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Shipping Container Frozen Door Question

NEplumber | Posted in General Questions on

I am getting started on a two step shipping container office / gym build.
Step one will be installing a glass sliding door and framed wall just inside the shipping container doors as well as insulating the inside of the container with rigid foam board and adding heat (detailed below).
Step two will be framing, mechanicals, etc.

My question today is about the container metal doors being frozen shut.
Located in the north east climate zone 5-6. Winters go down to -5f.
The doors will get frozen shut from rain that freezes over, snow / sleet that melts on the doors from the slight heat coming through the wall assembly. This happens to my vehicles every year as they get parked outdoors.
The metal container doors will be closed 50% of the year, generally overnight while the place is not in use. 
Reasons involve security, as well as keeping the container looking like a typical storage unit.

Inside the container the heat source will be a Viessmann 100 series boiler using LP.
The heating emitter will be a radiant wall (Creatherm panels) piped 6in on center reverse serpentine. 
I will also have a four pipe compact air handler hanging from the ceiling to add a boost if needed.
Note: There is not sufficient electricity at the site for any HP system.

To solve the frozen door issue I thought of three options. Possibly a blend of the few.

Have outdoor air vents one low and one high on the metal door.
This would allow the back of the door to be the same temperature as the outdoors.
This will aid in preventing the metal door from defrosting precipitation however won’t prevent the door from being wet and freezing overnight.
Another idea was to have a second radiant zone and string pex to the interior of the metal container door. Specifically near the edges. An outdoor switch along with a setpoint control wpuld trigger the system to keep the door surface above freezing when the conditions occur.
Last idea was a forced air style radiator that sits between the metal door and glass door wall assembly.
Same like the radiant door, this would be demand switch outside the container with a surface temperature cut out for when the door surface gets above 38f.

Curious on any other ideas I may have missed.


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  1. user-5946022 | | #1

    Door heater like they use for walk in freezers.
    It's like heat tape, goes on at a set temp, is a strip made for this purpose.

    1. NEplumber | | #2

      That is a great idea! I install alot of snowmelt systems on driveways and walk ways.
      They use a substantial btu especially when the wind picks up to 10mph.
      I dont have enough electricity at the location. Max is 15-20 amps of 120v.

    2. Trevor_Lambert | | #3

      Here's an idea, don't use a shipping container. This is a perfect illustration of why they don't make a lot of sense to build a living space out of. Look at all the hoops you're jumping through just so that you can probably expend more energy heating a steel door exposed to the outside than you'll expend heating the interior of the space.

      1. NEplumber | | #4

        Considering the container is a high cube, on site for years, is in perfect condition, doesn't need a permit, can be moved on a flatbed, lifted with a crane, secure, has resale value once built in excess of the cost of the build.... it seems like the perfect build for what I need.

  2. Expert Member
    BILL WICHERS | | #5

    I have used custom heat tapes around the perimeter of aluminum frame greenhouse doors to successfully prevent freezeup before. Humid greenhouse air leaks around the doors and would cause a buildup of ice in the jam that would freeze the doors shut. Putting the heat right into the frame where the ice would form allows for maximum freezeproofing with a minimum of energy.
    The systems would still run ~200 watts PER DOOR though.

    With a shipping container, you might be able to just glue some rigid foam onto the exterior of the door if you're already heating the inside of the container. The insulation would help to keep the door every so slightly warmer than the outdoor temperature, which would help to keep it from freezing -- at least until it got even colder than usual.


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