Loft insulation
SuperFOIL SF19+ explained
What SF19+ is, how it differs from the breathable SF19BB, what its certificates cover, and why it’s normally one part of a roof rather than the whole answer.
The product
What SF19+ is
SF19+ is the manufacturer’s current name for its multifoil insulation, used in specified roof, wall and floor systems. It’s a blanket of 11 layers of reflective foil facings, aluminium-coated foils and wadding, with a nominal thickness of about 45 mm on the manufacturer’s product page.
The manufacturer describes it as insulation, vapour control layer and radiant barrier in one. The next section explains why “vapour control layer” matters so much.
Source: manufacturer’s product page and declaration of performance, checked 3 November 2026.
Don’t mix them up
SF19+ and SF19BB are different products
The names are similar, but they do opposite jobs with water vapour. Fitting the wrong one in the wrong place could cause problems.
| SF19+ | SF19BB | |
|---|---|---|
| What it is | SF19+: Multifoil, declared as a vapour control layer | SF19BB: Multifoil combined with a breather membrane |
| Water vapour resistance | SF19+: 2050 MNs/g (resists vapour) | SF19BB: 0.115 MNs/g (lets vapour through) |
| Breathable? | SF19+: No | SF19BB: Yes |
| Typical position | SF19+: Decided by the design, because it limits vapour where it’s placed | SF19BB: Normally on the outside of a construction, as a secondary rain barrier |
| Interchangeable? | SF19+: No | SF19BB: No |
SF19+ isn’t breathable. Anyone who tells you otherwise is confusing it with another product. Where an existing roof already has a vapour-closed layer or foam, adding SF19+ without analysis could trap moisture.
Performance
Why one layer isn’t normally enough
Compliance with the Building Regulations belongs to the complete roof build-up, not to any one product. The usual standard for a renovated roof in England and Wales is 0.16 W/m²K.
On the manufacturer’s own figures, SF19+ on its own isn’t normally enough to reach that, so a combined build-up, with rigid board or mineral wool for example, is what we’d usually expect to specify.
The manufacturer’s published “roof performance” figure is the material’s R-value plus assumed air spaces under a stated test standard. It isn’t a U-value for your roof, so we don’t quote it as one. Your specification states the U-value calculated for your complete build-up.
Claims you won’t see from us
- “Equivalent to X mm of mineral wool”
- “Meets Building Regulations” about a product
- “Eliminates condensation” or “100% airtight”
- “Saves up to X%”
- “Suitable for any loft”
Certificates
What is and isn’t certified
| System | Kiwa Agrément certificate | Notes |
|---|---|---|
| Internal Wall Insulation | BAW-24-342-S-A-UK | Needs a project-specific design and a manufacturer-trained installer |
| Room-in-Roof | BAR-25-421-S-A-UK | Needs a project-specific design, a condensation risk analysis and a manufacturer-trained installer |
| Standard cold loft | None | No certificate exists for this use |
Certificates cover a product system, not an installer. You can check that a certificate is still valid on the Kiwa register.
Guarantees
Product and workmanship are separate
Manufacturer’s product guarantee
25-year manufacturer’s guarantee against material defects. It’s conditional on storage, handling and installation to the manufacturer’s instructions, doesn’t cover incorrect installation, and its terms are available from the manufacturer.
FAQs
SF19+ questions
Does it need an air gap?
The manufacturer’s published thermal values assume air spaces, and the Kiwa-certified systems require a cavity on each side. Your specification identifies them.
Will it stop condensation?
Not by itself. Condensation risk depends on how the whole roof is built, ventilated and used. Read more.
Is it safe with downlighters, cables and flues?
Clearances and electrical checks apply, and we identify them at survey. As a product it’s Euroclass F, and E as a tested system behind plasterboard, so the design matters.
Can I fit it myself?
The manufacturer sells it for DIY use, but condensation and ventilation design still apply, and the certified systems need a manufacturer-trained installer. We don’t publish installation instructions.
Are you approved by SuperFOIL?
SuperFOIL and SF19+ are the manufacturer’s product names. Nothing on this site means the manufacturer endorses our work.
Keep reading
Related pages
Specification and suitability
When multifoil may suit, and when something else is better.
Condensation and ventilation
Why moisture decides so much.
After foam removal
Moisture first, then a specification.
Request an Insulation Assessment
Whether SF19+ suits your loft is decided by a survey and a written specification, not by this form. Start with your name, postcode and how you’d like us to get in touch.
We reply as soon as we can.