Is Foil Blanket Loft Insulation the New Spray Foam?

And are we about to repeat the same mistakes?

Over the past decade, the UK insulation industry has already lived through one slow-motion disaster: spray foam.

It was sold aggressively. Marketed as a miracle. Installed incorrectly at scale.

Years later, homeowners were left dealing with failed surveys, mortgage refusals, insurance issues and expensive remediation — often long after the original installer had disappeared.

Now, we’re starting to see a very familiar pattern emerging again.

This time, it isn’t spray foam (click here to read more about spray foam). It’s foil blanket loft insulation — often sold under names like SuperFoil, SuperQuilt, multifoil or reflective quilt insulation — and increasingly marketed as a stand-alone replacement for traditional loft insulation.

That’s where the problem begins.

Why This Conversation Matters

This isn’t an attack on foil insulation as a product.

Used correctly, foil quilt insulation has a legitimate role in certain roof and insulation systems. It can be effective when installed as part of a properly designed build-up, alongside other materials, with ventilation and detailing done correctly.

The issue isn’t the product. The issue is how it’s being sold.

We’re now seeing foil blanket insulation promoted as a complete, one-solution replacement for mineral wool or other traditional loft insulation — and that simply doesn’t align with building regulations, EPC methodology, or how UK housing actually performs.

If this continues unchecked, many homeowners may find themselves facing the same consequences spray foam owners are dealing with today.

A Familiar Pattern Emerging

For anyone who followed the spray foam fallout, much of this will feel uncomfortably familiar. New companies appear, often with little or no long trading history, built around selling a single insulation product. Sales messaging focuses on urgency, savings and “modern upgrades”, while downsides are minimised or ignored.

Installations are pushed through quickly — sometimes within days — before homeowners have time to seek independent advice or understand long-term implications. Once the insulation is installed, the tone of the conversation often changes.

A Pattern We’ve Seen Before

What Foil Blanket Insulation Is Actually Designed For

Foil quilt insulation was never designed to replace loft insulation on its own.

Products like SuperFoil, SuperQuilt and other multifoil systems are intended to work as supplementary layers, not primary insulation.

In properly designed systems, foil insulation is typically used:

• Alongside mineral wool, PIR or other approved insulation
• As a radiant barrier, not the sole thermal layer
• With maintained air gaps
• As part of a wider roof build-up that manages heat and moisture

Its performance depends heavily on correct installation, correct spacing, and the presence of other insulation materials. Remove those elements, and performance drops sharply.

Where Things Are Going Wrong

The most concerning trend we’re seeing is this: existing loft floor insulation is removed, joists are left exposed, and foil blanket insulation is installed at rafter level only — with homeowners told it “outperforms 300mm of wool”.

That claim is, at best, misleading — and at worst, setting people up for future problems.

Foil insulation provides reflective benefit. Traditional insulation provides thermal mass.

They are not interchangeable.

The Thermal Reality Homeowners Aren’t Being Told

Even high-quality foil blanket systems:

• Do not achieve required U-values on their own
• Rely on perfect installation
• Depend on air gaps remaining intact
• Lose performance when compressed, punctured or bridged

Traditional insulation materials — mineral wool (including systems like Knauf), PIR, or modern systems like Hybris — provide consistent, measurable thermal resistance that doesn’t depend on ideal conditions to the same extent.

Foil Blanket Insulation vs Conventional Loft Insulation

Feature	Foil Blanket (Used Alone)	Mineral Wool / Knauf	Actis Hybris
Primary role	Reflective layer	Thermal mass insulation	Structural thermal insulation
Works as stand-alone?	❌ No	✅ Yes	✅ Yes
Relies on air gaps	✅ Critical	❌ No	⚠️ System-dependent
U-value consistency	⚠️ Highly variable	✅ Consistent	✅ Measurable
EPC recognition	❌ Poor	✅ Fully recognised	✅ Recognised
Surveyor confidence	❌ Low	✅ High	✅ When installed correctly
Condensation risk if misused	❌ High	⚠️ Low	⚠️ Low (system-led)
Best use case	Supplementary only	Standard loft insulation	Premium retrofit systems

Why EPCs Struggle With Foil-Only Lofts

Energy Performance Certificates are based on recognised insulation performance using SAP methodology. They don’t award credit based on marketing claims or brochure figures.

A loft with no floor insulation and foil blanket insulation only at rafter level will almost always be assessed as under-insulated, which can lead to:

• Lower EPC ratings
• Recommendations for “loft insulation installation”
• Problems with sales, remortgaging or lettings
• Additional work being required later

Surveyors Are Starting to Take Notice

RICS surveyors look for insulation arrangements that are conventional, compliant, understandable and maintainable long-term.

Foil-only lofts often raise questions, not because foil is inherently bad, but because the overall approach is non-standard and difficult to verify.

We’re already seeing survey language such as:

That kind of wording is enough to stall or derail a transaction.

The Condensation Risk That Often Goes Unnoticed

Foil insulation acts as a vapour barrier. Installed incorrectly, or without a proper ventilation strategy, it can trap moisture, restrict airflow, cool timbers unevenly and lead to condensation forming behind the foil layer.

Unlike mineral wool, these issues are often hidden. That’s a worrying parallel with spray foam — where damage occurred out of sight until it became unavoidable.

Where Foil Insulation Does Make Sense

It’s important to be clear: foil insulation itself isn’t the problem.

Used correctly, it can work well:

• As part of a hybrid system
• Alongside mineral wool or PIR
• Combined with modern systems like Actis Hybris
• Where ventilation is properly designed
• Where the entire build-up is planned, not improvised

Why Hybris Is a Different Conversation

Unlike foil blankets alone, Actis Hybris provides measurable thermal resistance, is designed as a primary insulation layer, and integrates predictably with other materials. The difference is intent — it’s used as part of a system, not sold as a shortcut.

Removing Loft Floor Insulation Is a Major Red Flag

There is rarely a valid reason to remove compliant loft floor insulation purely to install foil blankets.

Doing so can:

• Reduce thermal mass
• Increase heat loss
• Harm EPC performance
• Create survey issues
• Make rooms below colder

The Real Cost Often Comes Later

The biggest cost usually isn’t the installation fee. It’s the knock-on effects: failed surveys, reduced property value, delayed sales, forced remediation, re-insulating correctly later — and unnecessary stress and uncertainty.

What Homeowners Should Ask Before Agreeing to Foil Insulation

If foil insulation is being proposed as a stand-alone solution, homeowners should ask:

• Will existing loft insulation be retained or upgraded?
• What U-value will the full system achieve?
• How will this perform on an EPC?
• Is the approach compliant with Building Regulations?
• Will this be acceptable to a RICS surveyor?
• What ventilation strategy is included?
• Is the installation reversible?
• How long has the company been trading?

If the answers are vague, defensive or rushed — that’s a warning sign.

The Bottom Line

Foil blanket insulation is not spray foam. But the way it’s increasingly being marketed and misused is following an uncomfortably similar path.

Insulation is not about shortcuts or silver bullets. It’s about systems, compliance and long-term performance.

We ignored that lesson once. We shouldn’t make the same mistake again.