The Rise of Spray Foam Insulation

The rise of spray foam insulation, driven by government incentives and a push for energy-efficient homes, has led to unforeseen challenges for homeowners. This article examines the impact of the government’s “green” agenda on this issue, the differences between types of spray foam insulation, and the broader implications for property owners, particularly those with period properties.

Government initiatives such as the Green Homes Grant Scheme (2020-2021) were introduced to improve energy efficiency and reduce carbon emissions in domestic properties. These schemes made spray foam insulation an attractive option for homeowners, especially as the costs were heavily subsidised or fully covered for certain households.

Spray foam became a popular choice for insulating lofts and roof spaces because:

It promised excellent thermal performance.
It was marketed as a quick and cost-effective solution to meet energy efficiency targets.
Installations were carried out under the government-endorsed Trustmark accreditation, giving homeowners a false sense of security regarding the quality and suitability of the product.

However, the rush to meet demand led to substandard installations in many cases. The pressure to implement energy-saving measures quickly, coupled with limited regulatory oversight, created a perfect storm. For example:

Many contractors focused on volume over quality, sometimes overlooking critical factors such as the type of roof construction or the ventilation requirements of older properties.
Some installers lacked proper training, leading to inappropriate applications, particularly in period properties.

The result has been widespread problems, including structural damage, mortgage refusals, and increased insurance premiums, leaving many homeowners feeling “betrayed” by a government scheme that was intended to help.

Understanding Spray Foam Insulation: Open vs. Closed Cell

Spray foam insulation comes in two main forms: closed-cell and open-cell. Both types have distinct characteristics, but neither is without risk, particularly when applied inappropriately.

Closed-Cell Spray Foam

Characteristics: Rigid and dense when set, providing high thermal resistance (R-value) and an effective vapour barrier.
Applications: Previously marketed as a dual-purpose product for insulation and roof stabilisation.
Risks:
- Moisture Trapping: Its impermeable nature can trap moisture within the roof structure, leading to decay of timber elements.
- Structural Stress: The foam’s rigidity can exert pressure on roof timbers, causing deformation or cracking, particularly in older properties with less robust frameworks.
- Ventilation Issues: By creating an airtight seal, it prevents the natural “breathing” of the roof space, exacerbating condensation problems.

Open-Cell Spray Foam

Characteristics: Softer and less dense, with a “breathable” structure allowing some water vapour to pass through.
Applications: Typically used for insulation purposes only, not for structural stabilisation.
Claims of Breathability: While open-cell foam is marketed as a breathable solution, this claim requires scrutiny. Its breathability is limited by:
- The context of the installation. For example, if applied directly over a vapour-impermeable underlay (such as bitumen felt), it effectively creates a sealed system, negating any breathability.
- The risk of retaining moisture within the foam, which can lead to unseen damage to underlying materials.
- Its reliance on proper installation, as poorly applied foam can obstruct ventilation, leading to the same issues as closed-cell foam.

The Role of the Government’s Green Agenda

The Green Homes Grant Scheme, along with subsequent initiatives like the Great British Insulation Scheme, aimed to accelerate the adoption of energy-saving measures in line with the UK’s net-zero targets for 2030. However, this well-intentioned agenda has unintentionally created several problems:

Misaligned Incentives: Contractors were incentivised to install spray foam quickly to secure government subsidies, often prioritising speed over quality.
Inadequate Oversight: While Trustmark accreditation provided a veneer of legitimacy, it did not guarantee appropriate installation or long-term suitability, particularly in period properties.
Lack of Consumer Awareness: Homeowners were not sufficiently informed about the potential downsides of spray foam insulation, especially its long-term impact on property value and mortgage eligibility.
Pressure on Lenders and Insurers: The widespread installation of spray foam has left lenders and insurers wary. Properties with spray foam insulation are often flagged as high-risk due to concerns about hidden damage and the cost of remedial work, leading to mortgage refusals and increased insurance premiums.

Critically Appraising the Claims

The marketing of open-cell spray foam as “breathable” has contributed to its popularity, but this claim deserves a more critical examination:

Partial Vapour Permeability: While open-cell foam does allow some water vapour to pass through, this does not equate to full breathability in a traditional building sense. True breathability requires the entire system (including underlays and roof coverings) to work together to regulate moisture.
Compatibility with Traditional Materials: Many period properties rely on the natural permeability of materials like timber and lime mortar to manage moisture. Introducing even “breathable” spray foam can disrupt this balance, leading to condensation and decay.
Limited Scientific Validation: There is insufficient long-term research to conclusively prove that open-cell spray foam does not contribute to roof decay under specific conditions.

