DIY Coolbox?

[chrisbitz]

I noticed the other day, that my fancy looking coolbox actually had no insulation at all! It was purely an air gap between the inner and outer skin!

Having discovered this, I looked at a few others in shops, and they're all like that!

Would there be any advantage to making something with proper insulation, or doesn't it make that much difference anyway?

 

[sarabande]

the R-value (the resistance of a material to transmitting heat) is roughly as follows:


polystyrene 4.0
a 1 inch air gap 1.0.


The foam stuff wins hands down.

 

[Adrian_]

If you want serious cooling including a small freezing compartment (even during summer) think Waeco compressor units. Not cheap, but you can ocasionally find a bargain on ebay.

Peltier units simply won't cut it.

 

[prv]

the R-value (the resistance of a material to transmitting heat) is roughly as follows:

polystyrene 4.0
a 1 inch air gap 1.0.

The foam stuff wins hands down.

...and fancy house-insulating foam will do even better. You can replace a 4-inch slab of basic polystyrene with something like an inch of the right stuff.

Pete

 

[Chalker]

I'm just building a freezer.
Expanded Polyurethane insulation (Kingspan etc.) from Builders merchant or a DIY shed is better than expanded exp polystyrene and will not absorb moisture like exp polystyrene. But it's not 4 times as good, maybe 1 1/2 times.
I'm using exp polyurethane but sandwiching into it insulation from Nanopore. This is a super insulator which is then vacuum packed, generically known as VIP=Vacuum Impregnated Panels. This is 6 times as good as expanded polystyrene.
They make to your size panel in various thicknesses. Expensive alone but not bad when you also buying the compressor and evaporator. My freezer will be bout 2.5 cu ft. Without the Nanopore I'd need 4-6 inches of insulation and have enough space for 1 packet of sausages!
No commercial involvement, just a customer.

 

[lw395]

I'm just building a freezer.
Expanded Polyurethane insulation (Kingspan etc.) from Builders merchant or a DIY shed is better than expanded exp polystyrene and will not absorb moisture like exp polystyrene. But it's not 4 times as good, maybe 1 1/2 times.
I'm using exp polyurethane but sandwiching into it insulation from Nanopore. This is a super insulator which is then vacuum packed, generically known as VIP=Vacuum Impregnated Panels. This is 6 times as good as expanded polystyrene.
They make to your size panel in various thicknesses. Expensive alone but not bad when you also buying the compressor and evaporator. My freezer will be bout 2.5 cu ft. Without the Nanopore I'd need 4-6 inches of insulation and have enough space for 1 packet of sausages!
No commercial involvement, just a customer.

Interesting stuff.
Just how expensive is it?
I guess the corner and door/hatch details end up contributing a significant amount of thermal conduction?

 

[prv]

Expanded Polyurethane insulation (Kingspan etc.) from Builders merchant or a DIY shed is better than expanded exp polystyrene and will not absorb moisture like exp polystyrene. But it's not 4 times as good, maybe 1 1/2 times.

Fair enough. I can't remember what the stuff I was thinking of was called, but I'm reasonably sure it exists. I heard of someone using it under a rebuilt floor where the required thickness of jablite (polystyrene) would have ended up with a step or a slope in the doorway to the rest of the house. Thinner insulation kept it level.

Pete

 

[dancrane]

On August tenting trips I wrapped room-temp bottles of Champagne inside a rolled-up sleeping mat...and slept on a camp-bed.

I stuffed 'insulative' T-shirts above & below the bottle, and placed about 500g of purchased ice in with it, too...

...next morning, the wine made an icy-cold breakfast accompaniment, and to my amazement, much of the ice WAS STILL ICE!!

Decent quality insulation material makes a vast difference.

 

[Hoolie]

I bought some of this foil/bubble insulation from B&Q to lag my Eberspacher ducting (yet to do) though I have used it for pipes in the cellar.

It is 4mm thick and B&Q claims it's equivalent to 65mm of polystyrene. The downside for a fridge is it's not rigid and may be difficult to fix, though you could use several layers to improve performance as it's so thin.

 

[rotrax]

First mate and I used to go deep sea fishing in Florida. Taking our coolbox was a non starter. We would buy a polystyrene coolbox for about four dollars that would last the trip and kept our food, drinks and sometimes bait very cold. They were about 1.5 inches thick. The only cooling items used were a bottle of frozen water and a bottle of frozen orange juice. Often, despite the heat we would leave the bottles out for a while as they stayed too frozen to drink. Our experience is that thickish polystyrene is a first class insulator.

