SuperFOIL SF40BB Breathable Multifoil Insulation – High-Performance Breathable 3-in-1 Solution

SuperFOIL SF40BB is a high-performance breathable multifoil insulation designed for applications where increased thermal performance, vapour permeability, and moisture control are required. With a nominal thickness of 75 mm, SF40BB combines high-performance insulation, a reflective breathable membrane, and a radiant barrier in one advanced system.

It is suitable for roofs and walls, making it ideal for new builds, retrofits, timber-frame construction, and professional building applications where condensation risk must be carefully managed while achieving strong thermal performance.

This is a breathable multifoil insulation designed for vapour-open roof and wall constructions, allowing moisture vapour to escape while maintaining thermal efficiency.

For breathable systems such as SuperFOIL SF40BB, internal comparative assessments indicate that equivalent thermal performance varies according to product thickness and construction build-up and should be considered indicative only. As a reference within the SuperFOIL range, internal comparative assessments indicate that 65 mm of SuperFOIL SF40 can achieve thermal performance comparable to up to 450 mm of traditional mineral wool insulation (λ = 0.040 W/mK), depending on installation method, air gaps, and overall system design. Exact thermal performance must always be verified using the official SuperFOIL U-Value Calculator for the specific construction build-up, supported by the certified R-Values of each product.

Product Dimensions & Coverage

• Thickness: 75 mm

• Length: 10 m

• Width: 1.5 m

• Coverage: 15 m² per roll

• Weight: approx. 20 kg

3-in-1 Multifunctional Design

SuperFOIL SF40BB combines three essential functions in a single product:

• High-performance thermal insulation

• Reflective breathable membrane allowing moisture vapour to escape

• Radiant barrier that reflects radiant heat back into the building in winter and reduces solar heat gain in summer

This breathable construction helps to prevent the formation of mould and damp by reducing condensation risk within the building fabric, while still delivering excellent thermal performance.

Thermal Performance

SF40BB works across conduction, convection, and radiation, while remaining vapour-open — making it suitable for breathable construction systems where moisture management is critical.

Certified thermal performance (core value + air spaces, EN 16012):

• Core R-Value: 2.92 m²K/W

• Roof (incl. air spaces): 3.54 m²K/W

• Wall (incl. air spaces): 3.76 m²K/W

• Floor (incl. air spaces): N/A

• Emittance: 0.19 / 0.05

Emittance (0.19 / 0.05) reflects the dual-layer design of SF19BB.

The breathable membrane side has a higher emittance value (0.19) to allow moisture vapour to pass safely through the construction, which is essential for breathable building systems.
The reflective foil side has a very low emittance value (0.05), providing the same high level of radiant heat reflection found in standard SuperFOIL multifoil insulation such as SF40.

Although one surface is breathable rather than fully reflective, this does not reduce the overall thermal performance of the system. Instead, it allows SF19BB to combine effective insulation with moisture control, making it suitable for vapour-open roof and wall constructions where standard non-breathable products are not appropriate.

These values demonstrate SF40BB’s suitability for breathable roof and wall constructions requiring higher thermal resistance than entry-level breathable systems.

What does R-Value mean?

R-Value (m²K/W) measures a material’s resistance to heat flow.
The higher the R-Value, the better the insulation performance.

What does Emittance mean?

Emittance measures how much heat a surface emits (radiates).

A low emittance value (typically around 0.05) means very low heat emission and high reflection of radiant heat, improving overall thermal performance when installed with adjacent air spaces.

This interpretation is aligned with EN 16012 and reflects how reflective multifoil insulation performance is evaluated across EU technical documentation.

Performance vs Traditional Insulation

Thanks to its multi-layer reflective construction and breathable membrane technology, SuperFOIL SF40BB delivers strong thermal performance while allowing vapour to escape safely from the building structure.

This makes SF40BB particularly effective in timber-frame and vapour-open wall or roof systems, where traditional insulation combined with non-breathable membranes can increase condensation risk.

Exact U-values depend on the complete construction build-up. Bespoke U-value calculations are available for project-specific compliance.

Key Benefits

• High-performance breathable multifoil insulation

• Reduces condensation risk and helps prevent mould and damp

• Higher thermal performance than thinner breathable systems

• Replaces insulation, breathable membrane, and radiant barrier

• Easy to install – no specialist tools required

• Lightweight and flexible for faster installation

• Minimal waste compared to traditional insulation systems

• Ideal for new builds and retrofits

• Rated W1 for watertightness, providing a secondary rain barrier

• Made from up to 40% recycled materials

• Fully recyclable with a 50+ year service life

Applications

SuperFOIL SF40BB is suitable for use in:

• Pitched roof constructions

• Wall systems

• Timber-frame constructions

It is typically installed as part of a breathable building envelope, allowing moisture vapour to escape while maintaining thermal performance.

Fire & Safety Performance

• Reaction to Fire (Euroclass): Class F

• Watertightness: W1 rating

SF40BB – Quality & Certification

• Manufactured under a certified ISO 9001:2015 quality management system

• CE certified to EN 13859-1:2014 and EN 13859-2:2014 for breathable membrane performance

• Tested to meet current UK and EU building regulations when installed correctly

• Designed, tested, and supported by SuperFOIL technical specialists

• Independently tested and assessed as part of the SuperFOIL multifoil insulation range, including
  BBA testing (British Board of Agrément – independent product and system performance assessment)
  and LABC certification (Local Authority Building Control – approval for compliance with building regulations)
  at range level

Why Choose SuperFOIL SF40BB?

SF40BB is specified in projects where enhanced thermal performance is required alongside vapour permeability and moisture control. Its breathable design supports healthy building envelopes, simplifies detailing in timber-frame construction, and enables compliance with modern building regulations.

It is a strong choice for architects, engineers, and contractors seeking higher R-values in vapour-open roof and wall systems.

Compare the SuperFOIL Insulation Range

Summary

SuperFOIL SF40BB is a high-performance breathable multifoil insulation that combines insulation, moisture management, and radiant performance in a single integrated system. It delivers excellent thermal efficiency, supports vapour-open construction, and offers long-term durability — making it an ideal solution for professional roof and wall applications where condensation control is essential.