Bronze FR 4mm Fire Rated Reflective Foil Insulation
Fire rated double-sided aluminium foil bubble insulation for roofs, ceilings and walls. Reflects 98% of radiant heat, BS 476 Class 1 (Class 0 with 20 µm foil). 4mm, five layers, rolls 1.20 / 1.35 / 1.50 m wide, 12 to 72 m² per roll.
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Description
Bronze FR 4mm fire rated reflective foil insulation
Double-sided aluminium foil bubble insulation for roofs, ceilings and walls. Reflects 98% of radiant heat and is fire rated to BS 476 Class 1.
Bronze FR 4mm is a fire rated, double-sided reflective insulation built for buildings that take the full force of the sun. Two faces of 99% pure aluminium foil sit over a 4mm sealed air-bubble core, giving you a lightweight roof insulation sheet that blocks radiant heat, controls vapour and meets BS 476 Class 1 fire performance. It is the practical choice for warehouses, factories, homes and commercial buildings where metal roofs and ceilings turn heat into a daily problem.
Looking for the standard grade? See Alumix Bronze 4mm Basic / FR insulation. Need extra strength? See Bronze Net FR 4mm with 18 micron foil and reinforced net.
What is Bronze FR 4mm reflective insulation?
Bronze FR 4mm (product code AL-SL40-FR) is a five-layer radiant barrier and vapour barrier in one sheet. Its construction is foil / film / 4mm FR sealed air bubble / film / foil. The high-purity aluminium on each face reflects radiant heat away from the building in summer and helps hold heat inside in winter, while the sealed bubble core adds a thermal break and keeps the sheet light and flexible.
Because the core is fire retardant (FR) grade, Bronze FR is suited to projects where fire performance matters, such as industrial sheds, commercial roofs and public-facing buildings.
Key benefits
- Reflects 98% of radiant heat. The 99% pure aluminium surface has a very low emittance of 0.02 to 0.03, so it reflects heat instead of absorbing and re-radiating it.
- Fire rated to BS 476. Class 1 under BS 476 Part 7 (surface spread of flame). With the optional 20 µm FR foil upgrade it achieves Class 0 under BS 476 Part 6.
- Dual action: heat and vapour control. Foil on both faces acts as a radiant barrier and a vapour barrier, helping reduce condensation on roof sheets.
- Does not absorb moisture or support mould. The closed bubble core and foil faces resist water, so performance does not drop over time.
- No glass fibre, safe to handle. No itching, no dust and no special protective gear for installers.
- Lightweight and quick to install. Cuts to size on site with a standard knife. No special tools needed.
- Saves space. At just 4mm thick it fits where bulky insulation cannot, ideal for renovations and tight roof voids.
Technical specifications
| Product type | Double-sided pure aluminium reflective insulation |
|---|---|
| Product code | AL-SL40-FR |
| Construction | Foil / film / 4mm FR sealed air bubble / film / foil (five layers) |
| Outer face | 99% pure aluminium foil, both faces |
| Total thickness | 4 mm |
| Roll width | 1.20 m / 1.35 m / 1.50 m |
| Roll length | 10 to 60 m (12 to 72 m² per roll) |
| Radiant heat reflectivity | 98% |
| Surface emittance | 0.02 to 0.03 |
| Core thermal resistance (product alone) | R 0.12 m²K/W |
| High thermal equivalent | R 3.14 m²K/W* |
| Fire classification (BS 476 Part 7) | Class 1 |
| Fire classification (BS 476 Part 6, with 20 µm foil) | Class 0 |
| Options | Self-adhesive lap strip; 20 µm FR foil upgrade |
*Heat flow down, 2 x 50 mm air gaps, ε 0.02 to 0.03.
Thermal performance: R-value by assembly
Reflective insulation works best when installed next to an air gap. The total system R-value depends on how many reflective air cavities are created in the roof, ceiling or wall.
| Assembly / air cavity | Winter (heat flow up) | Summer (heat flow down) |
|---|---|---|
| Roof / ceiling, one 25 mm reflective cavity | R 0.61 | R 1.01 |
| Roof / ceiling, two 25 mm reflective cavities | R 1.10 | R 1.90 |
| Wall assembly, 38 mm cavity, horizontal heat flow | R 0.86 (one cavity) / R 1.60 (two cavities) | |
Values are total system R in m²K/W. Cavity resistance calculated to BS EN ISO 6946 (ref. BS EN 16012) for an unventilated cavity with a low-emissivity surface (ε 0.02 to 0.03). Core product R 0.12 m²K/W applies to the product alone without a reflective air cavity.
Applications
- Roof underlay and metal roofing, over the purlins or under the rafters
- Ceilings and attic spaces
- Walls and partitions
- Warehouses, factories and metal buildings
- Residential and commercial buildings
- New build and renovation projects
How to install Bronze FR on a roof or ceiling
- Measure the roof or ceiling area and work out the number of rolls needed for the total m².
- Set the purlins or rafters to the correct spacing.
- Lay Bronze FR over the purlins or under the rafters, with the foil face toward the heat source.
- Fix with screws and cut to length, keeping the sheet taut.
- Seal all joints and overlaps with aluminium foil tape.
Air gap tip: keep a 20 to 90 mm air gap on the reflective face for best performance, and maintain at least 75 mm clearance from downlights.
Testing and certification
Bronze FR 4mm is tested to BS 476 Part 6 & 7 (Class 1; Class 0 FR grade), ASTM C 1371, ISO 8301 / ASTM C 518 and BS EN ISO 6946. Test reports and certificates are available on request.
Frequently asked questions
What is Bronze FR 4mm insulation used for?
It is a double-sided reflective foil insulation for roofs, ceilings and walls. It is widely used under metal roofs in warehouses, factories, homes and commercial buildings to reflect radiant heat and control vapour.
Is Bronze FR 4mm fire rated?
Yes. It is classified Class 1 under BS 476 Part 7. With the optional 20 µm FR foil upgrade, it achieves Class 0 under BS 476 Part 6.
How much heat does it reflect?
The 99% pure aluminium foil surface reflects 98% of radiant heat, with a surface emittance of 0.02 to 0.03.
What is the R-value of Bronze FR 4mm?
The product alone has a core thermal resistance of R 0.12 m²K/W. Installed with reflective air cavities, total system R-values reach up to R 1.90 m²K/W in a roof with two 25 mm cavities (summer, heat flow down), and a high thermal equivalent of R 3.14 m²K/W with two 50 mm air gaps.
Do I need an air gap when installing?
Yes. Reflective insulation needs an air space facing the foil to work. Maintain a 20 to 90 mm air gap on the reflective face.
Does it contain glass fibre?
No. Bronze FR contains no glass fibre, so it is safe and comfortable to handle and install.
What roll sizes are available?
Rolls come in 1.20 m, 1.35 m and 1.50 m widths, with lengths from 10 to 60 m, covering 12 to 72 m² per roll. A self-adhesive lap strip is available as an option.
Will it cause condensation or mould?
No. The foil faces act as a vapour barrier and the sealed bubble core does not absorb moisture or support mould growth.
Get a quote for Bronze FR 4mm
Alumix Insulation Global manufactures reflective foil insulation, radiant barriers and vapour barriers for residential, commercial and industrial projects. Contact our team for pricing, bulk orders, technical data or test certificates, or email info@alumixinsulationglobal.com.
Values shown are subject to verification against current test reports. Thermal performance may vary with installation method, air gap and environmental conditions. Specifications subject to change without prior notice.
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