Walk-in freezer
KoolKat1978
| Posted in Energy Efficiency and Durability on
Building a large commercial walk-in freezer. Insulating contractor is wanting to blow in 5″ of closed cell polyurethane directly to building concrete walls without any vapor barrier. He claims the insulation acts as the vapor barrier. Two of the walls are exterior walls and two are inside the building. I have been advised by others this is not as proper vapor barrier and not to proceed with this method. The freezer will be running at 0 degrees F. we are in saint louis with 100 degree summers and high humidity. Would like your opinion. Thanks. Concerned
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Replies
KoolKat,
The vapor permeance of 2.5 inches of closed-cell spray foam is 0.8 perm. If you are installing 5 inches of closed-cell spray foam, the vapor permeance will be even less -- about 0.4 perm.
That means that 5 inches of closed-cell spray foam is a Class II vapor retarder. It also meets the definition of a "vapor barrier" in Canada, or the definition of a vapor barrier in older versions of most building codes.
So, will we have a problem with moisture and heat being drawn through concrete block walls into the freezer chamber without a actual vapor barrier applied and only having this blown in insulation? I am concerned especially with the two exterior walls.
The thing I'd be worried about is what if the foam separates from the substrate at some point due to seasonal wall movement?
With walk-in freezers it is important to note that the moisture flow is from the outside in, not the other way around. If you were going to use a vapor barrier, it would go on the outside of the CMU. The application of spray foam directly to the block will not be a problem from a moisture perspective as the dewpoint of your wall system will be within the foam and as Martin points out, the foam is a Class II vapor retarder. You should make sure that the CMU is painted on the exterior, with a quality waterproofing paint if possible. Also, make sure that no bulk water is getting inside the CMU at the top or other penetrations. Water in the block won't do much harm to the block or the foam, but it will find places to puddle and get gross over time.
You should also check your local codes about fire protection. In most commercial applications, spray foam cannot be left exposed to occupied spaces because it is a fire hazard. This can be even more of an issue in a walk-in as it can qualify as a confined space if it has few exits. The metal skins on prefab coolers serve as fire protection, but in a spray-on application you may have to install finish walls inside that will hold up to traffic, cold and frost. I designed a cooler a few years ago for a liquor store and we ended up with 5/8" DensArmor covered with reinforced fiberglass panels on the interior for protection against bumps from moving things around.
I'm curious about the floor and what prevents soil below it (if any) from eventually freezing.
Where I live and work there are dozens of large warehouses which look normal, but are in fact freezers. Many are built with very heavy concrete floors that are not on the ground, but have crawl space underneath to prevent the concrete heaving