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Vapour Barrier in Built-in Freezer

07/02/2017 12:17 PM

Hi all

We are in the process of building a freezer room inside a warehouse in Jamaica.

The plan called for a 4" subslab, 4" insulation, 6" concrete, with insulated metal panel walls and ceilings.

The floor contractor put the vapour barrier below the final 6" slab instead of below the insulation.

Might this create an issue with the freezer floor? Hoping as it's always in a warm climate and never below 65 it won't be a problem?

Thanks

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#1

Re: Vapour Barrier in Built-in Freezer

07/02/2017 12:37 PM

Not my area of expertise, but I would think that if the insulation were not inside the vapor barrier that the condensation would eventually ruin the insulation.

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#2

Re: Vapour Barrier in Built-in Freezer

07/02/2017 12:44 PM

Oops.

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#11
In reply to #2

Re: Vapour Barrier in Built-in Freezer

07/03/2017 7:47 PM

Whoever voted that OT, let's see what you say 10 years from now. Sheesh. Read up on ice lenses.

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#3

Re: Vapour Barrier in Built-in Freezer

07/02/2017 12:57 PM

It's atlas xps insulation which shouldn't absorb much moisture.

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#6
In reply to #3

Re: Vapour Barrier in Built-in Freezer

07/02/2017 9:36 PM

..."Water vapour diffusion resistance (μ) of XPS is around 80–250 and so makes it more suitable to wetter environments than EPS.

Water absorption of polystyrene foams[edit]

Although it is a closed-cell foam, both expanded and extruded polystyrene are not entirely waterproof or vaporproof.[33] In expanded polystyrene there are interstitial gaps between the expanded closed-cell pellets that form an open network of channels between the bonded pellets, and this network of gaps can become filled with liquid water. If the water freezes into ice, it expands and can cause polystyrene pellets to break off from the foam. Extruded polystyrene is also permeable by water molecules and can not be considered a vapor barrier.[34]

Waterlogging commonly occurs over a long period of time in polystyrene foams that are constantly exposed to high humidity or are continuously immersed in water, such as in hot tub covers, in floating docks, as supplemental flotation under boat seats, and for below-grade exterior building insulation constantly exposed to groundwater.[35] Typically an exterior vapor barrier such as impermeable plastic sheeting or a sprayed-on coating is necessary to prevent saturation."...

https://en.wikipedia.org/wiki/Polystyrene#Extruded_polystyrene_foam

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#7
In reply to #6

Re: Vapour Barrier in Built-in Freezer

07/02/2017 9:53 PM

Thanks - it won't be exposed to groundwater as it's on top of a subslab which is on a built up foundation out of the ground and we'll above the water table. Fingers crossed on the vapour barrier below the subslab.

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#8
In reply to #7

Re: Vapour Barrier in Built-in Freezer

07/03/2017 12:45 AM

Merely being above the water table is really sufficient.

Rain is not a rare occurence is Jamaca, right? High humidity is not unusual in Jamaca, right? Temperatures around and under the insulated space are likely to be often lower than the surrounding, right?....vapor will condense to liquid.

Now is the time to get the situation rectified.

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#4

Re: Vapour Barrier in Built-in Freezer

07/02/2017 1:10 PM

Just checked the structural drawings, technically they should have a vapour barrier under the subslab. Hopefully that was installed, will verify tomorrow.

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#5

Re: Vapour Barrier in Built-in Freezer

07/02/2017 1:23 PM

I guess it depends on if the insulation is exposed to moisture, and if the moisture would cause the insulation to degrade....If the structure is constructed above an existing floor, then there might not be a problem....You could add 4" of edge insulation around the slab as insurance....

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#9

Re: Vapour Barrier in Built-in Freezer

07/03/2017 2:20 PM

So there was a layer of visqueen put below the subslab. Here is the installed layers:

6" Finish Concrete Slab
Rebar (#4 @ 12" o/c each way)
Visqueen
4" Atlas XPS
4" Concrete Subslab (6x6 10/10 WWM w/fiber)
Visqueen
Well Compacted Fill

Hopefully that bottom visqueen vapour barrier keeps future moisture from entering.

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#12
In reply to #9

Re: Vapour Barrier in Built-in Freezer

07/04/2017 9:23 AM

I believe you have a good installation plan, however, perhaps an underlayment drainage should have been provided. You can still provide for that even at this late date, by adding gravel drainage at the perimeter, with appropriate water barriers to prevent water intrusion into that from rain events.

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#13
In reply to #12

Re: Vapour Barrier in Built-in Freezer

07/04/2017 9:27 AM

Thanks - the final slab height is 4' above the exterior ground, and the entire area will be paved and sloped off to drainage wells. The freezer section of the slab sits within the building, 4' at the closest from the perimeter wall. Thanks for everyone's help!

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#14
In reply to #13

Re: Vapour Barrier in Built-in Freezer

07/04/2017 10:17 AM

One final caution: I hope the foundations extend to bedrock, since we all known how Port Royal set up her own demise (that had little or nothing to do with Pirate debauchery, although it might have been fun to have such a place to go on vacation).

Jamaica still sits upon a small tectonic plate, that is jammed every which way by much larger plates, so she builds up her stresses quickly and releases quite a wallop when she lets go.

So hey man, if you wanna go, and have an earth moving experience, Jamaica is a good place to try, man. She is still situated in a good spot to intercept the booty traveling on the Spanish Main. We here in West Texas have a soft spot for pirates, buried treasure, booty (especially booty whether ill-gotten or not), and cannon. We sail the onshore trade winds a bit differently though.

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#10

Re: Vapour Barrier in Built-in Freezer

07/03/2017 3:39 PM

Without reading the other comments I have two things:

(1) I hope the ground this rests on is sitting on bedrock instead of a sand bar as Port Royal was, Jamaica is a tectonically active zone.

(2) The vapor barrier is to prevent moisture from infusing into the concrete, with the resulting freezing causing cracks in the slab.

I think you will be OK.

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