June 1, 2025
Spray foam insulation promises energy efficiency—but can it backfire by causing humidity or condensation problems in the loft? In this guide, we explore whether spray foam can trap moisture, how to spot the early signs, and what to do if your loft is suffering from damp-related issues in 2025.
1. How Spray Foam Works in the Loft
Spray foam expands to seal gaps and crevices in the roofline. While this reduces heat loss, it also significantly alters how your loft ‘breathes.’
Unlike traditional loft insulation, spray foam—especially closed-cell types—can block natural airflow. When this happens, any internal moisture from living spaces below can get trapped.
This increases the risk of:
2. Why Loft Condensation Happens
Condensation forms when warm, moist air hits a colder surface. In a typical loft, this happens when:
Spray foam insulation can contribute to this if it:
3. Warning Signs of Humidity or Condensation in a Spray Foam Loft
If you already have spray foam in the loft, watch for these red flags:
If these symptoms are present, your loft’s ventilation may be compromised—and structural damage may be developing.
4. How to Reduce Condensation in a Spray Foam Loft
To minimise humidity and protect your property:
5. When to Consider Spray Foam Removal
In many UK cases, removing the spray foam is the only long-term solution. Consider removal if:
Learn more: Spray Foam Removal Without Damage
6. Can Spray Foam Ever Work Without Causing Damp?
Yes—but only when it’s applied professionally with ventilation considerations in mind. Open-cell spray foam, for example, is more breathable and less likely to trap water vapour.
Still, even good installations can fail over time due to roof ageing, blocked vents, or changing moisture patterns.
A routine loft inspection is recommended every 1–2 years to ensure no early signs of humidity are developing.
Frequently Asked Questions
Can condensation form under spray foam?
Yes—especially if the foam is applied directly to the roof deck and airflow is blocked.
Will adding more ventilation help?
Yes, but only if it’s strategically placed and doesn’t compromise roof insulation.
Can condensation damage the spray foam?
Over time, yes. It can cause delamination, dark staining, and internal decay of timber.
Should I remove spray foam if I have condensation?
In serious cases—yes. Especially if timber rot or surveyor concerns are involved.
How do I check for moisture issues in a spray foam loft?
Use a moisture meter, inspect visually, or hire a RICS-accredited building surveyor.
Explore trusted Spray Foam Removal Locations or speak to Snug & Secure for expert advice on insulation issues in your loft.
Unsure if your spray foam insulation will impact home insurance coverage or claims? Find out how UK insurers view it in 2025 and what you need to disclose.
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