Insulated Shipping Container Help

[PJBuzz]

If the only solution that would work is spray foam, or redesigning from scratch, then that's ripping everything out and starting again, which basically means I would have to can the whole project.

I simply don't have the time or money to start again.

I have to do the best I can with the knowledge that I will never have a perfect vapour barrier and the steel will never have insulation directly attached.

The other issue with foaming all the walls is the cables are in the void. Although a lot of these foams do not directly corrode cables like polystyrene based insulation does, that's based on small areas of contact. If you foam up all the cables in such a way, Im not convinced it would be safe and within the spec of the cables.

What I can do, is ventilate the void and make small improvements to the vapour barrier.
I probably will also externally clad the roof in some way, perhaps not immediately.

I did start taking another ceiling board further into the workshop down, and I'm actually feeling good so far. It doesn't look like the issue at the "sealed" end is as bad as the "unsealed" end, which gives me a little confidence that I should be ok with these small improvements.

 

[Awac]

I have a guide for metal roofing here. Maybe you can get some ideas from it, as your walls are essentially metal roof panels. I remember reading about Australian metal roofing construction and how they combat cold nights combined with hot days condensation using insulated metal roofing panels. Maybe an Australian builder on here could comment?

 

[Ozi]

I had a house with a damp problem and had one of the loft fans fitted which I have been very pleased with, it helps keep bills down, I think partly by recovering some of the heat escaping into the loft but mainly by lowering the humidity in the house, dry air being cheaper to heat.

I tried a much cheaper idea with a concrete storage shed that had a slight damp issue and fitted 12 V fans intended for computer cases to the wall vents, these run from a small solar panel intended for an electric fence as my shed has no power. That little extra airflow has made the difference and I can now store items like washing powder without it turning into a brick, it's quite surprising how damp a space can be if only just the wrong side of the moisture balance. hope this helps

 

[jcassidy]

Maybe I don't understand the terminology, but pretty sure I have it between the battens, as in they sit inside the wooden structure, not on top or behind it.

Oh, it looked from your photos that it was sitting on top of the battens. Well, if you have cut the boards to fit between battens, then the installation guides say a vapour barrier is required. I know you have taped the gaps, but I suppose either the seal or the tape is not moisture proof.
But anyway, what's done is done - ventilate the gap, provide drainage, and you should be good?

 

[jcassidy]

My view ( and I am not an expert in this at all) is to exclude any air behind the insulation and bond all of your insulation to the inner steel surface, no gaps, no voids whatsoever. Then ensure the surface of the insulation facing the workshop is totally impermeable. The aim is to have no air (moisture) migration to the insulation/steel interface. The result should then be the only surface that can precipitate condensation is the inside surface of the insulation which standard ventilation, (opening windows, dedicated ventilation ports, open doors) should be able to mitigate.

This is what spray-on foam achieves, but even they install ventilation channels - I'm not entirely sure why, I only cursorily looked at it as a home-improvement before going a different route.

Spray-on insulation is probably a great idea for steel containers, but in this case, that boat has sailed. Also, relatively expensive, if I recall correctly.

 

[PJBuzz]

I have a guide for metal roofing here. Maybe you can get some ideas from it, as your walls are essentially metal roof panels. I remember reading about Australian metal roofing construction and how they combat cold nights combined with hot days condensation using insulated metal roofing panels. Maybe an Australian builder on here could comment?

I had a quick peek in there and it looks like some useful information. Probably delive into that on another day though

Again, I suspect the issue will be that I need to make the most of what I have rather than go for best practice, unfortunately.
If I was doing it again, I probably would get an insulation material that bonds directly to the metal and vapour barrier it, then run all the cables internal to the "box".

Where this information might be useful is if I decide to add an additional roof to the container, which is a reasonable possibility as I think it can be done on a reletively modest budget. I think that keeping the extremes off the roof could go a long way towards minimising the issue.

I had a house with a damp problem and had one of the loft fans fitted which I have been very pleased with, it helps keep bills down, I think partly by recovering some of the heat escaping into the loft but mainly by lowering the humidity in the house, dry air being cheaper to heat.

I tried a much cheaper idea with a concrete storage shed that had a slight damp issue and fitted 12 V fans intended for computer cases to the wall vents, these run from a small solar panel intended for an electric fence as my shed has no power. That little extra airflow has made the difference and I can now store items like washing powder without it turning into a brick, it's quite surprising how damp a space can be if only just the wrong side of the moisture balance. hope this helps

So this is pulling air from the void into the main "Box"?

