This has been the biggest hassle of the entire project. The contractor I hired to insulate with spray foam started the job on September 25th, and just got around to finishing it on October 22nd – 4 weeks later! There are still some issues with the work he did, but I am done with him now.
It all started on 9/25 when he showed up to do the spraying and the generator he rented was not big enough to do the job. He got about 15′ of wall space done before the generator started having problems. He then told me he would get a different generator that week and have it done by Friday. So, I show up at my cabin the next Weekend and nothing was done. I tried calling him on his cell and he would not return my calls, and did not return my many calls until later the next week when he said it was done.
On October 9th I went to the cabin to start hanging the drywall assuming the insulation was done. At first glance it looked as if everything was OK. I then started looking at it a little closer and thought the foam was a little thin. I got a nail and started probing the foam depth and found the newly sprayed foam was consistently less than an inch thick, and even as low as 3/8 of an inch in many places. BTW, the signed contract for the job specified 2″ of foam on the interior wall. After tracking him down I brought him out there to see what was done. He admitted that it was done incorrectly and told me it was one of his employees who had sprayed it. He said he would personally fix it and make it right that week. Needless to say, it took him another two weeks to finish the job and there were still some things he did not spray correctly.
OK, I’m done complaining about the insulation and will actually start talking about it. I had chosen to use a closed cell spray foam insulation to prevent any condensation from forming behind my walls. Since the steel walls of the container are a perfect vapor barrier, any water vapor that can get behind insulation in the cold months will readily condense on the steel walls. Two inches of sprayed closed cell foam insulation is not only a good insulator (R13), but it is also a seamless vapor barrier and will not allow any water vapor to travel behind it to the steel walls. I had them spray 2″ on the interior walls, 1″ under the containers, and 2″ on the outside top of the containers. While this is not a lot of insulation, keep in mind that this is mostly a three season cabin with a capable wood stove (Jotul 602) and very cheap wood.
I recognize that insulating the outside top of the containers is probably somewhat of a gamble. The conventional, and safe, choice would be to insulate the interior ceiling, although being 6’2″ tall I really did not want to lose any interior height. I also kind of like the look of the corrugated steel roof inside. The potential problem here would be the loss of heat at the edges of the ceiling causing condensation to form inside. If I do get some condensation, I plan on using an anti-condensation coating from Mascoat Industrial. This stuff is very different from the insulating paint scams that abound, and has been used successfully by boating enthusiasts to eliminate condensation in their boat hulls.
I will try and post a follow up sometime this spring to let everyone know how the external ceiling insulation worked.
I am enjoying your blog on the construction—just found it today. I would like your opinion of the the feasibility of a container house in central Alabama. Temps range from mid-teens to low-100s.
appreciate your time and effort to post the blog.
Elizabeth:
Shipping container homes have been successfully built in climates ranging from Canada to the tropics, so Alabama should be no different. Something to keep in mind about my project is that it’s a cabin and not a home. If I was building this as my primary residence, I would have done things very differently. I also would have hired an architect and builder who is familiar with this type of construction.
A great example of using shipping containers for a primary residence is the Maison IDEKIT home in Quebec – especially if you like contemporary architecture. They installed insulation and siding on the outside of the home which not only helps it look more traditional, but also increases its interior space as well. http://www.maisonidekithome.com/index_en.php
You might also want to search through the bobvila.com website. There are some good videos there about a container home that was built in Florida. The building methods for that house are probably more appropriate for your location.
Steve
Hey!
I have a couple of containers on my property. I modified one into a cabin of sorts and was referred here by another doing the same thing. Currently, my cabin is just a 40 foot box with a door and a few windows cut into the sides and an internal wall with another door and a window to use as the main entry when the big doors are opened.
The container is really raw inside yet, no insulation or anything. I think I would rather buy the kit and do it myself instead of hiring a contractor. Eventually, I will be spanning a floor and roof between the two containers to make a more livable space but when I am there, the box is fine for just me.
Dave:
If you are considering a DIY spray foam kit, I’m not sure you will save much money over a contractor. The ones that I priced were about the same as my contractor applied – about $2 per square foot (2″ thickness).
