Multifoil Insulation: What It Is and How It Performs

Multifoil insulation is a thin, flexible roll made of multiple layers of aluminium foil combined with layers of fibre wadding¹. Despite being only a few millimetres to a few centimetres thick, it is sold as a "3-in-1" product: insulation, a radiant barrier and a vapour control layer in a single material². It is used in roofs, walls and floors, and in outbuildings from sheds to conservatories, wherever losing space to thick insulation matters more than losing a little performance per centimetre³.

Its rated performance depends on something many households never hear about: unventilated air gaps either side of the material. With those gaps built in, SuperFOIL states its Multipurpose Wrap achieves R-values of 1.03 in a roof, 1.45 in a wall and 1.65 in a floor, tested to the European standard EN 16012⁴. Without the gaps, the reflective layers cannot do their main job, and the highest performance the products are designed to provide cannot be achieved⁵. This page explains how the material works, what the numbers mean, where it fits, and what it does and does not do for a home's energy independence.

Combining three functions in one foil and wadding sheet

Multifoil insulation is made using multiple layers of foil, combined with layers of wadding¹. SuperFOIL describes its own products as a combination of fibre wadding and layers of aluminium foil, and markets the result as a high performance, certified 3-in-1 product³. The three functions are worth separating, because they explain why a material this thin can be compared with much thicker alternatives.

The first function is straightforward thermal insulation: the wadding layers resist the conduction of heat through the material. The second is a radiant barrier: the shiny foil surfaces reflect radiant heat rather than absorbing it. The third is a vapour control layer, which slows the movement of water vapour through the build-up and helps protect against condensation⁶. Depending on the product chosen, that third function may instead be a breathable membrane⁷.

Some products fold all three into one roll. SuperFOIL's Multipurpose Wrap is described by the maker as providing high-performing insulation, a vapour control layer and a radiant barrier within a single product⁴. That bundling matters in retrofit work, where a separate vapour barrier would otherwise need to be fitted and taped as a second operation, adding time, cost and another layer of thickness.

The maker also states that multifoil is fully recyclable and highly sustainable, and that its products are manufactured from up to 40% recycled material⁶. These are the manufacturer's own claims about its own products, and a household weighing environmental impact may want to look for independent certification alongside them.

The science behind it: heat reflection and heat retention

Heat moves in three ways: conduction through materials, convection through air, and radiation across space. Multifoil insulation focuses on interrupting all three mechanisms⁹. The wadding layers are thermally non-conductive, so they slow conduction; the foil layers reflect radiant heat; and the product's role as an air and vapour barrier limits convective airflow through the build-up⁸.

The reflective part is the piece that separates multifoil from mineral wool or rigid board. SuperFOIL states that by having unventilated air gaps next to the shiny outer surfaces, multifoil insulation can reflect up to 97% of the radiant energy back to its source⁵. The principle is the same one behind radiator reflector panels, which independent guidance from Energy Saving Trust explains reflect heat from the back of a radiator back into a room, stopping it escaping through outside walls¹⁰. A foil surface facing an air gap works the same way: instead of absorbing radiant heat and passing it outward, it bounces it back.

The reflective coating brings a side benefit: it forms a radiant and vapour barrier, protecting the build-up from condensation⁹. Rigid PIR board uses a related trick on a smaller scale, with a foil backing that acts as a moisture barrier and reflects heat¹¹, but in multifoil the reflective layers run through the whole product, not just on its faces.

Two things follow from this. First, the reflective performance depends entirely on the air gap: foil pressed directly against another surface reflects almost nothing. Second, the emissivity of the surface matters, which is why products such as TLX Reflect+ are specified by their low emissivity surface¹². Both points shape how multifoil has to be installed, which the air gap section below covers.

Performance: R-values of 1.03 in roofs, 1.45 in walls and 1.65 in floors

The headline figures for a specific product make the pattern clear. SuperFOIL's Multipurpose Wrap is rated, for its core value plus two air spaces tested to EN 16012, at an R-value of 1.03 in a roof, 1.45 in a wall and 1.65 in a floor⁴. The same roll of material performs differently in each position because the air gaps either side of it differ, and because heat flows through roofs, walls and floors in different directions.

