Aerogel - Spaceloft Insulation for Fridge / Freezer

[antoha]

I bought directly from these folks: http://thermablok.com


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[YachtManuals]

Originally Posted by zboss

I think you guys are confusing aerogel with spaceloft which is perfectly suitable for insulation (3"= R-30), is hydrophobic, and is as mechanically sturdy as fiberglass batting- which btw also looses r-value when crushed. Certainly a lot more expensive than blue board but if you want to maintain the size of your fridge (we do) its your only real option besides the vacuum panels.

That's right, you don't use that light blue aerogel as fridge insulation. We used Aspen Cryogel 10mm (more like a blanket), in several layers, to achieve about double the insulation of polyurethane 'blue board'. It is hygrophobic, meaning water beads off (but that's not relevant). However it's not at all by itself impermeable to water vapor, which is the big problem as mentioned above. But the cryogel version does have on one side (outside) a vapor-proof aluminum foil which makes it suitable as fridge/freezer insulation, provided all internal joints are sealed with aluminum or mylar tape. The inner and outer box enclosures should be completely airtight and sealed against vapour (e.g. with coated FRP or metal). We have a small fridge with 5cm insulation and a BD30 compressor consuming 15 to 30 Ah/day (12V) depending on the season, covered many times by our solar panels. You may have to order Cryogel from the US. Or use more thickness of polyurethane board (very easy to find), finishing with a perfect vapor barrier on the inside (specially the bottom which gets wet) and outside, including inside any openings you have to make for tubing or wires. Good luck. Leo

[danman81]

Man, I love this forum! Does anyone know if it will be okay to use Silicone Caulk as a sealant to use with Spaceloft? Does anyone think it would melt the Spaceloft? I've also heard of using 3M 5200 as a sealant to use with spaceloft, but i need something that is more flexible and vibration dampening like 100% silicone, and not to mention silicone has it's own thermal benefits..

[antoha]

I couldn't get anything to stick to this insulation - ended up stitching layers with a thread when I had to. It was just so it wouldn't flap about as I was working with it; in the end, the insulation is completely encapsulated in fiberglass.


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[senormechanico]

We useda liberal application of 3m 77 spray glue. It stuck just fine.
Silicone or other stuff won't dissolve the aerogel as it's basically a form of sand in very long squiggly strands.

[scherzoja]

This is an interesting thread.
This week, I removed the fridge. Really, I removed the galley (got a little carried away with the sawzall! )

Anyway, I will rebuild the frige box. For discussion, let's say the outside dimensions of the fridge are: 45" wide, 35" tall, 24" deep.

For an R30, I would need to have 3" of spaceloft or 5" of ISO.
My surface area for that box is about 42 sqft; therefore, I would need ~$1900 of spaceloft for R30+

Spaceloft = $5 per 3/8" layer = $15/1" layer @ R10/inch
Therefore, R30 cost per sqft=$45
$45 / sqft x 42 sqft = $1900 for R30 insulation with spaceloft

Using ISO @ $2/1" @ R7/inch
1" = R7, 5" = R35
$2/1" sqft x 5" = $10/sqft @ R35

$10/sqft x 42sqft = $420 for R35 with ISO

Assuming my calculatios are correct, that is a difference in cost of $1500

With the room I have, if I use 5" of ISO, I would end up with a ~9cuft fridge box at R35

If I use spaceloft, I would end up with about the same R with ~11cuft fridge box.

Given that either net volume will be acceptable, why would I spend ~$1500 more on spaceloft?

Only reason I can see is related to possible condensation issues because ISO is hydroscopic.

Let's say I'm flat-ass broke and don't want to afford the extra $1500 for spaceloft, how would I mitigate the possible condensation issues?
Completely encapsulate the iso layers with epoxy/cloth? If so, the only condensation would with whatever moisture were present at time of encapsualtion.

Would it be helpful or detrimental to put a vapor barrier (foil, mylar???) between layers of ISO?

It's kinda late where I am and I'm kinda tired, so my calculations and logic might be a bit off.

Thanks ya'll

[zboss]

Money is almost always the driving factor in these types of decisions.

9 cuft is already a large fridge. We have a 7.8ish and its got a lot more room than we use.

If money were not important,you could use spaceloft to get that 11 cuft space and split the space into a separate fridge and freezer with independent systems. Then you could have a large freezer AND fridge!

[antoha]

For me, the main reason I used spaceloft was volume: our fridge is 20" on the longest edge, and one side is curved (it's next to the hull). We would have lost half the useful space to insulation if we went with regular; plus the curved side would have been hard to do. If it weren't for these reasons, I would have surely stayed with the cheaper and more conventional insulation.


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[Richard Kollmann]

We know that open cell insulation due to temperature cycling by thermostat creates a different problem in marine refrigeration than it does in space heating where open cell insulation is commonly used. A few years ago Vacuum Insulated Panels (VIPs) with open cell insulation were highly praised and experimented with in boat refrigerators.
Constant expansion and contraction of VIPs caused failures of airtight membrane barriers even welded thin aluminum sheet metal plates. VIPs are mainly used in short duration shipping containers and rarely used today in boat refrigerators because of their reliability.

It is true that open cell insulation in space heating is not prone to collect moisture but what about the dehumidifying effects of a marine cycling refrigeration system on open cell insulation?
If a boater spends time and money on Aerogel or Spaceloft or other open cell insulations the question will always be the service life of that system’s insulation do to open cell space water accumulation?

