frost heave protection for freezer room in warm weather countries 4

[alexander coletta]

HI All,



Im designing a cold room that will operate at - 4 farenheit. Local Climate all year round its warm : min 79 F mas 120 F



For Walls and roof will use expanded polystyrene Sandwich panels

Under the concrete Slab we will be using 2 layers of 2" of expanded polistyrene + Vapor Barrier

Should I be concerned about frost heave? As mentioned Before outside temperature will never drop below 79F

Thanks for your opinions and suggestions.

 

[r13]

No, if the floor insulation functions properly.

 

[cvg]

Frost heaving requires a frost-susceptible soil, a continual supply of water below (a water table) and freezing temperatures, penetrating into the soil.

use non frost susceptible soil
if there is not a groundwater source, it is not likely to occur

 

[jimstructures]

Anytime a temperature gradient occurs and the temperature transitions from non-freezing to freezing an ice lens can form and heave can occur, if there is moisture present. The moisture does not need to be liquid it can be moisture vapor.

So CVG is correct. Use a non frost susceptible soil and eliminate any groundwater source. Consider void forms between the insulation under the floor and the soil. If you use a vapor barrier make sure it can drain.

Jim

 

[r13]

About "rigid polistyrene" = These sheets resist the absorption of water, air, and gas and are widely used in cold-storage and packaging applications. Polypropylene-coated sheets have an added layer of moisture protection. Link

 

[jimstructures]

retired13,

When you are talking about polystyrene foam one must distinguish between expanded (open cell / bead-board) and extruded (closed cell) polystyrene foam. Open cell foam will absorb water and freeze into a block of water logged foam while closed cell foam will not allow the transmission of moisture and will not absorb water.

Jim

 

[r13]

jimstructures,

Did I say "rigid"? Please follow the link provided and read before shooting around. Unless there is sensitive soil, why the need for crushable layer? For refrigeration storage, heat exchange is to be prevented, and is doable by the correct insulation material and installation.

What is Expanded Polystyrene (EPS) foam?
The word Styrofoam™ is often used to describe expanded polystyrene (EPS) foam; however, ‘Styrofoam’ is actually a trademarked term for closed-cell extruded polystyrene foam made for thermal insulation and craft applications. EPS foam is the correct term for any form of expanded polystyrene.

Expanded Polystyrene insulation is a lightweight, rigid, closed cell insulation. EPS is available in several compressive strengths to withstand load and back-fill forces. This closed-cell structure provides minimal water absorption and low vapor permanence.

 

[r13]

Alex,

Your plan is fine. Pay attention to installation of the vapor barrier, which tends to be damaged easily. I think you would need a layer of fine sand, or fat/plastic clay, to protect the vapor barrier, which is essential to stop the transfer of groundwater/moisture. Also, you need to plan the interior drainage, and leakage (though the floor) prevention. A subdrain floor system seems suitable for your project.

 

[HTURKAK]

Should I be concerned about frost heave? As mentioned Before outside temperature will never drop below 79F]

I did not read carefully the other responds..
IMO, yes...you should concern. The heat insulation reduces the heat loss but eventually , the bottom ground will get frozen and if the soil material is frost susceptible, frost heave can occur.

The options depends on the ambient temperature, size of the chilled storage.. I will suggest two options ( since the other options are heating of the subbase and require energy )

- The raised base slab on dwarf walls , short columns etc so to allow for a ventilated space between the slab and ground level,
- The use of vent system with 150 mm PVC pipes which are installed into sub base on a slope to induce drafts .

The following snap from the book Cold and Chilled Storage Technology 2nd ed. by CLIVE V.J. DELLINO,

 

[jimstructures]

retired13,

Please get your acronyms correct.

Dow Chemical EPS is expanded polystyrene foam and is not waterproof, open cell bead-board and does absorb water and does freeze.

Dow Chemical XPS is extruded polystyrene foam and is closed cell foam and does not absorb water or moisture vapor to any significant degree.

Jim

 

[r13]

jimstructures,

You got a point, EPS does absorb more moisture than XPS, however, it does not behave as bad as your citation. However, there are different views around, read on.

