What is Open-Cell Spray Foam?

Open-cell spray foam is a lightweight, flexible insulation material made up of tiny, interconnected air pockets. These open cells give it a sponge-like texture, allowing it to expand significantly when applied—often up to 100 times its original volume. This makes it ideal for filling irregular spaces in walls, lofts, or floors. It’s soft to touch, and you can grab handfuls of it, reflecting its low density and pliable nature.

• Pros: Open-cell foam is relatively affordable and offers excellent soundproofing due to its soft, porous structure. It’s also less dense, typically weighing around 0.5 kg per cubic metre, which can reduce strain on older timber structures common in Cornish homes.
• Cons: Its open structure allows air and moisture to pass through more easily than closed-cell foam. Standards like BS 5250: Code of Practice for Control of Condensation in Buildings require adequate ventilation to manage this moisture, but if not installed with a proper vapour barrier—or if the barrier fails over time—this can lead to dampness trapping against timber roof structures. In Cornwall’s humid climate, this increases the risk of rot, a problem we’ve seen all too often at Kernow Insulation.

What is Closed-Cell Spray Foam?

Closed-cell spray foam is denser and more rigid, composed of tightly packed cells filled with a gas that enhances its insulating power. It expands less than open-cell foam—about 30-50 times its original volume—but forms a hard, protective layer once cured. It’s very hard to the touch, often used to consolidate roofs by adding structural strength, and requires sharp tools to remove it due to its toughness. It’s commonly applied in areas needing robust insulation, like external walls or under floors.

• Pros: Closed-cell foam has a higher R-value (thermal resistance) per inch, making it more effective at preventing heat loss. At around 1.7 kg per cubic metre, it also acts as a moisture barrier, reducing the need for additional vapour control layers.
• Cons: Its rigidity and density make it harder to remove, a challenge we tackle regularly at Kernow Insulation. More critically, if applied without proper ventilation as outlined in PAS 2035: Retrofitting Dwellings for Improved Energy Efficiency, it can trap moisture against timbers, leading to hidden rot—despite its moisture-resistant claims. Its higher cost also makes it a bigger investment, which can sting when lenders later flag it as a mortgage issue.

Why Spray Foam Becomes a Problem

Both types of spray foam have their benefits, but in Cornwall, where traditional stone cottages and exposed coastal homes dominate, they can pose risks when ventilation isn’t prioritised. Standards like PAS 2030: Specification for Installation of Energy Efficiency Measures and PAS 2035 set strict guidelines for retrofitting insulation, requiring ventilation to prevent condensation and dampness—issues BS 5250 also addresses. Yet, many installations, especially older ones from schemes like the Green Homes Grant, ignored these requirements. Open-cell foam’s moisture permeability and closed-cell foam’s potential to seal in dampness have led to countless cases of timber decay. This not only threatens your home’s structural integrity but also its mortgageability. Many UK lenders now refuse mortgages or equity release on properties with spray foam insulation, citing valuation concerns from the Royal Institution of Chartered Surveyors (RICS).

At Kernow Insulation, we’ve seen the fallout firsthand: homeowners unable to sell, remortgage, or access equity because of a decision made years ago. Whether it’s open-cell foam letting damp seep into your loft or closed-cell foam locking it in due to poor ventilation, the result is the same: a costly problem that needs expert removal.

The Health Risks of Spray Foam Removal

Removing spray foam insulation isn’t just a structural challenge—it can also pose health risks if not handled properly. The process can release harmful chemicals, including isocyanates, chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). These compounds can become airborne during removal and pose serious health risks if inhaled.

• Isocyanates: Found in most spray foams, these reactive chemicals can cause respiratory issues like asthma and bronchitis when airborne during removal. Prolonged exposure may lead to sensitisation, making even small future exposures dangerous.
• CFCs, HCFCs, and HFCs: These blowing agents, used to expand the foam during installation, can be released when it’s disturbed. Older insulation may still contain CFCs, which harm the ozone layer and are now banned but linger in some properties. Exposure to HCFCs and HFCs can cause headaches, dizziness, and irritation to the eyes, nose, and throat, with long-term risks including damage to major organs and the central nervous system.

At Kernow Insulation, we prioritise safety, using protective equipment and controlled removal techniques to minimise these risks for both our team and your household.

How Kernow Insulation Can Help

Removing spray foam isn’t a DIY job. Open-cell foam’s softness means you can pull it apart by hand, but its flexibility makes it tricky to extract fully without leaving residue. Closed-cell foam’s hardness, used to reinforce roofs, demands sharp tools and precision to avoid damaging your structure. Add in the health hazards and the need to comply with ventilation standards, and it’s clear why professional expertise matters. Our team at Kernow Insulation is trained to handle both types safely, offering:

• Safe, thorough removal tailored to your property, with strict controls to contain harmful chemicals.
• Roof health assessments to check for hidden damage caused by poor ventilation.
• Eco-friendly insulation alternatives that meet PAS 2030, PAS 2035, and BS 5250 requirements.

Final Thoughts

Open-cell and closed-cell spray foam each have their place, but for many Cornwall homeowners, they’ve become a liability rather than an asset—especially when ventilation standards like PAS 2030, PAS 2035, and BS 5250 are overlooked. Open-cell’s soft, handful-friendly texture contrasts with closed-cell’s hard, roof-consolidating strength, yet both can fail in Cornwall’s damp conditions if airflow isn’t managed. If you’re dealing with spray foam woes, don’t despair. Kernow Insulation is here to restore your home’s health and value, one safe removal at a time.