Are you building a “Corten Condo” or “Corten Cookery”?

26 Sep

For the last thirty some-odd years, we’ve been turning ISBU Shipping Containers into shelters, homes, and even (gasp!) commercial buildings.

And despite the intended use for the boxes, one material reigns supreme over all others, when considering using Corten Steel as your “cocoon of choice.”

In this exciting episode, we’re going to revisit that most dreaded and seemingly misunderstood of all building materials… Insulation.

While I had planned to take the next few posts and explore the conversion to 20′ High Cubes into “Corten Components – DIY Steel Building Modules” that could essentially be bolted and welded together to form a small home, I’m going to address an issue that is just terrorizing my email inbox this week.

Seriously, I got 32 emails this week alone asking me about “Magic Insulation” (ceramic snake-oil), or requesting information on how to turn an empty steel oven into a “GREEN Get-away“.

Perhaps it’s due to the fact that it’s barely dipped below 100 degrees in the South in the last week…

Perhaps it’s the economy, the horrible state of the housing market, or rampant unemployment…

Perhaps it’s due to the recent political song and dance that leaves many of us wondering “what’s next”…

Perhaps, just maybe, people are really starting to listen to my “rantings” and they’re finally understanding that you really CAN turn a cast-off series of metal boxes into a home, if your head, your back, and your heart are all aligned.

For whatever reason… quite possibly it’s the fact that my book:

“Introduction to Container Homes and Buildings”

… is doing pretty well. In fact, I’m being told that it’s becoming an “industry favorite”. As a result of that book, many families are now taking the plunge, and investing in things like welders, plasma cutters, and leather garments. And I’m not talking about “adult fun” either…

I’m talking about gloves and heavy welding jackets…

Many families are emailing me lately, in a marathon that covers more ground than all the cornfields in Kansas…

Overwhelmingly, the most common question I get asked is;

“But how do you insulate a steel box?”

We all know that living in an uninsulated metal box is akin to living in an oven. That’s a given. In fact, living in ANY uninsulated structure invites living conditions that can become… frankly… unlivable.

Since I started doing this in the 70’s (taking torch to ISBU in the quest for “Solid Steel Shelters”) I’ve watched the insulation industry evolve…
Compared to the way our forefathers did it, insulation has taken great strides forward and there have been many significant changes in the way we approach and even think aboutย  BEI – “building envelope insulation”.

Modern thinking and advanced design using composite materials have waged war with rising component costs, and it’s created an environment where the “building geeks”ย  (G-d Bless ’em!) are forced to devise more efficient and effective products and methodologies for us to harness, as we build the homes that will house our families.

Requirements for housing itself have changed, as well. We don’t build houses filled with low ceilingsn and little tiny rooms…

Can you say “McMansions”?

Most of the “typical” homes built today include elaborate ceiling schedules that include various types of ceiling configurations.

Even when constructing our homes built in the “alternative”: homes like strawbales, ISBU, or even cob…

It’s common to see rooms that don’t really lay themselves out for the use of the “traditional” materials like (gasp!) fiberglass batts. Design features placed almost randomly thru the floorplan can really make you scratch your head, when it comes down to closing eveything up and making the space habitable.

I’ve seen 16 foot foyer ceilings in ISBU homes that lead into great rooms that soar up three stories, to create 30 foot ceilings.

I’ve used barrel vaults in bathrooms, kitchens and bedrooms.

I’ve even done domes roofs atop staircase towers created by standing an ISBU “on-end”…

…and using it to create massive staircases (that double as “solar and light chimneys”)… linking floors together and drawing sunlight into the “bowels of the home”.

All these spaces need to be insulated.

Additionally, the lighting system in the home demands a real hard look at HOW you’re going to accomplish your insulation requirements.

Let’s face it… we use a lot of “light cans” (recessed lighting) in today’s home to illuminate those spaces we so carefully create. And each hole we cut, to provide light in the darkness, brings evil along with it. Why? Because it violates the sanctity of that “sealed insulation envelope” that we’re trying to create.

Think about it…

The actual process of lighting your home turned the insulation plan into “Swiss Cheese”.

