Building a Reefer Box with Aerogel

[GordMay]

Originally Posted by s/v Jedi

... So if you build a foam box to install in the galley, against the hull, cabinet etc. Tthen it is still a good idea to cover it with aluminum foil, shiny side out (as well as a moisture barrier that goes on first). Where this foil touches the hull, cabinet it’s useless, but when there is a void it will work.

Just to clarify:

Vapor barrier materials are installed on the warm side of the insulation, which, in a refrigerator, is on the outside of the insulation.

For a building assembly: In warm climates, it will be on the exterior of a building wall, and in cold climates, it will be on the interior.

Water vapor can move through many surfaces, through the process of permeation. This is when vapor molecules (in this case, water vapor) can move through a porous material, in the direction of high relative humidity, to low relative humidity.
If water vapor makes contact with a surface, whose temperature is below dew point, it can condense into liquid water, which reduces the effectiveness of the insulation, and which can then result in nasty biological growth.

“Vapour barrier in Cold Storage Design”
➥ http://www.ramesh-paranjpey.com/arti...Jan%202010.pdf

[rgleason]

GordMay has this absolutely correct, as it follows well known building practices. Think about where condensation occurs and where the dewpoint is most likely.

[s/v Jedi]

Originally Posted by GordMay

Just to clarify:

Vapor barrier materials are installed on the warm side of the insulation, which, in a refrigerator, is on the outside of the insulation.

For a building assembly: In warm climates, it will be on the exterior of a building wall, and in cold climates, it will be on the interior.

Water vapor can move through many surfaces, through the process of permeation. This is when vapor molecules (in this case, water vapor) can move through a porous material, in the direction of high relative humidity, to low relative humidity.
If water vapor makes contact with a surface, whose temperature is below dew point, it can condense into liquid water, which reduces the effectiveness of the insulation, and which can then result in nasty biological growth.

“Vapour barrier in Cold Storage Design”
➥ http://www.ramesh-paranjpey.com/arti...Jan%202010.pdf

Originally Posted by rgleason

GordMay has this absolutely correct, as it follows well known building practices. Think about where condensation occurs and where the dewpoint is most likely.

All that is for houses.

For a refrigerator on a boat, you have an inner liner, then the foam insulation which blocks both conduction and convection heat transfer, followed by a moisture barrier, then the radiation barrier and this is what is mounted, i.e. against the boat’s structure like the outer hull, a bulkhead, cabinet side etc.

It would be great when you can add an air gap between hull and box but for every such installation I have seen, this is not the case, simply because there isn’t enough room.

Same for something like a deck: the only radiation barrier we can make it white painted decks. There is no attic where we can create more elaborate barriers.

[rgleason]

Very sorry Jedi, but you can't go against physics. It just does not work, regardless of it being a boat or a house! You know that, dear friend.

[s/v Jedi]

Originally Posted by rgleason

Very sorry Jedi, but you can't go against physics. It just does not work, regardless of it being a boat or a house! You know that, dear friend.

What doesn’t work? The moisture barrier?

Edit: this is how it is on every boat with icebox. There isn’t room for proper radiant barriers, how can you think it’s different?

[rgleason]

Houses present similar problems and are also subject to physics. In this case

From Cold Inside to outside

insulation which blocks both conduction and convection heat transfer,
..moisture barrier,
then the radiation barrier

Optimal air space between the shiny side of the radiation barrier and the hull is 1/2" but even 1/4" will help. The air space will also help to vent moisture away.

We can learn from building construction sciences: In residential construction, in colder climates, Building Science supports two approaches for sprayed polyurethane foam insulation (which acts as an effective vapor barrier) against the underside of the roof deck, often used for cathedral type ceilings:

• one approach, sometimes required by the local code official, requires baffles to provide vented area just below the roof,
• and a second approach which permits sprayed foam direct to the underside of the roof provided it is of adequate thickness 3"-7" dependent on the climate due to the need to control dewpoint.

The second type of roofs in more northern climates do not use a reflective barrier (in that component of the roof), where practice has been not to use a reflective barrier and air space, presumably because that approach is more effective in warmer climates. With our interest in reducing energy use in buildings by at least 40% it is likely that a reflective barrier and venting air space will become fully expected and incorporated in new and retrofit roofs. This improvement will provide one small improvement, but I can understand why some boat owners would decide not to use a reflective barrier and air space simply because boat refrigerators are in a very tight space.

[s/v Jedi]

Originally Posted by rgleason

Houses present similar problems and are also subject to physics. In this case

From Cold Inside to outside

Optimal air space between the shiny side of the radiation barrier and the hull is 1/2" but even 1/4" will help. The air space will also help to vent moisture away.

We can learn from building construction sciences: In residential construction, in colder climates, Building Science supports two approaches for sprayed polyurethane foam insulation (which acts as an effective vapor barrier) against the underside of the roof deck, often used for cathedral type ceilings:

• one approach, sometimes required by the local code official, requires baffles to provide vented area just below the roof,
• and a second approach which permits sprayed foam direct to the underside of the roof provided it is of adequate thickness 3"-7" dependent on the climate due to the need to control dewpoint.

The second type of roofs in more northern climates do not use a reflective barrier (in that component of the roof), where practice has been not to use a reflective barrier and air space, presumably because that approach is more effective in warmer climates. With our interest in reducing energy use in buildings by at least 40% it is likely that a reflective barrier and venting air space will become fully expected and incorporated in new and retrofit roofs. This improvement will provide one small improvement, but I can understand why some boat owners would decide not to use a reflective barrier and air space simply because boat refrigerators are in a very tight space.

Yes, that is clear, but in boats they even pour expanding foam in a cavity between hull and icebox liner… no air gap, no radiation barrier, no moisture barrier. Again, all that is from code and descriptions from houses.

Show me a refrigerator home appliance with a radiation barrier with air gap. The best you can do is a stainless steel outside.

[Bowdrie]

Originally Posted by s/v Jedi

Yes, that is clear, but in boats they even pour expanding foam in a cavity between hull and icebox liner… no air gap, no radiation barrier, no moisture barrier. Again, all that is from code and descriptions from houses.

Quite true, and will be absolutely just fine, (with a caveat).
If you're going to bring the foam out to the hull surface, you need to pour the mixed liquid directly on to all of the required hull surface so that it expands inward, (no dry spots, liquid over every bit of area).
Just dumping a bunch of liquid into the cavity results in random expansion in which the foam can leave air pockets/voids against the hull.
When the liquid is poured against a surface and expands away, that surface becomes sealed against any air/moisture intrusion.
It's like when they spray the inside of a metal hull, it's the liquid mix that seals the metal with the expansion taking place away from the surface.
That same principle is best for the liner, with the liner upside down, (and a dam around it,) you pour the liquid across the bottom and down the sides before you install it.

[rgleason]

"(no dry spots, liquid over every bit of area)" - yes this is also absolutely the right thing to do.


For marine it is particularly important, I think, to use "closed cell" foam, not open, like iscynene. Another concern is bilge water and the foam being under water...