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Adding Extra Insulation to a Cooler/Refrigerator

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When I bought the DometIc I had some scraps of styrofoam insulation on hand and used them to insulate it. I was concerned that glueing it to the walls would void the warranty so I used bungee cords to hold it on instead. That worked extremely well and is now all I do.

Last week I did a review of my new Wytner 12 Volt Compressor Fridge, but I thought I should give you some ideas of how I add extra insulation to all my coolers. In the 11 years I have been living mobile, I have always used a cooler. Some people arrange their live so that they don’t need refrigeration. I envy that kind of simplicity but I have never been able to do it for several reasons:

  • I like cold drinks! For that alone it’s worth it to me to have a refrigerator.
  • In the city you are always surrounded by grocery stores so you can buy in very small portions, but that will cost you more than buying in larger sizes.
  • I love Miracle Whip and don’t like mayonnaise, so I buy it in 32 oz. jars and it needs refrigeration. And yes, that alone is enough reason to have a cooler.
  • I want to have fresh vegetables for salads and frozen fruits for smoothies. That requires refrigeration.
  • If you are a boondocker and living far away from cities, driving into town frequently to buy fresh meat, fruits and vegetables would be much too expensive in gas. The larger your fridge the longer you can sit and not burn gas driving into town for supplies.
  • I can’t afford to eat out all the time so I cook for myself. I prefer to cook a larger portion and then save it as leftovers to eat later. There are three reasons why leftovers work so well for me:
  • Cooking one large meal allows me to buy food in larger packs which saves money.
  • By cooking a large meal and then saving the left-overs, I reduce my cooking time and dishwashing. For example if I cook 4 hamburgers at once, I only have to wash the skillet once saving me time and effort.
  • Many meals taste better the second day!

When I started living in a van in 1995 I had no idea there was such a thing as a 12 volt compressor cooler (and solar was much too expensive then so even if I knew about it I couldn’t have one anyway). So I bought an Igloo 5-Day cooler and started buying bags of ice. Because I lived in a box van with very little ventilation, it got really hot in the summer which meant the ice melted fast. Right away I knew I needed to add more insulation! I had heavily insulated my box van with 2-inch-thick sheets of Styrofoam so I had some left over. There was no use letting it go to waste so I cut it into the right size and covered the cooler with it. After they were cut I used Gorilla Glue to glue it permanently to the sides and bottom of the cooler. Gorilla Glue 50004 Adhesive, 4-Ounces

The Dometic insulation from the front. Of course you MUST NOT in any way inhibit the vents for the compressor or the heat will destroy it. In this picture you can see that I used duct tape to tape several layers of Surplus GI closed cell phone sleeping pad on top of the lid.

The Dometic insulation from the front. Of course you MUST NOT in any way inhibit the vents for the compressor or the heat will destroy it. In this picture you can see that I used duct tape to tape several layers of Surplus GI closed cell foam sleeping pad on top of the lid. You can also see that it is sitting on top of a piece of the sleeping pad.

The top was harder because the lid had to swing open. I had some closed cell foam sleeping pads on hand so I cut them to fit and glued them to the top instead. I also placed one under the cooler for extra insulation. I had used those in my backpacking days and knew they were an excellent insulator! I’d slept on them at -30 below zero on top of snow and they kept me warm and the cold out of my sleeping bag. Remarkably, the snow never melted underneath me. I had found a whole bunch of them as surplus that had been issued by the U.S. Army to their cold-weather troops. They only cost $5 each so I bought enough to cover the entire floor of my box van as insulation and then threw carpet over it. When I sold the van, I kept several of them and I still have a few left today. is now selling the exact same pad, but they are a lot more than my $5 surplus ones! GI Closed Cell Foam Sleeping Pad
I could feel the top getting cold and so I was fairly sure I was still losing cold through it. So I took an old blanket and folded it up to fit and draped it over the top and then put a pillow on top of it. That seemed to help.

