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Old 19-11-2019, 11:19   #1
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best material for re-insulating a fridge insert

gday fleet of experts
i am currently in the process of destroying my galley in a frenzy to reinsulate a fridge insert to endure the tropical heat. just wondering if anyone has discovered the BEST INSULATION to use for this exercise. what experience do you have with it and what is the availability in mexico and south? my strawberry margaritas hang on the knowledge of the fleet. the area that the current inadequate spray in insulation from the eighties occupies cannot practically be increased (aside from cutting down the insert) this is a tangent i would like to avoid if at all possible.
thanks in advance to the well stocked knowledge vaults on this forum.
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Old 19-11-2019, 11:32   #2
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Re: best material for re-insulating a fridge insert

Aerogel is the best performing with a reasonable cost. About 3x insulation compared to the best foam. You cut it with scissors and stack it up to the thickness you want. While it does not absorb much moisture , it's best to wrap and tape it in plastic sheeting.

It may take some looking to find it outside the US. I've bought it through Ebay. The major brand is Aspen. This Ebay listing may be Chinese but other listings are for the genuine Aspen product.

https://www.ebay.com/itm/Silica-Aero...ef9f3c34cbe985
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Old 19-11-2019, 13:58   #3
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best material for re-insulating a fridge insert

I estimated that for my 11 c.u. box, Aerogel would be around $1800+ for R-30.
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Old 19-11-2019, 14:25   #4
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Re: best material for re-insulating a fridge insert

Perhaps considere Vacuum Insulated Panels for the major area and spray foam to seal the panels around the corners. Not sure about the availability of domestic production in Mexico but certainly very light to have shipped in a protective packaging.

The comparatively much smaller thickness requirement avails for garnering a considerably larger useful internal volume of your chilly boxes.

Reference: https://en.wikipedia.org/wiki/Vacuum_insulated_panel

Thermal performance
Heat transfer occurs by three modes: convection, conduction and radiation. Creating a vacuum practically eliminates convection, since this relies on the presence of gas molecules able to transfer heat energy by bulk movement. A small decrease in pressure has no effect on the thermal conductivity of a gas, because the reduction in energy-carrying molecules is offset by a reduction in collisions between molecules. However, at sufficiently low pressure, the distance between collisions exceeds the size of the vessel, and then the conductivity does reduce with pressure.

Since the core material of a VIP is similar in thermal characteristics to materials used in conventional insulation, VIPs therefore achieve a much lower thermal conductivity (k-value) than conventional insulation, or in other words a higher thermal resistance per unit of thickness. Typically, commercially available VIPs achieve a thermal conductivity of 0.004 W/(mK) across the centre of the panel, or an overall value of 0.006-0.008 W/(mK) after allowing for thermal bridging (heat conduction across the panel edges) and the inevitable gradual loss of vacuum over time.

Comparison to conventional insulation

The thermal resistance of VIPs per unit thickness compares very favourably to conventional insulation. For instance, standard mineral wool has a thermal conductivity of 0.044 W/(mK),[6] and rigid polyurethane foam panels about 0.024 W/(mK). This means that VIPs have about one-fifth the thermal conductivity of conventional insulation, and therefore about five times the thermal resistance (R-value) per unit thickness. Based on a typical k-value of 0.007 W/(mK), the R-value of a typical 25-millimetre-thick (1 in) VIP would be 3.5 m2K/W (20 hft2F/BTU). To provide the same R-value, 154 millimetres (6 in) of rockwool or 84 millimetres (3 in) of rigid polyurethane foam panel would be required.

However, thermal resistance per unit price is much less than conventional materials. VIPs are more difficult to manufacture than polyurethane foams or mineral wools, and strict quality control of manufacture of the membranes and sealing joins is important if a panel is to maintain its vacuum over a long period of time. Air will gradually enter the panel, and as the pressure of the panel normalizes with its surrounding air its R-value deteriorates. Conventional insulation does not depend on the evacuation of air for its thermal performance, and is therefore not susceptible to this form of deterioration. However, materials like polyurethane foam are susceptible to water absorption and performance degradation as well.

In addition, VIP products cannot be cut to fit as with conventional insulation, as this would destroy the vacuum, and VIPs in non-standard sizes must be made to order, which also increases the cost. So far this high cost has generally kept VIPs out of traditional housing situations, However, their very low thermal conductivity makes them useful in situations where either strict insulation requirements or space constraints make traditional insulation impractical. VIP performance is also temperature dependentwith increasing temperature, conductive and radiative transfer increase. Furthermore, typical panels cannot operate much above 100 C (212 F) due to the adhesive used to seal the thin envelope.
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Old 20-11-2019, 03:02   #5
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best material for re-insulating a fridge insert

Theres also the option of two part poured foam, which, if handled correctly, has an R value similar to rigid polyurethane panels.

But it can be a right PITA to work with.

Having recently blasted my fridge box out of its enclosure using two part foam, I gave up and went with extruded polystyrene panels. Their R value was good enough, but not great.
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Old 20-11-2019, 10:06   #6
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Re: best material for re-insulating a fridge insert

X2 on VIPs. 15 years on mine. So far still working fine. I did both VIP and 1" Urethane sheet with foam caulking and epoxy fiberglassed a new interior. Reduced power consumption by about 75%.
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Old 20-11-2019, 10:24   #7
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Re: best material for re-insulating a fridge insert

A friend of mine used vacuum insulated panels plus some foam to fill the odd gaps and was amazed at how much it reduced battery consumption.
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Old 20-11-2019, 11:49   #8
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Re: best material for re-insulating a fridge insert

it is possible to use pour in place foam and control it (some what).


Here is what I did and I am very happy with its performance.
Re-insulating My Refrig. Box the Hard Way.
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Old 20-11-2019, 16:27   #9
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Re: best material for re-insulating a fridge insert

I used Aerogel/Cryogel and had it shipped to the West Indies - very light, on a long roll.
Cut it with scissors for each layer of each panel - 2-3 layers [thicker is better] and interspersed with kitchen aluminium foil. Sides and bottom of inside of freezer. Made thin fibreglass internal box panels and spray glued all in place. Finished off with spray foam insulation to fill in gaps on outside of freezer box where insulation was missing. Made a huge difference to battery usage. Because it is so thin, I could use 2-3 layers and not lose much inside area of the freezer.
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Old 21-11-2019, 09:48   #10
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Re: best material for re-insulating a fridge insert

foil only adds insulation value if it's facing an air layer. but it is also a good vapor barrier. an effective vapor barrier on the warm side is essential to long life of foams.
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Old 21-11-2019, 09:49   #11
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Re: best material for re-insulating a fridge insert

I believe Beth Leonard listed vacuum insulated panels as one of their big disappointments. your results may vary
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Old 21-11-2019, 23:18   #12
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Re: best material for re-insulating a fridge insert

Freezer Insulation of R-40 per inch or better
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Old 30-11-2019, 08:39   #13
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Re: best material for re-insulating a fridge insert

Never use the residential Styrofoam that is made of little nuggets - the type that leaves round crumbs when you cut it. We had to refurbish our refrigerators and freezers and found the problem was the insulation was completely soaked with condensation water and making things worse.
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