Exterior Insulation
It is common practice to insulate a new or existing wall by applying an insulation layer to the outside of the supporting structure. The reason for this is, that an exterior insulation, from a constructional point of view, is less likely to cause problems than an inside insulation. An exterior insulation causes the dew point of the exterior wall to move further to the outside. Potential moisture can escape to the outside and is thus prevented from damaging the masonry or the insulation.
The storage capacity of the wall is preserved so that a pleasant surface temperature can be ensured. A lime plaster, which is open to diffusion, protects the insulation layer against driving rain and ensures that the exterior wall can dry quickly. The decision for an exterior reed insulation of Hiss Reet panels means the use of a completely ecological insulating material that can compete with other solutions both in terms of constructional qualities and price. At the same time the panels are easy to fit and guarantee a construction without thermal bridges. Using reed insulation panels as a means of exterior insulation has a long tradition and, in combination with lime plaster, it can be regarded as the oldest „thermal insulation composite system” of the world. Many of the remaining historical buildings demonstrate that reed is extremely resistant to rotting. This is a quality that can be explained by the naturally high concentration of silicate in reed. The shapes of the reed insulation panels make them easy to fit.
For walls with an exterior insulation the general requirements of the EnEV and DIN 4108 for exterior walls, as mentioned above, apply. For single or double shell wall constructions according to DIN 1053-1 as well as for the walls of timbered houses which use an exterior thermal insulation composite system (WDVS) and have a sd-value of the outer layers of < 2.0 m a calculation of potential condensate is not necessary.
Wall build-up 4: Wall of a timbered house with exterior insulation
Calculation of heat transmittance:
U-value without exterior insulation: 1.75 W/m²K
U-value with 8 cm insulation: 0.49 W/m²K
U-value with 10 cm insulation: 0.42 W/m²K
Details on the Use and Application of Reed Insulation as Exterior Insulation for Timbered Houses:
See wall build-up 3
Additions:
1) All joinings (cloth, mortar inside and outside) should be wind and air-tight and connect directly with the surrounding frame. As a first step you should have filled gaps between the frame and the beams with flax or similar.
2) The window ledge should protrude as much as possible over the insulation and the plaster. Furthermore it should feature a drainage that prevents water from running under it.
Wall build-up 5: Exterior insulation of masonry with a 80 mm reed insulation panel
Existence:
20 mm lime external rendering, brick wall 24 cm (ρ= ca. 1600 kg/m³), 20 mm lime interior plaster.
U-value without reed insulation panel: 1.76 W/(m²K).
General requirements:
EnEV: U = 0.35 W/(m²K
DIN 4108: R ≥ 1.20 (m²K)/W
Exterior Insulation:
80 mm Hiss-Reet reed panel, 20 mm lime plaster
U-value with reed insulation panel: 0.44 W/(m²K) also suitable for new buildings (although the use of a good quality stone e.g. Poroton is advisable).
Details on the Use and Application of Reed Insulation Panels as Exterior Insulation:
1) Fix a horizontal installation board (8 x 8 cm) with the help of mounting brackets or similar. Keep a distance of at least 30 cm to the floor to be safe from splash water.
The base of the wall needs a separate insulation (perimeter insulation with additional damp proofing).
2) The reed insulation panels are put on the installation boards and fixed to the wall with screws and wall plugs (5 fixings /m²) The reed stalks of the outer layer should have a horizontal orientation.
3) On the lower edge of the installation board a casing bead should be attached.
4) Lime rendering mortar can be applied directly to the reed insulation panels. The expert Gerhard Holzmann recommends the following plaster scheme consisting of four layers:
a. Apply a layer of 8-10mm of levelling fibrated mineral rendering mortar (class P II (DIN 18550) or CS II (EN 998-1) directly to the reed insulation. Then, key the mortar.
Corner beads should be implemented into the mortar layer.
b. After app. 5 days (depending on the weather) apply a 10-15 mm layer of cement-lime machine-applied light plaster of the mortar class II (DIN 18550) or CS II (EN 998-1) with lightweight mineral aggregate. Again, key the surface after a 1 day drying time. This layer should leave a level surface.
c. After about 12 hours (depending on the weather) apply a stopping coat of fibrated mineral rendering mortar (class P II (DIN 18550) or CS II (EN 998-1) with cloth insert (alkali resistant glass cloth, mesh width 6 x 6.5; tensile strength ≥ 2,8- 3,2 KN/ cm²) and plaster joints as well as web reinforcement at wall apertures. The cloth should lie in the upper third of the stopping coat. Again, key this layer in preparation for the final rendering.
d. Final rendering.
Alternative wall build-up 5: Exterior insulation of masonry with 2 x 50 mm reed insulation panels
Existence:
20 mm lime external rendering, brick wall 24 cm (ρ= ca. 1600 kg/m³), 20 mm lime interior plaster
U-value without reed insulation panel: 1.76 W/(m²K).
General requirements:
EnEV: U = 0.35 W/(m²K
DIN 4108: R ≥ 1.20 (m²K)/W.
Exterior Insulation:
2x50 mm Hiss-Reet reed panel, 20 mm lime plaster
U-value with reed insulation panel: 0.37 W/(m²K) also suitable for new buildings (although the use of a good quality stone e.g. Poroton is advisable).
120 mm Hiss-Reet reed panel, 20 mm lime plaster
U-value with reed insulation panel: 0.33 W/(m²K).
Disclaimer of Liability
The information given above is based on the calculations and information of HISS REET Schilfrohrhandel GmbH and the product specifications of the manufacturer. The content is only a selection of especially important information. The author reserves the right not to be responsible for the topicality, correctness, completeness or quality of the information provided. Liability claims regarding material or ideal damage caused by the use of any information provided, including any kind of information which is incomplete or incorrect, will therefore be rejected, unless there is evidence of intentional or gross negligence on part of the author.
The information provided cannot substitute individual specialist advice by a planner
Authors:
Dipl. Ing. Stefan Neumann
Dipl. Kfm. Philip Kullmann
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