Sandwich Panel Walls for Cold Rooms, Cleanrooms, Factories and Fire Walls: How to Choose
Insulated sandwich panel walls (also called Isowall in Thailand) serve very different jobs. A cold room needs insulation and vapour tightness. A cleanroom needs flush, cleanable, low-smoke surfaces. A factory wall must resist wind and rain. A fire wall must hold back fire for a stated number of minutes. This page sets out which core, thickness and joint system suits each application.
Contents
In short
- Cold rooms and freezers: PIR, thickness by temperature, e.g. 100 mm for −20 to −10 °C.
- Cleanrooms, pharma and food plants: PIR with flush, tight joints; FM 4882 panels are common for smoke-sensitive rooms.
- Factory and warehouse external walls: PIR secret-joint panels tested for wind load and weather tightness.
- Fire walls and acoustic walls: Rockwool. A 100 mm panel met 60 minutes fire resistance and held integrity for 4 hours (BS 476 Part 22).
Wall selection table
| Application | Core | Common thickness | Joint | Evidence to ask for |
|---|---|---|---|---|
| Air-conditioned / temperature-controlled room | PIR | 42–50 mm | Slip joint | λ, U-value |
| Cold room 0 to −10 °C | PIR | 75 mm | Slip / cam-lock | λ at low temperature, U-value |
| Freezer −20 °C and below | PIR | 100–200 mm | Slip / cam-lock | λ at low temperature, U-value |
| Cleanroom | PIR (Rockwool for fire separation) | 50–100 mm | Slip / frame joint | FM 4882, EN 13501-1 |
| Operating room | PIR | 50–75 mm | Slip / frame joint | EN 13501-1, ASTM E84 |
| Factory / warehouse external wall | PIR | 50–100 mm | Secret joint | FM 4880/4881, ASTM E330/E331 |
| Fire wall / fire compartment | Rockwool | 100 mm | Secret / slip joint | BS 476 Part 22 or EN 1364-1 |
| Acoustic wall | Rockwool | 50–100 mm | Secret / slip joint | Sound absorption data |
Cold room and freezer walls (cold room panel)
Cold room walls must stop heat entering the room and stop moisture migrating into the insulation, where it would condense. PIR is the best core: low thermal conductivity (λ 0.020 W/m·K at −10 °C), closed cells, and much better fire behaviour than PU. Thickness is chosen by operating temperature.
Details that matter in cold rooms
- Tight joints: slip or cam-lock joints, sealed on the warm side to keep vapour out.
- Avoid thermal bridges at corners, floors and fixings; metal passing through the insulation causes ice build-up.
- Freezer floors need floor insulation and, typically, protection against frost heave of the ground below.
- Freezers need a pressure relief valve: as air cools, room pressure drops, pulling on the panels and making doors hard to open.
- Cold room doors need the same insulation as the walls, plus gaskets and frame heaters for freezers.
Products: Cold room panel · Cold and dry truck body panel
Cleanroom walls (cleanroom wall panel)
A cleanroom controls the number of airborne particles. Its walls must be smooth, non-shedding, free of dust traps, easy to clean and tight enough for the room to hold pressure. PIR-core sandwich panels with pre-painted steel in RAL 9002 are the standard material.
| EU / WHO GMP | ISO 14644-1 | FED-STD-209E (legacy) | Typical use |
|---|---|---|---|
| Grade A | ISO 5 | Class 100 | Aseptic filling zone |
| Grade B | ISO 5 | Class 100 | Background to Grade A |
| Grade C | ISO 7 | Class 10,000 | Solution preparation |
| Grade D | ISO 8 | Class 100,000 | Raw material handling, packaging |
What a cleanroom wall should include
- Flush surfaces: windows and doors set flush with the wall.
- Coving at wall-to-floor and wall-to-ceiling junctions so dust cannot collect.
- Walkable ceiling for maintenance access above; openings for lights and HEPA filters cut on site.
- Return-air risers and conduits concealed inside panels to reduce dust-collecting surfaces.
- Non-progressive / frame-joint systems so single panels can be replaced when the layout changes.
- Door interlocks between rooms at different pressures.
Fire safety in cleanrooms
Pharmaceutical and food plants are “smoke-sensitive occupancies”: a small amount of smoke can ruin a whole batch. Insurers therefore often require panels approved to FM 4882 (Class 1 interior wall and ceiling materials for smoke-sensitive occupancies). SPS PIR Firewall panels are approved to FM 4882 for pharmaceutical manufacturing and storage areas and food preparation and storage areas. They also achieve EN 13501-1 B-s1, d0 (very low smoke, no flaming droplets) and a toxic gas index under EN 45545-2 of CITg 0.05 at 240 seconds (limit 0.75).
