A vacuum insulated panel (VIP) is a form of thermal insulation consisting of a nearly gas-tight enclosure surrounding a rigid core, from which the air has been evacuated. It is used in building construction to provide somewhat better insulation performance than conventional insulation materials.
By removing air from fiber, powder, or foam core materials VIPs achieve high thermal performance at a fraction of the thickness of cut-to-fit insulation materials. VIP products are made-to-fit architectural details, with specified service lives for floor, wall, and roof constructions. Quality control of component manufacture is important.
A VIP uses the insulating effects of a vacuum to produce much higher thermal resistance than conventional insulation. Conventional insulation produces anR-value of eight or less per inch (fiberglass being towards the lower end and foam panels towards the higher end). VIPs are commonly as high as R-30 per inch, and have achieved commercially viable levels of R-50 per inch.[citation needed]
VIPs consist of:
- Membrane walls, used to prevent air from getting into the vacuum area
- Core material, used to hold the vacuum inside the membrane while preventing the membrane walls from collapsing. (e.g.fumed silica, aerogel, glass fibers or foams)
- Chemicals to collect gases leaked through the membrane or offgassed from the membrane materials are added to VIP with glass fibers or foams cores, as core with bigger pore size requires vacuum level lower than about 1 mbar during the planned service life. (Getter)
VIPs offer very high R-value by thickness (30-50R value per inch compared with 5-8R/in for various foams and a lower 2-3.54R/in for common fiberglass batting), but by cost and lifespan it is less competitive. Compared to more conventional insulating materials VIPs have a high cost/r-value ratio. Unlike fiberglass (although foam insulation does age), VIPs age as it is impossible to completely keep air from filling the vacuum. As air leaks in and pressure of the panel normalizes with its surrounding air its R-value deteriorates.
Although their higher cost compared with fiberglass and foam generally keep them out of traditional housing situations, their spectacular R/in values make them useful in situation where high insulation requirements or space constraints make traditional insulation impractical. (Foam sheets are used over fiberglass often for the same goal of higher R/in, despite higher cost for the same R value).