VACUUM INSULATION PANELS

By:

Badar Ayub Izhar

Introduction to Vacuum Insulation Panels

(VIPs) are regarded as one of the most promising high performance thermal insulation solutions on the market today.

Thermal performances three to six times better than still-air are achieved by applying a vacuum to an encapsulated micro-porous material, resulting in a great potential for combining the reduction of energy consumption in buildings with slim constructions.

Vacuum insulation panels are defined as :

‘‘An evacuated foil-encapsulated open porous material as a high performance thermal insulating material’’.

A VIP uses the insulating effects of a vacuum to produce much higher thermal resistance 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

The R-value is a 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: 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)

Important for VIP core materials are the pore size distribution PSD and the largest pore size diameter: These define the range of vacuum necessary for the low thermal conductivity.

Fumed silica materials have their largest pore size (300 nm) in the same order of magnitude as the mean free path of air molecules at standard temperature and pressure (70 nm).

The outer envelope is one of the critical components of a VIP and is responsible to maintain the vacuum in the panel. The envelope of VIPs is composed off multi layer films covering the whole element, including the edges.

The multilayer films usable for VIP envelopes consist of different layers with an overall thickness of 40-150mm. Currently, three different film types are being used for VIP envelopes:

Metal foils consisting of a central aluminium barrier layer, laminated between an outer PET layer for scratch resistance and an inner PE sealing layer

Metallized films made from up to three layers of aluminium coated PET films and an inner PE sealing layer

Polymer filmswith different plastic layers laminated to each other. The gas and vapour permeation rate through these materials is higher than with metal or metalized films. These films are only useful if the required lifetime is not too extensive or if special getters are integrated in the VIPs .

[Left] Vacuum technology as building insulation: VIPs and [right] a comparison between a vacuum insulation panels and conventional insulation with the same overall thermal performance .

Getters, desiccants and opacifiers

Important for the service life of the VIPs is maintaining the inner vacuum. To increase their service life, getters and desiccants are often added in the VIPs: Continuously adsorbing the gasses

(getters) and the water vapour (desiccants) in the VIP core material, they prevent the increase of the internal gas and vapour pressure.

A getter is a reactive material used for removing traces of gas from vacuum systems, such as vacuum tubes. 

A desiccant is a hygroscopic substance that induces or sustains a state of dryness (desiccation) in its local vicinity in a moderately well-sealed container.

Hygroscopy is the ability of a substance to attract water molecules from the surrounding environment through it her absorption or adsorption.

An opacifier is a substance added to a material in order to make the ensuing system opaque. An example of a chemical opacifier is tin dioxide (SnO2), which is used to opacify ceramic glazes and milk glass; bone ash is also used.

TRADITIONAL INSULATION METHODS

The majority of thermal applications used today are made of an internal and external wall, with the thermal material in the middle.

The thermal material Generally consists of:

Foam Material – Polyurethane

Fiber Glass

External Wall

Insulation Material

Internal

Wall

STRUCTURE OF VACUUM INSULATION PANELS

Thick aluminum – completely insulated

Sealing material

Metalized –material

Filler

Insulation Methods Thermal conductivity

Traditional Insulation 36 mW/(mK)

Vacuum Insulation Panels (VIP)

4 mW/(mK) fresh

Gas-Filled Panels (GFP) 40 mW/(mK

Aerogels 13 mW/(mK)

Comparison [left] between the thermal conductivities of conventional and advanced insulation materials and solutions and [right] between the required thicknesses for conventional insulation (e.g. glass wool) and a VIP

ADVANTAGES High performance thermal

insulating. Increased floor area. Appropriate refurbishing of

existing buildings with high restrictions.

Up to now the only material for which 4 cm is enough to meet (most of) building regulations.

Lower operating temperature increases thermal

Advantages And Disadvantages Of Vacuum Insulation Panels For Building Purposes

Land Transport

Housing And Construction

Industry

Sea Transport

Refrigeration

ReferencesVacuum insulation panels for building

applications: A review and beyondRuben Baetens a,b,c, Bjørn Petter Jelle a,b,*, Jan Vincent Thue b, Martin J. Tenpierik d, Steinar

Grynning a, Sivert Uvsløkk a, Arild Gustavsen e

Gas-filled panels for building applications: A state-of-the-art review

Ruben Baetensa,b,c, Bjørn Petter Jelle a,c,∗, Arild Gustavsend, Steinar Grynninga

Advanced Thermal Building Insulation– From Vacuum Insulation Panels to Nano Insulation

MaterialsBjørn Petter Jelleab and Arild Gustavsenc