Vaccum Insulation Panel (VIP)
From Swikipedia
Introduction
The insulation value of some materials can be dramatically increased by maintaining them in an evacuated environment. How much vacuum is required and how much improvement is gained depends on the material and the level of vacuum.
A Vacuum Insulated Panel (VIP) uses the insulating effects of a vacuum to produce much higher R values than conventional insulation. Conventional insulation produces an R-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. (R value is the measure of thermal resistance used in the building and construction industry, the bigger the number, the better the building insulation's effectiveness.)
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. aerogel)
• Chemicals to collect gases leaked through the membrane or offgassed from the membrane materials
Brief Description
Making a Flat Vacuum Insulation Panel
A flat Vacuum Insulation Panel involves insulation technology which goes beyond that of common foams and fiberglass batt (which rely on "trapped air"). It is advantageous in terms of the superior insulation value afforded by a vacuum. The major technical challenges in making a flat vacuum insulation panel include:
1. Support of the flat walls: Atmospheric pressure exerts approximately 15 psi (pound per square inch) of pressure on the evacuated panel. This means that a vacuum panel which is 20" square has 3 tonnes (6,000 lbs.) of force compressing it. Since it is not practical to make the walls thick enough to support such pressure (remember, the walls themselves will conduct heat where they join together), a suitable internal support material is needed. This material (often called a "core" material) has to be strong enough to take the tremendous pressure without collapsing and yet not transfer too much heat itself.
2. Gas Impermeable Membrane: Since the thermal performance of the panel will be proportionate to the internal pressure, a membrane (i.e. "wall") material was needed which would minimize the influx of gases into the evacuated space. Additionally, this material had to be low in cost, easy to work with and easy to join together in an air-tight seal. Lastly, the material has to be thin enough so as not to conduct a significant amount of heat around the edges thus providing a "short circuit" for heat flow.
3. Getters and Desiccants: Getters and desiccants are used to absorb gases (getters) and moisture (desiccants) within the evacuated envelope and prevent (or at least delay) an elevation of the internal pressure and the degradation in "R" value that would result. This gas and moisture may enter the vacuum panel in a number of ways including permeation of the membrane material, permeation of the sealing seams and out-gassing of the core material and membrane itself.
Advantages of VIPs
o Up to 10 times higher insulation performance compared to conventional insulations
o Space saving but highly insulating constructions possible
o High quality and long product life time
Covered by the high barrier film the vacuum panels are automatically protected against external humidity. Thus a major problem of conventional insulations (e.g. fibers or aerogels) is solved.
References:
http://www.glacierbay.com/vacpanelinfo.asp
http://en.wikipedia.org/wiki/Vacuum_insulated_panel
