Vacuum Insulation Panels Push the Envelope to R-30 Per Inch

Dow Corning’s VIPs are composed of a fumed silica cake, with silicon carbide and polyester fibers for structural support, encased in an inner layer of polyethylene and an outer layer of polyethylene, polyester, and aluminum. The panels are vacuum-sealed, and the edges are heat-sealed.

Because of the construction, the panels have thermal bridging at the edges—much like windows—and as a result, the whole-panel R-value is lower than that of the center. The center-of-panel insulation value for Dow Corning’s VIP is R-39 per inch, but a standard 2' x 4' panel provides approximately R-30 per inch overall. R-value does increase linearly with increased thickness, according to Charlie Zimmer, global program manager for high-performance insulation at Dow Corning. So a 1" panel will have roughly double the R-value of a ½" panel, he explained, but as panel size increases, thermal bridging along the edge of the panel is reduced relative to the size of the panel, meaning total R-value (and thus cost-effectiveness) increases with panel area. Although there is no air movement through the panels, they must be sealed at the seams (with tape, for example) to prevent leakage there.