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Green Building Bible, Fourth Edition
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    • CommentAuthorIanBaker
    • CommentTimeOct 28th 2019
     
    I have just bought a 20 ft shipping container for use as storage, utility room & workshop. Looking at options to insulate to prevent condensation - has anyone done this already? Advice / tips welcomed please. Thanks, Ian.
    • CommentAuthorGreenPaddy
    • CommentTimeOct 29th 2019
     
    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" :devil:)
  1.  
    As GP said above better to insulate the outside. So why not use the 100mm of EPS on the outside fixed with adhesive and made nice with an adhesive coat and render coat of your colour choice - just like you would do any wall.
    Down side there might be an amount of echo inside unless enough soft(ish) contents are put inside
  2.  
    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.
      DSCF3394 - Copy - Copy.JPG
  3.  
    And another pic
      DSCF3392 - Copy - Copy.JPG
  4.  
    Would it not be better to just build a timber frame in that case?
    • CommentAuthorIanBaker
    • CommentTimeNov 3rd 2019
     
    Thanks for all your helpful comments, much appreciated. I am likely to insulate inside; has anyone used steicoflex. I want to use an eco-friendly product. I also have a dismantled wooden stables, which is constructed with panels bolted together. I am thinking of using the panels as cladding, partly to cover the steel which isn't very pleasing to the eye. Thanks again. Ian.
    •  
      CommentAuthordjh
    • CommentTimeNov 3rd 2019
     
    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?
  5.  
    Agree with djh. I'd be really worried with Steico wood fibre inside a steel box. External is good. Internal is worrying. I regard vapour control layers as things to leak.

    *Edit to point out: I know that one of wood-fibre's strengths is that it usually functions without a VCL (no VCL = VCL can't be damaged and compromised) but in this instance, installing porous insulation inside 'a bucket' and adding water (initially in vapour form but the chances of condensation behind the insulation layer seem very high) seems like it might be asking for trouble.
    • CommentAuthorLF
    • CommentTimeNov 5th 2019
     
    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
    • CommentAuthorCWatters
    • CommentTimeNov 5th 2019
     
    We rented a totally unmodified container for storage some years ago. Never had an issue with condensation because It was kept closed for months at a time and there was never anything wet or breathing in it. However it got incredibly hot in the summer and I don't just mean uncomfortable I mean truly roasting. Lucky we didn't have anything that would be damaged by heat.

    I think if I had to insulate one internally I would have fitted timber studs with spray foam between. Then a well detailed vapour barrier and plasterboard. Surface mounted wiring so no penetrations? Something like that.
  6.  
    <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?
    • CommentAuthorCWatters
    • CommentTimeNov 6th 2019
     
    Thought I would do some sums...

    Google says 20ft shipping containers go for about £1200 plus VAT depending on condition.

    I estimate that to build a similar size "box" (walls, floor and ceiling) all from treated 2x4 on 480mm centres and 12mm WBP to prevent racking it would cost about the same excluding labour.

    So 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.

    I know which would be easier to add windows to.

    Your mileage may vary.
    • CommentAuthorCWatters
    • CommentTimeNov 6th 2019
     
    Actually I may have allowed for too much 2x4 in my calculation but forget nails etc.
  7.  
    Is 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?

    Thank you Lee, that is excellent information.
  8.  
    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!)
    • CommentAuthorLF
    • CommentTimeNov 6th 2019
     
    Pressure treated shed for scouts storage shed last summer was just over 2k from eBay supplier in Birmingham delivered and effected. It was fine. Felt roof though.. 20 ft by 10 ft

    Note Green Paddy's tip about folding back the steel to talk windows and doors ... That is a clever way to deal with sides not being flat. We used welded in box section but had to ship things afterward s.

    Shade sails are cheep and may give a simple/funky way of dealing with summer heat build up. A bit like external shutters on windows.
  9.  
    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
    • CommentAuthormikael
    • CommentTimeNov 10th 2019
     
    I have insulated three containers with closed cell polyurethane spray insulation on the inside. Messing about with boards etc just lets air get to the steel, condense and cause dampness. Closed cell foam prevents any damp air getting to the steel on the inside.
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