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Fig. 1: Forklift instead of scaffolding – the large prefabricated elements are hung on retainers in the facade.
© IWU, Darmstadt
Prefabricated vacuum panel
Projektinfo 04/2008
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Building refurbishment - highly insulative large elements

As a result of increasingly strict legal stipulations, and high energy prices, the thermal insulation of buildings is improving continually. However, the insulation packed in front of exterior walls is also becoming correspondingly thicker. In new construction projects, such structures can be taken into account in the planning from the very beginning, but upon implementation of measures for existing buildings, the spatial conditions often limit the thickness of the external insulation.

In addition, retroactive application of thick insulation reduces the amount of light which shines through the existing window openings, and is often seen as a design compromise in this regard.

Here, vacuum insulation panels (VIPs) can prove advantageous: they achieve the same effect as conventional insulation materials, with considerably less material thickness. However, the panels, which comprise an evacuated powder core enveloped in a thin, metal-coated plastic film, are very delicate. If the outer shell is breached, and air penetrates to the insulation core, the effectiveness decreases considerably.

One way to install the vacuum insulation panels without damaging them, is to integrate them into prefabricated elements. Prefabrication of the elements in the factory, realised by qualified staff, enormously reduces the risk of damage, compared to installing the unprotected VIPs on the construction site, and also offers additional advantages. The experience gathered using this method for new buildings has been positive.

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For the first time, in the support initiative EnSan (for enhanced building fabric performance), the German Federal Ministry of Economics and Technology (BMWi) supported a solution with prefabricated elements for existing buildings as well. For refurbishment of three residential buildings in Hofheim, Germany, prototypes were developed, installed, and tested.

As these old buildings were built right on the edge of the footpath, their front facades offered little room for retroactively applied insulation. As a means of achieving high-quality thermal insulation regardless, the planners decided to use vacuum panels. Here, a combination with so-called large-element insulation technology was tested, which (also as part of a research project) was originally developed for conventional insulation.

Storey-high elements, prefabricated in a factory, with the new windows already integrated, are hung on a fastening system, which is installed on the facade beforehand. This allows rapid installation with a perfect fit, and requires little reworking on the construction site. Thermal bridges in the structure can be minimised in advance.

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Addresses

Client
HWB GmbH

Project coordination
IWU GmbH

large element insulation technology
IGKB mbH

Architecture
planungsgruppe DREI