Fridge insulation

[ailsaboat]

I’m about to start fitting a top loading fridge.
I was going to insulate it with polystyrene sheets – 1 ½ inch thick, cut and bonded together to produce insulation of about 6 inch.
But as the fridge box is shaped roughly to the hull ie wider at the top than the bottom and will be mounted as close to the hull as possible, there will be lots of ‘odd’ shapes (frames/stringers etc) I’m not sure I would get all the gaps insulated.

So,
Having never used two part expanding foam before – do you think it is possible for a beginner?
If I do use it, can you mix too little, see how far it expands, then mix more to ‘top it off'?

Or, for ease of use, can I use the aerosol type expanding foam – is this suitable, and, the same question – can you keep adding to the reqd. level.

Finally, if the two part is the way to go – where do you get it from?

Thanks for any advise given.

 

[asj1]

I used one -part foam foam - there seesm to be different sorts some of which claim to be better at insulation than others. The best one I found to work with was from a hardware shop in France - and less than half the cost of the UK - sorry not much help I know. For the flatter sides The high tech insulating board now sold at all builders merchants is much better than polysterene, and much more expensive I'm afraid. I don't know the trade name but it is a fairly hard board with foil on one side and easily cut with a sharp knife - it comes in many thickesses and so it is easiest ti get a thinner one and then build up the thickness -- I'm sure the purists wouldn't agree.

Regards

 

[FirstAway]

I did something using a 'builder's insulation' called Kingspan. It was very easy to cut to shape and to build up a good thickness in several layers. I used the sheet vertically and it was OK to cut to the curvature of the hull. I didn't bother sealing between each and it is a huge improvement.

The only area where I tried to use the one part foam was a disaster - expanded too much and I had to cut most of out again.

Regards

Bob

 

[Phoenix of Hamble]

If you do use expanding foam, the secret is not to worry about how to get the foam into hidden spaces, but how to let trapped air out ( /forums/images/graemlins/blush.gif )..... lots of little vent holes, and then the foam will find and fill any voids..... very messy job though!

 

[pampas]

I used 45mm foam sandwich the type as asJ1 suggested, cavity board I think they called it about 18" -36" very efficient, wish now that Id used three thinner sheets and glued together, Seen the ships side bulge out because some idiot forgot to cut and exit hole for the excess, so be careful

 

[ParaHandy]

The one advantage of using a two part foam is that you don't have to wet the area before you spray it .. however .. I made several mistakes with a 2 part foam when doing the same as you intend. The cans were heated to begin with and the stuff absolutely rocketed out but the evaporation cooling effect was far far greater than I envisaged and before even a quarter was used, the cans were too cold, the nozzle froze and that was it. What I should have done was given it a 5 second burst, heated the cans, another 5 sec burst and so on; perhaps had to change the nozzle.

The small kits have only one spare nozzle whereas the large kits have several. Small kit costs £35 and large kit >£200. A small kit ought to do. You can get a kit from here and they give some good advice.

Once you've finished, tap the sidewalls to find out if you've left any voids. You'll easily recognise the sound of a hollow bit. If so, drill into the void and get some more foam into it. This is where it can get tricky. If you top it up with 2 part foam, you will need two kits because by the time you've done the first filling and allowed to set, the first kit will have set solid. But, if you use a one part foam, then you must squirt or spray water in first and this isn't easy given what you are trying to do.

Two part foam is reputed to be far denser and thus much more effective.

Just a thought, I used the silver backed PU foam 2" thick for the flat bits and the PU foam, backed with ply, for the odd-shaped bits all with a min thickness of 2". Are you sure about making it 6" - that seems a lot and a lot of space will be taken up by such a thickness ....

 

[rogerthebodger]

On my previous boat I used 50 mm thick PU foam sheets I gat from a company who make insulated truck bodies. On my new boat I will be doing the same but 150 mm thick. The increase is due to the higher temperatures where I sail and that I wished to reduce the electural load on my battries.

 

[ailsaboat]

Hi everyone, thanks for the advise so far.
ParaHandy, I have a book about building marine fridges and it says 6 inch insulation is what you should aim for. This is my only reason.
I will probably end up with between 4-6 inch. It also says that polystyrene sheets are ok, but 2 part expanding foam is better - but offers no advise on using it.

 

[HenryB]

I rebuilt my fridge after I found that it was running for about 70% of the time when I was based in Greece. I used the best insulation that I could find at a reasonable price - sheets with an aluminium foil facing made by Celotex. It has an insulation factor (R) of more than 7 per inch. Its easy to shape and I found that there was no need for any expanding foam because it was easy to fit odd shapes together to fill the awkward bits.
It is well worth covering all the panels in polythene to stop them getting wet with condensation. I used about 6 inches at the bottom and 4 inches on the sides and top. The fridge running dropped to about 25% of the time in the Greek summers.

 

[ostra4]

i just bought some kingspan from b and q .8 by 4 sheet for £18 a sheet .Excellent to work with.