Experimental and numerical investigation of thermal bridging effects of jointed Vacuum Insulation Panels

Abstract

Vacuum Insulation Panels (VIPs) are characterised by very low thermal conductivity, compared to traditional insulating materials. For this reason, they represent a promising solution to improve the thermal behaviour of buildings, especially in the case of energy retrofitting (where a higher performance and less thickness is desirable). VIPs are insulating components in which a core material is surrounded by an air tight envelope which allows a high degree of internal vacuum to be maintained. Such features, on the one hand, allow excellent thermal insulation properties to be achieved, but, on the other, require the manufacturing of prefabricated panels of fixed shape/size. This means that the use of these super insulating materials in the building envelope involves the problem of joining the panels to each other and of fixing them onto additional supporting elements. As a result, purposely studied supporting structures or systems are required. However, these structures and systems cause thermal bridging effects. The overall energy performance of the resulting insulation package can therefore be affected to a great extent by these additional elements, and can become significantly lower than that of the VIP panel alone. In order to verify the incidence of thermal bridges on the overall energy performance of an insulation system that makes use of VIP panels, an experimental campaign has been carried out using a heat flux meter apparatus and analysing different joint materials/typologies. First, a measurement method was proposed, tested and verified on the basis of data from the available literature. A series of measurements on different samples was then performed. The experimental results were then used to calibrate and verify a numerical

Thermal bridges in vacuum insulation panels at building scale

“…In particular, a 3·5-mm width of air joint between the panels was selected according to Lorenzati et al (2016). This width can be considered as an average value commonly adopted in real building applications.…”

“…The equivalent thermal conductivity of the air gap between two panels (air joint VIP assembly) used in the model was evaluated (BSI, 2007c) following the procedure adopted by Lorenzati et al (2016).…”

“…Lorenzati et al (2016) carried out experimental and numerical analyses of different VIP assemblies, investigating thermal bridge effects on the geometry of the air joint between two adjacent panels, the type of structural joints and the panel size/shape. The experimental results were also used to verify a numerical model.…”

Effect of Thermal Bridges in Insulated Walls on Air-Conditioning Loads Using Whole Building Energy Analysis

“…Although expensive, vacuum insulation panels (VIPs) are characterized by very low thermal conductivity, compared to traditional insulating materials, and hence, can improve the thermal behavior of buildings, especially in the case of energy retrofitting [15]. However, VIPs require the manufacturing of prefabricated panels of a fixed shape/size, which means that their use in the building envelope involves the problem of joining the panels to each other and of fixing them onto additional supporting structures.…”

“…The energy performance of the resulting insulation package can therefore be affected to a great extent by these additional elements and can become significantly lower than that of the VIP panel alone. Using a heat flux meter, Lorenzati et al [15] carried out experiments in order to verify the effect of thermal bridges on the energy performance of VIPs. Results were used to calibrate and verify a numerical model that allowed the performance of various VIP joint materials/typologies to be predicted and the performance of the overall package to be optimized.…”