Something I would consider if I were to do it again would be a hybrid approach with both foam boards and DIY spray foam. Glue as much 2″ foam board as possible to the walls at just $0.60/sq ft, and then spray foam the seams, corners, and edges to seal everything up. As long as the all the seams are sealed, water vapor should not get behind the foam to the colder steel walls.
Steve
The Foam board/spray at the joints isn’t a bad idea and is very easy to do even for someone who isn’t heavy into DIY. Did you paint the interior metal walls prior to installation of framing? Like a “rustoleum” style paint to prevent it from rusting inside out?
Joe:
The inside walls were already painted, and since the containers were new it was in excellent condition. The spray foam sticks to the painted surface like glue and is actually hard to scrape off. The other thing to keep in mind is that these containers are made of Corten steel which naturally resists rust through.
Steve
Thanks for sharing. I have a 20ft container and would like to get another one. I’m excited about getting it to a livable state. I am still not sure how I want to go about insulating and I would like to cut the least amount of holes into the containers. If you were to insulate again would you do it differently. Do you think it’s worth insulating the floor ? I am on the west coast, so it dips below 0 but not often, it’s the dampness and condensation that I worry about.Thank you again and I expect to be sending many ??? your way.
Denise
Hi Denise:
The only thing I would for sure do differently would be to find a different contractor, or do it myself. As I discussed in one of my responses above, I might also consider doing a hybrid approach with both foam board and spray foam. The single most important thing in my mind though is to use closed cell foam insulation. It’s critical that all of the metal walls be covered with foam to prevent condensation behind the finish wall. I did take a risk by insulating the ceiling on the outside, but so far it seems to be working well.
In regards to insulating the floor in your climate, you could always try it for a single winter and see how it works. My new containers were sprayed on the underside with some sort of protective black undercoating that would probably be a good defense against any dampness. You might want to check and see if your container has anything similar underneath. If that doesn’t keep you warm enough, you could consider just gluing 1″ foam board to the wooden portions of the floor on the underside. You could also spray foam on top of that if you needed more.
Please keep me up to date on your container build.
Steve
hi Steve, thank you for your ideas on the 20×8 Your time and energy spent on your site is very much appreciated. I have not progressed very far with my container. I have put down the flooring and am now trying to figure out how to easily and least expensively insulate the walls and ceiling. I am thinking of using the stiff 2inch insulating sheets and then foaming any gaps with foam insulation. So as not to lose anymore space then necessary I thought I would frame it out with 1x2s. Will this be enough to keep away condensation, mold and all the ugly things that go with trapped H2O ? Thanx again for sharing.
Denise
Denise:
I really don’t think 1x2s have enough structural strength to support any type of wall covering. I have seen where others have used 2x2s that are glued to the metal walls with construction adhesive, but I would not personally be comfortable with that since I think some sort of insulation needs to be on the walls. The smallest wood stud I would be comfortable with is a 2×3. The smallest stud I would ever consider using would be the 1 5/8″ steel studs that I used in my existing cabin, although I would decrease the stud spacing considerably in the areas that were not tied in with spray foam.
If I were going to use larger studs, like 2×3′s, I would make sure to space them so that they lined up with the outward corrugations of the metal walls. You might have to deal with some non-standard stud spacing, but it would provide the most space for insulation between the steel wall and the stud.
Steve
It is too late for you, but a proper foam insulation job should be something like:
http://www.youtube.com/watch?v=VFjxWdPPY1Q
I found your website last night. In reviewing your construction notes, where you had problems with the insulation contractor, then you had to fabricate stud walls, etc., I just purchased and installed this product in the basement of my home:
http://insofast.com/index.html
It is a green product that installs rapidly, has built-in electrical chases and non rotting studs, is inexpensive, insulates to R14 and the company is easy to work with. Much less hassle to install, and is a natural for container construction. Worked great in my basement, used construction adhesive to attach it to the concrete walls and screws to attach it to the one half wall I constructed from dimensional lumber. I plan to use it in a transportable house I’m planning now. Interestingly, it’s not much of a leap from transportable houses to container houses, as I have found a few people mounting the containers on transport wheels to move them around. Let me know what you think about this product.
