Aerogel vs Cryogel

[jordanbigel]

I'm starting on a project this month to re-insulate my (top-loading) reefer/freezer boxes. Luckily I have a skilled shipwright working with me, though he has no experience with insulating reefer boxes, so I am taking the lead and working out a plan for that.

I'm planning to use combination of materials including aerogel, polyiso (pink board) and XPS (blue board). I've read a ton of threads here on the topic of insulation, and based on that I am planning on 1" of blue board next to the box (which is GRP) for its superior moisture protection as I understand it followed by 3 layers (30mm) of aerogel and 2 layers (2") of polyiso for the fridge, and for the freezer, 1" blue board followed by 3 layers (3") of polyiso and 4 layers (40mm) of aerogel which should give me 4" total (appx R30) for the fridge & 5.6" total (R40) for the freezer (the boxes are separate, by side by side with a 2 or 3" gap between them).

I have three questions on my mind:

1. Aerogel vs Cryogel?
My understanding is that they are the same substrate and that Cryogel has a foil vapor barrier on one side but aerogel is less "dusty". My main question here is do I want vapor barrier on each layer of the Cryogel if I have 3 or 4 layers of it stacked up. I read one post where the member described removing the foil barrier from each layer except the outer layer (or is it the inner layer - details details). Other members described using Aerogel (comes without a vapor barrier) and then adding a single vapor barrier layer to the outer layer (or is it the inner layer) using 3M 77 adhesive. Seems like a pain to buy Cryogel and then remove the barrier from each layer except one.

Related question - if I go with the Aerogel what exactly do I add as a vapor barrier? Or should I just use the cryogen and leave the barrier on each layer - is that bad? I know nothing about insulation except what I've researched and read online, so I am not familiar with the different properties or brands of materials used for vapor barriering. Help?

Also, if the whole stack of aerogel/cryogel is encased in plastic wrapping, isn't that a vapor barrier?

2. Everyone describes wrapping the aerogel in plastic and taping it shut with foil vapor tape. Cool. What kind of plastic. I've got a huge roll of 6mil plastic from Home Depot used for blocking off areas during construction, etc., etc - is that okay, or is there a specific optimal type and thickness of plastic wrap to use for this purpose?

3. What I've read in at least one thread was the advice to a) create a box with blue board (XPS?) which fits around the GRP box, then fill in the gaps between the box and the blue board with spray expanding foam. How on earth can this be done? Assuming you tape the blue board to the sides and bottom of the box with foil vapor tape - how the hell do I get the foam to go in between the board and the box? Certainly I can't cut holes in the blue board at regular intervals and inject foam until it runs out the holes? If I try and inject it from the top down between the blue board and the box (which should be a tight fit to begin with) won't the foam expand and stop long before it reaches the bottom, or do I stick in a really long thin hose/tube? I've obviously never done this before, and I am having trouble picturing how to proceed - would be grateful for more details from someone who has done this procedure.

Thanks to everyone who has already shared their knowledge on this topic, I feel like I am close to having a grasp on this thanks to your collective contributions here.

[Bellinghamster]

A couple thoughts: Moisture is coming from the outside trying to condense on the cold materials (box exterior, layers of insulation close to the box). 6mil poly sheeting around the outside of everything will prevent moisture ingress into the insulation but will be hard to work with (stiff, non-stretchy) and it needs to be perfectly sealed, any leaks will allow moisture in but it'll have a hard time finding its way back out again if/when you turn off the fridge/freezer for an extended period of time. Unfortunately I don't have any recommendations for plastic, but thinking either shrink wrap or cling film (the heavier stuff used for wrapping pallets might do the trick. Bagging each layer of insulation sounds like a great idea to "isolate" them, but in practice sounds like it'll be hard to assemble them. Another option is to fiberglass-wrap the outside of the assembled insulation to seal it, which would be a more permanent sesal than plastic and tape. Be sure to plan and seal up any penetrations through the insulation (i.e. refrigerant lines).

You can poke (drill) holes in the blue board to squirt expanding foam between the box and board. The foam will plug the holes. Be aware that the expanding foam will also push the foam board away from the box wall. I'd probably only do this in the corners if there is a gap (i.e. the box is molded with radiused corners) and not worry about the flat planes.

[Bowdrie]

Originally Posted by jordanbigel

What I've read in at least one thread was the advice to a) create a box with blue board (XPS?) which fits around the GRP box, then fill in the gaps between the box and the blue board with spray expanding foam. How on earth can this be done? Assuming you tape the blue board to the sides and bottom of the box with foil vapor tape - how the hell do I get the foam to go in between the board and the box?