[scherzoja]

Thanks Richard, and zboss for the comment on 9 cuft might be overly large.

I had a hunch there was more to this than just R value.

Although this thread started several years ago, it is very helpful because I know very little about refrigeration properties in this context.

If I understand correctly, Spaceloft, et.al. are open-cell materials and air can pass through them; whereas, polyiso is closed-cell; therefore air cannot move through the material.

Mitigating the movement of air through open-cell material by encapsulating (i.e. VIP) is a short-term solution because the temperature cycling of a marine refrigerator box leads to expansion/contraction of the sealed block of insulation, causing cracks in the encapsulating boundary, thus rendering the encapsulation useless. Once air resumes movement through the open-cell material, it will bring water vapor which will condense at the dew point boundary, leading to water accumulation and loss of R. The dewpoint boundary will vary its position within the insulation depending on exterior and interior temperature differences, causing water accumulation throughout the thickness of the insulation medium.

Comparing open-cell with closed-cell material, through which air cannot move, leading to no risk of water accumulation at the dew point boundary , except for any finite amount of water vapor that might have entered the closed-cell medium during manufacture, closed-cell looks like a better long-term insulator for marine refrigeration.

Unless the integrity of the encapsulation of open-cell spaceloft can be assured, it seems that the only reason to use spaceloft is if net volume would be severely diminished because of the increased insulation thickness of closed-cell material.

I have read, perhaps misread, that polyiso is hydroscopic. To what degree would that aspect put polyiso at a disadvantage relative to the air movement issue of spaceloft?

If I understand this correctly, in my situation with a gross outside dimension of 45" x 35" x 23", the use of polyiso would be appropriate because I can achieve a min. R30+ and still have at least 6 cuft, likely more net interior.

Am I missing anything else in my understanding of this?

Thanks for helping me understand.

[s/v Jedi]

The thing to understand is that you need stop three mechanisms that transport heat as well as block moisture entering the isolating materials.

The three are convection, conduction and radiation.

When you encapsulate an insulating material with say fiberglass, then you need to be aware that you can't encapsulate individual panels and then put them together; you need to create the complete structure and then encapsulate it so that there is nothing other than the insulating material between the outside and the inside surfaces of the box. If using encapsulated panels put together, you create channels that conduct heat much better than the insulating material, killing the overall performance of the box.

[senormechanico]

Years ago, I made the mistake of building a box with Thermax, a polyisocyanurate rigid home insulation which is hygroscopic. I didn't know it at the time.

After about ten years, I rebuilt the box with Aerogel, and when I disassembled the old insulation, it was mostly wet throughout at the bottom and a few inches up the sides.

[antoha]

Another comment I wanted to make: I too ripped the galley apart to rebuild the fridge. I kept track of the time I was spending: about 400 hrs of work total. So in retrospect, I wish I had gone with full price spaceloft instead of the deal I found (scraps), because in the grand scheme of things, even though I may have saved 30% in spaceloft costs, it's all kind of insignificant compared to the amount of work you have to do.
I guess all I'm sayen' is: it's so much work, you might as well do it right...

[zboss]

I'm following this thread very carefully because we plan on doing this job starting in the next 4 weeks. We are strongly considering spaceloft because if we do use traditional foams, we will end up with a thermos cup for a fridge and freezer!

Originally Posted by scherzoja

If I understand correctly, Spaceloft, et.al. are open-cell materials and air can pass through them; whereas, polyiso is closed-cell; therefore air cannot move through the material.

I've contacted a distributor for spaceloft and their solution to this is to wrap the spaceloft with a plastic barrier - you don't just put the spaceloft on raw. They gave lots of examples but the general application is:

1. Build an inner (or outer if going the other way) fiberglass shell
2. wrap shell with radiant barrier of some sort
3. Apply spaceloft
4. wrap spaceloft with plastic sheet barrier
5. tape over barrier with foil tape all around the spaceloft
6. Place in the outer shell and seal

Unless you drill through or puncture the wrap it should be fine for a long time. So, yes, application takes care but you are going go do that anyway right?

Also, aerogels claims "No reduction in R-value with water ingress".

I'm sure there are a few variations on this theme but spaceloft is used in lots of commercial applications for refrigeration. It also has the advantage that it doesn't disintegrate over time like through out gassing. They claim a 50 year life with only a 2% loss of insulation.

[Celestialsailor]

I'll chime in here and say it has been over 2 years with my custom aerogel blanket insulation. As mentioned above, I built a male mold and gelcoated and laminated a box. Came out perfect. I then wrapped the outside of the box with many layers of plastic food wrap. then 3m contact three layers of the Aerogel blanket, followed by more wraps of plastic wrap, then clear tape to stop the chalking it does. I was told NOT to inhale the dust. I had my little Canon camera 10ft. away and it got into the shutter and ruined the camera, so be careful.
After it was all encapsulated, I forced it into the refer area and filled the large voids with blue foam and smaller areas with pour foam. I have anywhere from 3"s to 5"s of insulation. I couldn't tell you what the R factor is or care since it is what it is.
What I can tell you is that my draw on my little air cooled Adler/Barbour is anywhere from 1.25-1.5 amps per hour. It doesn't change much. Mind you, my box is under 3 cu.ft.