Short answer
“Foil wrap insulation” is a shopping term covering five products — bubble roll, foam roll, reflective VCL, reflective breather membrane and multifoil quilt. Only the multifoil is certified primary insulation; the rest are accessories or components.
- Five products, one term
- Only multifoil is certified insulation
- Thin foils suit sheds and radiators
- Never sole insulation in a heated room
Five things people mean by foil wrap
| Product type | Typical thickness | Primary purpose | Air gap needed | Typical applications | DIY or pro | Indicative material cost |
|---|---|---|---|---|---|---|
| Reflective bubble roll | 3 – 8mm | Radiant barrier, draught reduction | Yes, both faces | Sheds, garages, behind radiators, campervans | DIY | £3 – £8 per m² |
| Reflective foam roll | 5 – 10mm | Radiant barrier with a little conductive resistance | Yes | Garage doors, floors under laminate, outbuildings | DIY | £4 – £10 per m² |
| Reflective vapour-control membrane | <1mm | Vapour control with a low-emissivity face | Yes, on the reflective face | Warm side of roof and wall build-ups | Pro | £2 – £5 per m² |
| Reflective breather membrane | <1mm | Weather protection plus a reflective face | Yes | Under tiles or cladding | Pro | £3 – £6 per m² |
| Multifoil quilt | 30 – 45mm | Certified thermal insulation | Yes, both faces (20–25mm) | Rafters, loft rooms, stud walls, floors | Pro (DIY possible) | £15 – £30 per m² |
The first two are accessories. The membranes are components of a build-up. Only the multifoil quilt is a primary insulation with third-party certification. They are not interchangeable: a 4mm bubble foil stapled under rafters will not insulate a loft room, whatever the packaging says.
Where foil wrap works
- Lining a garage, shed, workshop or garden room where 5–10°C of comfort and draught control is the goal.
- Behind radiators on external walls, reflecting heat back into the room.
- As a radiant barrier in a roof that already has proper insulation, to cut summer overheating.
- Under laminate or engineered flooring as a thin thermal and acoustic layer.
Where it does not
- As the only insulation in a habitable loft room or bedroom ceiling.
- Compressed between two solid surfaces with no air gap — it becomes a vapour barrier in the wrong place.
- In a cavity wall, or anywhere it can trap moisture against timber.
- Over an open loft floor instead of mineral wool.
When it supplements, and when it must not replace
Thin foil is a good addition to a correctly insulated element: over the top of loft wool under boarding, or on the warm side of PIR to add a low-emissivity air space. It must never replace primary insulation in a roof, wall or floor of a heated room. If a quote proposes thin foil as the sole insulation for living space, get a second opinion.
Air gaps, condensation and vapour control
Every reflective product needs an air space facing its reflective surface to deliver radiant performance. Vapour behaviour varies: most internally fitted bubble foils and multifoils have significant vapour resistance and can act as part of the vapour-control strategy when sealed to their specification, while some reflective membranes are deliberately vapour-open. A vapour-resistant layer on the warm side with a ventilated or vapour-open cold side is useful; the same layer on the cold side of an unventilated build-up traps moisture on timbers. Full detail: air gaps, condensation, vapour barriers.
Questions homeowners ask
Is foil wrap the same as multifoil?
Can I use foil wrap in a loft?
Which way does the foil face?
Does foil wrap stop condensation?
- Energy Saving Trust — Roof and loft insulation — checked 2 September 2026
- SuperFOIL — product range — checked 2 September 2026
- BSI — BS 5250:2021 Management of moisture in buildings — checked 2 September 2026