Va-Q-tec VIP Lifetime Analysis

Performance test of panels 7 years after production

This report presents va-Q-tec’s VIP lifetime analysis. The panels used for this analysis were 

produced according to va-Q-tec quality standards. Specifically, va-Q-tec uses three main quality 

aspects which are necessary to guarantee the VIP function shown in the results:

1. Test of the thermal conductivity of each core material lot (tested in a vacuum panel)

2. Test of the diffusion rate of the film and the sealing for each production lot of film (tested 

in a vacuum panel)

3. Test of the inside gas pressure for every single vacuum panel within three days of

production.
Lifetime Analysis 

Performance test of panels 7 years after production

 

ISO Dok. Nr.: 

Version: va-Q-tec AG 

Erstellt von: Jochen Hiemeyer Karl-Ferdinand-Braun-Str. 7 

Erstellt am: 09.09.2010 12:14 97080 Würzburg/ Deutschland 

Druckdatum: 09.09.2010 12:15 info@va-Q-tec.com

Seite: 1 von 1 www.va-Q-tec.com

 

 

1. Intention: 

Vacuum insulation panels show an increase in gas pressure over time as gas molecules diffuse 

through the high barrier film. Depending on the pore size of the core material this leads to an 

increase in thermal conductivity and thus a performance degradation of the vacuum panel. 

To predict this aging properties the diffusion properties of the high barrier film need to be 

characterised. The diffusion rates for these films are extremely low, so that common test methods 

cannot be used to quantify this rate. Va-Q-tec uses a sophisticated test method to qualify each 

batch of high barrier films before releasing them for production (cf: proceedings of the 7th

International Vacuum Insulation Sympossium, Duebendorf, 2005, Dr Roland Caps). 

From these tests an increase in gas pressure of less than 1 mbar per year is predicted for the 

highest quality metallized films which are used for va-Q-tec panels (for a 20 mm thick panel at 

ambient temperatures and normal humidity). 

To validate these values and show the lifetime stability of the film composite 116 panels which had 

been produced in December 2003 were analysed. 

2. Proceedings: 

The 116 panels which are regarded had been produced in December 2003. The panels are made 

up of a silica core and a metallized film and were drawn from a normal production run. The panel 

size is 346 x 263 x 20 mm3. The 116 panels were produced in two production lots (#03067708: 66 

pcs; #03067008: 50 pcs). Internal gas pressure of the panels had been measured with the va-Qcheck system (cf: Quality control of vacuum insulation panels: Methods of measuring gas 

pressure, Vacuum 82 (2008), Dr. Roland Caps et al). 

The panels were stored on a pallet at ambient temperature. In March 2010 all panels were 

controlled for internal gas pressure with va-Q-check. 

To control the long term reliability of the va-Q-check measurement, for several panels the inside 

gas pressure was controlled with other means yielding good consistency. 

Also the thermal conductivity of some panels was measured to control that the measured gas 

pressure is consistent with the expected thermal values. 

3. Results: 

The following table shows the results of the gas pressure measurements for the two production 

lots: 

Lot 1 (#03067708) Lot 2 (#03067008) 

Number of panels 66 50 

Mean gas pressure December 2003 1,5 +/- 0,2 mbar 0,8 +/- 0,2 mbar 

Mean gas pressure March 2010 4,0 +/- 0,6 mbar 8,8 +/- 2,3 mbar 

Total increase in gas pressure 2,5 +/- 0,5 mbar 8,0 +/- 2,2 mbar 

Increase in gas pressure per year 0,4 mbar / year 1,3 mbar / year 

4. Discussion: 

None of the panels is showing an increase in gas pressure that exceeds 2 mbar / year. Also 

within one production lot the increase in gas pressure for different panels is similar. 

No unexpected discrepancies to lifetime expectance based on our diffusion rate tests or 

accelerated aging were discovered. 

Also the high influence of production parameters (comparison between lot 1 and 2) can be seen. 

Only an accurate control of these parameters can guarantee sufficient quality. 

For refrigeration applications the expected diffusion rates are reduced by the lower temperatures. 

An increase rate of 1 mbar / year would mean a 15% increase in thermal conductivity during a 

refrigerator lifetime of 15 years.