The way they “used to do it”, typically the (gasp!) fiberglass batts were just held 4″ away from the installed light cans (to prevent fire, for one thing), and we used a ton of them to get the desired lighting effects.ย  As you can see, it’s a labor intensive, expensive, and “ugly” solution.

Is this process worth repeating?


Recessed lighting installed this way just destroys the effectiveness of the building envelope.

So, stay tuned as we examine insulation and how it’s actually used to create a livable environment inside a Corten Steel castle…


21 Responses to “Are you building a “Corten Condo” or “Corten Cookery”?”

  1. Brad September 26, 2010 at 12:07 pm #

    Knowing that within every question, therein lies the answer however I’ll proceed with the question. What are some possible solutions to insulating an ISBU? I saw the question, read the post but did I miss something?
    Thanks for you helpful information thus far. I’ve enjoyed the site and insight.

    I’m in serious persuit of putting a home together in Houston/Pasadena TX area. Any sources you might know of or recommend for welding/retrofitting a custom design?

    • Renaissance Ronin September 27, 2010 at 3:14 am #

      Hi Brad,

      Thanks for your comments.

      We’ve spoken about applying insulation to ISBU Containers here many times over the last few years. I’m a big fan of SPF (Closed Cell Spray Foam) and rigid insulation boards.

      In the follow-up post to the article you just read, I’m going to talk more specifically about insulation practices. It’s such an important issue, it’s worth re-visiting.

      Depending on the complexity of your design, most metal workers will be able to make the modifications that you require, to turn an ISBU into a home. Many “industry types” (who are more concerned with creating profit than creating affordable housing) would have you believe that this is a difficult process, but in reality, it’s not rocket science. If you want to talk about YOUR design, perhaps we can shed some light on how you can proceed.

      Stay tuned.


      • Brad September 27, 2010 at 6:19 am #

        Hi Ronin,
        Thanks for your response about insulation. Since I’m new to your site I suppose I missed previous comments about the subject. I appreciate the input and above all your belief that this is not rocket-science and can be done inexpensively.

        Just yesterday I was looking into closed-cell foam and rigid board as options and then recieved your email backing up that idea. I want to insulate the exterior. Have you seen furring strips attached, then foam sprayed between strips and then siding attached to the furing strips. My question here is how to attach furring strips to the metal container without penetrating the metal wall. The interior wall I would like to remain corrugated metal and just paint, as it is. How difficult is the metal to penetrate with screws and drills suited for the job?

        You asked about my particular design so I’ll describe it for you. (I have a degree in architecture, btw, and practiced residential + hospitality design 25 years.) The shell is simply 2-40ft high cubes (9’6″high) with the 40 sides of each unit joined side by side to form a rectangle (16×40). Currently I have two-8′ sliding glass doors joined and centered on the front 40′ wall. Then within each of the 4 corners (left to right) is kitchen, office, bath/closet/storage and bedroom. The plan is open with no doors but with 21 LF of interior partion (most of this partition forming closet and closing off bath area). 2 windows, one kitchen + one office. The 2 doors at the end of each container would be in the bath (shower/toilet) area and bedroom area. If money held up (did I mention 30-50k max) I would intall sliding glass doors just within clearance inside of the container metal doors. Allowing what you have already seen done before, the metal doors opened and exposing the sliding glass door for light and air. Basically the center area of the 2 units joined would be the living/work/open area. This area is currently 15’8″ x 12’8″ which flows without walls into ajoining spaces excluding the bath/storage area which is entered around the corner partition from the bedroom space. Confused? More than you wanted right? So the plan is 640 sq.ft. with about 950 sq.ft. of exterior wall to insulate.

        I want a roof garden to do the insulating on the top of the units. A feature in Dwell mag had a unit in San Antonio with a beautiful roof garden. Do you know if 12″+ of soil will insulate the roof? The Ford motor plant in Detroit uses a green roof for cooling and a variety of sedum grows there.

        Sorry for the rambling I just had coffee.
        thanks for your help, Ronin.


  2. Brad September 26, 2010 at 12:07 pm #

    I hope your son is feeling better.