Raleigh:
While an interesting product, I would never use it for insulating a shipping container. As a rigid and flat product, there will naturally be an air space between it and the exterior container wall – remember that container walls are corrugated. Any crack, hole, or other opening through this product would allow moisture laden warm air to enter into that air space. This moist air would eventually condense on the cold steel walls and form puddles behind the insulating panel. And since the panels are themselves a vapor barrier, the water would not be able to evaporate out. I would never want to rely upon the long term integrity of a separate vapor barrier to keep humid air away from the container walls.
As problematic and expensive as it is, I just don’t think there’s an alternative to spray foam insulation for shipping containers used in cold climates. This is the only way to create a vapor barrier that is integrated into the container walls. The only exception to this would be if you wanted to insulate the outside of your containers, which can be a perfectly acceptable method of insulating.
I do appreciate you looking out for different ideas though.
Regards.
Steve
This product has been used on the outside of conventional homes. I hadn’t considered the corregated walls since my basement doesn’t have them. Worked great in my application, and I would think simply taping the seams would complete the vapor barrier. Water is insidious, though.
Where did you buy your containers and were they HQ? I’m also 6’2 and think the higher HQ containers would be best. Any idea on approximate cost of new versus used? Also, any idea on various siding options to cover the exterior in florida? I saw Bob Vila’s videos on the St. Petersburg, Fl house and they welded steel sheet panels onto the container to make a flat finish then applied ceramic paint. It looked like a painted steel box and not very attractive. I’m just wondering how you would attach siding to the outside. With furing strips???
Hi John:
I purchased my containers new from Cherokee West Enterprises (530-547-5408), although they were not high cubes. I thought about high cube containers, but the extra height (and associated extra cost) just wasn’t worth it to me. If a high cube was tall enough for a functional lofted area, 10-11 feet maybe, I might reconsider. In any case, my ceilings are close to 8′ high (93″) which is more than adequate for a cabin.
I never really compared the cost of new vs used since I had always planned to use new containers. The advantages of new containers far outweighed, at least for me, what I could have saved by going used. I was able to get three containers from the same manufacturer, with the same dimensions, same door mechanisms, and the same color. If you’re going for the distressed, mismatched look, then by all means save some money and get used.
In regards to the exterior, I feel if you’re going to use containers, then your building should look like one. The steel exterior of a container is one of it’s strongest attributes, so why would you want to cover it up? If you must cover it up, you can attach vertical wood strips to the exterior with welded on L-brackets and side as usual. I would also give serious thought to insulating the exterior in that case as it will save considerable interior floorspace in the process – if you like metal walls as your interior finish.
Steve
We have just purchased a 20ft opensided container to convert into a catering facility. We are thinking of building stud walls and using celotex/kingspan as insulation and board with a product called Respetex (wbp plywood 11mm and lamented covering). We would leave a small gap between the stud walls and exterior, then would put a few vent grills in the walls. The container is going to have a roof and be clad on the exterior with timber (log cabin look alike) which again would help with insulating. As we live in rural Wales (UK) the prices are extremely expensive for the spray foam insulation. But this issue with condensation and not knowing what is going on once you put those boards up is extremely worrying. Our temperatures range from -5 to 25 degrees, but it is damp – that’s why Wales is so green!!! What to you advise??
Susan:
Using outside vents to allow moisture to escape from the walls is an interesting idea, but not one I would personally use. It’s not that it wouldn’t work, it’s just that I wouldn’t be comfortable doing it.
The first problem I could see, which may not even apply in your climate, is if you would ever want to use air conditioning. In this case you would have a cooler interior wall that warm moist air from the outside could reach and condense on. The second problem I would worry about would be insects and other pests. Unless your vents are perfectly sealed, with properly sized screen, insects could find their way into the wall cavities and nest there.
As I have said before, the only insulation I trust to be used on the inside of a shipping container is closed cell spray foam. If I absolutely had to use something other than spray foam insulation, I would install it on the outside. In that case you just weld some small metal tabs to the exterior, affix some wood strips/boards to them, insulate between the strips, and then install some siding as usual to the wood. This has the added advantage of giving you more interior space to work with.
Steve
Thank you so much for your comments.