Here I have draped a blanket over the top of the Whytner. It hangs over enough to hopefully insulate the seal around the lid.

Here I have draped a blanket over the top of the Whytner. It hangs over enough to hopefully insulate the seal around the lid. The insulation is held in place by bungee cords.

Finally, there was one other thing I did to the cooler that helped it to stay cold and made using it much more pleasant, and that was using a kitty litter tub to hold the ice instead of just dumping it in the cooler. Cold transfers very easily through water and plastic so as the ice melted and the cooler filled with water its cold went straight out. By putting it in the Kitty Litter tub the water stayed inside it and never directly touched the walls. Instead it was surrounded by air which is a far superior insulator. As a bonus, my food was no longer swimming in ice water and that saved me a fortune in foo not thrown away!

Adding extra insulation made a big difference in how long it stayed cold when it was hot. There’s no doubt in my mind it was well worth the little bit of money and effort it cost me to insulate it. I used that cooler for 7 ½ years and the glue and the Styrofoam held up well. I highly recommend it as well as putting the ice in a kitty litter bucket.
In 2009 when I bought my Dometic 25 quart 12 volt compressor fridge, I was not inpressed with how thick it’s walls and lid were so there was no doubt that would add extra insulation to it as well. At that time I only had 55 watts of solar and I was not at all confident that would be enough, so in order to make it run as little as possible I wanted it to be super-insulated. So I did exactly what I had done to the ice chest. The result was that the compressor only came on 3-5 hours a day. Even so, it was a constant struggle with having enough power so six months later I added a second 135 watt panel and that solved all my power problems. Unless it is cloudy, I always have all the power I need.
My Kyocera 55 watt and 135 watt panels. I have since transferred to the top of the trailer. They provide me with all the power I need.

My Kyocera 55 watt and 135 watt panels. I have since transferred them to the top of the trailer. Their 195 watts provide me with all the power I need.

As you know, I just recently bought a new Whytner 65 quart refrigerator. While I am very impressed with the thickness of its wall, and how little it runs to stay cool, there was still no doubt I would extra insulation. This is one of those few cases were more is better! Because I didn’t have 100% confidence in the compressor in it, I thought if adding extra insulation reduced the amount of time it ran, it would be just that much longer before I had problems with it. In other words, if the compressor ran half the time, it would last twice as many years.
I did one thing differently this time, instead of using standard white, pink or blue Styrofoam I used a different type of foam board called Polyiso. I had only recently learned about it and researched it and there is no doubt I will only be recommending it from now on. A 4×8 sheet of it costs $20 at Home Depot and it has an R-Value of 6.2 per inch, the highest of all foam boards (for comparisons sake, the R-Value of pink spun fiberglass batt insulation is only R 4 per inch). It comes with a very heavy aluminum foil reflective barrier on both surfaces and was much easier to cut than standard white Styrofoam because it doesn’t have all the little white balls that break off with every cut; I hate the mess they leave! Polyiso is very highly recommended! More info here:
For the first time I took pictures of how I insulated it, so here they are. I hope they give you some ideas of what you can do with your own cooler whether it uses ice or is 12 volt.



  1. Nemo

    I’m with you on the Miracle whip.. I’m gonna miss it now that I found out they use GMO items in it 🙁

    • Bob

      I don’t know Nemo, I think I have to keep eating it!

  2. Gennifer

    Great tips, Bob! Thanks for all the pics!

    • Bob

      You’re welcome Gennifer.

  3. Brian Howard

    Bob, when ever I take a cooler and fill it with food and ice I always lay a thick layer of newspaper inside on top . It about doubles the length of ice life. I’ve opened the cooler and found no ice melting at times. Works great if you have a old Sunday newspaper laying around. Insulates from the inside first before it has a chance to get threw the top.

