Vacuum Insulation Panels – Exciting Thermal Properties and Most Challenging Applications

Abstract

Vacuum insulation panels (VIPs) have a thermal resistance that is about a factor of 10 higher than that of equally thick conventional polystyrene boards. VIPs nowadays mostly consist of a load-bearing kernel of fumed silica. The kernel is evacuated to below 1 mbar and sealed in a highbarrier laminate, which consists of several layers of Al-coated polyethylene (PE) or polyethylene terephthalate (PET). The laminate is optimized for extremely low leakage rates for air and moisture and thus for a long service life, which is required especially for building applications. The evacuated kernel has a thermal conductivity of about 4 × 10 −3 W · m −1 · K −1 at room temperature, which results mainly from solid thermal conduction along the tenuous silica backbone. A U-value of 0.2 W · m −2 · K −1 results from a thickness of 2 cm. Thus slim, yet highly insulating façade constructions can be realized. As the kernel has nano-size pores, the gaseous thermal conductivity becomes noticeable only for pressures above 10 mbar. Only above 100 mbar the thermal conductivity doubles to about 8 × 10 −3 W · m −1 · K −1 , such a pressure could occur after several decades of usage in a middle European climate. These investigations revealed that the pressure increase is due to water vapor permeating the laminate itself, and to N 2 and O 2 , which tend to penetrate the VIP via the sealed edges. An extremely important innovation is the integration of a thermo-sensor into the VIP to nondestructively measure the thermal performance in situ. A successful "self-trial" was the integration of about 100 hand-made VIPs into the new ZAE-building in Würzburg. Afterwards, several other buildings were super-insulated using 1 1124 Fricke, Schwab, and HeinemannVIPs within a large joint R&D project initiated and coordinated by ZAE Bayern and funded by the Bavarian Ministry of Economics in Munich. These VIPs were manufactured commercially and integrated into floorings, the gable façade of an old building under protection, the roof and the facades of a terraced house as well as into an ultra-low-energy "passive house" and the slim balustrade of a hospital. The thermal reliability of these constructions was monitored using an infrared camera.

Traditional, state-of-the-art and future thermal building insulation materials and solutions – Properties, requirements and possibilities

“…Beck et al (2007), Simmler (2007, 2008), Caps and Fricke (2000), Caps (2005), Caps et al (2008), Fricke (2005), Fricke et al (2006), , Simmler and Brunner (2005ab), Simmler et al (2005c), Sveipe et al (2011), Tenpierik andCauberg (2007a), Tenpierik et al (2007bc, 2008, and Zwerger and Klein (2005), where comprehensive reviews on VIPs for building applications have been made recently by Tenpierik (2009) and Baetens et al (2010a). Centre-of-panel thermal conductivity for VIPs with a fumed silica core as function of elapsed time.…”

Vacuum insulation panels for building applications: A review and beyond

“…Furthermore, the extinction coefficient E in Eq. (9) is the reciprocal of the mean free path of length l ph of thermal photons and has to be estimated by fitting experimental data: For opacified silica cores, a value of l ph % 100 mm is given by Fricke et al [15] which means that VIPs of 2 cm block off infrared radiation. More attention to the function of opacifiers in fumed silica cores will be paid in Section 1.4.…”

Vacuum Insulation Panels (VIPs) for building construction industry – A review of the contemporary developments and future directions

“…However, the range of useful life time 30 to 50 years is wide and life time needs to be specified more precisely to build the confidence in manufacturers and users. A combination of polymers and thin metalized films or metal foils is currently employed to produce VIP envelope [10,29]. Generally, permeance of multilayer film envelope of a VIP depends on temperature, relative humidity and size of panel [30].…”

“…The thermal conductivity ( of VIP core can be reduced by suppressing the thermal conductivity terms shown in the right hand side of equation (1) to minimum and is expected to be in the range of 0.004 W m -1 K -1 [10,42]. In equation (1) represents coupling effect which becomes evident at higher pressures for powders and fibre materials due to interaction between them in the VIP core.…”

“…Dewar's flask a vacuum insulation, first used by Sir James Dewar in 1892 consisted of a double wall separated with an evacuated space to store liquid gases [9]. The idea was commercially employed in 1904 by Thermos GmbH in the production of vacuum flask called Thermos [10,11]. Frick et al [11] described US patent 236788 as the first precise vacuum insulation panel in which Bovenkerk [12] used an improved welding of glass fibre kernel to walls of panel envelope.…”