I've converted these for garden rooms/offices.

Theoretically, you should put the insulation on the outside, so the totally vapour impermeable metal skin is kept warm, and does not start to condense. That sort of defeats the purpose of buying a ready made waterproof structure, and adds cost in making a "nice" waterproof protection for the insulation.

So people take the easy route of internal insulation. If you don't liberate much moisture, and ventilate sufficiently, then you can get away wit this, but "sufficiently" implies that it's enough to NOT have condensation...

Storage, with maybe frost heating, workshop/office with heating for occasional use, all good. Utility space with water liberated you'll almost certainly get internal condensation and water running off ceiling and walls behind the insulation.

Depends on your planned usage. If mostly summer usage, wanting to stop it becoming a sweat box, and keep the chill off in the shoulder seasons, then internal insulation. I use 100mm EPS with 9mm plasterboard glued to it (PVA glue). Then pink foam that laminate onto ceiling then walls. One 2.4m sheet stretches across the container, so that makes it easier. I then glue 20x90 timber over all the board joins and at corners, to avoid tape/fill which would likely crack with movement, and adds to the joining strength a little bit.

I cut out the openings for doors/windows, and then re-cut those cut-outs to use the already 90o folds in the sheets as angle, to mount the windows/door, and also act as a head/cill to shed rain water. If you're not using the large doors, remember to permanently lock them from the outside, so some diddy doesn't force their way in, and wreck all the insulation fixed to the inside (for "diddy" read "client" )

How about this? Sorry there was not an earlier pic.

Insulated produce store. Sadly none on floor (long story!), but 100mm on walls and roof, outside, then battens, then feather-edge board.

In an organic garden near Sheffield.

Would it not be better to just build a timber frame in that case?

Posted By: IanBakerI am likely to insulate inside; has anyone used steicoflex. I want to use an eco-friendly product.

Insulating internally with a breathable insulation is practically guaranteed to cause condensation on the inside of the steel, and ultimately rot the structure. External insulation is much better, since it raises the temperature of the steel and so protects it against condensation. If you can't or won't do that then I think the only possibility is to prevent any leakage at all of water vapour out through the insulation. The easiest way to do that, used commercially and on boats, is to spray PU foam on the steel. You can get somewhat more 'eco-friendly' versions of the foam. Just don't have a fire.

I must admit I'm not clear why you can't insulate externally if you're planning to clad it with timber anyway?

Hi, Lee here a new poster, but long time reader and appreciator of the wisdom and motivation of this group.

I have had a fair bit of experience with shipping containers used for industrial equipment housing purposes.

Agree with Paddy’s comments

Do you need insulation? It is ventilation that will stop condensation and not putting wet stuff inside.

I have seen unvented sealed containers with water dripping off the ceilings spoiling the insides, opening the door stops this happening. Doors are very well sealed when closed. If you cannot leave door open then need some other form of vents.

If you are sat in it a lot of the day, then that is different lack of insulation will impact your heating costs.
Or a long table cloth over the desk and your feet under it with a little heater keeping it the small space warm – I think they do this in parts of Spain rather than heating larger spaces? I have not tried a tealight candle in a plant pot but have heard they are OK somewhere and that would not need power. IR heaters/bathroom heaters are also quite good too for outside spaces to warm the skin but not trying to heat everything up.
Once it starts getting a lot hotter inside then out then the condensation issues start and that needs air changes are needed and that increases the heating costs as you are venting the hot air.
Oh and your mobile phone will likely not work inside with door closed as it is a metal box/faraday cage …
An uninsulated container will get very hot in summer, as there is so little air movement inside it as there is lots of hot steel lots of steel mopping up the solar gain. That warms the air that can then carry more water vapour to condense on the steel when it turns cooler overnight.
Depending on location and whether there is some shade you may need to do something on the roof in terms of insulation ( or shade sails over the roof ?)
Ventillation. Passive cross flow vents, with cowls to stop rain and vermin getting in. Could close some vents when you are working inside and it is very cold. 3 or 4 inch vents are easier with the castellation in the steel walls. Fans would need less holes in the walls but need power.
In my experience, you do not seem to get dew on the inside only on the outside. Thermal mass or something may be just keeping it a bit warmer and not the coldest bit.
If you have moisture sensitive stuff to store – put it in air tight storage with desiccant bags. Or simply keep it away from walls and do not sit it directly on the floor as these will be wettest areas for any condensation as it is colder.
If you really need insulation then it is because you want the inside warmer than outside (and maybe it is too hot in the summer inside even with vents)
Internal insulation , I suspect you will still get condensation on the lovely cold steel on any moist air that gets to it, through the insulation. As walls and roof are not flat you may well have voids behind the insulation. Shipping containers are Corten steel so will not rust anything more than cosmetically as they have copper in them but suspect mould and gunky stuff could follow, if people are inside it for any length of time or some other form or high moisture. Ventilation will be key to keep humidity down below the steel temperature which will be wind chill temperature when windy and wet outside.
When they ship containers on the seas, desiccant bags are used for sensitive stuff are used as there is virtually no air changes in a standard unmodified container.
My experience for putting equipment inside for long term was not to insulate for heat but more often for noise. I have seen various insulation inside but you end up with temperature controlled ventilation system to keep them dry. You tend to end up with ply or something lining them which is good for fixing things to.
There is not much width or height inside - so insulating outside would be better for internal space. (10 ft high rather than 8 ft high make a huge difference if you can get one.)

