The energy efficiency of household appliances such as refrigerators largely depends on the properties of the thermal insulation solution used. The challenge lies in how to reach top performance levels without restricting internal dimensions or changing standard sizes.
The thermal conductivity of VIPs is 6-8 times smaller than bulky PU foam insulation, therefore VIPs represent an exceptionally efficient solution to dramatically upgrade the efficiency rating of the appliance or increasing the useable internal volume, without the need for extensive constraints or modifications to the structural or external design. In addition VIPs can contribute to solving sweating problems in areas where there is no room for a thick insulation layer.
Through the use of VIPs, household and commercial fridges qualify for superior energy ratings (from U.S. Energy Star or European A+++) effectively and economically.
VIPs for fridges are commonly made from two different types of core materials: glass fibers (fiberglass), and silica powder (fumed silica).
Fiberglass cores provide low center of panel thermal conductivity. While economical to produce, fiberglass is extremely sensitive to gas and moisture permeation. Therefore, most fiberglass panels used in refrigerators are produced with aluminum foil-based envelopes. The heat conducted by the relatively thick aluminum foil causes a thermal bridge that can have substantial negative impacts on the performance of the panels, and consequently, the energy consumption of the refrigerators.
Hanita offers a hybrid solution for fiberglass cores — a "combination envelope" — Hanita's aluminum foil laminates on one side of the VIP's bag with Hanita's ultra-high-barrier metallized films on the other side of the bag. This combination envelope dramatically decreases the effects of the heat bridge and substantially reduces moisture vapor and oxygen and nitrogen molecule gas permeation compared to envelopes with metallized films only to provide an optimal solution for fiberglass VIPs in refrigerators.
A fumed silica core generally shows a higher center of panel thermal conductivity, but due to its nanoscopic pores size, metallized laminates can easily be used for the envelope material to limit the thermal bridge effect with almost no degradation along the life time of the appliance. As a result, the total insulation gained by the combination of the fumed silica core and metallized laminates (λeff) is substantially superior to that achieved by glass fiber/aluminum foil panels. Using the most effective metallized barrier laminate will deliver very low heat conductance through the envelope and more effective overall insulation performance for the entire life of the panel.
Hanita's ultra-high-barrier multilayer metallized laminates are ideal for silica powder-based core materials. Hanita's range of premium metallized laminates provides exceptionally low Moisture Vapor Transmission Rate (MVTR) and oxygen and nitrogen transmission rates (ONTR) to increase panel longevity and improve functionality. These polyester and polyethylene laminates are interlayered with thin high-barrier metallization layers and provide the highest level of protection against permeation of atmospheric gases and moisture, reaching MVTR <0.01 gr/m2day (38°C, 100% RH), and oxygen transmission rate below detection level.
Vacuum Insulation Panels are integrated into appliances with sustained elevated temperature levels such as hot snack vending machines, rice cookers, or hot water boilers/heaters. In addition to energy efficiency, a major advantage of VIP usage in these applications is space saving, which affects both the appliance size and its internal volume.
Here Hanita's hybrid solution, its combination envelope of exceptional high-barrier metallized laminates, ensures minimal levels of thermal bridge to give outstanding efficiency throughout the panels' life.
We recommend using hybrid envelope constructions for elevated temperature applications. Hanita's aluminum foil laminates on the high-temperature side paired with Hanita's metallized laminates on the cooler-facing side. This optimal construction minimizes the thermal bridge effects and provides effective insulation during the lifetime of the appliance.
Hanita VIP ultra-high barrier laminates are available in rolls, or pre-formed as hybrid or standard envelopes.