An R-value measures thermal resistance: the higher the number, the more a layer resists heat flow. A fuller explanation of how R-values and U-values work is on our U-values and R-values page. What matters here is that a multifoil's declared R-value is a system value, not a material value: it includes the contribution of the air spaces either side, which is why the same product earns three different numbers.

That has a practical consequence when a home is assessed. Under the RdSAP conventions used for Energy Performance Certificates, when multi-foil insulation is entered, the thickness is entered as twice its actual thickness¹³. The convention is a way of crediting the reflective and air-gap performance within a survey method that otherwise works on thickness and conductivity. A household should not expect an EPC to record the manufacturer's full laboratory R-value.

Building Regulations set the targets any insulation helps to meet. The Welsh Approved Document L consultation lists a U-value of 0.35 for pitched roofs with insulation between the rafters in one column of its notional building specification¹⁴. A multifoil build-up in a rafter space has to be designed against that kind of target, and the maker offers U-value calculations for specific projects, covered in the buying section below.

Air gaps of 13mm, 20mm and 50mm explained

The single most important rule of multifoil installation is the air gap. Leaving an air gap increases the R-value of the installation⁵. The depth required depends on the direction of airflow, and SuperFOIL states the rule is consistent for every one of its products, whether the project is a new build, retrofit, refurbishment or extension⁵.

• Roofs, vertical airflow: minimum 13mm air gap⁵
• Walls, horizontal airflow: minimum 20mm air gap⁵
• Floors, downward airflow: minimum 50mm air gap⁵

Two air gaps, one on either side of the insulation, are what the rated figures assume¹⁵. The gaps must also be the right kind. To gain the best thermal value, the air space must be unventilated; if it is deemed to be slightly ventilated, a different, lower value applies, and if it is well ventilated, no thermal resistance from the air space is achieved at all⁵.

This is where multifoil earns or loses its performance. Installed with the correct unventilated gaps, the reflective faces can do their job of bouncing radiant heat back⁵. Installed without them, the product still works as an insulating wadding and a vapour barrier, but, as the maker puts it, "without an air gap, you can't achieve the highest possible performance the multifoils are designed to provide"⁵. In practice the gaps are created with timber battens, which also carry the fixings and the finishing layer, so the batten frame and the air gap are designed together.

Suitable locations: roofs, walls, floors, sheds and conservatories

Multifoil can be installed almost anywhere: roofs, floors, walls, garden buildings, campervans and boats are all listed by the maker⁷. SuperFOIL's Multipurpose Wrap is described as applicable across roofs, walls and floors, and also in caravans, greenhouses, garage doors and garden buildings⁴. The material suits both new build and retrofit projects⁹.

In pitched roofs, SuperFOIL offers options for both under-rafter and over-rafter applications¹⁶. For under-rafter work, the maker points to its high vapour-resistant properties and a continuous layer design that minimises thermal bridging; for over-rafter work, it cites a W1 watertight property and the same continuous-layer benefit against thermal bridging and condensation¹⁶. The pitch here is that multifoil can significantly reduce the build-up thickness compared with conventional materials¹⁶. Our roof insulation and loft conversions and room-in-roof pages cover where rafter-level insulation fits in a whole-roof strategy.

Garden buildings are a natural fit. SuperFOIL's three-step shed insulation guide covers choosing materials, preparing the space and installing multifoil or bubble foil, including the two air gaps either side of the insulation¹⁵. Conservatories and summer houses follow the same logic: thin walls and roofs where a bulky insulation would eat the space.

There is also a tax angle that applies to insulation generally. Insulation for walls, floors, ceilings, roofs or lofts, or for water tanks, pipes or other plumbing fittings, is listed among energy-saving materials in the relevant legislation¹⁷, and HMRC's manual confirms the same qualifying locations¹⁸. A household buying insulation should check the current VAT position at the time of purchase, as the rules on reduced-rate VAT for energy-saving materials have changed in recent years.

Multifoil versus glass wool versus board: price, thickness and fitting

The honest comparison is that each material wins on a different axis. SuperFOIL's own position is that multifoil is more expensive than glass wool but cheaper than most board or sheet insulation³. Independent and official guidance fills in the picture around it.

