Insulation for cold rooms: flooring, vapour barrier and frost-free freezing in the insulation

Solutions & Applications · Industrial Refrigeration

The cold store is the only building application where the flow of water vapour has a constant direction, twelve months a year. In a residential property, the direction reverses between winter and summer, and mistakes are forgiven. Not here: moisture always pushes inwards, and whatever gets in does not come out — it freezes.

The four challenges

Challenge	What happens if this is ignored?
Mechanical strength of flooring	Clark, pallets and shelving cause the insulation to sag; the slab cracks and thermal performance is lost locally
Water vapour management	Water vapour condenses and freezes within the insulation; the ice expands and irreversibly ruptures the structure
Thermal bridges	Any discontinuity is a point of permanent condensation — and continuous operation of the compressor
Ground frost heave	In ground-level freezer rooms, the ground beneath the slab gradually freezes, expands and lifts the floor

The fourth is the least well-known and the most destructive, as it only becomes apparent years after completion.

Maintenance or deep-freezing: two different projects

The operating temperature does not merely alter the thickness of the insulation. It alters the system itself:

Decision	Storage room (above 0 °C)	Freezer compartment (below 0 °C)
Ground frost heave	Not available	Frost-protection heating or ventilated cavity, at ground level
Consequences of a barrier discontinuity	Moisture in insulation	Ice in the insulation, which expands and causes it to rupture
Doors & thresholds	Perimeter waterproofing	And insulation of the frame and sill, to prevent the waterproofing from freezing
Final floor finish	Epoxy paint suitable for food contact	Coating with a specified operating temperature below the chamber temperature
Floor maintenance works	With the chamber in operation, from +8 °C	They require the temperature to be restored to the working range

The floor: the point where two loads meet

The floor of a cold store is subjected simultaneously to the greatest structural load and the highest moisture pressure in the installation. The choice of XPS is based on the design load, not on compressive strength:

Slab	CS(10)	Maximum design load	Thicknesses	Where it fits
FIBRANxps 300	250–300 kPa	< 130 kPa	30–100 mm	Walls and ceiling of a built-in room
FIBRANxps 400	400 kPa	< 150 kPa	30–100 mm	Flooring using pallet racks and lightweight shelving
FIBRANxps 500	500 kPa	< 170 kPa	50–160 mm · 2500 × 600 slab	Flooring with Clark, load-bearing shelving, heavy-duty refrigeration

CS(10) is the stress that causes 10 per cent deformation in a test — not a load that is permitted to remain permanently. Permanent loads, such as the legs of a pallet rack, are checked against the design load, which takes creep into account. And because the legs concentrate the weight over a few centimetres, the wear plate is reinforced to distribute it before it reaches the insulation.

All three boards have a water absorption rate WL(T) < 0.7 per cent and a water absorption rate after freeze-thaw cycles FTCD < 1 per cent by volume — a property of particular relevance to freezer compartments. A porous insulating material that absorbs moisture loses its performance every year; XPS does not.

The sequence of layers in the floor is not optional: sub-base → vapour barrier → XPS → separation sheet → reinforced wear course. The insulation must never come into direct contact with wheeled traffic.

Two layers laid crosswise

Where the required thickness is achieved with two layers, the boards are laid crosswise, with offset joints. The reason is quantitative: a continuous joint running through the entire thickness of the insulation acts as a linear thermal bridge along its entire length. Offsetting breaks it down into two independent, non-aligned discontinuities. FIBRANxps 500 up to 160 mm often allows the thickness to be covered with one fewer layer.

The vapour barrier: position and position alone

FIBRANskin BARRIER 2400 has an equivalent air thickness Sd = 2400 m (minimum declared value 1500 m) with an aluminium foil, zero air permeability and an operating temperature range from −40 °C to +80 °C — practically impermeable to water vapour, even at freezing temperatures.

The crucial factor is not the value but the position: the vapour barrier is always installed on the warm side of the insulation. In a cold store, the warm side is the external side — the opposite of a domestic property, where the vapour barrier is installed on the internal side. A vapour barrier installed on the cold side does not prevent water vapour from passing through; it traps it inside the insulation.