  4. Marshall

    Fantastic! Our Engel travels between the front seats over the drive train and that area tends to get hot. I made a box out of 6X6 and plywood and stuffed it with styro to mitigate the heat.
    Excellent reasons for a refer Bob. It extends our range and truly saves on gas. That $375 refer has saved us easily WAY more in gas than the refer cost in having to travel for ice. Having an ice cold drink is priceless. As I said before, solar and refrigeration are must haves and not luxuries for the serious vandweller. We will not be beholden to no man for anything. I learned my lesson as a scout to be prepared.
    Thanks for the info!

    • Bob

      You’re welcome Marshall! And I agree, the more self-reliant you are the better off you are and the solar and refrigeration is a step in the right direction.

  5. CAE

    The refrigerator is about the most consumptive critter of the bunch and fairly important. How did people live without them for thousands of years???
    Since I’m on a boat a lot, I just put things in a net and drop them about 40 feet down. Beer stays pretty cool that way, as do other well packaged items.

    • Mary

      Drying was how they mostly preserved food. Lots of natural saturated fat preserves food. Salt and sugar preserves food. And smoking preserves food. We just have echos of these techniques today in our food preparation but they were essential before refrigeration.

    • Bob

      You’re right CAE, it really is a total luxury! I could do without it but I don’t want to! I want civilization to fail, but until it does I am going to take as much advantage of it as I can.

  6. Mary

    I’m going to have to look into that Polyiso. I insulated the cabinet for my built in fridge with Reflectix and pink board and it makes a huge difference. With all the problems I’ve had with it, it works pretty well as an icebox. I put the bag of ice in a bucket too and it is much easier to manage.
    Why did you face the aluminum outward? Do they require an airspace between the aluminum face like with Reflectix to get the full R value cited?

    • Bob

      Mary, Insulating against the different kinds of heat is a complicated subject, and I am going to do a post on it soon. Aluminum foil only has value against radiant heat and inside the van there isn’t any radiant heat, only the windows have radiant heat from the sun. So the aluminum foil has virtually no affect on the R-Value of the polyiso. This polyiso had aluminum foil on both sides. But even if it had it on only one side I would have put it on the outside. if you notice in the pictures it is just inside the front door and sometimes the sun can shine in through it. By having the aluminum on the outside it can reflect the heat off the fridge.

  7. Karen

    When we had our 1972 VW vanagon which had only a cooler, we would chose our meat purchases first when we went shopping. We would stick them in the store’s freezer cases and by the time we finished shopping they would be partially frozen. This worked very well and gave us a day or two extra time before the meat had to be used.

    • Bob

      Karen, what a great idea! I’ve never even thought of that but I can see that would work really well. Thanks!

  8. randy(livinfree 1964)

    I definitely agree with you about the Miracle Whip….YUUUMMMMMMM! Life’s too short not to eat what you want…Do what you want…ect…. Thanks for the detailed info on insulating of the fridge! I had a question about what size /guage wire did you use to run your new fridge as i’m considering buying one also and want to set-up/plan for it. THANKS! Randy

    • Bob

      Randy, it uses a standard cigarette lighter plus which is very low draw. 18 gauge wire would be okay but I used 14 gauge because I had it on hand I usually use too big a wire.

      • randy(livinfree 1964)

        Thanks….i am surprised it could run on such a small guage wire…..that’s good to know…Take care!

        • Bob

          Randy, it is surprising, but most cigarette lighter plugs have a 10 amp or less fuse and that is very little power. The one reason to go larger is if it will be a long run of wire, but even so 14 gauge should handle any distance in a van. I’ll do a post discussing wire gauges and wire size calculators coming up sometime soon.

  9. cleanheart

    Wonderful diy Bob! I’m heading south soon and this will really save me! Thanks so much for all you do!

    • Bob

      Thanks cleanheart! I’m sure it has more than paid for itself many times over!

  10. 37C

    I haven’t looked into it, but it seems like aerogel would be perfect for this application. It’s the most insulating material on earth, very thin and lightweight – although expensive.
    See for example: (Disclaimer: I am not affiliated with them) Check out the dry ice test chart. Pretty darn impressive if you ask me.