It would be reletively straight forward and very cheap for me to mod a computer fan into the ceiling to pull air from the void into the box... don't think it would save me any money on heating but I'm not facing huge rent bills for this place as it's a family friend's farm. My hesitation here is that it is a quite obvious, and quite permanant break in the already not perfect vaour barrier.
I have a pretty good 3D printer at home and could do Polycarbonate or Carbon Fibre Nylon, both pretty stable filaments, so a nice looking and safe 120mm fan enclosure, with a shutter when not running, is not outside the relms of possibility.

The other option I have been looking at is a bathroom type transformer that has a built in timer, I can just loop that off one of the lights, then run that up to a caravan style 12v extractor to vent the void to the outside world... but I don't know if it's just airflow that I need, or if it's actually much better to have positive pressure in this scenario. Given my obvious ignorence from the very start of this, I don't know if I should trust my own scientific knowledge, but I would have thought positive/negative pressure preference would be an, "it depends on the outside conditions" as what you actually want is to equalise the humidity as best as possible. Maybe just extracting humidity vapour is the safer bet.

Oh, it looked from your photos that it was sitting on top of the battens. Well, if you have cut the boards to fit between battens, then the installation guides say a vapour barrier is required. I know you have taped the gaps, but I suppose either the seal or the tape is not moisture proof.
But anyway, what's done is done - ventilate the gap, provide drainage, and you should be good?

That's because I taped up the beams as well

My thinking here currently is that it actually is reletively moisture proof, and the issue is primarily at the end of the unit where the double doors are, as I didnt complete the seal at this end. The end of the ceiling and walls near the double doors are open to the void. This is where I was experiecing the water literally dripping into the "Box", and the beams that you could see when I pulled the ceiling down were more moist at the very end, then basically dry towards the middle.

THis is why I have started pulling down another ceiling panel. I want to see how damp the beams are at the other end, how much water is pooled up, and how much condensation is on the underside of the roof.
This should help give me an idea if the problem is the same all the way down, or if it was worse at one side... which in turn gives me a good indication how effective the cheap solutions are going to be. Hopefully the heaters and dehumidifiers running overnight don't skew the observations... I'll report back later

Thanks again for the help so far everyone.

 

[Lefley]

You need the vapour barrier on the warm side and the cold to warm zone where the two temperstures meet needs to be 1/3 in from the warm side into the insulation. If there is not enough insulation sometimes this area is actually inside the building and you get huge condensation. If that insul board is on the outside of container, or inside but towards the outside and then 2x4 walls with more insulation, the vapour barrier is in the wrong place. From a Canadian Point of view.

 

[Ozi]

I had a quick peek in there and it looks like some useful information. Probably delive into that on another day though

Again, I suspect the issue will be that I need to make the most of what I have rather than go for best practice, unfortunately.
If I was doing it again, I probably would get an insulation material that bonds directly to the metal and vapour barrier it, then run all the cables internal to the "box".

Where this information might be useful is if I decide to add an additional roof to the container, which is a reasonable possibility as I think it can be done on a reletively modest budget. I think that keeping the extremes off the roof could go a long way towards minimising the issue.


So this is pulling air from the void into the main "Box"?

It would be reletively straight forward and very cheap for me to mod a computer fan into the ceiling to pull air from the void into the box... don't think it would save me any money on heating but I'm not facing huge rent bills for this place as it's a family friend's farm. My hesitation here is that it is a quite obvious, and quite permanant break in the already not perfect vaour barrier.
I have a pretty good 3D printer at home and could do Polycarbonate or Carbon Fibre Nylon, both pretty stable filaments, so a nice looking and safe 120mm fan enclosure, with a shutter when not running, is not outside the relms of possibility.

The other option I have been looking at is a bathroom type transformer that has a built in timer, I can just loop that off one of the lights, then run that up to a caravan style 12v extractor to vent the void to the outside world... but I don't know if it's just airflow that I need, or if it's actually much better to have positive pressure in this scenario. Given my obvious ignorence from the very start of this, I don't know if I should trust my own scientific knowledge, but I would have thought positive/negative pressure preference would be an, "it depends on the outside conditions" as what you actually want is to equalise the humidity as best as possible. Maybe just extracting humidity vapour is the safer bet.


