Refrigeration Box Insulation

[Matt Johnson]

I don't understand everyone saying not to use spray foam. Isn't it closed cell foam? Now, I'm not sure about the DOW foam, but I know foam-it green is a closed cell foam. What would be the issue with this?

[daddle]

Originally Posted by funjohnson

I don't understand everyone saying not to use spray foam...

Because in professional tests as well as personal experience it compares poorly with proper products. Looking like insulation is different than being good insulation.

The spray stuff is meant to seal building gaps from infiltration, drafts, which is a completely different application than thermal insulation.

[Bill_E]

This is a HUGE issue for me. I should have redone my refrigerator boxes before leaving Florida but here I am and I'm going to do it right. I've found, on my cruise so far, that my compressors are running a lot! And, one of my compressors just crapped out. I haven't figured out why yet but it can't help that it is the one that seems to run the most.

I used to work on the periphery of insulation technology and I think that there are two issues in foam insulation. The first is closed cell!! If you have open cells water will quickly diffuse into the pores, condense, and leave you with a rotten R value. Unless, you are sailing the Sahara!! The second consideration is "pore size". If the bubbles are too small (density is too high) then there is more polymer than "air" voids and that doesn't work well. If the pores are too large there will be convective heat transfer across the voids. It would help to fill the pores with helium but that isn't likely!!

There are several foam materials that work well. I think that extruded polystyrene can have an R value around 5 per inch and some of the polyurethane and polyisocyanurate foams can go as high as 8 per inch. I'm not sure if these are easily available on the commercial market.

Most of these are not hydrophillic so, in principle, they don't have to be "bagged" but I wonder if it wouldn't help to vacuum bag them before installation. Additionally, a layer of reflective mylar would probably really help reduce radiative heat transfer.

And...it's really important to avoid gaps and channels because the heat leak through an imperfection could ruin all of the cost and effort in getting good insulation material.

I'm seriously thinking of trying one of the inorganic foam materials with very high R values.

I wonder if anyone has any experience with these. I know they can be very expensive and have some structural, vibration problems.

Also, has anyone found a refrigeration compressor that is much more efficient than the standard marine ones? It might be worth considering novel technologies for cooling as well.

Bill

[daddle]

Neither polyurethane and polyisocyanurate are good with moisture over a period of time. They must be tightly sealed from exterior moisture. For this reason extruded polystyrene is the preferred choice for common materials even though it has a somewhat lower initial R-Value. Exotics can be much better but cost much more.

The Danfoss-type compressors in a proper installation are nearly as efficient as one can get without going to some exotic refrigerant like ammonia (very hazardous). Thick insulation around the smallest possible box has the biggest payoff.

Bill_E is correct: a tiny flaw in the insulation, like a drain or a leaky hole where the refrigerant tubes enter can really destroy your system's performance. Don't use a drain, pump the water out. You don't want fresh water in the bilge anyway.

[maarty10]

I suggest you remove the counter top and take out the ice-box liner and lay up extruded poly styrene board as thick as you can go. It is water proof.

If you have the budget there is catalyzed spray foam that is moisture proof with a comparable r value to the poly board, and would go in in no time at all relative to hand cutting poly board. There are companies that specialize in doing only this in the housing renovation business. It would be less than an hour of work for them; they might cut you a break on price especially if you offer cash.

If the icebox is water tight and fitted snugly you have no worry about moisture penetrating the foam.

You could at this point also instal a new counter top.

[lancelots]

The ever present insulation question, I might take the liberty of jumping in here if I may.


Let me state that I am by no means an expert. But at one stage I owned and ran a housing insulation business in the tropics, although on the surface you may say nothing like refrigeration insulation but I’d beg to differ.


You do not lose cold you gain heat, cold does not travel heat does. Refrigeration is the process of removing heat (in simple terms).


Now the process of insulation works in many ways to exclude heat from traveling into the refrigerated compartment. In a case such as the void in question (without seeing pictures) the factors that influence this are the ambient temperature of the air in the void (best measured with the unit off for obvious reasons) the temperature of the hull. These temperatures will change during the course of day night and whether that hull side is facing the sun where you are cruising (water air temperature). What you may find is that you will gain in some situations and lose in others no matter the insulation used as heat will still travel through (irradiate) to the box if the hull is warmer (albeit at a slower rate). Any insulation will attempt to reach the ambient temperature it is in, hence the refrigeration to remove the heat that is traveling into the box.


Now the principle for insulating houses can be developed into refrigeration. When building a brick veneer or even a timber clad house it is common to put a layer of insulating foil on the frame with an air gap either side. In concrete block housing batons are placed on the inside of the walls and the foil is placed on the batons and then Gyprock sheeting over the top.

The Foil reflects back 95% of irradiated heat (remember heat travels not cold). Now this efficiency is only where the foil is not touching anything, gluing it to the hull or the box would be inefficient as the heat would then just transfer. The same system is used under tiled roofs, and often ceiling insulation (with glass batts or other material i.e. Polyester) is also used creating a secondary barrier to heat although this must be done with a ventilated cavity between the foil and the ceiling insulation to stop a build up of heat bringing the ceiling insulation to ambient roof temperature and still transferring heat (albeit at a slower rate).