Products: Clean room panel · Non-progressive system panel · AHU panel
Operating room and hospital walls
Operating room walls follow cleanroom principles: flush surfaces with no joints where bacteria can collect, resistance to disinfectants, and low smoke in a fire. PIR panels of 50–75 mm are common, paired with automatic sliding doors, flush windows and coving all round. Anti-fungal or chemical-resistant coatings can be specified to suit the hospital.
Products: Operating room panel
Factory and warehouse external walls (industrial / warehouse wall panel)
Factory and warehouse walls must resist wind, keep out rain and cut solar heat gain. The right panel is PIR with a secret joint: the fixing screws are hidden in the joint, so the wall is clean and the screw heads are protected from water. It suits tall warehouse walls.
| Test | Standard | Result |
|---|---|---|
| Wind pressure (external wall) | FM 4881 | +/−40 psf (approx. ±1.9 kPa), Zone NTC |
| Hail | FM 4881 | Moderate hail rating |
| Structural performance | ASTM E330 | Proof load ±2,000 Pa with no permanent damage to panels, fasteners or anchors |
| Air infiltration | ASTM E283 | 0.07 m³/h·m² at 75 Pa |
| Water penetration | ASTM E331 | No leakage at 137 Pa for 15 minutes |
| Large-scale fire spread | FM 4880 | Class 1, no height restriction |
- Panel widths 1,000 and 1,100 mm; Flat, Mesa or Micro profiles.
- Install as tested: the wind rating applies only with the support spacing and fasteners in the FM report.
- Heat control: a 50 mm PIR panel has a U-value of about 0.46 W/m²·K, far less heat gain than single-skin metal cladding.
Products: PIR wall panels · PIR panel · FM Approved panels
Fire walls (fire-rated wall panel)
Fire walls divide a building so that fire cannot spread from one part to another, for example around flammable stores, electrical rooms, or between warehouse zones. A fire wall must have a fire resistance result in minutes, and should use a non-combustible Rockwool core.
| Criterion | Time achieved |
|---|---|
| Integrity (flame and hot gases) | 240 minutes (test stopped at 4 hours) |
| Insulation (temperature on the unexposed side) | 62 minutes |
The wall therefore met 60 minutes fire resistance on both criteria and stopped flame passing through for 4 hours.
What makes a fire wall work in practice
- The whole system must match the test: thickness, core density, joint system and fixing method.
- Openings must match the wall rating: fire doors, and fire-stopping at every pipe and cable penetration.
- Supports must not fail first: the steel frame carrying the wall may need protection or a fire-resistant design.
- PIR panels are not fire walls, even when hard to ignite and FM 4880 approved: those tests measure fire spread, not fire resistance in minutes.
Products: Fire proof panel
Factory acoustic walls (acoustic wall panel)
Acoustic walls enclose machine rooms, generator rooms and pump rooms, or separate noisy production from offices. Rockwool cores outperform foam because stone wool fibres absorb sound energy. Absorptive acoustic panels usually have a perforated inner skin so sound reaches the stone wool.
| Thickness | 125 Hz | 250 Hz | 500 Hz | 1000 Hz | 2000 Hz | 4000 Hz |
|---|---|---|---|---|---|---|
| 50 mm | 0.30 | 0.85 | 1.00 | 1.00 | 0.96 | 0.84 |
| 100 mm | 0.70 | 1.00 | 1.00 | 1.00 | 0.99 | 0.89 |
Low-frequency noise such as engines and compressors (around 125 Hz) is the hardest to absorb. At this frequency a 100 mm panel absorbs more than twice as much as a 50 mm panel.
Products: Acoustic panel
Roof and other uses
- Sandwich panel roof (Square Roof): PIR roof panels with screws hidden under a joint cover to prevent leaks, lower heat and rain noise, and a light structure. See PIR roof panel.
- AHU double-skin panels: insulated casings for air handling units that cut cooling losses and fan noise.
- Refrigerated and dry truck bodies: lightweight insulated panels that keep cargo at temperature in transit.
- Industrial roller shutter doors for loading bays in sandwich panel buildings.
