Vacuum insulation panels: why the catalogue figure does not hold in the field

A vacuum panel promises thermal conductivity far below classic foams. The value to design with is roughly double the one measured after production.

22 October 2022Updated 28 September 2026

Short answer

The catalogue figure for a vacuum panel (0.004-0.0048 W/(m·K) for a silica core) is the centre-of-panel value right after production. The declared effective value including ageing and the edge thermal bridge is 0.007-0.008 W/(m·K) over 25 years, about double. In a punctured panel conductivity rises to about 0.020; aerogel at 0.015-0.020 is a more durable but thicker solution.

The catalogue figure for a vacuum insulation panel (VIP) is the centre-of-panel value measured just after production. The number to use in the field is about double: gas and moisture entering through the barrier over time and the thermal bridge at the edge raise conductivity.

Condition	λ, W/(m·K)
VIP, after production	0.004-0.0048
VIP, including 25 years and edge effect	0.007-0.008
Punctured VIP	0.020-0.023
Aerogel, 20 °C	0.014-0.020

Edge and size. IEA Annex 39 recommends panels of at least 0.5 m x 0.5 m and close to square: because the foil conducts heat at the edge, many small panels do worse than a few large ones. A VIP cannot be cut on site, so the layout is drawn up in advance.

Damage and aerogel

In a punctured panel the vacuum is lost and conductivity rises about fivefold. Aerogel is insensitive to puncture and can be cut, but it is not as thin as a VIP. When buying, ask whether the figure includes ageing and edge, and how a puncture would be noticed.