    • Renaissance Ronin September 27, 2010 at 3:16 am #

      Finally, he’s back to being the tyrant that we all know and love. You can tell he’s feeling better, he’s “getting in trouble” about every 5 minutes! ๐Ÿ™‚

      I love him dearly. I just hope that I survive him! Oy! ๐Ÿ˜‰

  3. Brandon September 28, 2010 at 2:44 pm #

    I just bought a little piece of land in another state and will be building a shipping container cabin to put on that land while I build my house. I’ll be picking up a reefer shipping container that already is insulated. I learned about the insulated ones recently on a farm near my house. They are 40ft High Cube containers. I got to see a cross section of the containers. They are basically corrugated steel sandwiched by two layers of flat steel and completely filled with closed cell foam. I believe the foam layer is about 2″ thick. The owner of the farm had about 3 of them and kept some temperature sensitive stuff in there. The reefer unit was removed from the back of the container and they installed a typical window air conditioner to keep the contents in the 70 degree range. Given the excellent insulation value and the totally sealed design of the unit, the A/C did not have to work very hard to keep the inside cool despite being in direct sunlight half the day.

    Once the reefer unit is removed, there is a nice little space in the back of the unit that is protected by steel that would be excellent to place a battery array. A simple hinged door on top and it would keep the batteries and any other energy storage (like Propane) secure when you are not around. A few solar panels on top and some creative plumbing should result in a completely self contained, somewhat mobile cabin.

    The only draw back is the insulated containers are a bit more expensive than your typical container(anywhere from 1000 more to 3000 more). However I think the turn key solution to insulation is worth it. They also give you the eye pleasing straight walls both inside and out. In fact, they are probably cheaper to buy than it would be to spray foam a non-insulated container, not to mention sandwich both sides in steel afterward.(spray foam is expensive!)

    I’m new to this blog, but I haven’t seen this mentioned yet. I wonder if it is in the ebook. I’ll have to buy that now and check it out.

    • Renaissance Ronin September 29, 2010 at 12:56 am #

      Hi Brandon,

      We’ve talked about insulated “refrigerator containers” (called “reefers”) here before, several times.

      The reason that most people DON’T use “refrigerated containers” as a starting point for ISBU Home construction is that (predominantly) the units are made of ALUMINUM. This means that just like the 40′ HUB containers (which are also made of aluminum), as housing material they are useless.

      While they ARE indeed insulated, that 2″ of foam insulation is only going to get you an R value of about 14, maximum. You still need an insulated roof (of increased value) and for that matter, an insulated floor.

      So, they cost more money, they aren’t up to the required task, and you still end up doing more insulation work to get what you need.

      If you have a STEEL ISBU that has been insulated and converted to a “reefer” (there are some out there, I’ve sen them), you’re in better shape… but you still have your work cut out for you.

      For the additional money you pay for the STEEL “reefer” container, you would do better buying a regular (uninsulated) HIGH CUBE and then insulating it yourself to get the desired R values you require.

      And I’ll also point out that your battery arrays for your photovoltaic arrays should never be stored in an area directly adjacent to your lifespace. It invites an infiltration of offgassing, and it’s stuff that you don’t want to breathe.

      You use the term “somewhat mobile camp”. Does your “reefer” have wheels? As in, is it a tractor trailer? If so, I can almost guarantee you that the box is aluminum and not steel. And, if it’s on a trailer, you have much bigger problems that will come with it’s high center of gravity, and the fact that it’s just a “big aluminum sail” waiting for high winds to toss it around.

      • Brandon September 29, 2010 at 12:25 pm #

        Thanks for your reply.
        It is indeed a STEEL High Cube Container. I wouldn’t mess around with aluminum ones. Lucky for me, I’m getting my container for a good deal. It’ll be the same cost as an uninsulated one. I can only get one at this price though so I’ making the most of it. It will be primarily a summer cabin in a pretty temperate climate, so I’m sure the insulation value will plenty.