Sandwich panel wall project steps
- Survey and brief
Room sizes or building drawings, operating temperature, type of use, and fire or insurance requirements. - Design and specification
Select core, thickness, joint, finish and accessories; calculate U-value and wind load. - Shop drawings
Panel sizes, door and window positions, penetrations and corner details. - Manufacture
Panels cut to ordered length on a continuous line with quality control. - Delivery and installation
Frame, wall and ceiling panels, flashings and sealant, installed as tested. - Inspection and handover
Check joint tightness and surface finish; commission the room, e.g. temperature or cleanroom pressure.
Common mistakes when choosing walls
- Using PIR as a fire wall. PIR is hard to ignite but has no fire resistance rating in minutes like a Rockwool wall.
- Choosing cold room thickness on price. Panels that are too thin raise energy bills and cause condensation or ice on the outside face.
- Reading test results for the wrong thickness. A fire test applies only to the thickness and system tested.
- Forgetting openings in fire walls. One unrated door or penetration defeats the whole wall.
- Installing differently from the test. Changed screw or support spacing voids wind and fire approvals.
Frequently asked questions
What insulation and thickness for cold room walls?
Use PIR, which insulates best and has closed cells. As a guide: 50 mm for 0 °C and above, 75 mm for −10 to 0 °C, 100 mm for −20 to −10 °C, and 125–200 mm for freezers below −20 °C.
How are cleanroom walls different from ordinary walls?
Cleanroom walls must be flush, non-shedding, coved at floor and ceiling, with flush windows and doors and tight joints so the room holds pressure. Pharmaceutical and food plants often specify FM 4882 panels.
Should factory walls use PIR or Rockwool?
General external walls use PIR with secret joints for low weight and good insulation. Fire compartment and acoustic walls use Rockwool. Many factories use both in one building.
How many minutes can a sandwich panel fire wall resist?
It depends on thickness and test. For example, a 100 mm Rockwool sandwich panel wall tested to BS 476 Part 22 in 2023 held integrity for 240 minutes and insulation for 62 minutes, meeting 60 minutes on both criteria.
Can sandwich panels be used for tall warehouse walls?
Yes. PIR panels approved to FM 4880 carry no height restriction, and the external wall system is rated for +/−40 psf wind pressure under FM 4881 when installed with the tested supports and fasteners.
How much heat does an insulated factory wall keep out?
A 50 mm PIR panel has a U-value of about 0.46 W/m²·K, letting through only a small fraction of the heat that passes single-skin metal cladding, which has almost no thermal resistance. The effect on indoor temperature also depends on the roof, ventilation and internal heat sources.
What thickness for a factory acoustic wall?
50 mm Rockwool absorbs almost all mid- and high-frequency sound. For low-frequency engine or compressor noise, use 100 mm, which absorbs 0.70 at 125 Hz against 0.30 for 50 mm.
What does a freezer room need besides walls?
Floor insulation, frost-heave protection under the slab, a pressure relief valve, insulated doors with frame heaters, and thermal breaks at every fixing.
What is a non-progressive panel system?
A wall system in which any single panel can be removed or replaced without dismantling its neighbours. It suits cleanrooms that need maintenance access or layout changes.
How long does sandwich panel wall installation take?
Much faster than masonry, because panels arrive cut to size and need no curing time. Actual duration depends on area, number of doors and windows, and readiness of the structure.
About the author
This guide was prepared by Square Panel System Co., Ltd. (บริษัท สแควร์ พาแนล ซิสเต็ม จำกัด), which designs, manufactures and installs insulated sandwich panel walls in Thailand. Founded in 2000. Factory in Si Mahosot District, Prachinburi; ISO 9001:2015 certified; cleanroom, cold room, operating room and factory projects in Thailand and abroad.
Domestic references International references Download catalogues PU, PIR, Rockwool guide Request a quotation
Tel. +66 2 744 6300 · Line: @squarepanel · Email: [email protected]
References
- Square Panel System, data sheets “SPS PIR Firewall” and “SQUAREROCK™ Panel” (2026)
- FM Approvals, Approval Report Project No. PR464932, SPS PIR Firewall, Class 4880/4881/4882 (31 July 2025)
- Fire Safety Research Center (FSRC), Faculty of Engineering, Chulalongkorn University, Test Report FSRC-044/66, Sandwich Panel Model SPF-100, BS 476 Part 20 & 22:1987 (21 December 2023)
- ISO 14644-1:2015 Cleanrooms and associated controlled environments · EU GMP Annex 1
- ASTM E283, E330, E331 · EN 13501-1 · EN 45545-2 · BS 3638:1987