Sorry, didn’t explain myself properly. The shipping container already has two sets of air holes (vents) at the top on the back wall. The vents we would put in would be on the interior walls (either top or bottom), maybe we should close the outside vents (no insects) and hoping that the air from the inside would stop the condensation??
As we will be cooking in the unit. Most of the front will be open all day so air conditioning (even though I would love it) would not work for us.
The remarks you make about insulating the outside is interesting, as every inch inside is valuable. What would you use between the timbers??
Just for your information we currently have a catering trailer which is made of 18mm insulated GRP panels. This is 10 years old and we don’t freeze in the winter or overheat in the summer and condensation is not a problem as whilst cooking the hatch (10ft long) is open. What worries me is the steel from the container??
Thanks for your advice.
Susan:
What you propose here would be a bad idea. You are basically allowing warm moist air (think cooking) from the interior to enter behind the paneling and condense on the cooler steel container walls. While water vapor in the air will pass easily behind the walls, once it condenses it will form puddles on the floor that will take much longer to evaporate.
I don’t think it matters so much what type of insulation you would use on the outside so long as it’s properly applied. Spray foam would still be the best as it is more space efficient than virtually anything else – you could probably get by with 2×2 furring strips. If you use fiberglass, you will basically have to build 2×4 or 2×6 frame walls and a roof on the outside of the container which almost makes using the container moot.
Nothing beats spray foam insulation for shipping containers.
Steve
I am responding to the point where you say “Something I would consider if I were to do it again would be a hybrid approach with both foam boards and DIY spray foam. Glue as much 2″ foam board as possible to the walls at just $0.60/sq ft, and then spray foam the seams, corners, and edges to seal everything up. As long as the all the seams are sealed, water vapor should not get behind the foam to the colder steel walls. ” and later you refer to ‘insofast” an say that “As a rigid and flat product, there will naturally be an air space between it and the exterior container wall – remember that container walls are corrugated. Any crack, hole, or other opening through this product would allow moisture laden warm air to enter into that air space. This moist air would eventually condense on the cold steel walls and form puddles behind the insulating panel.” My question is since 2″ form board is ridge, how would you suggest not recreating the spaces and condensation that insofast would? Thanks. PS! Your Blog is very helpful. I appreciate all your help.
One more thing… What do you think of Prodex total insulation 48?
Jack:
Interesting stuff, but I have a real hard time believing a 5mm (13/16″) flexible sheet can have an R-value of R16. They’re basically saying that their 13/16″ flexible sheet has more insulative value than a full 3″ of extruded polystyrene foam. If something sounds too good to be true, it usually is.
Even if this was good insulation, it probably still wouldn’t work too well. Where it would fail is on all the nooks and crannies and odd angles present around the perimeter of the container wall. If you could apply this to the corrugations, and if you could seal the seams, and if you could then spray foam around the edges and into the nooks and crannies, then it guess it might work. I wouldn’t personally take that chance though.
Steve
Hi Jack:
The Insofast system is an insulated panel with integrated attachment studs for drywall. As it’s designed, the system would need to be installed as a vertical plane against the corrugated walls. This would create a significant air space behind approximately 50% of the insulated panel.
What I was proposing would involve cutting the rigid EPS panels to a width that would fit within, and on top of the corrugations. The panels for the externally protruding corrugations would have their edges angle cut to fit precisely within the corrugation. The panels for the internally protruding corrugations would either but up against, or be over sized to overlap the other panels. The panels would also be glued into place for support, and so that there would be virtually no air space behind them. Spray foaming the edges should then lock everything into place while also theoretically creating a seamless barrier.
While this would be time consuming, it would also save a considerable amount of money. I do think a complete closed cell spray foam job is the best for shipping container insulation, but if you don’t have the money for it, this hybrid approach would probably be the best alternative.
Hope this helps.
Steve
Excellent site Steve. I am embarking on a cottage project, built from seven 20′ one trippers, and I am at the debate stage with my designer (I’m getting building permits) about insulation strategy. I’m in Ontario Canada. I am a big fan of the raw container look, inside and out. I really like the idea of using a ceramic coating on the inside walls and ceiling as my sole source of insulation (no studding, no cavities, no loss of space, no drywall), and spray foam the underside of the plywood floors.