• Cost. Official guidance for heat pump projects notes that some insulation measures, like adding mineral wool to a loft, are cheap, effective and relatively easy, while others, like new glazing or external wall insulation, are more costly and difficult¹⁹. Citizens Advice notes mineral wool may be cheaper and better at insulating than spray foam²⁰, and the Centre for Sustainable Energy states spray foam is much more expensive to install than standard mineral wool loft insulation²¹. Cellulose, another niche option, is reported by Uswitch to cost up to twice that of mineral wool or rigid foam²².
• Space. SuperFOIL claims multifoil provides the same or better insulation than glass wool while taking up as little as half of the space³. This is the maker's headline argument, and it is the reason multifoil is chosen where headroom or rafter depth is limited.
• Installation. Mineral wool rolls can be DIY installed and are inexpensive, with non-irritant options available²³. Multifoil is also a DIY-friendly material, needing no specialist tools⁶, but it demands more precision: the air gaps, overlaps and taping all have to be right for the rated performance to materialise.
• In timber frame walls, the Mineral Insulation Manufacturers Association describes mineral wool as more cost effective than any other material available²⁴.

For floors, the common alternatives are solid insulation boards, mineral wool and sprayable foam²⁵, and multifoil competes where floor height is at a premium. A household comparing options in the loft may find our multifoil vs mineral wool comparison useful, and the wider material trade-offs are set out on our insulation materials compared page.

Where a multifoil sits in the price range matters less than the system it belongs to. SuperFOIL describes two configurations: DUET, where the product is used both internally and externally for maximum performance, and COMBI, where it is combined with other insulation types such as mineral wool or foam board². Layering materials this way can deliver performance that neither achieves alone at the same thickness.

DIY fitting: overlapping, fixing, sealing and finishing

Multifoil is a realistic DIY material. It needs no specialist tools or PPE⁶, no professional tools are required¹, and it is lightweight and clean to handle. The skill is not in cutting and stapling; it is in building the layers correctly so the rated performance is actually achieved.

The maker's installation guidance gives specific numbers. Runs of multifoil should overlap the previous run by about 50mm¹⁵. Fixings should be no more than 300mm apart¹⁵. Where a timber batten frame is used, the space between battens should be no more than 600mm at any point¹⁵. Those three figures, plus the air gap depths above, are the geometry of a correct installation.

Sealing is what turns the roll from insulation into a barrier. Sealing is done by using foil tape over all joints, gaps and tears⁷. The same principle applies to reflective membranes such as TLX Reflect+, which the maker states delivers an airtight system when installed with aluminised tape¹². A poorly taped layer insulates; a well-taped layer also controls vapour and draughts.

The finishing layer depends on the application: plasterboard is the most common and often easiest to work with for roof and wall insulation, while plywood or a similar board is used for floors¹⁵. The batten frame that holds the air gap also carries this finish, so the sequence is: fix battens, staple the multifoil to them with the right overlaps, tape the joints, then fix the plasterboard or plywood over the top.

Whether to do it yourself is a fair question. Mineral wool can be bought from DIY stores or builders merchants and installed by a householder with reasonable DIY skills²⁶. Warm loft insulation is harder than laying rolls, and Which? recommends a professional installer, though it can still be a DIY job with the skills²⁷. Cavity wall insulation is not a DIY job at all and needs a registered installer²⁸. Multifoil sits with the DIY-able options, provided the manufacturer's instructions are followed exactly.

Durability, financial benefits and the remaining unknowns

SuperFOIL states its multifoil products have a durable lifespan of over 50 years³, and elsewhere describes a 50+ year lifespan for its insulation products⁶. For comparison, official statistics put basic, correctly installed roof insulation at a typical lifespan of 15 to 30 years, with some types such as rockwool lasting up to 60 years²⁹. The maker's figure is its own claim; the official range is the independent benchmark. Once installed, multifoil has no moving parts and nothing to service, so maintenance is essentially nil unless the layer is pierced or disturbed by later work.

