.

Fig. 31: Only trained personnel are allowed to install the vacuum panels.
© HASIT

Fig. 32: Quality assurance and control on the building site play an important role in using VIPs.
© HASIT

Fig. 33a: Positioning the VIPs between timber battens ensures relatively easy installation and enables the VIPs to be visually and tactually inspected until they are clad.
© Lichtblau Architekten

Fig. 33b: Positioning the VIPs between timber battens ensures relatively easy installation and enables the VIPs to be visually and tactually inspected until they are clad.
© Lichtblau Architekten
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Building with vacuum insulation

Vacuum insulation needs to be precisely thought out and detailed right from the initial planning phase. Not only is it necessary to take the building physics aspects into account but the required panel sizes must also be determined and a layout plan drawn up. On the building site, the deployment of the fragile VIPs needs to be precisely planned, ranging from their transport and storage to the installation and coordination with other trades on site.

In order to decide whether and in which areas vacuum insulation panels are suitable for a building project, the client and all those involved in the planning must be aware of the properties and special characteristics ofVIPs. VIP manufacturers and suppliers should be involved in the design process from the earliest possible stage. If no national technical approval is available for the intended application, itwill be necessary to apply for individual approval for using the VIPs. That requires sufficient forward planning.

Design values, thermal bridges and vapour diffusion

The design value for the thermal conductivity that are stipulated in the national technical approvals and that need to be used by the designer take into account not just the ageing but also the thermal bridging effect caused by butt-jointed VIPs. A small ‘failure rate’ due to aerated VIPs is also included in the calculation. The thermal bridging effects caused by anchors and fixing elements that can only be applied in the joints between two panels need to be taken into account separately. Double-layered, offset installation of the VIP insulation panels or an additional cover layer of conventional thermal insulation material that is just a few centimetres thick help to reduce increased thermal flow across any possible gaps in the joint area between the panels.

In comparison with standard thermal insulation materials, vacuum insulation is extremely impermeable to water vapour and therefore, from a hygric point of view, generally less critical than conventional thermal insulation solutions. In case of doubt, specialists should analyse and assess the planned structure using computer programs that simulate the building physics (e.g. WUFI, DELPHIN).

Inspections and the replacement of aerated VIPs

Although aerated panels cannot be repaired, they still provide twice the thermal insulation effect as conventional thermal insulation materials of the same thickness. In accordance with the stipulations provided by the corresponding national technical approval, the structure should be so designed that even if all panels are aerated, the minimum required thermal insulation is provided in order to prevent mould forming. In order to ensure the high quality of the vacuum insulation solution, the panels should be visually and tactually inspected before and after their installation. If by means of skilful planning it is possible to utilise panels that have just a few different sizes or even just standard dimensions, this will make it easier to replace any faulty VIPs with panels of the corresponding size. Otherwise, re-manufacturing and re-supplying replacementswill delay the construction timetable. Since it is usually difficult to replace defective panels once the insulation structure is completed, particular care must be taken when handling them.

Bills of materials and layout plans

Since VIPs cannot be adjusted in size on site, the fixed panel sizesmust already be determined during the detailed design stage. Reducing the different panel sizes facilitates their processing. Bills of materials and layout plans must be drawn up as early as possible in close collaboration between the designers and the VIP suppliers. The layout plans must be drawn up after conducting precise measurements on site, taking into account the production tolerance for the panels of around 2-3 mm. All penetrations and fixing points must be precisely determined during this phase in conjunction with the various specialist trades involved. Thismay require specially customised VIPs.

VIPs on the building site

There is a considerable risk that the VIP envelope could be damaged during transport, storage or installation – particularly on the corners and edges. Exposed nails, protruding burr from the substructure, stones or sand, or even knocks against the corners, are enough to damage the vacuum envelope and thus aerate the VIPs. Correspondingly labelled and sufficiently secure storage areas should therefore be provided on the building site. Base and cover layers in the structural assemblymade of soft, flexible material, such as just a few millimetres or centimetres of polystyrene foam, considerably reduce the risk of damage. The proper handling of VIPs therefore requires considerable care – and trained personnel. The training must be carried out by the VIP manufacturer in accordance with the national technical approval. VIP manufacturers and various skilled trades have therefore joined together to form networks for this purpose.

Constraints affecting their installation

Before installing VIPs, it is essential to ensure their compatibility with the other construction materials. Various adhesives or an alkaline substructure, such as fresh concrete, have proved critical in the past.

User information

If VIPs are not installed in a manner that prevents subsequent damage, tenants, owners and workmen should be informed and – for example by means of warning labels – notified about the fragile content of the building structure.

Quality check

  • The VIP elements should be visually inspected on delivery. The high barrier film must tightly seal the supporting core.
  • The VIP elements must not be mechanically damaged through sawing, cutting and drilling.
  • The substructure on which the VIP elements are laid must be smooth and must not have any edges or burring.
  • The VIP elements must also be sufficiently protected against damage during their period of use, e.g. through covering them with cladding.

Thermal bridges take on increasing significance

Thermal bridges become much more significant with high-performance insulation systems: the problem intensifies by roughly the same extent that the thickness of the thermal insulation layer can be reduced through using VIPs (5- to 10-fold). Even quiescent air or conventional thermal insulation material represent a thermal bridge in comparison with a vacuum insulation panel. Increased heat transfer cannot be avoided where there are fixings or connections. The effective heat transfer coefficient (U-value) averaged across the entire surface of VIP thermal insulation systems is therefore higher than for VIPs alone.

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