I see your link to the Mascoat Industrial Anti-Condensation Insulation. I concur with the comment about ceramic paint suppliers seeming sketchy (except Mascoat as an example). I have just sent a note to Mascoat to get more information and to discuss my application with their experts. I am heating my place with free fire wood and only use the place one weekend per month, so I don’t need R20-walls or R50-ceiling insulation performance like typical building code in my area.
I might be trying too hard for the holy grail insulation solution, but I will be searching high and low over the next couple weeks to find a ceramic coating solution worth spending the money on (and taking the risk on). Any leads or additional thoughts on this topic would be helpful. I will repost what I decide to do, and hope to start a website for my project as well to share my project experience with others.
Thanks, Jason
Jason:
Do not, under any circumstances, waste your money on an insulating paint. I urge you to read the following articles:
Product Test – Nansulate and Super Therm
Insulating Paint Merchants Dupe Gullible Homeowners
An Insulating Paint Salesman Is Tripped Up By His Own Product
Insulating Paint Additive Manufacturers Exaggerate Energy Cost Savings
As for the Mascoat, I’d be wary using it in an application such as yours. I had only considered it as an adjunct to my external ceiling insulation if it was found to be wanting – fortunately it wasn’t. Mascoat’s not cheap, not easy to apply, and you’d probably need several layers to provide even a minimal amount of insulation.
When building a shipping container home or cabin, the old adage of there’s no such thing as a free lunch applies.
Good luck, and keep me informed.
Steve
Hi Steve,
I’m in Australia in a mild/cool climate. Achieving the required insulation r value here is not an issue. I’m having difficulty in working out the insulation method/product. What do you think:
Subfloor- damp proof barrier on ground(say concreters black poly) and 100-200 mm rock wool. Similarly, rock wool on a chicken wire mesh can be used to raise the insulation where stumps are high.
Wall- damp proof paint (bituminous or fiberglass) on container wall and rock wool in between plaster and metal)
Ceiling- batten the container roof on both inside and outside. On inside, rock wool insulation on plasterboard. Any condemnation on tin will drop onto the rock wool and dry. This is similar to the standard tin roofing construction. On the outside, paint the roof with damp proof paint or put down black poly with rockwool on top.
Thoughts!?
Theoretically, this gives us a good insulation rating as well as being the cheapest
Hi Ron:
I’m having a hard time responding to your question since I’m not at all familiar with your climate, and I’m wary of recommending anything other than spray foam insulation.
In regards to the subfloor, are the containers going to be on the ground or raised. If they’re on the ground, a vapor barrier of some sort could be useful. Insulation may also not be necessary in your mild/cool climate considering the container’s 1 1/2″ marine plywood floor – especially if it’s on the ground. My cabin only has 1″ of spray foam underneath the elevated containers, and I have felt comfortable in temperatures down to -10F.
Does the damp proof paint you’re considering for the walls prevent moisture from forming, or is it just resistant to it? If it’s the later, you’ll still have a problem with moisture forming behind the drywall. As I’ve mentioned before, you can try to install a vapor barrier to prevent moisture from getting behind the wall, but it would need to be absolutely perfect everywhere to work correctly.
Your ceiling comment scares me as you’re already planning for condensation to form. You also assume that it will be able to dry out somehow. Something I’ve found in working with containers is that water vapor has nowhere to go in a closed container. Most traditional houses have some level of air leakage that can deal with a small amount of water vapor, but a closed container does not. I guess if your container is always open and ventilated this might not be a problem.
I’m sorry to be on the negative side with this reply, but I’m going to stick to my recommendation of only spray foam insulation.
Regards.
Steve
Steve,
Thanks for creating this forum, very helpful.
Here are a couple of ideas I’ve come up with for insulating a container for Canadian climate conditions:
The most space-efficient AND energy efficient method seems to be to tack-weld furring strips on the interior walls -horizontally. Then closed-cell spray foam. The foam should be able to get behind and inside the furring strips. But because the furring strips are horizontal, whatever panels you’re screwing to them would normally be oriented vertically, i.e. with vertical seams. Okay for drywall, because you’re taping the seams, maybe not so pleasing if your panels are plywood. This is just an aesthetic thing – vertical seams throw me off.
