Tag Archives: Closed Cell Foam

Strong Foam makes Strong Container Homes…

16 Dec

Greetings Campers!

It’s time for another exciting episode of;

“Man, that Ronin guy is a Container Home Building Idiot!”

Lately, I’ve been asked a certain question several times, even though I’ve talked about the answer endlessly.

No! It’s not the question of my sanity and the rapidly shredding thread that seems to hold everything all together.

I’ll have you know that electro-shock therapy, the lobotomy, heavy dosages of meds, and 72 hours periods of confinement have seems to slow the symptoms down remarkably well… 😉

It’s the question about Spray Foam Insulation, and why it’s better for your container home.

And I was asking myself why people were asking the same question over and over again, every 3-4 months or so…

The SPRAY FOAM question…

… not the “Is Ronin Insane?” one… stop it!

I can see you spitting at the monitor! Oy, you’re gonna get electrocuted if you keep that up!

The answer?

Well, it occurs to me that there are a lot of new people looking at this Container Home Building blog lately. As the economy gets worse and worse, and housing gets harder and harder, more and more people are searching for answers, solutions, and alternatives…

So, if you’ve been here for a while, please indulge me as I attempt to write the “Complete Spray Foam  Insulation”  – “Don’t ever ask me again”… basics – primer.  😉

I’ve talked a lot about how spray foam insulation (the closed cell variety, please) is the best way to insulate a container home ( or most homes for that matter).

Closed cell foam is easily applied to the outer surface of your Containers, allowing the elimination of cold spots.  In most markets, a confident and handy person can apply it themselves, using a rented sprayer. YMMV (your mileage may vary).

You can even buy kits now (using the same exact foam), to let virtually anyone insulate their house, at a price that is way below what a professional applicator would charge.

I’ve even seen cooperating ISBU Container Home building families all pitch in together to buy a really good system, and then just pass it from family to family, until everybody got the job done. And then… CRAIGSLIST!

Why would anyone do this? I mean, it sounds like a lot of hard work…

You’re going to get about r7 for every inch of closed cell foam that you apply to your Container Home. So, a few inches  (3 of ’em) gets you an r21 on the walls, and a couple of inches more than that ( for a total of 5) will get you an r35 in the floor if you want  (or need) it.

Now remember, spray foam is just a part of your arsenal against the “hot and cold running beasties…”

We all know by now that Ronin highly recommends using SIPs (structural insulated panels) to form your roof.  Using SIPs you can easily build an r50 roof.

Cold outside? I spit at the cold! In my spray foam and SIPs cocoon I’m all snuggley warm! Hey, my house is so tight that I can heat it with this Ronco Lighter! 🙂

But, this post is about “Spray Foam.”

Putting insulation on the outside of a container just makes sense.

There isn’t any good reason for making the inside of a small box even smaller. The POINT of Container Home Building is to take a readily available component (in this case an ISBU Shipping Container made of Corten Steel) and squeeze every square inch out of it that you can, to make a wonderful, sustainable, energy efficient home.

Spray Foam Insulation (SPF) is just another component in that puzzle. Because it fills every single nook and cranny, you don’t waste energy by letting heat out in the winter or cool air out  in the summer.

Plus… Closed cell foam is exactly that. Closed cell. This means that once applied, it forms a vapor barrier. That’s even more insurance against nasty energy leaks. And because it’s closed cell, there aren’t any moisture leaks either, because it forms a moisture barrier. Talk about getting your money’s worth!

And it also forms a really efficient sound absorber to quiet your house down. It just keeps getting better and better.

But wait, there’s more!

And there really IS more! Using SPF actually reinforces and strengthens your home. It’s like wrapping your house in duct tape!

If you’ve got a NASCAR watching bone in your body, you know how important duct tape is! Right? I mean, it’s good for everything!

I even use it around the house!

But… seriously… SPF Polyurethane Foam will help to strengthen your Container Home.

Just like in any other home, the walls in your Container home are a part of the structural component system of the building. In residential construction, the weight of the actual roof, the weight of the shingles, any standing moisture (like rain water and snow) add “weight” to your house.

This exerts “compression.”

Compression is the downward forces on the walls that comes from this weight being piled on top of them.

Now, it doesn’t stop there, either.

Strong winds, tropical storms, tornadoes and hurricanes can  impose “lateral forces” onto your home’s walls.

This lateral force is called “shearing force.”

Ask any Planning and Zoning Nazi, and they’ll tell you that building codes require that your home’s walls must be designed to withstand all these various forces and excessive loads.

However, when walls are built to just the minimum standards (like in most wood houses, for instance), while they still might be safe, evidence of this kind of “movement”  (like creaking and shaking during high winds) occurs.

Putting higher density, closed cell spray foam insulation inside your walls fully adheres to both the exterior sheathing and the walls themselves, in effect reinforcing both of them in a great big “foamy sandwich.”

While I’m often accused of being “too rigid,” this kind of rigidity is good. With this added strength, wall movement due to wind, vibration, and even MP3 blaring occupants is reduced to a minimum.

And, yes, there’s more benefit from this collaboration. Now not only do you have tight, well-insulated walls, your walls have “greater than code” required resistance to those forces we talked about that create “racking events…” such as hurricanes or other heavy weather events.

SPF also can add A MASSIVE AMOUNT of structural strength to other types of buildings. A study by the National Association of Home Builders (NAHB) Research Division demonstrated that SPF filled walls could add from 75% to 200% racking strength to walls of OSB, plywood, light gauge metal, vinyl siding or gypsum board.


Listen to  “Crazy Old Ronin…” and use Spray Foam on your Container Home project. Not only will you be warm… you’ll be safer.

And, that’s money worth spending.

Stay tuned.

The Renaissance Ronin1. Test results are reported in “Testing and Adoption of Spray Polyurethane Foam for Wood Frame Building Construction” (May 25, 1992) prepared by NAHB Research Center for The Society of the Plastics Industry/Polyurethane Foam Contractors Division. 2. Test results are reported in a letter from Bob Dewey, Mechanical Engineer, NAHB Research Center to Mason Knowles, The Society of the Plastics Industry/Spray Polyurethane Foam Division (November 18, 1996).