        Onto the batteries. I won’t be using traditional Lead acid batteries, but rather NiFe batteries. The cabin will be unoccupied for many months at a time, and I need(and want) batteries that can survive long periods of discharge without damage.NiFe Batteries fit this bill and also last basically forever (100 years or more). NiFe batteries may not have the same performance as lead acid batteries, but I’m building them myself to the specs I need to work for my system. The nice thing about Nickel Iron batteries is that the electrolyte is an alkaline(KOH) instead of acid, and I don’t believe the gas that they give off is toxic.

        Maybe you could answer a question for me on that spray foam stuff though(because I know it is quite awesome but quite expensive). Just how much is it going to cost to insulate the container with those do it yourself kits? It seems to me that the kits are rated to cover 300 sq feet or so 1 inch thick. The kits I’ve seen that cover this much cost around $600. 1 inch of SPF is rated at around R7. TO get R14 you’d need 2″. So to cover just the long sides and roof of a shipping container with 2″ of foam, you’re looking at $1800. Now you still have to cover the foam with siding if your into appearances at all. So you’re easily into $2500+ to insulate your typical container, and you still have corrugated walls on the inside (yuck!)

        An insulated steel container already has the 2″ foam insulation in addition to 3(count em) layers of steel. This gives you straight walls, additional strength and a decent level of insulation. If you shop around, you can score one of these for 1k more than a typical container.

        SPF and typical corten steel containers are great if that’s what you have to work with, and they sure are more plentiful. You can spray on the desired thickness of SPF to whatever insulation value you need. But I think that by the time you spend all that money on insulation, you’ve spent more on the whole “system” than just buildng a stick house of comparable size with spray foam.
        Just my $.02

        • Brad September 29, 2010 at 6:17 pm #

          Hi Brandon,

          Congrats on the ISBU -STEEL- reefer. This sounds like yet one more thing I can investigate. I agree with your comment about the cost to insulate. In Ronin’s description he didn’t give a dimension on the wood furring strips therefore I have know idea what amount or thickness of spray foam he had in mind for the exterior walls. Rvalue of 14 is a standard jumping off point depending on location/climate. Verbal descriptions of building components are challenging compared to drawings though.

          Next week I’ll be hunting the Houston port area for containers and that includes reefers.


          • Brandon September 30, 2010 at 7:05 pm #

            I believe furring strips are 1X2. So he was probably suggesting 2″ of foam insulation. However you could do 3.5″ of insulation by using 2X4’s

            • Renaissance Ronin October 1, 2010 at 1:53 am #


              You’re correct about furring strip dimensions.

              But remember that the actual dimension of your furring strip will be determined by the depth of insulation required to accomplish the task.

              In many instances you’ll be ripping them yourself from dimensional lumber, to get what you need.

              That’s why there is NO “pat” answer.

              And who the heck is “pat”, anyway? Is he related to “Murphy”? ๐Ÿ™‚


      • lilchoke October 1, 2010 at 7:22 am #

        Thank you for all the info. Why are the aluminum “reefers” useless as housing material? Is it because the aluminum is a soft metal?? I was planning on using 4 of these for a project. I am trying to figure out the insulation part. I been inside a reefer that had been sitting out in the GA heat all day and it was very cool inside it. This is what led me to want to use them. I am and have been trying to figure out a good way to do the insulation on the exteriro and have gotten stuck at times. any help will do. Thanks

        • Renaissance Ronin October 4, 2010 at 3:08 am #

          Hi there,

          ISBUs made from aluminum are referred to as “hubs”. They are built from aluminum to allow them to be placed on trailers for overland transport, and by reducing the weight of the boxes, you make the movement of cargo more efficient and affordable.

          These HUB boxes are also configured to be used as “reefers” – refrigerated storage containers.

          And, there is even a “separate species” of reefer boxes that is based on the ISBU configuration. I’ve seen at least 5 variations on the Aluminum box theme, in the last few years.

          It should also be noted that none of these are to confused with the reefer trailers that you usually see being hauled via Peterbilt or MACK down the highway on top of “reworked flatbed trailers and axles”.

          Even insulated and clad with steel sheeting (it’s usually very lightweight as well, and varies from manufacturer to manufacturer) you simply don’t end up with enough STRUCTURE that can be safely used to create housing using the Aluminum containers as a base.