 

[Chalker]

Set of Nanopore panels for approx 50x50x25 cm box was £115 plus postage. Off to collect see how they are made on Monday.

I'll take a look at the B&Q stuff to improve my fridge.

 

[Rigger Mortice]

It is 4mm thick and B&Q claims it's equivalent to 65mm of polystyrene.

I don't know how they can claim that. It has an R value of 1.46 which is considerably less than that of polystyrene.
It probably reflects a bit of radiant heat but it has little insulating value.

 

[dancrane]

The B&Q claim does sound optimistic - maybe the 4mm foil & bubble (toil & trouble?) is equivalent to 6.5mm of polystyrene?

What's the ultimate insulative material? What does NASA use?

 

[Chalker]

I believe that the quoted figure is for an installation to thir instructions. These include a large air gap
For example see. http://m.screwfix.com/reviews.htm?id=76477

 

[lw395]

First mate and I used to go deep sea fishing in Florida. Taking our coolbox was a non starter. We would buy a polystyrene coolbox for about four dollars that would last the trip and kept our food, drinks and sometimes bait very cold. They were about 1.5 inches thick. The only cooling items used were a bottle of frozen water and a bottle of frozen orange juice. Often, despite the heat we would leave the bottles out for a while as they stayed too frozen to drink. Our experience is that thickish polystyrene is a first class insulator.

I would agree with that.
It is certainly cost effective.

The latent heat of ice is 334kJ per kg.
The conductivity of polystyrene is around .03 w/mk
So if the inside of the coolbox is at zero, and the ambient is say 30 deg C,
guess the area as 2 sqm
Thickness 5cm?
Heat gain will be about 30 x 2x.03 /.05 =36watts
So a kilo of ice should take 334,000/36 = 9277 seconds to melt

That's only a bit over 2.5 hours.
You can scale that for more ice, or less surface area, or a different thickness...
In reality, the whole outside of the coolbox is not at 30, and the inside is not uniformly at zero.
But it shows that improving insulation has potential.

 

[john_morris_uk]

What's the ultimate insulative material? What does NASA use?

I don't know what NASA uses, but I understand that the ultimate in insulation for boat fridges and freezers are vacuum panels.

You can get them custom built from Glacier Bay (http://www.glacierbay.com/) or Rparts (http://www.rparts.com/) but they are not cheap. (I ended up using a mixture of Celotex and expanding foam.)

 

[Chalker]

See below at #4 and #10, Nanopore almost make these panels in the UK, although it seems to be a branch or similar of a US company.

As earlier they are not cheap, but have you looked at the price of compressors and evaporators if building a new fridge or freezer?

At one time I believe that Glacier Bay stopped making one-offs

http://www.nanopore.eu/
http://www.nanoporeinsulation.com/vip_basics.html

I'm just a customer.

 

[grafozz]

D/glazing panels

When I built an extra fridge in a locker under a bunk I searched around (a Greek island ) for insulation material , and found excellent insulation panels in a scraps bin at a D/glazing firm .
It is high density 30mm foam with aluminium on both sides which is powder coated white.
it is easy to cut , shape and fit and the finish is better than most fridge interiors .
The joints were sealed with minimal white sealant .
The panels are used in external door manufacturing , typically the lower panel of a half glazed door , I gather the insulation properties are quite efficient .
Even so , additional insulation was added outside the fridge sides .

 

[ditechspain]

If you want serious cooling including a small freezing compartment (even during summer) think Waeco compressor units. Not cheap, but you can ocasionally find a bargain on ebay.

Peltier units simply won't cut it.

If you buy a Waeco/Dometic fridge it's worth investing in their thinsulate jackets if you're going somewhere hot. Each layer produces about a 5 degree C drop in temperature compared with the outside. So with two layers the skin of the fridge is about 10 degrees below ambient, or in other words the fridge behaves as if it's somewhere about 10 degrees colder than it actually is.

 

[Kelpie]

NASA uses Aerogel- very low density foam material.

I turned a locker in to a coolbox. Searched on a website that sells plastic boxes and found something that would fit the locker with a couple of inches to spare all round. Lined the locker with Kingspan offcuts from a building project. Used low expansion foam to fill remaining gaps. The plastic box simply acts as an easily cleaned liner.
Total cost was about ten quid, and it's very effective. Absolutely night and day compared to our old coolbox, and it doesn't get on the way either.