The prevailing mode of thermal conduction in conventional thermal insulation is the conductivity of the enclosed still air. If air is totally removed this part of thermal conductivity is zero. Thus only a small thermal conductivity by radiation and by the solid skeleton of the highly porous material is remaining.

The material has to have open pores in order to be evacuable and it has to sustain the enormous pressure load by the atmosphere, which is equivalent to 10 tons per square meter. Despite this load its density and thermal conductivity should be as low as possible. Suitable materials are microporous powder panels, glass fibers and open-porous foams.

Silica powder has the same chemical structure as ordinary sand. Due to a special process, however, extremely fine powder particles (several millionth of a millimeter small) are produced. These silica powders are pressed to boards with voids being a factor of 20 to 100 smaller than of other materials like perlite powders, glass fibers or organic foams. The requirements to the level of vacuum are also a factor of 20 to 100 lower. With microporous silica powder boards it is possible to reach a very low thermal conductivity even with a moderate vacuum (10 to 100 mbar).
With special high gas barrier foils as envelope it is possible to maintain the required vacuum level for many decades. These foils contain only extremely thin layers of aluminum, which does not enhance thermal conductivity. With these high barrier films a typical increase of gas pressure within the vacuum panel of less than 1 mbar per year is possible. With microporous silica boards as filler thus a life time of the vacuum insulation panel of several decades is possible.

The high barrier film around the vacuum panel must not be damaged. If the plastic film is hurt and air flows in the thermal conductivity rises up to 0.020 W/mK. It is not possible to cut vacuum panels to the appropriate size at the location. Also it is not allowed to puncture them with dowels or similar. Besides these limitations vacuum panels may be glued to other surfaces and integrated to different construction with appropriate covers.

In general, thin vacuum panels can be curved to cylindrical forms within some limitations. The thinner the panel the smaller the curvature possible. However, plane vacuum panels can not be formed to complex forms with two-dimensional curvature like spherical parts. New technologies allow to produce more complex shapes and VIPs even with holes. Please ask for details If you have special requirements.(=> VACI-Projekt).

For a rational production vacuum panels with standard sizes are preferred. va-Q-tec, however, can also produce custom size panels. Largest sizes are 1000 mm x 600 mm and 1000 m x 500 mm. Larger panels easily can be assembled by smaller ones. Standard thicknesses are 10 mm, 20 mm, 30 mm and 40 mm.

 

The microporous filling can sustain temperatures up to 900 °C without damage. The outer plastic barrier film, however, disintegrates at temperatures above 150°C - 200°C. Vacuum panels have been tested for function within an environment of 80°C for more than one year. The increase of gas pressure here still was moderate. For long life times vacuum panels should be kept at temperatures below 30°C, but occasional higher temperatures up to 80°C are not harmful.

High relative humidity may be harmful to vacuum panels, if they are exposed to it for longer times especially in combination with high temperatures. Therefore humidity barriers should be constructed in such a way that the vacuum insulation panel is kept dry.

 

The high barrier film is folded around the panel in a special procedure yielding wrinkle free edges and surfaces. Vacuum panels from va-Q-tec may be joined together without gaps minimizing heat losses. The gas pressure of every vacuum panel from va-Q-tec which leaves production has been monitored by the unique quality assurance system "va-Q-check". Even the user may control the gas pressure of the panel easily with a hand-held version of the va-Q-check test system. The quality checked high barrier films used by va-Q-tec warrant a very long life time.

The core material of the vacuum panels, e.g. microporous silica, is a valuable raw material, which may be reused. There are no harmful influences to the environment and health by the core and cover material.