Under corrugated steel (often called Tin) roofing a material known as Anticon is used this is foil with glass fibre blanket applied to one side and is pulled tight so that it comes into contact with the steel the purpose of this is to stop condensation on the highly heat conductive steel (when it gets cold outside warm moist air from inside the roof cavity condensates on the lower temperature steel).

It is important that in the case that the hull temperature is hotter than the ambient air temperature that any heat that does transfer through can escape from the cavity (heat rises) filling this gap may negate any bonus of this effect this may be why the cavity is there it may also extend under the box, remember that the other sides may be subject to the same ambient air temperature not the hull temperature. This is the only time that you will need to be worried about that air gap and possibly your best solution would be to build a small frame with a layer of cladding foil (not cooking foil) heavy duty Roof Sarking may be best, and just slip this down the cavity.


Or you could use a Polyester Ceiling batt, it is possible that the heat will rise through the expanded structure of the batt (don’t compress it) faster than it transfers through, which may be the simplest method to give you peace of mind it could be attached to the box with self adhesive Velcro (the hooks side) and still leave an air gap for heat to escape from the cavity. This will also help with any condensation building up and running off the box.


I hope this helps in your efforts.


Good luck and
Kindest Regards


Lancelots

[maarty10]

I have to wonder. Do you think that the still air of the cavity is a better insulator than the insulation itself? If heat has penetrated the insulation to the cavity that is adjacent to the box where do you think it will go? I think the heat will go into the box.

I like your idea of a reflective surface, but I think it is more effective on the warm side.

If heat is to escape from the cavity there are three modes of travel: convection, conduction and radiation. Of these, which is the most likely? If it is conduction, it is into the wall surface of the box. If the air has movement it has to convect to somewhere. and be replaced with cooler air; if this is happening, unless it is a closed system, it will have moisture in it, and it will condense upon the surface of the box.

[skipgundlach]

OY!

Where do I begin...

My original project was to add insulation to my icebox, which had been upgraded with two cold plates driven by engine or 110V air-cooled compressors - they were split, meaning either could supply them.

Turns out the counter top was not only tabbed to the hull, it was back-screwed from the engine room. Not only that, the cold box was machine-screwed to the top of the counter, but the nuts weren't locked down. That meant the screws to the top could not be removed because the nuts would spin; without the screws being removed, we couldn't get the countertop out, even if the other challenges hadn't been present.

We wound up cutting it all out and building a new floor where the old one had rotted from a leaking hose in the drain, along with a new wall on front and sides, before we replaced the counter top.

To all 4 sides, bottom and top, I added aluminum foil (reflective barrier), battens made from door skin (convective barrier) and then 6 inches of extruded polystyrene board (pink or blue board, depending on Dow or Owens-Corning). The original box had conformed to the hull; I sprayed two-part (two cans looking like freon cans) stuff coming through two hoses through a triggered nozzle, water resistant polystyrene foam, VERY CAREFULLY (see prior comments about expansion), a little at a time until it was full, yielding 14" down to 6" as the hull curved, R value of 30 minimum throughout, cut off the lumpy extras, and slid the new top in under the cabinets.

I coated the extruded with epoxy after cutting each piece to size, to help minimize any potential water intrusion (belt and suspenders; the poly is supposed to be "waterproof"), and did stair-step laps on the joints of the boards, to help make any migration of air more difficult, epoxying as I went. Laid fiberglass on all surfaces, then gelcoated. Of course, the top went on after all the hardware was installed; we went with a top freezer (due to how it was set up/access), and front reefer, door, and double gaskets (one on the interior level and the other at the door face level). Early pix in my gallery are largely devoted to this project if you'd like a look...

I used a spillover fan in the center of the divider, with a matching air gap at the top in square inches (turned out to be an inch open space at the top), with dual Carel thermostats, the fan controlling the spillover volume into the reefer side, along with a keel cooler and evaporative plate for the freezer side. Both sections also have circulation fans controlled by the thermostats; when the cooling cycle is happening, the circulation fans are running to even out the temps in the given space.

You will find a HUGE difference between tropical water and temps and more temperate zones; heat intrusion is what you're fighting, and your hull is the temperature of whatever the water is; inside the boat, it's whatever the air temperature is. Thus, it's entirely possible to run the compressor double in the tropics vs cooler temps.

That said, we have a very efficient box, and the smart speed controller keeps the compressor running about 90% of the time, the most efficient for an evaporative system, at whatever speed is needed (less when less heat intrudes), to keep the freezer at 8 and the reefer at 32 F.

If you're serious about it, this is probably what you'll have to do to achieve your target. If you can get the top off, and the old box, along with the no-doubt useless insulation (if it's over, say, 20 years old), out, without having to go through what I did, it will be easier, but my build-out is an ultimate without resorting to vacuum panels.

If you can get to the box, but don't want to cut it out, you may be able to add extruded polystyrene as I did, to the interior. But even something as simple as some of the bubble-pack-looking stuff that you can buy at the home improvement stores will make a tremendous difference to your insulation qualities, if that were all you were to do.