External insulation
Suspect that as no cold surface that damp on the steel very much less likely if insulated externally. I have never insulated one externally but if it is not moving anywhere after it is done then that is where I would put my efforts. You have naturally very air tight enclosure so should get very low overall heat loss and very stable temperature inside ... passivhaus type outcome.
You only have to get rid of moisture from breathing and get rid of the CO2 you are breathing out …
Under floor are steel rafter with about 28 mm ply on top. Pretty vermin proof. I would prefer to see some air movement under the container for long term to keep it less damp. Insulation here might be useful too.

All the strength is in the outside rails, so you have to have to support it there and not in the middle/rafters which are not as strong. Breeze locks or something – especially at the corners.

If you had not taken the plunge then a refrigerated container or lorry body may be a better option as it is all insulated from the start and may work out cheaper overall. Then clad with wood to make it look nicer.

Sorry this is a bit ramblng but I hope you find comments useful.
Good luck and let us know how what you end up going with.

Lee

<blockquote><cite>Posted By: IanBaker</cite>I have just bought a 20 ft shipping container for use as storage, utility room & workshop. </blockquote>

Can I ask a basic question:

Why? As in, why a shipping container, rather than something that's actually designed for the purpose you want to use it for?

Does it somehow make sense financially?

I don't get the obsession with shipping containers being used in situations where people want an insulated and habitable space. There's a clue in their name, as to what they are designed for. Insulating on the inside creates all sorts of issues, and insulating on the outside means you are only using them as a structural frame, which could be made from something else, like timber, which would also allow for things like windows to be easily formed.

Why not just buy a shed?

Actually I may have allowed for too much 2x4 in my calculation but forget nails etc.

The one we did was primarily for frost-free winter storage of crops, and secure storage of anything that needed to be secure. No on-site security, so container a good idea from that POV.

The organic garden sells veg, and one of the unexpected benefits was that it is cool in Summer, allowing it to be used for packing veg boxes. The only other 'indoor' space up to then was a polytunnel, which meant waiting almost till dark before packing could start.

'Ours' is vented - you can just see 2 passive stacks (75mm fall-pipe) silhouetted against the garden wall (other parts of which were heated - with coal - so not so environmentally sensitive nowadays!)

Posted By: CWattersSo I think it only really makes sense to use a container if you are making use of the fact that it's already waterproof and insulate on the inside. If you are insulating on the outside both need an additional waterproofing layer.

If you are insulating on the outside then the standard EWI as used for houses i.e. adhesive render coat with thin film acrylic render to finish is probably cheaper than wood cladding with a couple of hundred colours to choose from.

Posted By: LFShade sails are cheep and may give a simple/funky way of dealing with summer heat build up. A bit like external shutters on windows.

+1

Posted By: WillInAberdeenIs part of the thinking that you would sell on the container later, when you no longer require it? (EG once you have built something more permanent)

Also might it make planning permission easier, as local authority will not think it is a permanent building?

+1

Thank you all for your valued comments. Good to see such an interesting response to this issue. A little more background to justify the shipping container. I have planning permission for a small domestic build (100 sq m single storey), which is in the corner of a field on the footprint of a disused stables. I would not get permission for any further structure, hence the 'temporary' shipping container.
My plan is -
To insulate the inside & outside - let me explain my seemingly extravagant logic. The inside to improve the 'living' space & the outside for aesthetics. The house will be British Red Cedar clad, so this container needs to 'blend in'. I am also planning a roof to create an attic for storage. This is also to mount solar (pv) panels. Additionally, during the build (which is now in progress), I need secure lock-up for tools & materials/site office.
In summary, from the various posts from you all, long as I insulate inside with a material that is 'closed cell', & ventilate sufficiently, then it should work. On the basis that the outside will be clad, so protected from the elements, I'm reckoning it should work.
I welcome further comments please. Thanks. Ian

Posted By: lineweightIf your local authority were to question it, once you've built a pitched roof on it and clad it in cedar, is the fact that there's a faux-portable shipping container buried inside it actually likely to make any difference to how it's viewed legally?

Shouldn't make any difference. IMO anything added to a temporary structure or entity can not be viewed as any more permanent than the item to which it is attached.

Now if you put a free standing pitched roof over the container and independent of the container then that might be a different matter.

The patios and extensions I've seen added to the so called 'mobile homes' beggars belief but they seem to get away with it.

Posted By: IanBakermore a case of a temporary structure doesn't require planning permission

Only if the building IS temporary, which means is only there for 28 days! You'd more likely be looking at permitted development rights as a reason for not needing planning permission.

The cladding I refer to is only going to be effectively a fence for aesthetics.

If it's over 2 m high then it too needs planning permission.