That's because I taped up the beams as well

My thinking here currently is that it actually is reletively moisture proof, and the issue is primarily at the end of the unit where the double doors are, as I didnt complete the seal at this end. The end of the ceiling and walls near the double doors are open to the void. This is where I was experiecing the water literally dripping into the "Box", and the beams that you could see when I pulled the ceiling down were more moist at the very end, then basically dry towards the middle.

THis is why I have started pulling down another ceiling panel. I want to see how damp the beams are at the other end, how much water is pooled up, and how much condensation is on the underside of the roof.
This should help give me an idea if the problem is the same all the way down, or if it was worse at one side... which in turn gives me a good indication how effective the cheap solutions are going to be. Hopefully the heaters and dehumidifiers running overnight don't skew the observations... I'll report back later

Thanks again for the help so far everyone.

Hi

I was thinking to increase the air flow through the void so assuming you have four vents two on each side I would look to extract air on the side away from the prevailing wind and maybe draw in on the windward side but try as you have suggested to keep the inner box as vapor tight as possible. For my shed I found some cheep exterior vent plates that would mount directly to 110mm pipe and cut down the square van housing to fit snugly into short stubs of 110mm soil pipe, 113mm core drill through the consrete and it almost looks like I new what I was doing. Where I draw air into my shed I have a lean to mower shed with slatted sides so I don't get rain directly on the intakes. The air flow isn't much from memory about 40 cfm per fan and they rum pretty much all the time as long as the battery is OK - I tend to use batteries near the end of their useful life for this wet soap is better than escaped animals

Ozi

 

[Misterdog]

When your dehumidifier arrives run it 24hrs a day and try turning off your heating.

Though if you have bought a 'compressor' DH the 12L/day quoted is with air temp. at 30 degrees C and humidity of 80% !!
At 26.7 degrees and 60%RH the rate of extraction plummets to 7.5 Litres /Day.

I have both the desiccant and the compressor types. The desiccant types give out more heat thus cost more to run, though the heat is useful if you are in the room. The heat from one improves the efficiency of the other, as I run both.
Maeco DH's have a tube to drain off the water externally which is useful as they switch off when the collection tank is full.

Removing the moisture to a low level should cure the problem to a greater extent.
Many boat owners run DH's constantly over winter.

 

[PJBuzz]

You need the vapour barrier on the warm side and the cold to warm zone where the two temperstures meet needs to be 1/3 in from the warm side into the insulation. If there is not enough insulation sometimes this area is actually inside the building and you get huge condensation. If that insul board is on the outside of container, or inside but towards the outside and then 2x4 walls with more insulation, the vapour barrier is in the wrong place. From a Canadian Point of view.

Not totally sure I follow what you're saying about the "1/3rd in" bit?

Though if you have bought a 'compressor' DH the 12L/day quoted is with air temp. at 30 degrees C and humidity of 80% !!
At 26.7 degrees and 60%RH the rate of extraction plummets to 7.5 Litres /Day.

I have both the desiccant and the compressor types. The desiccant types give out more heat thus cost more to run, though the heat is useful if you are in the room. The heat from one improves the efficiency of the other, as I run both.
Maeco DH's have a tube to drain off the water externally which is useful as they switch off when the collection tank is full.

Removing the moisture to a low level should cure the problem to a greater extent.
Many boat owners run DH's constantly over winter.

It's a compressor one that I bought. For the moment i have left separate heaters also running just until the existing build up of moisture is gone, then I'll ditch the heaters and just run the dehumidifier I think.

I took the rest of the ceiling down today and unfortunately I was wrong. The issue is right the way across the container and... well... I'm not too hopeful.

Talking to the chap who helped me put this together who is also trying to find a way to resolve this without ripping everything out and I think he is also starting to lose a bit of hope.

 

[TomGW]

I think that you have already identified a significant part of the problem i.e. the open end of the ‘cavity’, which is allowing an unlimited amount of moist air into the void.
If this was closed and sealed I would be considering a cross ventilation system, from diagonally opposite corners of the void, routed in a closed loop through the dehumidifier. The fan within the dehumidifier would move the air through the void, whilst drying it, thus ‘killing two birds with the one stone’.
In this system the air would be circulated and dried, minimising the condensate, and would constantly mitigate any leakage through your current insulation layer.
Fairly easy to set up. Create an air tight box to enclose the DH with one inlet and one outlet ducted to diagonally opposite corners of the void. Pipe the condensate to the outside.
You have suggested a second outer roof. Assuming that your existing container is not leaking, I don’t know what you would hope to achieve. Steel is a very effective thermal conductor and the whole of the container structure will very rapidly heat and cool according to the ambient temperature.