Cork insulation vs Foam - Choosing the right insulation for your project

Choosing the right insulation material can make a major difference in your home’s comfort, energy bills and environmental footprint. A natural dilemma is cork vs foam, in which you have two materials that perform admirably but have very different characteristics.

In this guide, we’ll compare both options in detail to help you choose.

Summary

Understanding your insulation options

The purpose of insulation is to act as a barrier to heat transfer; this helps to keep a comfortable temperature inside. But not all insulation works the same way: some materials are more conducive of heat, or help control moisture better; not all are equally friendly to the environment and, of course, cost also varies.

Cork and foam are both excellent performers, but they appeal to different priorities, differing one from the other in all these factors.

What is cork insulation?

Cork is a natural resource - in fact, a type of bark. It’s harvested without damaging the beautiful cork oak and, after expanded through the use of heat and steam, the granules are pressed into boards.

• Key properties:
• Thermal performance: λ-value of 0.037-0.040 W/mK, offering solid insulation against heat loss;
• Acoustic insulation: cork’s unique cellular structure absorbs sound very effectively;
• Sustainability: renewable, recyclable and carbon-negative production process;
• Breathability: moisture can pass through, which prevents condensation;
• Durability: resistant to rot, mould and pests, with a lifespan of several decades.

Cork insulation is the perfect choice for environmentally minded homeowners, heritage renovations and breathable wall systems that prioritize healthy air quality.

What is foam insulation?

Foam is made from synthetic materials such as polyurethane (PU), polyisocyanurate (PIR), or expanded polystyrene (EPS); it can come in the form of rigid boards or spray, depending on the application.

• Key properties:
• Thermal performance: λ-value between 0.020 and 0.030 W/mK, showing high efficiency in thin layers;
• Easy installation: spray foam can fill hard-to-reach gaps, while the boards are light and easy to cut;
• Moisture resistance: closed-cell foams act as vapor barriers and reduce the risk of damp;
• Cost: widely available; often cheaper than natural alternatives;
• Fire resistance: varies depending on the product; some require protective layers.

Foam is commonly used in modern buildings and renovations that require high thermal performance in thin layers and airtight construction.

Pros and cons of cork insulation

Pros:

• 100% natural, renewable and non-toxic
• Breathable and mould-resistant
• Excellent soundproofing qualities
• Long-lasting and stable performance
• Carbon-negative material

Cons:

• More expensive than foam per square metre
• Heavier and more labour-intensive to install

For more information on this topic read our article Cork Insulation: All Pros and Cons Explained. 

Pros and cons of foam insulation

 Pros:

• Very high thermal efficiency
• Easy to install and lightweight
• Excellent moisture and air sealing properties
• Cost-effective for large-scale projects

Cons:

• Made from petrochemicals
• Non-breathable and can trap moisture if misused
• Some types may emit VOCs
• Disposal and recycling are difficult

Which insulation is best for your project?

All depends on your plans.

• Choose cork if you like the idea of a natural, breathable material that makes the space more comfortable. Cork is perfect for traditional buildings, timber structures and eco-friendly projects.
• But opt for foam if you’re looking for maximum thermal performance, moisture resistance and a lower upfront cost: a frequent choice for new builds, extensions and cavity wall applications.

Cost comparison and long-term value

Foam typically costs less upfront than cork but may have higher environmental costs over its lifecycle. Cork, although more expensive, can reduce condensation-related issues and help to improve the air quality inside, adding long-term value.

Example:

• Cork boards: around £40-£60 per m²
• Foam boards: around £20-£35 per m²

Installation tips and considerations

• Cork insulation: Cut with fine saws and fit snugly between studs or rafters. Avoid vapor barriers, which would block its breathability.
• Foam insulation: Ensure surfaces are dry and clean before applying. For spray foam, use certified installers and maintain proper ventilation.
• Hybrid approach: In some cases, the cosier cork can be used internally while foam boards are installed externally.

Professional installation may be a good idea in either case, to ensure the best performance and that everything is in compliance with building regulations.

Final thoughts - cork insulation vs foam

Both cork insulation and foam offer effective ways to reduce heat loss, but they suit different priorities. Cork promotes better air quality and shines in acoustic performance; it’s also more eco-friendly. Foam wins in terms of efficiency and is easier to install, aside from being cheaper.

Portuguese Treasures offers a wide range of cork insulation perfect for use in exterior, interior and cavity walls, slabs, floors, roofs and ceilings.