I know what you’re thinking… Ted! Stop it! This is a family show! 🙂
Readers of this blog know that this week, I started a series of posts on ISBU insulation.
It’s the hardest part of ISBU construction, to hear people tell it. Who tells it that way?
Um… well… people who are either “idiots”, people who have never done it, or people who are insulation professionals who want an unhealthy chunk of your building money, to send their kids to college or pay for that second honeymoon…
Okay, okay, maybe it’s not that bad… 🙂 but from the email I get, you wouldn’t believe the things that are happening out there.
As I wrote the first post, I knew in my gut that I was going to immediately get hammered by readers. And, I was right. By Monday night, I had 27 emails in my Inbox, all asking for “insulation help”.
I’ve found that using reader mail to address ISBU issues has been pretty productive, so I’m going to take one of the letters I got and share it with all of you, so you can see how this works.
Brad’s mission is to build a (2) container ISBU home, using a pair of 40′ High Cube containers as the shell. He’s going to do this in the Houston area of Texas. When you read his letter, you’ll see just how much thought he’s put into this and you can see that he’s intent on achieving his goals.
Let’s see if we can help him.
Thanks for your response about insulation. Since I’m new to your site I suppose I missed previous comments about the subject. (Editors note: READ the ARCHIVES!) 🙂 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.
First, welcome to the fray.
Second, start hitting the archives. There’s a ton of stuff in there.
Third, you’re on the right track. Regular readers of the blog know that I ALWAYS insulate on the EXTERIOR of the ISBU when given that option. Sure, some people like the industrial look and want a “Mad Max” front yard, but most don’t. 😉
And, that insulation of choice is SPF, every time.
That leaves the trick;
How do you attach the insulation and the siding to an ISBU, to form your finished exterior?
The idea of drilling and then attaching fasteners, hence puncturing the sanctity of that weather resistant Corten Steel shell is crazy!
What is SPF? GLUE.
Your furring strips are made of WOOD, right?
How do you attach wood to metal? You can use fasteners, and make a mess of that waterproof box, or you can use construction adhesive to glue your furring strips into place. Sounds crazy, right?
Here’s what I often do;
I just fab a long steel “L” out of lightweight sheet steel (think gutter or flashing), that runs along the top and bottom of the container. Using light enough steel, you can literally do this using a “brake” made out of dimensional lumber. Seriously. Just weld it into place, like a bizarre flashing. Top faces down, bottom faces up. Are you seeing it?
Now cut your furring strips to length so that they fit inside that “tray” up against the container corrugation. That added metal lip is just going to help hold everything in place.
Apply glue to the furring strip, and then stick it where it needs to be located. The “siding flashing” will help hold it in place. Once your furring strips are “glued” into position, drill your holes and run a fastener (screw) into each furring strip thru the flashing and into the furring strip.
Congrats! Your furring is now “glued and screwed”… with “ZERO Penetration” to the box.
NOW… insulate using SPF. SPF applied between the furring strips is going to glue the entire thing together in one huge monolithic mass. Think about this. The foam is going to expand to fill the cavity between the furring strips and the corrugated container, in effect gluing everything together. It’s what SPF does! The end result is going to be a vapor barrier, a moisture barrier, an insect retarder, insulation, and even some structural assistance to help your home deal with racking and shearing.
Apply siding. Predrill, and use SCREWS! If you work fast, that insulation will even help GLUE the siding to the house…
Trust me, once the SPF sets up, that entire wall section isn’t going ANYWHERE. I’ve come back after the fact to add more containers (7 years later) and getting that “siding mass” off the house and out of the way was an ORDEAL. We inspected the removed panels for “insulation or furring strip failure”. Zip. Stuck like Chuck.
Would your typical Planning and Zoning Nazi like this? Nope. They’ll have kittens. But, the insulation and siding that you install in this fashion will be a part of that house until the houses demise.
Sounds simple, right? Too simple, maybe? Build a dummy panel in your garage, and then test it, if you don’t believe me. Try to pull it apart in 24-48 hours after the SPF has set up. You’ll see what I mean.
Now, let’s address that “Green Roof”:
First, how are you reinforcing your roof, to accommodate that “green roof” dirt load? And better still, what are you going to use as insulation, below it?
The corrugated steel roofing isn’t going to support the weight of a realistic Green Roof. That roof isn’t even “structural” in the traditional sense. It’s simply there to keep water out of the cargo. Any ideas about building “Green Roof Surfaces” has to include a structural support system.
The R-value of dirt always varies greatly depending on its composition, and how high the moisture content is.
We all know that in the construction world, the term “R value” is used as the reciprocal of thermal conductivity…
A pile of dirt equals “thermal mass”, right? Big pile, big mass.
But it gets tricky. “Thermal Mass” isn’t the same thing as “heat transfer resistance”. And, for those of us working in the biz, we figured out long ago that R-Value is just heat transfer resistance.
A check of the material tables will show you that (typically) R-value for earth is R0.25 per inch.
That means that the foot of dirt that you’re talking about isn’t going to go very far against the heat of Houston, Texas Summers. You’re gonna get about R3, tops. And… the “thermal coefficients” aren’t “bankable”, they are affected by several other factors, and the biggest killer is soil moisture content.
Granted, this can get pretty complicated and we’re not going to cover it here, suffice to say that soils are inherently “heterogeneous and nonlinear.” That’s a couple of three dollar words, huh? 😉
Translation: Get soil really wet, and it’s worth about zilch as “insulation”.
Really want that Green Roof?
Start with SIPs (Structural Insulated Panels) to get both your insulation and your roof support. Then top with a waterproof membrane system. Once that is applied, you can go as green as you want, without fear of a roof failure from wet soil due to that Corten Steel’s longterm exposure to moisture.
Third – I’ve sketched out your floorplan, from the notes you’ve left.
If I’m understanding it correctly, have you considered putting the bath and kitchen close enough to each other to save some plumbing costs? Say, back to back? With the budget that you’re working with, every penny you save is going to count.
What are you doing for a foundation? NOT an uninsulated slab, right? Readers here know that putting a container onto an uninsulated slab means that you’re just hemorrhaging energy directly into the ground. You’re insulating the bottom of the containers, right?
A tight, super-insulated box is a happy box.
I hope that I’ve given you some ideas, and some things to think about.
“Living in a box” means “thinking OUT of the Box”.
Some of the tasks that you’ll complete will be accomplished differently than in a “traditional” housing situation using conventional materials. But if you keep your wits about you, take your time, and exercise “care and caution”… soon, you’ll be living in a sturdy, affordable Corten Castle of your very own.
My Thanks to Brad, for sharing his project with us.
Keep us posted!