• Continued: overlaps and taping at every joint. A barrier with 99 per cent coverage acts as if it were not there at the remaining 1 per cent — and that is where all the ice forms.
• Penetrations: refrigerant pipework, cabling and supports must be sealed individually.
• Perimeter: the floor barrier continues and joins the wall barrier. A discontinuity at the floor-wall junction is the most common point of failure.

Panel-built room: the flooring is to be provided as part of the project

Most modern cold rooms are constructed with walls and ceilings made of thermal insulation panels and sliding refrigerated doors. The chamber manufacturer supplies the shell; however, the insulated floor is constructed on site, and it is here that the quality of the installation is determined:

• The panel-to-floor joint: the floor insulation and the vapour barrier must meet the insulation and the outer face of the panel without any gap. If the panel rests on the screed, whilst the insulation stops further inwards, the perimeter becomes a thermal bridge along its entire length.
• The door threshold: this is where the insulation must be interrupted to allow the pallet truck to pass through. In the freezer, the frame and threshold are heated to prevent the waterproofing strip from freezing.
• Sanitary sealing: the wall-to-floor joint inside the building is sealed with sanitary-grade silicone, resistant to hot water and cleaning chemicals, so that it does not trap residues.

In the building envelope, on walls and ceilings, the mechanical requirements are lower and FIBRANxps 300 meets the need. Where drainage slopes are required — floors with drains, ceilings with condensate drainage — FIBRANxps INCLINE provides the slope within the insulation itself, without the need for an additional layer of mortar that would create a thermal bridge.

The floor after insulation

The wear layer above the vapour barrier has a problem that few anticipate: it dries out only upwards. Beneath it lies the vapour barrier, so the moisture in the concrete escapes much more slowly than in a standard slab — and the room usually needs to be handed over quickly. SINMAST S2 Wet on Wet is a solvent-free epoxy primer for fresh or wet concrete, offering reliable adhesion at the interface and applicable from +8 °C.

The final coating is selected based on the operating temperature:

Coating	What it means	Where it fits
SINMAST RM 22	Solvent-free · food contact to EC 10/2011 · resistance to bacteria and fungi to MIL-STD-810B · application from +8 °C, service temperature from −10 to +48 °C	Maintenance rooms, preparation rooms
SINMAST RM 32	Solvent-free · CE marked in accordance with EN 1504-2 · impact resistance > 20 Nm (Class III) · resistance to severe chemical attack in accordance with EN 13529 · application from +8 °C, service life down to −25 °C	Freezer rooms, flooring with Clark

Both are solvent-free and non-flammable — a prerequisite for working in an enclosed space without ventilation.

In adjacent areas — dry storage, packing area, loading and unloading — where there is no chemical exposure, TILT HIT is laid without adhesive on top of the existing floor, with a wear layer of 2.70 mm, and can withstand pallet trucks.

Design series

1. Operating temperature: storage (above 0 °C) or freezing (below 0 °C). The answer determines whether measures to prevent ground frost are required and what type of floor covering is needed.
2. Installation: on ground level, in a basement or on a floor — this radically alters the floor detailing.
3. Handling loads: type and weight of forklift, load per shelf level, point load from forklift feet — these are checked against the design load of the XPS.
4. Thickness calculation: based on the temperature difference and the energy costs of operation, not on a general rule.
5. Designing the continuity of a barrier: route, overlaps, penetrations, corners — before placing an order.
6. Interface with the panels: where the panel is fixed, how the floor insulation meets the wall insulation.
7. Door details: door frames and thresholds are the largest individual thermal bridges in the building.
8. Final surface: primer to treat slab moisture and a coating with an operating temperature that covers the chamber.

Why ARGYNET

• Energy saving: a properly designed building envelope means fewer operating hours for the compressor — the installation’s largest operating cost.
• Certified properties: collaboration with manufacturers who declare values in accordance with European standards, with a Declaration of Performance (DoP) for each thickness.
• Technical support: selection of materials based on a site survey and calculation of materials per m².

Flooring & Vapour Barrier

Building envelope: Walls, Roof & Slopes

Finished Surfaces & Adjoining Areas

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