You don't put the blue-board box against the FRP and try to inject/spray foam to fill a tiny gap,
You space the blue-board box away from the FRP box by 1>2in. and use poured foam, you pour the liquid down the sides of the FRP and let it expand away from the FRP, this insures a sealed surface on the FRP without any entrapped air against the FRP, this is an important 1st step in preventing condensation on the exterior surfaces of the FRP from migrating into the foam.
Whatever you do/use on surfaces exterior to the blue-board is your choice.
Good insulation starts from the exterior of the FRP and works outward from there.

[jordanbigel]

Originally Posted by Bowdrie

You don't put the blue-board box against the FRP and try to inject/spray foam to fill a tiny gap,
You space the blue-board box away from the FRP box by 1>2in. and use poured foam, you pour the liquid down the sides of the FRP and let it expand away from the FRP, this insures a sealed surface on the FRP without any entrapped air against the FRP, this is an important 1st step in preventing condensation on the exterior surfaces of the FRP from migrating into the foam.
Whatever you do/use on surfaces exterior to the blue-board is your choice.
Good insulation starts from the exterior of the FRP and works outward from there.

Thank you - this sounds more doable. Not sure how you handle the bottom, how to keep a gap so the box stays 1-2" above the bottom blue board. A lot of tricks involved in this process. Maybe turn it upside down and do three sides, then attach the bottom blue board and pour the foam down the 4th side into the bottom? Sorry, I am sure its more simple in reality than it sounds in my mind.

[Bowdrie]

Originally Posted by jordanbigel

Thank you - this sounds more doable. Not sure how you handle the bottom, how to keep a gap so the box stays 1-2" above the bottom blue board. A lot of tricks involved in this process. Maybe turn it upside down and do three sides, then attach the bottom blue board and pour the foam down the 4th side into the bottom? Sorry, I am sure its more simple in reality than it sounds in my mind.

You're getting it.
You do have the box upside down and pour all 4 sides first, then lay the box on a side and pour the bottom.
You can also pour the bottom first.
I wish I could draw a diagram that I could post that would show how the sequence goes using simple pieces of plastic covered plywood as spacers for the last pour on the bottom.
The simplest way is the box upside down, but with the blue board box extending the full thickness of the bottom insulation and pouring the whole thing, down the sides, then the bottom.
Then, using the blueboard as perimeter guides you board-sand the poured foam flush with the blue board and give it a couple of coats of epoxy.
That way precludes blue board on the bottom, but blue board can be used with a slightly more involved method.
As with your description, my description probably sounds much more involved than it really is.
I wish I could make a YouTube vid, but that's beyond my pay grade.

What we're after is for the sides and bottom of the FRP to be incased in a liquid pour that expands outward from the FRP.
What we do after that is icing on the cake, and there are many ways to apply/spread the icing.

[jordanbigel]

Originally Posted by Bowdrie

You're getting it.
You do have the box upside down and pour all 4 sides first, then lay the box on a side and pour the bottom.
You can also pour the bottom first.
I wish I could draw a diagram that I could post that would show how the sequence goes using simple pieces of plastic covered plywood as spacers for the last pour on the bottom.
The simplest way is the box upside down, but with the blue board box extending the full thickness of the bottom insulation and pouring the whole thing, down the sides, then the bottom.
Then, using the blueboard as perimeter guides you board-sand the poured foam flush with the blue board and give it a couple of coats of epoxy.
That way precludes blue board on the bottom, but blue board can be used with a slightly more involved method.
As with your description, my description probably sounds much more involved than it really is.
I wish I could make a YouTube vid, but that's beyond my pay grade.

What we're after is for the sides and bottom of the FRP to be incased in a liquid pour that expands outward from the FRP.
What we do after that is icing on the cake, and there are many ways to apply/spread the icing.

Thanks, very helpful. The simple method you describe, working upside down and pouring onto the bottom with the XPS on the side as a form sounds pretty easy. The "plastic covered plywood as spacers" is a mystery to me so far, but I think I get the basic idea and will work out the rest. Thanks.

[ilCigno]

Almost all plastic foils are not airtight, so I learned from someone who is very skilled in vacuum infusion. He uses a specific plastic foil which is airtight. Could this type of foil be of any help for this project?

[Celestialsailor]

I've used Aerogel and it is really dusty.

[akopac]

Consider 3 types of heat transfer:
1. Conducted
2. Convective
3. Radiant
I’m in Mazatlan for hurricane season. Right now the water is 88F air 90F. Next month water 90F Air 100F. Every day is a high UV day. The Sea or Cortez is the same.
My bats are full at 10:30 am. Give yourself a airgap and foil barrier. I glasses and epoxy painted the outer shell of my box withe epoxy paint pigmented white with titanium dioxide and foil protected my box. That took care of a lot of the UV radiation and the foil took care of the rest. The foil will reflect the UV radiation into something either the box shell or back out through the hull. I will say I’ve seen an awefull lot of windshield reflectors hanging over the side of boats who didn’t account for radiant heat though :-)