On savings, the honest position is that insulation performance is measured in R-values and U-values, not pounds, and no multifoil-specific bill saving figure has been established here. What official and independent guidance does establish is the scale of what insulation addresses: without loft insulation, a home could be losing as much as a third of its heating costs through the roof³⁰. That is the scale of fabric loss that insulation of any type can attack, and a multifoil build-up that makes insulation possible where thicker materials would not fit contributes to exactly that reduction.

For energy independence, multifoil does what all fabric insulation does: it cuts the amount of heat a home needs, which cuts the amount of energy that has to be bought. A thinner multifoil build-up in a rafter space or over a floor can make insulation possible where thicker materials would not fit at all, and that is a genuine gain. What remains dependent is unchanged: the home still needs a heat source, and the less heat it needs, the smaller and cheaper that source can be. The material itself carries no grid, cloud or app dependence once installed, though its performance depends on the manufacturer's certification and on the installation being done to specification.

Handling and safety

Multifoil is among the least hazardous insulation materials to work with. SuperFOIL describes its product as innovative and non-hazardous, with no specialist health and safety provisions needed for installers and occupants⁸. The maker also states multifoil products do not need any PPE at all¹⁵, do not require specialist equipment or PPE², and need no professional tools to install¹.

That contrasts sharply with the independent guidance for mineral wool. Which? states that for DIY loft insulation, a face mask, goggles and gloves are the minimum protective clothing²³. The difference is fibres: mineral wool sheds irritant fibres when handled and cut, while a foil-and-wadding laminate does not. A household sensitive to loft-insulation work may find multifoil materially more comfortable to install.

Two cautions apply from the reflective membrane data. Bare electrical wiring must not be allowed in contact with TLX Reflect+, and electrical cables may need to be de-rated, with guidance to be sought from a qualified electrician³¹. The same product should not come into contact with heat sources above 80 degrees Celsius, such as hot pipes or flues, nor with organic solvents³¹. These are sensible rules for any foil-based product near wiring and flues, and they are points to raise with an electrician where cabling runs through an insulated build-up.

Approvals, Building Regulations and TLX Reflect+

Certification is what turns a maker's claims into figures a building control officer can accept. SuperFOIL's move in 2025 towards certified Insulation Systems, starting with a KIWA BDA certified internal wall system, and its 2026 KIWA BDA Agrément for its Room-in-Roof insulation system, mark the direction of travel: products being certified as complete systems rather than as rolls in isolation. Building Regulations compliance is the end goal of that process, and our insulation standards and certification and Building Regulations Part L pages cover the framework.

TLX Reflect+ illustrates what a certified reflective product looks like. The maker describes it as a high performance reflective vapour control layer, compliant with Building Regulations, that uses a low emissivity surface to enhance the thermal performance of a building¹². It is suitable for masonry, timber or steel construction, and can be used to enhance the thermal performance of walls, ceilings and floors³¹. A UKCA certificate for the product is dated May 2026³¹.

Its specification shows how a reflective membrane is meant to be used:

The still-airgap requirement echoes the multifoil rule above: reflective performance needs still air. The humidity limit is worth noting for bathrooms and kitchens, where a different product may be needed. The insulation of walls, floors, ceilings, roofs or lofts is a recognised energy-saving category in the legislation underpinning these schemes³², which is the regulatory hook most insulation work hangs from.

Purchasing, free samples and technical help

SuperFOIL's multifoil range comes in various sizes and thicknesses to suit budget, thermal requirements and space availability¹⁶, supplied from its Lincoln headquarters⁶. Free sample insulation kits are available on request⁶, sent free of charge with postage covered by the manufacturer³. Ordering a sample before a full order is the sensible way to judge whether the material suits the job.

Because a multifoil's performance is a system value, the maker's technical support matters more than with most materials. The SuperFOIL team assists with technical queries, product recommendations, installation advice, U-value calculations and guidance on building regulations⁸, and can be reached on 16336 639900². A U-value calculation for the specific build-up, including the air gaps, is the figure a building control body will want, not the headline R-value on the packaging.

For households comparing routes, the wider decision is covered across this site: loft insulation, floor insulation and solid wall insulation each have their own pages, and the costs of every option are pulled together on our insulation and glazing costs page. Multifoil is not the answer to every insulation question, but where space is the constraint, it is the one material designed around that constraint.