XPS - Extruded Polystyrene Foam Panels - The blue, pink or green ones (eg. Styrofoam):
XPS is Rated at R5 per inch, but it will off-gas and lose some insulation performance over time - especially below-grade and when tested in real-world applications. Above grade XPS foam acts as a vapour retarder (and becomes even less moisture permeable the thicker it is - 1 inch is about 1 perm, 2 inches about .5 perms); when taped it can act as an air barrier; the manufacturers and standardized testing state that it does not absorb moisture, nor is it affected adversely by it. However, with some of the EcoHome team having real world experience to the contrary, we "dug-deeper" and found that many contractors have also noticed potential issues with XPS foam boards retaining moisture, backed up by reports like this citing a large source of correlated testing and which would lead us to conclude that XPS rigid insulation panels should be avoided for below-grade applications like basement insulation - which is the opposite of much of the information out there.

Rated at R4 per inch; EPS foam insulation boards are more permeable to air and moisture than XPS, but it doesn't retain moisture to the same extent because of it's more closed cell structure and it's breathability which lets it dry out. Two inches of EPS foam board has a moisture permeability rate of between 60 and 75 ng (1 to1.25 perms), which is on the cusp of qualifying it as a type II vapour retarder, but on the more 'breathable' side of the scale which we would probably consider a good thing in most applications.
For reference sake, the traditional 6mil polyethylene vapour barrier has a permeability rating of 3.4 ng, making it about 18 times more vapour resistant than building codes allow.

Note that I am citing the view from one source and have high lighted the important messages. But it does not mean I am drawing conclusion based on this single source, I think more researches are required for those interested parties. However, at this moment, I still think EPS is fine, with the proper installation of the vapor barrier.

 

[r13]

Opposing view:

EPS and XPS are resistant to moisture; however, XPS is more common for below-grade waterproofing and roof systems where insulation is placed over the roof membrane (IRMA, or inverted roof membrane assembly). The IRMA concept is also utilized for insulating building walls, where polystyrene insulation is placed over a barrier membrane, with the siding or cladding system installed over the insulation layer.

 

[r13]

I vote for HTURKAK's first approach.

 

[r13]

Another argument:

Facts About EPS and Water Absorption
Posted on May 17, 2016 by Doug Wehrwein
By: Doug Wehrwein, Sales Representative

Extensive testing has confirmed that the closed-cell structure of EPS reduces moisture absorption over prolonged periods. Even when moisture absorption has reached the maximum threshold there is minimal effect on the thermal performance of EPS insulation. When you review the Expanded Polystyrene Industry Alliance Technical Bulletin 103 you’ll see that even when the moisture absorption level reached 4.8% the EPS insulation’s R value was still at 94% of what was expected. Conversely, the R-value of a comparable sample of XPS was only at 52% of what was expected and moisture level of the XPS sample was 18.9%.

The area in which water can migrate into in the EPS material is the tiny channels (or the interstitial space) between the fused beads of expanded polystyrene. These channels naturally exist in EPS rigid insulations boards and serve as the means to easily release the water when drying occurs. Moisture is present in the EPS long enough for adverse effects to take place. When XPS is exposed to bulk moisture repeatedly over long periods it may allow water in, where it them becomes trapped. See Expanded Polystyrene Industry Alliance Technical Bulletin 104 and 105. Generally, neither water nor water vapors affect the properties of EPS.

Foam-Control Plus+® Architectural EPS Insulation is a very cost-effective way to provide both superior thermal resistance and protection for underlying foundation moisture protection systems.

 

[r13]

While we are back and forth arguing the moisture absorbing potential of the EPS insulation board, we have to recognize that it's not the most important feature this product/material to offer in this project. The vapor barrier should be so selected to keep moisture out and not relying on the insulation board. The insulation, then, is to perform its most important function - keep the cold air stay out and not passing it to the other medium (soil below).

I guess your quotes came from Dow Chemical, the owner and manufacture of XPS foam board, or its alliance/distributors. A fact cannot be ignored in our research. I've specified the use of EPS under SOG since 90s, so far no complain yet.