At Pyramid Eco, we’re committed to retrofit solutions that prioritise safety, sustainability, and long-term value. As part of that commitment, we’re phasing out EPS insulation across all projects and adopting mineral wool as our new standard.
This isn’t just a material swap. It’s a move to future-proof homes, enhance fire safety, and help our clients avoid issues with resale, compliance, and long-term performance. Read on to learn why we made the switch, how EPS compares to mineral wool, and what it means for your next retrofit.
What Is EPS Insulation?
EPS insulation stands for expanded polystyrene insulation. It’s a type of rigid foam created by expanding polystyrene beads with steam and fusing them together in moulds. The result is a lightweight, closed-cell material that offers good thermal insulation at a relatively low cost. It’s typically cut into large flat panels known as EPS boards, which are used extensively in construction projects for insulating external walls, floors, and roofing systems.
Due to its low material cost, EPS has become a popular choice in both new builds and retrofits. It’s easy to transport, simple to cut, and straightforward to install when the structure is uncomplicated. However, despite these advantages, EPS has several limitations.
EPS Insulation vs Mineral Wool: Why Pyramid Eco Made the Switch
Mineral wool outperforms EPS insulation in safety, resilience, and long-term value. Here’s how this shift enhances every Pyramid Eco project and what it means for your property’s future.
1. Fire Performance
When lives may depend on how a building performs in an emergency, the materials we choose must meet the highest possible standards. Fire safety is non-negotiable.
EPS insulation is very flammable, meaning it can ignite and propagate flames. The Euroclass system sets the standard for fire performance in building materials. A1-rated mineral wool is non-combustible, while EPS, typically rated Euroclass E — which is the second-lowest fire rating score — offers much lower fire resistance and is less suited to safe retrofitting.
As more homeowners extend into lofts and upper storeys in areas like South East England, safe and rapid evacuation becomes more difficult — especially for the elderly or mobility-impaired. In such cases, the insulation system must support life safety.
At Pyramid Eco, we believe fire performance should never be compromised. Adopting mineral wool helps us meet the gold standard and provides our clients with confidence that their buildings are as safe as they are efficient.
2. Installation Requirements and Detailing
Installing EPS board insulation to a compliant standard is far more complex than it may appear on paper. To meet fire safety regulations, EPS systems require continuous fire breaks around:
- Window and door openings
- Party walls and eaves
- Flues and ventilation ducts
These added details create material wastage, increase labour hours, and raise the risk of error. Even small oversights in fire detailing can lead to significant compliance issues.
Mineral wool allows for simpler detailing that inherently meets fire resistance requirements. The material’s structure does not need additional fire stopping, streamlining installation and reducing opportunities for failure.
From an operational perspective, this makes mineral wool a safer and more cost-effective option in the long run.
3. Moisture Resistance and Breathability
A crucial but often overlooked aspect of internal and external wall insulation is how it handles moisture. EPS is a closed-cell material with very low vapour permeability. This means if moisture enters the system due to poor detailing or minor breaches in waterproofing, it can become trapped behind the insulation layer.
Over time, trapped moisture can lead to:
- Internal damp or mould
- Degradation of adhesive bonds
- Frost damage during freeze-thaw cycles
- Declining thermal performance
Mineral wool is highly breathable. It allows vapour to pass through while repelling liquid water, supporting healthier indoor environments and improving the longevity of the structure.
Related: The Importance of Proper Home Ventilation
4. Compatibility in Hybrid Systems
Some retrofit providers use hybrid systems. They combine EPS and mineral wool on different sections of a building. While this may seem like a cost-saving measure, research has shown that using different materials on the same elevation can compromise long-term performance.
EPS and mineral wool differ in their:
- Thermal expansion rates
- Moisture absorption behaviour
- Mechanical stiffness and flexibility
The junctions between these materials become stress points that are difficult to seal reliably. Over time, this can lead to multiple issues, including:
- Surface cracking
- Moisture ingress
- Air leakage
- Aesthetic degradation
In an industry increasingly expected to deliver long-term performance guarantees, introducing known failure points through incompatible materials is simply not a risk we’re willing to take.
5. Impact on Resale, Insurance, and Mortgage Lending
There is a growing trend among lenders, surveyors, and insurers to scrutinise properties insulated with EPS-based systems and spray foam insulation. This is particularly true in the wake of the EWS1 requirements, which originally targeted high-rise buildings but are now being applied to low-rise and even terraced housing stock.
For homeowners and landlords, this can mean:
- Additional surveys and documentation
- Lower property valuations
- Delays in refinancing or sales
- In some cases, mortgage refusals
At Pyramid Eco, we want our retrofit work to support our clients’ financial futures — not hinder them. By standardising non-combustible mineral wool insulation, we help property owners and housing associations future-proof their assets for performance and marketability.
Leading the Shift to Safer, Smarter Retrofitting
Pyramid Eco is proud to be part of the movement away from outdated insulation practices. Regulations are tightening. Consumer awareness is rising. And funding bodies are becoming more selective about the systems they support.
We are choosing to lead this change — not follow it.
While switching from EPS to mineral wool carries added costs, we are absorbing much of that cost ourselves to keep our services accessible. This is not just a business choice. It’s a reflection of our values:
- Safety over shortcuts
- Quality over cost-cutting
- Long-term impact over short-term gain
Rejecting EPS as an insulation material has already led to us losing out on projects. Some clients want the cheapest possible insulation material, regardless of the implications. We just can’t consciously recommend it, and we don’t want to install it, even if that means turning down work.
Your Partner in Safe, Future-Proof Insulation
At Pyramid Eco, we deliver retrofit solutions that prioritise fire safety, long-term performance, and regulatory peace of mind. By choosing mineral wool, we help you avoid the risks of EPS and future-proof your properties.
Backed by industry certifications and a 24-month guarantee, we’re a trusted partner for sustainable insulation. Book a free consultation today and take the first step toward a safer, more resilient retrofit.
Frequently Asked Questions
EPS insulation, or Expanded Polystyrene, is commonly used in external wall insulation systems, underfloor insulation, and flat roofs. It’s valued for its lightweight properties and affordability, but it falls short in fire safety and long-term performance compared to mineral wool.
EPS is a combustible material. In the event of a fire, it can ignite and contribute to flame spread. That’s why it has a lower fire safety rating (typically Euroclass E) compared to A1-rated mineral wool, which is non-combustible and significantly safer for residential applications.
Yes, EPS is still permitted under certain regulations. However, many providers, lenders, and insurers are moving away from it due to growing concerns about fire safety, moisture retention, and resale complications. At Pyramid Eco, we’ve chosen to stop using EPS to ensure higher quality and peace of mind for our clients.
Mineral wool systems can be more expensive initially. However, at Pyramid Eco, we absorb most of the added cost to keep our services competitive. The long-term value in safety, durability, and fewer compliance issues often outweighs the short-term savings EPS may offer.
Yes. We’re seeing increasing cases where lenders and insurers require EWS1 forms or additional safety checks for properties with EPS-based EWI systems. This can delay valuations, increase costs, or even result in mortgage refusals — issues that can be avoided by using A1-rated mineral wool.
EPS is a petroleum-based plastic product that is not biodegradable and has limited recyclability. Mineral wool, by contrast, often contains recycled materials and supports better building breathability, making it a more sustainable choice for eco-conscious retrofit projects.