If not any/all of the above, and you can find a space for it, the Engel reefer/freezers are very efficient. If you're going to be living aboard the boat, refrigeration may well be your single biggest energy cost; a serious review of your amps usage, and your ability to replace them, is in order, unless you go to engine-driven cold plates (not a very even temp solution).

Our electrical system is heavy solar and wind, along with a Honda eu2000i suitcase generator which we can tie into our shore power system when there's not enough wind and sun. We do just fine in our semi-tropical location in the Bahamas; our system as a whole was designed for the tropics.

I highly commend Richard Kollmann's book on refrigeration, and a browse around rparts.com for you to get a start on understanding what you're really up against. If you're going to be keeping the boat for any serious amount of time, it's well worth the effort and investment to do this part right...

L8R

Skip

[maarty10]

Hey Skip,
Thanks for the description. I love hearing about people's projects! I am going to check out your gallery.
Maarten

[lancelots]

Hi maarty10


Of course a closed cavity will do less to stop heat transfer than insulation; the object of insulation is to slow the heat transfer. However it is a better to remove the heat source from aside the insulation this can be done if the cavity is ventilated and the ventilated ambient air temperature is less than the temperature of the hull (it’s better to remove the heat and try to reflect it) if it is a closed cavity then the heat will travel into the box. So the best placement for the opening is at the top with a second at the bottom to increase the air flow.


The foil is in position to reflect ‘irradiated heat’ (just as a mirror reflects light and helps when there is either plenty of airflow or none). Just remember the closer to the heat source the more cavity heat is built up and the more heat is transferred through (remember it reflects 95% of irradiated heat) it depends on your hull material as to how much heat it will transfer and how much irradiated heat it will reflect back at the foil. So once again it is important that the cavity between the foil and the hull is ventilated to remove the heat build up. Half way is probably a good position between the box and the hull this will hopefully allow adequate ventilation on either side of the foil perhaps two foil layers( separated by a ventilated air gap) if it is a major problem i.e. next to a hot engine room or a steel hull facing the sun .


One of the ideas of the polyester batt is to stop the condensation effect. In effect due to its structure it creates a greater surface area for the warm moist air to contact and also this has the effect of balancing the hot cold effect that creates condensation. It also has the ability to dry out as the airs moisture levels fluctuate but it also requires ventilation.
Off course if you are really worried put a layer of polyester batt and a double foil layer


It’s also a good idea not to pull the foil ‘drum tight’ they are normally poly cored (foil either side ) and need room to expand and contract (not much but some).


You could probably pick up some decent size scraps that would do the job at a building site (just remember to ask permission even when pulling it from a skip bin)


Hope that helps


Good luck and

Kindest regards


Lancelots

[Minggat]

Originally Posted by Bill_E

Also, has anyone found a refrigeration compressor that is much more efficient than the standard marine ones? It might be worth considering novel technologies for cooling as well.

Bill

Try here. Lots of positive discussion.

http://www.cruisersforum.com/forums/...s-12685-2.html

[Minggat]

Just to Clarify, Although link says Coleman.... I'm refering to the Global Cooling/Twinbird SC-JS04 or 5.

I have the SC-JS05.

Stolen from that that thread:

http://fpsc.twinbird.jp/drawing_COOLCARGO_100V.pdf
http://fpsc.twinbird.jp/drawing_COOLCARGO_200N.pdf
Product: SC-JS04 Stirling Refrigeration Unit
Product: SC-JS05 Stirling Refrigeration Unit

[svpresent]

I really had to start from scratch with our fridge.
I opened up my original fridge and took out the extruded polyurethane foam. It was soaking wet. The condensation point must have been in the middle of the foam (we have been in the tropics for 3 years now).

In my opinion even this so called closed cell foam is accepting water vapor and it will collect the condensed water in time. In the new fridge I made sure there were multiple layers of plastic sheeting. The objective is to keep the water vapor out from the outside and moisture out from the inside.

So there is a layer of plastic directly on the outside of the foam and there is a layer on the inside of the foam where the actual box is located. I even wrapped the individual blocks of foam in plastic sheets and used this aluminum tape to close them off completely. The room for the tubes (refrigerant as well as drainpipe) was cut out in time so these spots are nicely protected by the plastic in the same process. No chance of wetting the foam there...

I would also use plastic when filling up voids with bottle-foam from the builders supplies. I would put in a plastic bag first and fill it up with the tube on the bottle.

Cheers,
Len.

[svpresent]

Skip,

Would you know if Richard Kolmann is still in business?
His website is getting spammed a lot. Looks like he's just letting it happen. And I am not able to get a reaction from him.

Thanks, Len.

[skipgundlach]

Originally Posted by svpresent

Skip,

Would you know if Richard Kolmann is still in business?
His website is getting spammed a lot. Looks like he's just letting it happen. And I am not able to get a reaction from him.

Thanks, Len.

Sorry, I don't know. However, he was a fixture at SSCA shows and some other boat shows.

Drop him a line and ask him: Richard@kollmann-marine.com <Richard@kollmann-marine.com>

L8R

Skip