    • Bob

      WOW!! R-40 per inch, I never even imagined that was possible. It must be terribly expensive!

  11. Eric

    Nice website. Good job. Great info and tips. Keep up the good work.
    One note on insulation products, be very very careful with how you manage your wiring and other heat generating items. This Youtube video will adequately relate the potential danger.
    The fumes from burning insulation are highly toxic. And it is stunning how quickly it can spread.

    • Bob

      Eric, thanks for that tip! Bob

  12. RD

    Hi Bob,
    Thank you so much for creating and maintaining this website. It has been very helpful for our partial van conversion. We have tent camped for years and just started van camping and hope to progress to longer and longer trips. We are a family of 4 (2 adults, 2 kids). We just did our first test run trip in an E150. It went well except for the refrigeration issues. We tried adding extra insulation but we should have checked your website first! I have a hard time justifying an expensive fridge/freezer for 2 week trips multiple times a year. I would normally not consider it at all and just go to the store except that we have multiple food allergies and need to eat food that is not always available in stores. For the last 5 years the four of us have tent camped out of our Rav4 with 3 coolers: one used as a freezer, one as a fridge, and one as an every day cooler. Shopping at high end stores helps us find safe food, but the prices are outrageous. I share this to ask the following questions in hopes you can help us make some decisions before the next trip in a few weeks:
    1. Is it possible with your modifications to a standard cooler to get one to act like a “freezer” and keep food frozen for more than 7 days.
    2. Which cooler would you recommend for modifying.
    3. What is your opinion of electric coolers and do you think they could be modified for our purposes.
    4. Have you heard of off brand electric freezers such as Modawn and if they are any good or reliable
    I am sorry this is so long. We want to take longer trips but can’t because of the food issue. The food issue has been more of a problem than figuring out where all of us were to sleep!
    Thank you for your time,

    • Bob

      1. Is it possible with your modifications to a standard cooler to get one to act like a “freezer” and keep food frozen for more than 7 days. I can’t say for sure but I doubt it. The more insulation and the more ice the longer it will take to thaw, but it will all thaw and I’d guess 1-2 days at the most, but that is just a guess.
      2. Which cooler would you recommend for modifying. I think all of the “5-day Extreme” coolers are about the same. Just add a lot of insultion to all 6 sides.
      3. What is your opinion of electric coolers and do you think they could be modified for our purposes.They will suck your batteries dry! They are only good while you are driving but if you drive a lot and put ice in it then they may be worth a few dollars. Being plugged in while you are drying will help the ice last longer.
      4. Have you heard of off brand electric freezers such as Modawn and if they are any good or reliable. I have never heard of it so I can’t really comment. Generally you get what you pay for.

  13. John Wright

    I have been reading about how sailors build their own iceboxes. 6 inches insulation for fridge, 8 inches for freezer. If you never really open “freezer” then yeah I have read 2+ weeks. But for van this would make a huge cooler, maybe 3x size, 50 qt capacity but 150 qt size. Your video about the person with a insulated container was neat. I think the best idea is the 2 or 3 smaller cooler idea.
    Thanks for all the wonderful videos!

  14. underfloor insulation

    Lower temperatures are proven to suppress your immune system. When we go outside in the middle of the winter, we don’t head out in shorts and a t-shirt.

  15. Jamie Karl

    I’m building a little tiny house, offgrid. I found this decent sized (not full at all, 140L fridge freezer) that fits my space better, but it’s not quite as efficient as some of the smaller RV fridge/freezers. So I figured I’ll build it into a cabinet that’s about eight inches bigger than the fridge, and jam it full of that iso stuff. The compressor is a remote unit, so, I figure if I do that I can make it way more efficient. Thanks for the tips.

  16. acoustic insulation

    Because spray foam insulation is comprised of inert polymers, it is able to last almost indefinitely.

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