raised. As a result, the temperature gradient that linearly determines the passage of energy decreases accordingly.

4) Effects of sun exposure:

Depending on the time of year and the degree of coverage, more or less large amounts of irradiated energy can be recorded on sun-drenched areas, which lead to the facade panels heating up beyond the temperature of the outside air. Surface temperatures of over 40 ° C and outside air temperatures around 0 ° C were measured in March. It must therefore be considered with regard to the energy balance, the extent of heat transfer from the outside in to the wall structure.

When comparing coated and uncoated facade panels, it must be taken into account that depending on the surface color, the facade panel is heated by absorption of the non-reflected light. This creates a temperature gradient between the facade panel and the air layers on both sides. Compared to the environment, the energy input is partly convectively, partly reduced by radiation. This loss of energy has to be accepted. Since even heating of the entire material can be assumed in the case of thin facade panels, there is also a desired internal energy transfer in order to improve the energy balance. This depends partly on the temperature gradient between the plate and the wall construction, but also on the radiation processes between the plate and the wall.

Here, reflectively coated panels differ from uncoated material. The reflective layer is a bad radiator, so that thermal energy is poorly broken down by radiation. The result is a higher heating of the coated material than is the case with the uncoated material. As a result, the coated plate has a considerably greater temperature gradient between the plate and the outer wall behind it. Assuming that the rooms behind the outer wall are brought to a room air temperature of +20 ° C and that the wall surface has a permanent temperature of +10 ° C due to heat conduction, there can be a temperature difference between the plate and the wall surface of 30 ° C and come beyond, although winter conditions exist. In contrast to the known solution with non-reflective coated facade panels, the present construction therefore has a temperature gradient from outside to inside with a corresponding energy flow. In the case of the coated construction, depending on the radiation coefficient of the reflection layer, approximately 20% of the thermal energy is transferred inwards by radiation. A further energy transfer takes place via convection, which occurs whenever the temperature difference between the plate and the inner wall becomes significant. Then the standing layer of air starts to move, whereby small-sized turbulences are to be assumed, which cause the convective energy transfer. The transfer of energy from the outside to the inside is promoted by the increased moisture in the fabric in the front edge zones of the masonry, which is created by condensation during irradiation phases. Overall, there is a self-control effect in the design, which is due to the fact that the sum of convective and radiant heat energy remains basically the same. Theoretically, this effect can be justified from Stefan - Boltzmann's radiation law, empirically based on the knowledge about convective energy transfer, which is characterized by the fact that this potentially increases or decreases with the flow velocity.

The derived form of the radiation law by Stefan-Boltzmann is:

E = C x (T / 100) ⁴ in watts.

E stands for energy, T for the absolute temperature in Kelvin, C for the radiation coefficient as part of the Stefan-Boltzmann constant 5.67.

Compared to standing air layers, the heat transfer coefficient "Alpha" in W / m ² x K has to be increased by the value 12 xw ^{1 2} according to generally accepted rules of thumb. Here w is the flow velocity in m / s the heat transfer can be up to 50 times greater than is assumed for standing air. At the end of the radiation, the swirled air layer comes to rest and is then an effective insulation layer again. The advantage of the wall structure according to the invention is that it favors the transfer of energy from the outside in, but hinders the transfer of energy from the inside out. In this, the present wall structure differs fundamentally from the conventional insulation technology, the advantage of which is to reduce the transmission heat loss from the inside to the outside, but the decisive disadvantage of which is the hindrance of the exogenous energy input. It should be appreciated that in the time distribution of core heating and heating transition times, the hindrance to exogenous energy input due to external insulation layers worsens the year-round energy balance, although the thermal conductivity figures are significantly improved

In the construction described here, the outer wall surfaces are almost completely equipped with electrically conductive material. This also leads to a certain shield against electromagnetic waves. It turned out that the reception for the widespread radio telephones is obviously significantly deteriorated. In view of the concern that an excess of electromagnetic waves can lead to health damage, it is conceivable that the wall structure according to the invention is also advantageous in this regard.

Claims

Expectations

1. Wall structure for a brick outer wall of a building, with a rear masonry and a facing shell, characterized in that the facing wall (2) is at least partially made up of building elements (11), in particular bricks, building blocks or the like, which are only on their backing walls (5th ) facing side are designed to reflect heat radiation.

2. Wall structure according to claim 1, characterized in that the components (11) are provided on their side facing the rear masonry (5) with a heat radiation reflecting layer (8).

3. Wall structure according to claim 2, characterized in that the components (11) are vapor-coated with heat radiation reflecting material on their side facing the rear masonry (1).

4. Wall structure according to one of the preceding claims, characterized in that the components (11) of the facing shell (2) are coated on their inside at least in regions with aluminum or an aluminum alloy.

5. Wall structure according to one of the preceding claims, characterized in that an essentially standing air layer is formed between the facing wall shell (2) and the rear masonry (5).

6. Wall structure according to one of the preceding claims, characterized in that the facing shell (2) has a thickness of more than 60 mm.

7. Wall structure according to one of claims 1 to 5, characterized in that the facing shell (2) is constructed from facade panels coated with reflective material only on the inside.

8. Component, in particular brick, building block, facade panel or the like, for use in the manufacture of the facing shell of a wall structure according to one of the preceding claims, characterized in that it has a heat radiation reflecting layer (8) on its inwardly facing side in the walled-in state is provided.