          I have personally seen Aluminum HUB ISBUs fail. (They were “scavenged” to use as “barn buildings”.) And it’s generally catastrophic. In one case, some of the livestock were killed.

          To recap:

          IMHO – You CANNOT use aluminum HUB ISBUs as “primary structural elements” in a project like you’re suggesting. It won’t work. It won’t hold up, it won’t last thru decades of residential use, and it won’t offer enough protection in heavy weather.

          At least, I wouldn’t and I definitely wouldn’t allow any family I was working with to do it.

    • ted yrizarry September 30, 2010 at 5:59 am #

      A little food for thought while your still in the designing stage. Windows. As I am going to guess that you would prefer to see out (?heehee?) do you know how many windows you will be adding/cutting in? I menition tis for two reasons. one is that each and every window (and door) is a hemoraging climate loss. They cost more energy to heat and cool simply by their existance. And while they add to Passive solar heating I personally think that is marginal. ut they do allow heat to esacpe and cold outside to radiate in…eating more energy to compensate for it.
      The other factor is security. Since you cabin will be “un-manned” a good portion of the time I would think it prudent to find a way to secure these entry points. And though I don’t doubt it has been coverd by Alex and others many times I haven’t heard it lately. The ages old idea of “Shutters” seems a great solution to both your (and mine) needs. If you plan it ahead of time you could create some very useful ones. I’m going to do the same on my own when it comes time for similar reasons. I hope to build them as essentually insulated “hatches” that can be closed to fend off the brutalest of weather. Locked in place from the inside so when I’m gone I won’t worry about an intrusion. And when they are opened they will provide an awning effect to keep the glaring sun from cooking me. The reason I mention to plan this in early is so you can subtract the quantity of insulation from the window area. Though the reality is it will be a wash once the shutter is built.?. But I should think it easier to build the window frame and shutter mount before insulating the rest of the box.
      Just a rambling idea I thought may be useful for you. If I’m off base maybe Ronin will correct me…?

      • Brandon September 30, 2010 at 6:59 pm #

        Great minds think alike. I plan to use the cut out section of the container as a shutter to use when I am gone. Both the door and the window frames will be square steel tubing welded to the inside and outside steel of the reefer container. I’ve always wanted a steel door frame ever since a friend of mine had his front door kicked in by a burglar. The dead bolt was locked but only a fraction of an inch of molding holds the door shut. A swift kick was probably all it took to knock the door in. I will probably leave the glass windows uninstalled until it reaches its final destination, since the container will likely bend and bow when it is being moved. I wouldn’t want to install some nice new windows only to have them shattered when the container flexes as it is set on its foundation. I still am deciding on how to install them in such a way as to allow me to shut the steel shutters while allowing me to keep the windows installed. They cannot occupy the same space within the wall of the container. I think I may build a steel window sill around the windows that the shutter hinges to. Then I can shut them have even pad lock them from the inside when I am gone.

        One Idea I had to let more light in but still remain secure(ok so its not MY idea, I got it from my architect friend who designs shipping container homes) is to install a sliding glass door against the steel shipping container doors. When you are home, you can unlock the doors and let all the light into the container, but still have it totally secure when the steel doors are shut. Great for summer time. BTW, I plan on having my “front” door cut into the side of the container, and again make the door out of the cut out piece.Very secure door that is also insulated. I’d like to build a porch off this side of the container, which really helps increase the perceived living space.

        I think this blog needs its own discussion board! It would be a mad success and would increase views dramatically! Discussion boards always do. The cutting edge of ISBU living spaces!

        • Renaissance Ronin October 1, 2010 at 1:57 am #

          Um… accusing TED of being in possession of a “great mind” is like implying that my 3 year old (in two weeks… where did the time go?) is gonna grow up to be Albert Einstein, just because his DAD is a genius… ๐Ÿ˜‰

          You guys are on the right track with security shutters, but I’ll go you one better. When I build “remote” ISBU homes, not only do the shutters fold DOWN, the decks actually fold UP against the home when they are vacant, to provide yet another level of security to the dwelling.

