Eco-Products and Eco-Design
Vacuum panels simplify renovation
The Fraunhofer Institute has developed composite vacuum insulation panels with thermal conductivity ten times lower than common insulation materials, reducing insulation thickness markedly.
The existing building stock is responsible for about a quarter of the energy consumption in Germany alone. Consequently, better insulation of the building envelope can save significant amounts of fossil fuels and reduce the emission of carbon dioxide appreciably.
Building designers are constantly striving to improve thermal insulation to reduce the exchange of heat between the outer and inner walls without increasing wall thickness. However, because of rising building standards, thermal insulation in houses has been getting steadily thicker despite the relatively low heat conductivity of the insulation materials. This is a particular problem in renovation.
Working with two industrial partners, the Fraunhofer Institute for Solar Energy Systems[1] (ISE) in Freiburg, Germany has developed composite vacuum panels offering particularly effective insulation for the facades of buildings. While conventional insulation systems have reached thicknesses of 20 to 30 cm, LockPlate® composite panels are only 9- to 11-cm thick – ideal for renovating older buildings.
Thermos flask approach
Conventional insulation materials such as polystyrene foam, mineral wool, cork or hemp fibres are not fully able to prevent heat exchange because of the conductivity of the air or other gases are trapped in their interstices. The ideal solution is a vacuum as found in a thermos flask. Researchers at the Fraunhofer ISE therefore set out with two industrial partners – Porextherm Dämmstoffe[2] GmbH and Maxit Deutschland[3] – to developed vacuum insulation panels (VIPs) suitable for thermal insulation in construction work.
“The vacuum insulation panels are made up of a porous supporting structure encased in a special film that is not permeable to water vapour or gas,” explains ISE project manager Dr Werner Platzer. “These bags are evacuated to just a few millibars and sealed. This greatly restricts the mobility of the few air molecules in the pores. As a result, the air’s thermal conductivity is suppressed and hardly any heat is exchanged.”
There was still one problem: sharp objects can easily damage the film, quickly destroying the vacuum. This was overcome by encasing the film-faced panels in a thin layer of polystyrene foam. The result is a practical composite thermal insulation system that is easy to handle on a building site. Fraunhofer indicates thermal conductivity for the VIPs is ten times lower than that of other common insulation materials. LockPlate® is expected to be certified as a building system very soon.
Easy to adapt
“Our panels are designed so that 95% of the overall wall surface can be covered with only three standard sizes,” says Platzer. “The panels can be cut to shape in certain places. That was never possible with other vacuum insulation systems.”
More information: werner.platzer@ise.fraunhofer.de
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