As for the ceiling, since closed-cell foam is paintable, why not plan for minimal framing in the ceiling, spray-foam it, and paint the foam? I don’t need a drywall ceiling. I only need a strip of framing down the centre in case I want to mount a light fixture or something.
The problem you’ve pointed out with flat panel insulation being glued to the interior walls is correct – the spaces in the corrugations behind the panels would be problematic. Here is the hybrid solution for the do-it-yourselfer: spray-foam the cavity portions of the corrugations, use your knife or saw to slice off the excess, and then glue the rigid panels. While it may seem finicky and time-consuming, it would use much less spray foam than a normal complete 2″ coating, and the rigid insulation panels are a nice surface to glue your finishing panels (drywall, plywood, whatever) to.
You thought I was never going to pose a question – here it is. If I put minimal framing in my ceiling and then put a 2″ closed cell foam on it, what do you think would happen if I walked on the roof? Would the flexing damage the seal of the foam?
Aaron
Aaron:
I really like your hybrid idea of filling in the protruding corrugations with spray foam then using flat panels on top of that. The only problem I see is finding a secure way to attach drywall or paneling to it – I’m not sure I would trust glue exclusively to hold my drywall in place. What about vertical studs spaced to be directly over the spray foamed corrugations with foam panels in between? I’ll have to give this some more thought.
The bad news is that I’m going to have to nix your ceiling idea. I looked into the same thing myself, and interior spray foam needs to be covered by a fire barrier. The International Building Code requires foam insulation to be separated from the interior of a building by an approved thermal/fire barrier of 1/2-inch gypsum wallboard or equivalent.
In regards to your ceiling question, I’m not sure what would happen. I know that my container roof with 2″ of spray foam on the outside doesn’t flex when I walk on it, although it did beforehand.
Regards.
Steve
Steve, you went with a single 2 inch application, for R-15. Now, granted, you are using this for a hunting cabin, so winter occupancy is limited. You do not, so far as i can see, give a location, which would help a great deal.
I am currently planning out a single 40 foot container for full-time residential use. it must be able to go anywhere in the USA, so I think R30 is called for. Is there any conceivable problem or benefit to going 2 inches inside and 2 inches outside to get R-30? Due to shipping constraints, I’d REALLY rather not mess with the exterior at all (I dont know if being another 6 inches wider makes a different re: putting it on a semi for shipment elsewhere) but given interior constraints, I do not have much choice.
Last question. Homes need breathability. Shipping containers seal up water tight – meaning air tight. How does one add breathability without losing the ability to seal up water tight – all the while maintaining a controllable temperature? Nearest thing I can think of is small vents floor and/or ceiling with a double sided rubber plug drawn together by a bolt to seal the vent when needed or desired.
Derek:
My cabin is in northern Wisconsin, so it can get plenty cold here. I’ve been in the cabin when it was -10F outside, and was very comfortable with just my Jotul 602 stove. I feel my stove could easily keep the cabin warm even in -25F weather if necessary – if it was any colder than that I’m not sure why I’d be there in the first place.
Something else to consider is the type of heat you have planned for your cabin. Since I have a wood stove, the cost of firewood in northern Wisconsin is dirt cheap. I’m not sure I’d ever get a return on my insulation investment if I used more than 2″ of insulation. I also believe that wood stoves should be run at hotter temperatures to prevent creosote buildup, so too much insulation or too big a wood stove can actually be a problem.
I’m not a fan of spray foam insulation on the outside of cabins, although there can be some advantages to that for some people. While my walls only had 2″ of spray foam, I think I could have gotten another inch sprayed on them without moving the walls inward any. I can’t imagine ever wanting more than 3″ of spray foam, especially considering how air tight and thermally isolated the walls of my cabin are.
I’m still working through the whole ventilation thing with my cabin. For now, I’ve been doing it the old fashioned way by opening windows – even in winter. I plan to add a powered vent to the bathroom someday, but I haven’t had any problems so far. I do have two passive vents at the front left and rear right of the cabin that are original to the containers, and those do help some.
Steve
Absolutely fantastic, brill detail. I live in Ireland, everything is green and humid ( drinched wet) to be honest. I plan on living in a container some day. Il be referenceing what youve done no end. Keep up the reports