          After all, there be “lions and tigers and bears out there”… Oh my…


          • ted yrizarry October 1, 2010 at 7:09 am #

            Dang Ewe Alex! Not fair calling a spade a spade! I can’t help it if I’m just a dummEE. LOL! But all I don’t know I learned from you! haHA!
            Brandon, IIRC it was *cough-cough* Ronin that suggested using steel angle for the openings instead of square tubing?? If you install the inside of one face on the inside of the conatiner and the other side facing out 90* you would have surfave to build with easier. You could also find it easier to prefab the frames and maybe that angle is less expensive than tubing? The loking mech. can be as simple or as complex as you wish. As long as the shield/shutter can’t be pried away easily you should be golden.
            And while the zombie repellant draw bridge walls would keep it safe I would say that seems overkill even in my overkill enjoyed world. The added complex design may be worthwhile…but not something I would do. You’d have to engineer a way to raise and lower it without blowing out your “O” ring each time you leave it. An electric winch (WINCH Alex, NOT Wench!) would do the job but why? *shrugs* I’d rather set the boobie traps…

            • Renaissance Ronin October 1, 2010 at 8:33 am #

              Okay Ted, no confusing the pilgrims…

              Your doors and windows are build out of steel tubing subframes that form the rough openings.

              Not only does it help create a strong opening, it gets welded between the top and bottom (side)rails, and that helps strengthen the box.

              Angle iron is used as a retainer for the furring strips (if you insulate outside the box) and for the SIP roof assembly to sit on.

              When you remember that you’re going to use a Steel “box” made out of light plate steel to actually form your opening (inserted inside that steel tubing) it will give you ample ability and leeway in devising and attaching your shutters.

              If you hang your shutters (tip: use louvers) over the window, you can just drop them straight down when you’re not home, and padlock them to the plate steel window frame you fabricated.

              A simple pulley system hung on the edge of your roof soffit will raise or lower the shutters.

              Usually your overhead shutter drops down to recess inside the steel frame. Open the window from the inside, and then attach the padlock. That keeps people or bears, or zombies from prying or cutting the locks off from the outside.

              If this doesn’t make sense (after all… I have to explain things to TED with crayons…) ๐Ÿ˜‰ I’ll draw it out for a future post. ๐Ÿ™‚


            • ted yrizarry October 1, 2010 at 8:43 am #

              Crayons too advanced…I am Army remember? And I wasn’t trying to offer, confusion…I was simply trying to offer a little idea-R. I would have used some pictures and discriptives from the “big book” but…well, uh…
              Funny thing is when I lay out the erector set next to the lincoln logs it all makes perfect sense…? *scratches head and looks confused*…

  4. mark October 3, 2010 at 1:11 pm #

    I just purchased 5 high cube 40’s and I am going through plan check with my plans for a 4 container house and using only SuperTherm coating for my insulation. I have read here that this is not the way to go?? I purchased enough for 3 containers, did I get ripped off? I too watched Bob Villa and did more research and found third party test results that I requested from the company.

    • Renaissance Ronin October 4, 2010 at 2:58 am #

      Hi Mark,

      If you read the blog, you know that I have less than trust for Ceramic Coatings as Insulation.

      In a nutshell, the material would have to defy the laws of physics to perform the task they claim. I’m not the only one who thinks this, many engineers and architects think similarly.

      Further, most of the “third party results” I’ve seen waved like a banner are “irrelevant or miscast” to imply that you can paint something on your ISBU that will allow you to take it ANYWHERE and live comfortably, just like if you insulated it with a traditional material.

      I wish it were true, and that we had testing and product data (that could be duplicated and confirmed the claims of manufacturers) that allowed us to take the material into Planning and Zoning and get a green light. But alas, it just isn’t so.

      Until manufacturers can PROVE beyond a shadow of a doubt that their coating concoctions can indeed be used to replace insulation on a Steel ISBU for habitable use in all zones, I’m not buying.

      Why risk the safety of your family on “corporate claims?” We all know how that usually turns out.

      Just out of curiosity, I have two questions for you (three actually);

      (a) Where is your project located?

      (b) How much ceramic coating material did you buy? and…

      (c) what did it cost you for the material?


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