Implications for Period Properties

Spray foam insulation is particularly problematic in historic and period properties due to their reliance on traditional construction methods. These buildings were designed to “breathe,” and any alteration that interferes with this natural process can have severe consequences. Issues commonly observed include:

Accelerated timber decay due to trapped moisture.
Loss of heritage value if traditional materials or techniques are compromised.
Increased costs for removal and restoration if the insulation causes damage.

The Government’s Response and Homeowner Responsibility

The UK Government has faced criticism for its limited response to the challenges caused by spray foam insulation installed under schemes like the Green Homes Grant. In June 2022, the government stated that it had “no plans to intervene” in cases where property values or mortgage accessibility had been affected, maintaining that:

The availability and terms of mortgages are matters for lenders.
It is the responsibility of homeowners and installers to decide whether to use spray foam insulation.

Additionally, in March 2022, the government noted that homeowners who believe they have been misled may be able to seek redress under the Consumer Protection from Unfair Trading Regulations 2008, which require traders to act honestly and transparently.

While this offers a potential legal route, navigating consumer protection laws can be complex and intimidating, leaving many homeowners feeling abandoned and burdened with the financial and practical fallout.

The Challenges of Spray Foam Removal

Removing spray foam insulation can be a costly and challenging process, and ensuring it has been properly removed is crucial, particularly when properties are being used as security for equity release or mortgages. Unfortunately, we recently encountered a case that highlights these difficulties.

An elderly homeowner, hoping to secure equity release to fund a final visit to family in Australia, was persuaded by a door-to-door spray foam insulation company to install foam on the underside of his roof for £5,000. Promised significant energy savings, he agreed to the work, only to find that the insulation rendered his property unmortgageable and unsuitable for equity release.

Following the lender’s surveyor’s advice, the owner arranged for the foam to be removed at a similar cost. However, when we were instructed to inspect the property post-removal, we discovered the following issues:

Ventilation Blockages: The eaves vents were still obstructed by foam, preventing proper airflow to the roof.
Compromised Felt Overlaps: The roofing felt overlaps were glued shut by residual foam, further hindering the roof’s natural ventilation.

We advised the owner that these issues needed to be rectified before we could confirm that the roof was no longer affected by spray foam. After additional remedial work and a subsequent inspection, we were finally able to issue the required confirmation. Sadly, by this time, the homeowner had missed his opportunity to visit family overseas—a stark reminder of the far-reaching consequences of poorly considered spray foam insulation.

This case underscores the importance of working with trusted professionals, both for the removal process and for a thorough inspection to ensure the property is suitable for lending criteria.

Spray foam insulation can rarely, if ever, be completely removed from the underside of a roof without leaving some residue. This presents challenges when attempting to remortgage a property. The critical point is whether the level of removal is sufficient to satisfy lenders and allow a surveyor to adequately assess the condition of the roof structure and to confirm that there is adequate ventilation.

What Level of Spray Foam Removal is Acceptable?

The general expectation is that enough of the foam must be removed to:

Expose the Roof Timbers: The rafters, joists, and any associated structural elements must be visible to ensure they are not compromised by moisture, rot, or decay.
Permit a Structural Assessment: A professional surveyor or timber specialist must be able to inspect the roof timbers fully and confirm their condition.
Demonstrate Proper Ventilation: Any residual foam must not obstruct ventilation pathways, as poor ventilation can exacerbate damp or condensation issues.

Proper ventilation and the complete removal of residual foam are essential to restore the roof’s functionality and the property’s value.

Rethinking Our Homes and Expectations

The push for energy efficiency under government schemes has inadvertently left many homeowners in a precarious position. Spray foam insulation, while effective in certain contexts, is not a one-size-fits-all solution, particularly for period properties. Modern insulation techniques can play a role, but they must be applied thoughtfully and with an understanding of a building’s unique characteristics.

To mitigate future issues:

Homeowners must seek advice from qualified surveyors before opting for spray foam insulation.
Policymakers should ensure stricter oversight of energy-efficiency schemes, with better consumer protections.
The industry must improve transparency about the risks and limitations of spray foam products.

In a broader context, the question of insulating and heating our homes invites us to reflect on our expectations. Historically, families adapted to colder winters by concentrating their activities in smaller, communal spaces and relying on simpler, localised heating methods.

While we do not need to see a return to Dickensian times, our modern preference for large, open-plan homes—where every corner of the house is expected to be warm—places immense demands on energy use and drives the pursuit of unsuitable insulation solutions.

Perhaps part of the solution therefore lies not just in retrofitting our homes but in rethinking how we use them. Focusing heating on key living spaces or embracing layered clothing indoors could complement energy-efficient measures. These small shifts in behaviour could reduce the need for aggressive interventions in our homes and make ‘sustainability’ more achievable.

Spray Foam Insulation | A Growing Problem for UK Homeowners