Engineer-office work-formation and construction-biology Peter Rauch  
(This page was automatically translated from German. Wärmebrücke1)

Heat-bridge between a heat insulation

Heat-bridges are component parts where a lower surface temperature is available in the comparison to adjacent component parts and component part-sections respectively. The consequences are a higher moisture-encumbrance, that leads to the known mold-appearances and to the elevated material-waste. With the following cases in point, heat-bridges are built through the later appropriate more outer heat insulation.

(The humidity in the air condenses at the cool surface since the air cools off here and less water can be picked up in steam-form. For example the air with a temperature of 20 ºC and a relative humidity of 60 per cent is reduced on 12 ºC, so the relative humidity is with 100 per cent. Dew-water refines.)

At the following cases in point, it is shown that becomes little visible in appearance of stepped knowledge domains exactly through the later installed heat insulation first until now.

In the illustration 1 and 2, it is represented the temperature graphic chart and the isotherms at a monolithic one and work period-construction (outside-heat insulation).

Wärmebrücke an einem Fenster  Wärmebrücke an einem Fenster bei einer Außendämmung

At the underside of the windowsill, the temperature-difference is made worse by the heat insulation of 5 K on 23 K. The consequence should be a soaking of the component part-section. The effect of the heat insulation gets hereby worse at what once again and the temperature-difference increases.

Similarly, it looks with the intrados of the window menus. In the copy 3, a monolithic wall with box-window menu is represented. Takes place the adiabatic between the two systems (indoors and outside) over the wall-plain, intrados of the window menus and box-window menus. The temperature-difference between the 3 component parts is not very big in the relationship, only with high temperature-differences. The humidity can accumulate (adsorption) evenly at the wall-surface so approximately everywhere.

Copy 3:  Wärmefluss durch eine Außenwand

The same wall-setup with an outside-heat insulation and new window menu is displayed in the copy 4 with Isolierverglasung. The temperature at the inner-wall-surface becomes higher through the Dämmwirkung. Was allowed to as well *) the surface temperature at the window menu-glass higher than at the box-window menu is.

Copy 4:  Wärmefluss durch eine Außenwand mit Wärmedämmung

Surplus atmospheric humidity could be picked up by almost the entire space-enclosing plain until now. Now, the Fensterlaibung, that shows the most lowest surface temperature, only remains at the outside-wall. A box-window menu has a width of 15 cm, that one Isolierverglasung 6 cm. The distance of the heat flux at the wall-connections is more than halves. The heat insulation of 1 or 2 cm at the more extrinsic intrados of the window menus reduces the problem, however, it cannot remove. The consequence is an elevated mold-formation. (The other elements of the more unfavorable convection-heater should not be accepted further like denser window menus and the change of the heater of the radiation-heater here.)

In Zwickau, 3 became at a multiple-family dwelling Q An or installed Q 6 of 1965 an outer heat insulation with the financial recovery. (Copy 5.

Through this measure, the thin staircase-wall turned in the ground floor into the "heat-bridge." The temperature at the internal wall-surface of the kitchen amounted to 12-13ºC, with a space-temperature of 19ºC and a relative humidity of 43 per cent. At the wall-surface, this relative atmospheric humidity amounts about. 70%. (In the kitchen, the humidity is otherwise over this value and already with 55 per cent surely, this amounts about at the wall-surface. 80%.) The financial recovery took place in the kitchen and in the hall to the staircase with an inner-heat insulation (20 mm calcium-silicate-plates / climate-plate). With the redevelopment / modernization in Leipzig, one had positioned in the staircase a radiator and had avoided the high temperature-differences so from the start.

With the roof-projectile-development, also these problems step exactly reinforced on. Different thickness of the heat insulation in the Kehlbereich, wall, - tube - and window menu-connections partially lead to considerable temperature-differences. More to knowledge domains into the acticle to the Roof-development

*) for an exact statement, a measured value must as well as is available at the developed box-window menu and at the Isolierfenster.

Illustration 1 and 2 from balance brought forward of Prof. Dr.-Ing. habil. C. Meier Quedlinburg 10.02.2001

Ingenieurbuero Peter Rauch

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Engineer-office work-formation and construction-biology Peter Rauch - Leipzig -